WO2016040653A1 - Production de bioplastique à partir de matière carbonée non-sucre - Google Patents

Production de bioplastique à partir de matière carbonée non-sucre Download PDF

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Publication number
WO2016040653A1
WO2016040653A1 PCT/US2015/049455 US2015049455W WO2016040653A1 WO 2016040653 A1 WO2016040653 A1 WO 2016040653A1 US 2015049455 W US2015049455 W US 2015049455W WO 2016040653 A1 WO2016040653 A1 WO 2016040653A1
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microorganism
coa
genetically engineered
carbon source
enzyme
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PCT/US2015/049455
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English (en)
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Gianguido COFFA
Marthah Jeanne Margaret DE LORME
Joel SEVINSKY
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Coffa Gianguido
De Lorme Marthah Jeanne Margaret
Sevinsky Joel
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Publication of WO2016040653A1 publication Critical patent/WO2016040653A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P7/00—Preparation of oxygen-containing organic compounds
    • C12P7/62—Carboxylic acid esters
    • C12P7/625—Polyesters of hydroxy carboxylic acids

Definitions

  • the present invention relates to biosynthesis of polyhydroxalkanoates using a microorganism.
  • the present invention is directed to a biosynthesis process using a genetically engineered microorganism to synthesize polyhydroxalkanoates from a low value carbon source.
  • Plastic materials have become an integral part of contemporary life because of their many desirable properties, such as durability and resistance to degradation.
  • the widespread use of plastic is increasingly regarded as a source of waste management problems and an environmental pollutant.
  • biodegradable plastics have become excellent alternatives to traditional plastics.
  • Biodegradable plastics are biopolymers that are degradable either by non-enzymatic hydrolysis or by the action of enzymes secreted by microorganisms. Estimates of the current global market for these biodegradable plastics may be up to 1.3 billion per/year.
  • PHAs polyhydroxyalkanoates
  • microorganisms are affected by the bacterial species and their growth conditions.
  • PHAs may- accumulate in bacterial cells as discrete granules, the number of granules per cell and size of can vary among different bacterial species.
  • PHAs are categorized by the length of the monomer units in the PHAs. Short-chain (8C) PHAs have monomers of 3-5 carbon atoms, while medium-chain (MC) PHAs have monomers of 6-14 carbon atoms. The PHAs with monomer units longer than 14 carbon atoms are long-chain (LC) PHAs.
  • the biosynthesis of PHAs by microorganisms and the enzymes involved are described in detail by the paper "Occurrence, Metabolism, Metabolic Role, and Industrial Uses of Bacterial Polyhydroxyalkanoates," Microbiological Reviews, vol. 54, pages 450-472, 1990 authored by Anderson et al.
  • a major drawback for producing PHAs using these microorganisms is the high production cost, making them substantially more expensive than traditional plastics, partially due to the low level of PHA biosynthesis by the natural wild-type microorganisms.
  • microorganism comprises at least one modification in at least one gene encoding a protein involved in biosynthesis of PHAs, which causes overproduction of medium or long chain PHAs relative to PHA production of the corresponding wild-type microorganisms.
  • Rhodococcus eutropha is taught as a possible choice for the genetically engineered microorganism. Pyruvate and octadetane are mentioned as examples of carbon sources.
  • U.S. Patent No. 6,117,658 discloses a method of producing PHAs using a host cell containing at least one recombinant nucleotide sequence that encodes an enzyme in PHA biosynthetic pathway, and at least one recombinant nucleotide sequence that encodes an enzyme in a succinic semialdehyde metabolic pathway that metabolizes succinic
  • the host cell may be one of Escherichia coli, Klebsiella (particularly Klebsiella aerogenes and Klebsiella oxytoca), plant host cells, insect host cells and spider host cells.
  • the carbon source for the growth of the host cells may be sugar containing a 5 -carbon or 6-carbon ring, such as glucose.
  • Patent Application Publication US 2013/0071892 discloses a method of producing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (i.e. P(3HB-co-3HHx)) using a vegetable oil as the starting raw material.
  • the method uses a genetically engineered microorganism with an exogenous gene encoding R-hydratase that converts a fatty acid ⁇ -oxidation system intermediate to a monomer, 3-hydroxyacyl-CoA, which is then polymerized to form the P(3HB-co-3HHx).
  • the microorganism may be a Cupriavidus necator strain with an enhanced ability of producing P(3HB-co-3HHx).
  • U.S. Patent No. 6,492, 134 provides a method for production of PHAs using a genetically engineered eukaryotic cell, which comprises an engineered eukaryotic pathway involved in PHA biosynthesis.
  • the eukaryotic cell has exogenous genes that encode for thioesterase, acyl-CoA synthetase, a thiolase, a yeast, (R)-3-hydroxyacyl-CoA
  • the eukaryotic cell may be a yeast cell or an insect cell.
  • the carbon source for the PHA biosynthesis may be fatty acids, gluconate, lactate, glycerol, and hexoses.
  • U.S. Patent No. 7,276,361 discloses a method for producing a biodegradable poly (3 -hydroxy alkanoate) polyester by a microorganism comprising an evolutionary- engineering poly(3-hydroxyalkanoate) biosynthetic enzyme (e.g., PHA polymerase).
  • the carbon source used for the microorganism may be carbohydrates such as glucose, fructose, sucrose and maltose.
  • the present invention provides one or more genetically engineered microorganisms and processes that produce PHAs cost- effectively from a low cost carbon source such as coal, biomass or industrial waste.
  • An aspect of the present invention provides a method for synthesizing a PHA from a low value carbon source, comprising the steps of oxidizing the low value carbon source with at least one oxidizing agent to produce a modified, partially solubilized low value carbon source; and contacting the modified, partially solubilized low value carbon source with a genetically engineered microorganism adapted for growth in the modified, partially solubilized low value carbon source, which is derived from a wild-type microorganism comprising a PHA biosynthesis pathway from acetyl-CoA, wherein the genetically engineered microorganism comprises at least one genetic modification selected from; (a) increasing an enzymatic activity of at least one enzyme in the PHA biosynthesis pathway relative to the activity of the same enzyme in the wild-type microorganism, (b) decreasing an enzymatic activity of at least one enzyme in fatty acid ⁇ -oxidation pathway relative to the activity of the same enzyme in the wild-type microorganism, and (c) decreasing en
  • Another aspect of the present invention may be a genetically engineered microorganism derived from a wild-type microorganism of the genus Rhodococcus, which comprises a PHA biosynthesis pathway from acetyl-CoA, wherein the genetically engineered microorganism comprises at least one genetic modification selected from; (a) increasing an enzymatic activity of at least one enzyme in the PHA biosynthesis pathway relative to the activity of the same enzyme in the wild-type microorganism, (b) decreasing an enzymatic activity of at least one enzyme in fatty acid ⁇ -oxidation pathway relative to the activity of the same enzyme in the wild-type microorganism, and (c) decreasing enzymatic activity of PHA depolymerase relative to the activity of the PHA depolymerase in the wild-type
  • Figure 1 is a flow chart that shows a method for biosynthesizing a PHA from a low value carbon source, according to one embodiment of the present invention.
  • FIG. 2A shows an overview of a PHA biosynthesis pathway starting from acetyl- CoA.
  • the PHA biosynthesis pathway comprises a fatty acid synthesis portion and a PHA polymerization portion.
  • Figure 2B shows a fatty acid elongation cycle of the fatty acid biosynthesis portion of the PHA biosynthesis pathway in Figure 2A.
  • Figure 2C shows a polymerization portion of the PHA biosynthesis pathway in Figure 2A, wherein monomers for the PHA polymerization are derived from intermediates of the fatty acid biosynthesis as shown Figure 2B.
  • Figure 2D shows a fatty acid degradation pathway (also known as fatty acid ⁇ oxidation pathway).
  • Figures 3A-3H show examples of vectors that can be used to genetically engineer a microorganism.
  • Figure 4A is a schematic representation of a gene knock-out process where a gene in the microorganism host genome is deleted.
  • Figure 4B is a schematic representation of a gene knock-in process where a fragment in the microorganism host genome is replaced with an exogenous DNA sequence.
  • Figure 4C is a schematic representation of a gene knock-in process where an exogenous DNA sequence is inserted into the microorganism host genome.
  • Figure 5 represents three promoter/terminator systems that may be used in the present invention.
  • Figures 6A-6C represent the structure and sequence of the three
  • Figure 7 is a schematic representation of a pretreatment method for converting a carbonaceous raw material to a feedstock for microorganisms.
  • Figure 8 is a flow chart depicting a pretreatment method for black liquor to obtain a feedstock for microorganisms.
  • Figure 9 is a flow chart depicting a pretreatment. method for black liquor according to another embodiment, wherein selected organic polymers are recovered from the raw black liquor and only selected components of the black liquor are used to generate one or more organic compounds comprising from about 2 to about 20 carbon atoms, which can be used as a feedstock for microorganisms.
  • Figure 10 is a flow chart depicting a pretreatment method for black liquor according to yet another embodiment, wherein only selected components of the black liquor are used in to generate one or more organic compounds comprising from about 2 to about 20 carbon atoms (used as feedstock for microorganisms.
  • Figure 11 is a flow chart depicting a pretreatment method for black liquor according to yet another embodiment, wherein selected organic polymers are recovered from the raw black liquor, and only selected components of black liquor are used to generate one or more organic compounds comprising from about 2 to about 20 carbon atoms (used as feedstock for microorganisms).
  • Figure 12 shows Rhodococcus bacterial strains grown on petri dishes that were transformed by plasmids pCE7 and pCE8, together with negative controls.
  • Figure 13 shows the results of gel electrophoresis for mutant microorganisms prepared in Example 5 using a gene knock-out process.
  • Figure 14 shows the results of gel electrophoresis for different microorganism colonies after a second recombination as described in Example 6.
  • Figure 15 shows the results of gel electrophoresis for different microorganism colonies after a first recombination as described in Example 7.
  • Figure 16 shows a fluorescence photo of Nile Blue stained Rhodococcus ruber DSM 44190 cells grown on a pretreated coal.
  • algae concentrate refers to an algae paste or an algae cake, which is a residue obtained by separating algae from the medium in which they grow.
  • the medium in which the algae grows is typically water based.
  • the algae concentrate may be able to be processed in a form containing a small amount of residual water.
  • the algae concentrate may be separated from the medium in a variety of ways, for example, by filtration.
  • biomass refers to virtually any plant-derived organic matter containing cellulose and/or hemicellulose as its primary carbohydrates.
  • Biomass can include, but is not limited to, agricultural residues such as corn stover, wheat straw, rice straw, sugar cane bagasse and the like.
  • Biomass further includes, but is not limited to, woody energy crops, wood wastes and residues such as trees, including fruit trees, such as fruit- bearing trees, (e.g., apple trees, orange trees, and the like), softwood forest thinnings, barky wastes, sawdust, paper and pulp industry waste streams, wood fiber, and the like.
  • perennial grass crops such as various prairie grasses, including prairie cord grass, switchgrass, Miscanthus, big bluestem, little bluestem, side oats grama, and the like, have potential to be produced large-scale as additional plant biomass sources.
  • potential biomass includes yard waste (e.g., grass clippings, leaves, tree clippings, brush, etc.) and vegetable processing waste.
  • Yard waste e.g., grass clippings, leaves, tree clippings, brush, etc.
  • Biomass is known to be the most prevalent form of carbohydrate available in nature and corn stover is currently the largest source of readily available biomass in the United States.
  • biosynthetie pathway also referred to as “metabolic pathway,” as used herein refers to is a set of anabolic or catabolic biochemical reactions for transmuting one chemical species into another.
  • Anabolic reactions involve constructing a larger molecule from smaller molecules, a process requiring energy.
  • Catabolic reactions involve breaking down of larger molecules, often releasing energy.
  • Gene products belong to the same
  • biosynthetie pathway if they, in parallel or in series, act on the same substrate, produce the same product, or act on or produce a metabolic intermediate (i.e., metabolite) between the same substrate and metabolite end product.
  • carbon bearing material refers any high carbon-content material that exists in a subterraneous formation.
  • Examples of carbon bearing material include, but not limited to, oil shale, coal, coal seam, waste coal, coal derivatives, lignite, peat, oil formations, tar sands, hydrocarbon-contaminated soil, petroleum sludge, drill cuttings, and the like and may even include those conditions or even surroundings in addition to oil shale, coal, coal seam, waste coal, coal derivatives, lignite, peat, bitumen, oil formations, tar sands, hydrocarbon-contaminated soil, petroleum sludge, drill cuttings, and the like.
  • carbon source means any source of carbon containing molecules that has at least one carbon atom.
  • low value carbon source includes biomass, industrial wastes (such as sewage sludge), carbon bearing materials, or derivatives thereof.
  • low value carbon sources include coal, lignite, tar sands, tars, peat, pitch, resins, lignin, latex rubber, waxes, agricultural wastes, bark, wood, any type of renewable biomass and other products from trees, algae cake, and other recalcitrant organic matter, and may also include lower-valued by-products from petroleum refining and chemical manufacturing, such as crude oil atmospheric bottoms, crude oil vacuum residues, residua from fluid catalytic cracking, petroleum coke, coker and other thermal cracking gas oils and bottoms, raffinates, asphalts, polynuclear aromatics, and the like, as well as synthetic polymer wastes such as polyethylene, polypropylene, polystyrene, polyesters, polyacrylics, and the like.
  • coal refers to any of the series of carbonaceous fuels ranging from lignite to anthracite.
  • the members of the series differ from each other in the relative amounts of moisture, volatile matter, and fixed carbon they contain.
  • Coal is comprised mostly of carbon, hydrogen and entrained water, predominantly in the form of large molecules having numerous double carbon bonds.
  • Low rank coal deposits are mostly comprised of coal and water.
  • Energy can be derived from the combustion of carbonaceous molecules, such as coal, or carbonaceous molecules derived from the solubilization of coal molecules. Of the coals, those containing the largest amounts of fixed carbon and the smallest amounts of moisture and volatile matter are the most useful.
  • endogenous to an organism as used herein refers to molecules, and in particular enzymes and polynucleotides, that originate or are found in the organism in nature. It is understood that expression of endogenous enzymes or polynucleotides may be modified in genetically engineered microorganisms.
  • enzyme refers to any substance that catalyzes or promotes one or more chemical or biochemical reactions, which usually includes enzymes totally or partially composed of a polypeptide.
  • enzyme activity refers to a function of the enzyme for catalyzing the chemical or biochemical reaction without destruction or modification at the end of the reaction.
  • the enzymes involve in metabolism in a microorganism have the enzymatic activity of converting one metabolite to another.
  • exogenous to a organism refers molecules, and in particular enzymes and polynucleotides, that are introduced into the organism.
  • the molecule can be introduced into an organism, for example, by integration of a nucleic acid into the host chromosome or as non-chromosomal genetic material such as a plasmid. Therefore, the term as it is used in reference to expression of an encoding nucleic acid refers to introduction of the encoding nucleic acid in an expressible form into the microorganism.
  • expression of a gene sequence refers to transcription of the gene and, as appropriate, translation of the resulting mRNA transcript to a protein.
  • expression of a protein results from transcription and translation of the open reading frame sequence.
  • the level of expression of a desired product in a host cell may be determined on the basis of either the amount of corresponding mRNA that is present in the cell, or the amount of the desired product (protein) encoded by the selected sequence.
  • mRNA transcribed from a selected sequence can be quantitated by qRT-PCR or by Northern hybridization (Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press (1989)).
  • Protein encoded by a selected sequence can be quantitated by various methods, e.g., by ELISA, by assaying for the biological activity of the protein, or by employing assays that are independent of such activity, such as western blotting or radioimmunoassay, using antibodies that recognize and bind the protein.
  • fatty acid refers to a compound having the formula RCO 2 H, wherein R is at least two carbons in length and generally R is between 4 and 32 carbons in length. Fatty acids may be saturated or unsaturated. R can be linear or branched. As used herein, the term “fatty acid derivative” means products made in part from
  • fatty acid derivative also includes products made in part from acyl-ACP or acyl-ACP derivatives.
  • exemplary fatty acid derivatives include, for example, fatty acids, acyl-CoAs, fatty aldehydes, short and long chain alcohols, hydrocarbons, fatty alcohols, ketones, and esters (e.g., waxes, fatty acid esters, or fatty esters).
  • the term "fermentation” or “fermentation process” is defined as a process in which a microorganism is cultivated in a culture medium containing a carbon source, wherein the microorganism converts the carbon source into at least one desirable product.
  • gene refers to a nucleotide sequence of a nucleic acid molecule (chromosome, plasmid, etc.) related to a genetic function.
  • a gene is a genetic unit of an organism including, for example, a polynucleotide sequence occupying a specific physical location ("genetic locus") in the genome of a microorganism.
  • a gene may code for an expression product such as a polypeptide or a polynucleotide.
  • a gene includes a coding sequence, such as a polypeptide coding sequence, and may also include non-coding sequences, such as a promoter sequence, a polyadenylated sequence, or a transcription control sequence (e.g., an enhancer sequence).
  • a promoter sequence such as a promoter sequence, a polyadenylated sequence, or a transcription control sequence (e.g., an enhancer sequence).
  • a transcription control sequence e.g., an enhancer sequence.
  • geneticically engineered or “genetically engineering” as used herein refers to altering the genetic material (DNA or RNA) existed in a natural microorganism, or introducing exogenous genetic material into a natural microorganism.
  • the gene when an exogenous gene encoding a protein is introduced into a natural microorganism, the gene can be codon-optimized for expression in the microorganism.
  • genetic engineered microorganism or “non-natural microorganism” as used herein refers to a microorganism that has at least one genetic alteration not normally found in a naturally occurring strain of the referenced microorganism species, including wild- type strains of the referenced species.
  • wild-type refers to the common genotype or phenotype, or genotypes or phenotypes, of a microorganism as it is found in the nature for the given microorganism species. Genetic alterations include, for example, a gene deletion or some other functional disruption of the genetic material.
  • Genetic alterations also include modifications that introduce expressible nucleic acids encoding metabolic polypeptides, other nucleic acid additions, nucleic acid deletions and/or other functional disruption of the genetic material in the microorganism.
  • modification include, for example, coding regions and functional fragments thereof, for heterologous, homologous or both heterologous and homologous polypeptides for the referenced species, (jeneticaily engineered microorganisms are often derived from wild-type microorganisms by making one or more genetic
  • genetically engineered microorganism refers not only to the particular genetically engineered microorganism but also to the progenies of such a genetically engineered microorganism. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent microorganism, but are still included within the scope of the term as used herein.
  • the term "genus” as used herein is defined as a taxonomic group of related species according to the Taxonomic Outline of Bacteria and Archaea (Garrity et al, 2007, TOB A Release 7.7, Michigan State University Board of Trustees).
  • homologous recombination refers to the process wherein two nucleic acid molecules associate with each other in regions of homology, leading to recombination between those nucleic acid molecules.
  • homologous recombination is determined according to the procedures summarized by Paques and Haber, Microbiology and Molecular Biology Reviews, vol. 63, pages 349-404, 1999.
  • Homologous recombination can cause reciprocal exchange of a region on the genome of the microorganism and a region on a vector.
  • the term is intended to encompass the reciprocal exchange of any nucleic acid segment, including the reciprocal exchange of a short segment of a gene as well as the exchange of an entire gene.
  • knock-in refers to a genetic engineering technique that replaces a genetic sequence (e.g. a target gene, a promoter) on the host microorganism genome with a different genetic sequence. Knock-in technique can modify an endogenous gene sequence to create a loss-of-function or gain-of-function mutation.
  • a genetic sequence e.g. a target gene, a promoter
  • knockout means a genetic engineering technique that renders deletion of a sequence segment from a microorganism genome. Knock-out often causes inactivation of the product of a target gene. Knock-out can be, for example, deletion of the entire gene, deletion of a regulatory sequence (e.g. promoter) required for transcription or translation, deletion of a portion of the gene with results in a truncated gene product or by any of various mutation strategies that inactivate the encoded gene product.
  • a particularly useful method of gene knock-out is complete gene deletion because it reduces or eliminates the occurrence of genetic reversions in the genetically engineered microorganisms of the invention.
  • microorganism As used herein, the terms "microorganism,” “microbial organism,” “microbe,” or “microbial” is intended to mean any organism that exists as a microscopic cell that is included within the domains of archaea, bacteria or eukarya, including bacteria, archaea and eubacteria of all species as well as eukaryotic microorganisms such as yeast and fungi.
  • the microorganisms may include at least the following types of microorganisms: Thermoto gales, Cytophaga group, Azospirillum group, Paracoccus subgroup, Sphingomonas group,
  • Nitrosomonas group Azoarcus group, Acidovorax subgroup, Oxalobacter group,
  • Rhodococcus group Thiobacillus group, Xanthomonas group, Oceanospirillum group, Pseudomonas and relatives, Marinobacter hydrocarbonoclaticus group, Pseudo alter omonas group, Vibrio subgroup, Aeromonas group, Desulfovibrio group, Desulfuromonas group, Desulfobulbus assemblage, Campylobacter group, Acidimicrobium group, Frankia subgroup, Arthrobacter and relatives, Nocardiodes subgroup, Thermoanaerobacter and relatives, Bacillus megaterium group, Carnobacterium group, Clostridium and relatives, and archaea such as Archaeo glob ales, Methanobacteriales, Methanomicrobacteria and relatives, Methanopy rales, and Methanococcales.
  • Some species of microorganism are selected from Escherichia (and particularly E. coli), Corynebacterium, Clostridium, Zymonomas, Salmonella, Rhodococcus, Pseudomonas, Bacillus, Lactobacillus, Enterococcus, Alcaligenes, Klesiella, Paenibacillus, Arthrobacter, Brevibacterium, Pichia, Candida, Hansenula, Synechococcus, Synechocystis, Anabaena, Ralstonia, Lactococcus, or Saccharomyces.
  • operably linked indicates that nucleic acid sequence elements are arranged to permit the general functions of the elements. Therefore, a certain promoter operably linked to a coding sequence (e.g., a sequence coding for a polypeptide of interest) may enable expression of the coding sequence in the presence of a control protein and a suitable enzyme. In some cases, such a promoter is not necessarily adjacent to the coding sequence as long as the promoter can direct the expression of the coding sequence.
  • operon refers to two or more genes which are transcribed as a single transcriptional unit from a common promoter.
  • the genes comprising the operon are contiguous genes. It is understood that transcription of an entire operon can be modified (i.e., increased, decreased, or eliminated) by modifying the common promoter.
  • any gene or combination of genes in an operon can be modified to alter the function or activity of the encoded polypeptide.
  • the modification can result in an increase in the activity of the encoded polypeptide.
  • the modification can impart new activities on the encoded polypeptide. Exemplary new activities include the use of alternative substrates and/or the ability to function in alternative environmental conditions.
  • overexpressed refers to a level of expression of a gene in a genetically engineered microorganism which is greater than the level of the gene in the wild type microorganism under the same condition. Overexpression can be achieved by removing repressor of gene expression, or adding activators of gene expression, adding multiple copies of the gene to the cell, or up-regulating the endogenous gene, and the like. Overexpression thus results in a greater than natural level of the gene production, or "overproduction" of the target gene product in the microorganism.
  • underexpressed or "underexpression” as used herein refers to a level of expression of a gene in a genetically engineered microorganism that is lower than the level of the gene in the wild type microorganism under the same condition. Underexpression leads to production of lower level of the gene product.
  • PHA polyhydroxyalkanoate
  • PHA PHA
  • n can range from 2 to several thousand
  • R is H or straight- chain or branched alkyl.
  • PHA further includes branched and unbranched PHA polymers, substituted and un- substituted PHA polymers.
  • PHA also refers to blends, co-polymers, and mixtures of PHAs as defined herein.
  • long chain PHA refers to PHA containing at least 15 carbon atoms, or at least 17 carbon atoms per monomer in the PHA.
  • intermediate chain PHA refers to PPIA containing from 6 to 14 carbon atoms in the monomers of the pHA.
  • PHA PHA containing less than 6 carbon atoms in the monomers of the pHA.
  • Common PHAs include, for example, polyglycolic acid (“PGA”), polylactic acid (“PLA”), polycaprolactone (“PCL”), polyhydroxypropanoate (“PHPp”), poly(3-hydroxybutyrate) (“P3HB”), poly(4- hydroxybutyrate) (“P4HB”), polyhydroxyvalerate (“PPIV”), polyhydroxypentanoate
  • PGA polyglycolic acid
  • PLA polylactic acid
  • PCL polycaprolactone
  • PHPp polyhydroxypropanoate
  • P3HB poly(3-hydroxybutyrate)
  • P4HB poly(4- hydroxybutyrate)
  • PPIV polyhydroxyvalerate
  • PHPt polyhydroxyhexanoate
  • PHp polyhydroxyheptanoate
  • PHO polyhydroxyoctanoate
  • co-polymers e.g., alternating, periodic, random, statistical, and block co-polymers
  • a "polypeptide” as used herein is a single linear chain of amino acids bonded together by peptide bonds.
  • a "polypeptide” also includes a polypeptide modified after translation.
  • the terms “protein” herein can encompass a single polypeptide chain or complexes of two or more polypeptide chains.
  • the term “protein” may also include a fragment, an analog, or a derivative of a natural protein.
  • pretreatment refers to any step, i.e., treatment intended to alter native carbon sources so they can be more efficiently and economically converted to reactive intermediate chemical compounds such as sugars, organic acids, etc., which can then be further processed to an end product such as 3-HP, ethanol, isobutanol, long chain alkanes, etc.
  • Pretreatment can reduce the degree of crystallinity of a polymeric substrate, reduce the interference of lignin with biomass conversion by hydrolyzing some of the structural carbohydrates, thus increasing their enzymatic digestibility and accelerating the degradation of biomass to useful products.
  • Pretreatment methods can utilize hydrothermal treatments including water, heat, steam or pressurized steam pre treatments, including, but not limited to, wet oxidization, hydro-thermolysis pretreatment and liquid hot water pretreatment, further including, for example, acid catalyzed steam explosion pretreatment.
  • Pretreatment can take place in or be deployed in various types of containers, reactors, pipes, flow through cells and the like.
  • promoter refers to a regulatory DNA sequence which is necessary to effect the expression of coding sequences to which they are operably linked.
  • promoter refers to a region located upstream or downstream from the start of transcription and which is involved in recognition and binding of RNA polymerase and other proteins to initiate transcription.
  • stable transformation or “stably transformed” as used herein means that a nucleic acid is introduced into a host cell of a microorganism and integrates into the genome of the cell.
  • the integrated nucleic acid is capable of being inherited by the progeny of the microorganism, more particularly, by the progeny of multiple successive generations.
  • Stable transformation as used herein can also refer to introducing a nucleic acid that is maintained extrachromasomally in a microorganism host cell, for example, as a plasmid in a microorganism, yeast artificial chromosome, bacterial phage, all of which can replicate autonomously in the microorganism host cell .
  • substrate refers to any substance or compound that is converted or meant to be converted into another compound by action of an enzyme.
  • the term includes not only a single compound, but also solutions, mixtures, and other materials, which contain at least one substrate, or derivative thereof.
  • Substrates include suitable carbon sources ordinarily used by microorganisms.
  • substrate encompasses not only compounds that provide a carbon source suitable for use as a starting material, such as any biomass or carbon bearing material, but also intermediate and end product metabolites used in a biosynthesis pathway of a genetically engineered microorganism as described herein.
  • thermochemical treating refers to a process in which the chemical nature of a low value carbon source comprising carbon-containing compounds is changed by the treatment conditions including application of elevated temperatures. More particularly, a thermochemical treatment can be selected from gasification, pyrolysis, reforming, and partial oxidation.
  • transformation and “transfection” as used herein refer to the process by which an exogenous nucleic acid molecule is introduced into a microorganism host cell.
  • a “transformed” or “transfected” cell is a host cell into which a nucleic acid molecule has been introduced by, for example, molecular biology techniques.
  • transformation encompasses all techniques by which a nucleic acid molecule might be introduced into such a host cell including, without limitation, transfection with a viral vector, conjugation, transformation with a plasmid vector, and introduction of naked DNA by electroporation, lipofection, and particle gun acceleration.
  • the nucleic acid may be inserted into a chromosome or replicated as
  • extrachromosomal material e.g. a plasmid in bacteria.
  • vector refers to a nucleic acid, which once is introduced into a host cell, can either be recombined with the genome of a host cell or autonomously replicate within the host cell as an episome.
  • a vector may be a linear nucleic acid, a plasmid, a cosmid, an RNA vector, or a viral vector.
  • yield is defined as the amount of product obtained per unit weight of carbon source and may be expressed as gram product per gram carbon source (g/g). Yield may also be expressed as a percentage of the theoretical yield. "Theoretical yield” is defined as the maximum amount of product that can be generated per a given amount of carbon source as dictated by the stoichiometry of the metabolic pathway used to make the product.
  • the present invention provides a method of producing a PHA using a genetically engineered microorganism from a low value carbon source such as biomass, carbon bearing materials and industrial wastes.
  • the method comprises an oxidizing step 100 wherein one or more components of the low value carbon source are oxidized with at least one oxidizing agent to produce a modified, partially solubilized low value carbon source; and a contacting step 200 wherein the modified, partially solubilized low value carbon source is contacted with a genetically engineered microorganism adapted for growth in the modified, partially solubilized low value carbon source, which is derived from a wild- type microorganism comprising a PHA biosynthesis pathway from acetyl-CoA.
  • the genetically engineered microorganism has one or more genetic modifications selected from at least one of the following genetic modifications: (a) an increased enzymatic activity of at least one enzyme in the PHA biosynthesis pathway relative to the activity of the same enzyme in the wild-type microorganism, (b) a decreased enzymatic activity of at least one enzyme in the fatty acid ⁇ -oxidation pathway relative to the activity of the same enzyme in the wild-type microorganism, and (c) a decreased enzymatic activity of PHA depolymerase relative to the activity of the PHA depolymerase in the wild-type microorganism.
  • the PHA biosynthesis pathway comprises two portions: a fatty acid biosynthesis portion and a PHA polymerization portion.
  • the fatty acid biosynthesis portion produces intermediates of fatty acid biosynthesis from acetyl-CoA, while the PHA polymerization portion converts these intermediates to monomers that are subsequently polymerized to form a PHA.
  • the fatty acid synthesis portion starts from acetyl-CoA and produces acyl-ACP (an acyl group covalently linked to the acyl carrier protein (ACP)).
  • acyl-ACP is hydrolyzed to form a fatty acid, catalyzed by a thioesterase.
  • step (2) the fatty acid is converted to acyl-CoA, catalyzed by acyl-CoA synthase.
  • Both acyl-ACP and acyl-CoA can be converted into monomers for PHA polymerization, thus producing PHA.
  • the produced PHA may be stored within the microorganism cells or secreted by the microorganism cells to a form an extracellular matrix.
  • the fatty acid biosynthesis portion of the PHA biosynthesis pathway uses acetyl- Co A as a starting material to produce intermediates such as acyl-ACP, 3-ketoacyl-ACP, 3- hydroyacyl-ACP and enoyl-ACP.
  • Fatty acid biosynthesis includes an elongation cycle where the length of acyl group in the acyl-ACP may be extended by two carbon atoms (from acetyl - Co A) per cycle as shown in steps c, d, e and f of Figure 2B.
  • step (a) acetyl-CoA is converted to malonyl-CoA, catalyzed by acetyl -CoA carboxylase.
  • the malonyl-CoA is in turn converted to malonyl-ACP, catalyzed by malonyl-CoA:ACP acyl transferase.
  • the malonyl-ACP is a feed material that provides two carbon atoms for elongating the acyl group in the acyl-ACP as it goes through the elongation cycle.
  • step (c) The elongation cycle starts at step (c) where an acyl-ACP is combined with malonyl-ACP to produce 3-ketoacyi- ACP, catalyzed by ⁇ -ketoacyl-ACP synthase, as shown in the following reaction scheme:
  • step (d) the 3 -ketoacyl-ACP is reduced by NADPI1 to form 3-hydroxyacyl- ACP, catalyzed by ⁇ -ketoacyl-ACP reductase.
  • the 3-hydroxyacyl-ACP is then dehydrated to form trans-2-enoyl-ACP (step e), which is catalyzed by ⁇ -hydroxyacyl-ACP dehydratase.
  • step (f) a NAD(P)H-dependent enoyl-ACP reductase reduces the trans-2-enoyl- ACP to form acyl-ACP.
  • the acyl-ACP produced in step (f) has two more carbon atoms than the acyl-ACP used as the substrate in step (c), thus it becomes an elongated acyl-ACP.
  • the elongated acyl-ACP may continue through the elongation cycle to make acyl-ACP with an even longer acyl group.
  • Step (f) is represented by the following reaction scheme:
  • the intermediates in the fatty acid biosynthesis can ail be converted to monomers for PHA polymerization.
  • the four intermediates of the elongation cycle: acyl-ACP, 3- ketoacyl-ACP, 3-hydroxyacyl-ACP and enoyl-ACP acyl-ACP can be converted to acyl-CoA, 3-ketoacyl-CoA, 3-hydroxyacyl-CoA and enoyl-CoA respectively as shown in step (g) in Figure 2C.
  • These conversions are catalyzed by a CoArACP acyltransferase, which transfers the exchange of the acyl group between CoA and ACP.
  • This enzyme has broad substrate specificity, which also catalyzes the transfer of a 3-ketoacyl group, a 3-hydroxyacyl group and a 2,3-enoyi group between CoA and ACP (Rehm et al., "A New Metabolic Link between Fatty Acid de NovoSynthesis and Polyhydroxyalkanoic Acid Synthesis: THE PHAG GENE FROM PSEUDOMONAS PUTiDAKT'2440 ENCODES A 3 -HYDROXY ACYL- ACYL CARRIER PROTEIN-COENZYME A TRANSFERASE," /. Biol Chem., vol. 273, pages 24044-24051, 1998).
  • acyl-ACP can be converted to acyl-CoA by a two- step process, in a reaction catalyzed by thioesterase and acyl-CoA synthase as shown in steps (1 ) and (2) of Figure 2 A, discussed above.
  • the monomer for PHA polymerization is 3-hydroxyacyl-CoA.
  • the other compounds, acyl-CoA, 3-ketoacyl-CoA, and enoyl-CoA can be converted to 3-hydroxyacyl- CoA by various enzymes.
  • acyl-CoA is converted to 3- ketoacyl-COA, in a reaction catalyzed by beta-ketothilase, as shown in the reaction scheme below:
  • step (i) 3-ketoacyl-CoA is converted to 3-hydroxyacyl-CoA, in a reaction catalyzed by 3-ketoacyl-CoA reductase.
  • step (] enoyl-CoA is converted to 3- hydroxyaeyl-CoA, in a reaction catalyzed by 2,3-enoyl-CoA hydrase.
  • the monomer, 3-hydroxyacyl-CoA is polymerized to form a PHA, in a reaction catalyzed by PHA polymerase, as shown in step (k) of Figure 2C.
  • the PHA may be a monopolymer, but is often a copolymer with the 3 - hvdroxyacyi groups in the monomers having different lengths or a branched or linear carbon- chain.
  • the enzyme PHA polymerase when obtained from different sources, may have differing preferences for monomers with different types of 3-hydroxyacyl group
  • the PHAs produced by the present invention may be long chain PHAs, medium chain PHAs or short chain PHAs, depending on the length of the 3-hydroxyacyl group in the monomers used to synthesize the PHAs and the characteristics of the microorganisms used to synthesize the PHAs.
  • the average molecular weight of the PHAs may be at least 400,000 Da, alternatively the average molecular weight may be at least 700,000 Da, alternatively the average molecular weight may be at least 1 ,000,000 Da, or alternatively the average molecular wei ght may be at least 2,000,000 Da, or alternatively the average molecular weight may be at least 4,000,000 Da, or alternatively the average molecular weight may be at least 6,000,000 Da.
  • the synthesized PHAs may be stored in the cells of the microorganism.
  • the PHAs within the ceils of the microorganism may comprise up to about 80% of the dry weight of the cells of the microorganism, or up to about 60% of the dry weight of the microorganism cells, or up to about 40% of the dry weight of the
  • the synthesized PHAs may be secreted out of the microorganism cells.
  • the secreted PHAs may form an extracellular matrix.
  • the secreted PHAs are significantly easier to recover from the medium while permitting continuous fermentation.
  • Type I secretory systems involve a single-step translocation system with a protein traveling across both the inner and outer membranes.
  • Components of this system include inner membrane proteins HlyB and HlyD, as well as the outer membrane protein TolC. These three proteins interact to form a channel that spans the cell membrane. Proteins as large as 4000 amino acids can be secreted through the type I secretory system. Unlike in the type II secretory system, the signal peptides for the type I secretory system remain attached to the protein after being exported out of the cells of the microorganism.
  • the type II secretory system involves a two-step process.
  • the protein to be secreted must first be exported into the periplasm by a translocase. After entering the periplasm, translocation of the protein into the extracellular medium is carried out by a multi- component membrane transportation system, which employs a 12-16 core protein complex present in many gram-negative strains, including E. coli K-12.
  • the type II secretory system may have its efficiency improved through the overexpression of type II secretion machinery proteins, like TorD and SecYEG
  • the permeability of the microorganism cell membrane may be improved mechanically, such as by application of ultrasound, or through chemical treatment by Triton X-100 or 2% glycine.
  • the genetically engineered microorganism may coexpress genes such as kil, out, and tolAIII, that cause cellular lysis and subsequent release of PHAs from the microorganism cells.
  • acetyl-CoA is an important product of metabolism of proteins and carbohydrates.
  • a common source of acetyl- CoA is the tricarboxylic acid (“TCA”) cycle, also known as the Krebs cycle, in which pyruvate can be converted into carbon dioxide and hydrogen as follows:
  • the TCA cycle is an essential biochemical activity for microorganisms.
  • the genetically engineered microorganism can utilize one or more nutrients in a growth medium to naturally generate acetyl-CoA using the TCA cycle.
  • the present invention avoids using an expensive sugar based feedstock, such as glucose, sucrose or glycerol for this purpose, as is the case in many prior art processes for the production of PHAs.
  • the present invention involves pretreatment of a low value carbon source by oxidation of one or more components of the low value carbon source to provide nutrients for the genetically engineered microorganism as shown in Figure 1.
  • Oxidizing 100 components of the low value carbon source to produce a modified, partially solubilized low value carbon source typically involves breaking down large, insoluble molecules to produce smaller, soluble molecules that can be used as nutrients by microorganisms. Metabolism of these smaller molecules by the microorganisms, through TC A as well as other routes, leads to generation of acetyl-CoA.
  • Examples of such small molecules that may be present in the modified, partially solubilized low value carbon source after oxidation of one or more components of the low value carbon source include fatty acids, hydrocarbons, oxides, aldehydes, alcohols, aliphatic and aromatic compounds such as polycyclic aromatics and aromatic carboxylic acids.
  • an indirect coal liquefaction (ICL) process consists of a gasification step at temperatures greater than about 700 °C in the presence of oxygen or air to make syngas (a mix of CO & H 2 ) followed by at least one catalytic step which converts syngas to liquid hydrocarbons.
  • a direct coal liquefaction process converts one or more components of the low value carbon source directly into one or more liquids, without the intermediate step of gasification, by breaking down high molecular weight molecules with application of solvents and catalysts in a high pressure and high temperature environment using hydrogen. Since liquid hydrocarbons generally have a higher hydrogen to carbon molar ratio than a low value carbon source, either hydrogenation or carbon-rejection processes may be employed in both ICL and DCL technologies.
  • the gasification process consists of feeding a low value carbon source into a heated chamber (the "gasifier") along with a controlled and/or limited amount of oxygen and optionally steam.
  • Gasification processes produce a raw gas composition comprising CO, H 2 , H 2 S, and NH 3 .
  • the primary gasification products of interest are H 2 and CO. See Demirbas, "Recovery of Energy and Chemicals from
  • the oxidizing step 100 uses mild conditions for efficient oxidative depolymerization large carbonaceous molecules in the low value carbon source.
  • the oxidizing step 100 is performed in the presence of at least one oxidizing agent, and optionally at least one solubilizing agent.
  • the oxidizing step 100 may comprise heating the low value carbon source to a temperature below 300 °C and at a pressure below 1230 psig.
  • the oxidizing step 100 may comprise using a combination of steam and air in a solid- vapor (non-aqueous) environment for treatment of the low value carbon source.
  • the conditions of the oxidizing step 100 in terms of the ratio of 0 2 /low value carbon source, the ratio of steam/low value carbon source, vapor and solids residence times, and temperature can be varied to alter the final product distribution, gain selectivity and to yield specific chemical products.
  • This oxidizing step 100 does not require pure oxygen, nor is pure oxygen desirable.
  • the mild conditions for the oxidizing step 100 allow the production of various product distributions based on varying operating conditions.
  • the oxidizing step 100 can simultaneously oxidize, depolymerize, reform and/or solubilize high molecular weight large molecules in the low value carbon source to smaller low molecular weight hydrocarbons, oxo-chemicals and other chemicals. This conversion of large molecules to small molecules provides nutrients suitable for use by the genetically engineered microorganisms.
  • oxo-chemicals are organic compounds that comprise at least one oxygen atom.
  • a mixture of aliphatic and aromatic carboxylic acids can be produced.
  • a mixture of these oxo-chemicals and waxy hydrocarbons containing paraffins and olefins having chain lengths ranging from C 10 to C44 can be produced.
  • the small molecules in the modified, partially solubilized low value carbon source resulting from the oxidizing step 100 are often water soluble and may be used by microorganisms as nutrients (biodegradable), thus producing acetyl-CoA for the PHA biosynthesis process.
  • the oxidizing step 100 may comprise raising the temperature of the low value carbon source to a desired temperature and/or keeping the low value carbon source at a pressure at or above the steam saturation pressure.
  • the product after the oxidizing step 100 may be used as a feedstock for the genetically engineered microorganisms.
  • the product may optionally be subjected to chemical and/or physical separation before being used as a feedstock.
  • Chemical and/or physical separation may be employed for separation of various components in the product. For example, some high- valued minerals and chemicals may be retrieved from the product using conventional chemical and/or physical separation methods. Such chemicals include, for example, oxo-chemicals.
  • Applicable chemical and physical separation technologies include any of those known to one skilled in the art, including fractional distillation, liquid/liquid extraction, adsorption, ion exchange, membrane filtering, and hybrid systems.
  • the low value carbon source may be too impermeable, e.g. due to limited porosity, to be efficiently treated by the oxidizing step 100.
  • the low value carbon source may be preprocessed (e.g. comminuted) to increase its permeability or available surface area, thus increasing the susceptibility of the large carbonaceous molecules in the low value carbon source to the oxidizing agent of the oxidizing step 100. Any method known to a skilled person in the art that is suitable for reducing the particle size and/or increasing surface area of the low value carbon sources may be used.
  • preprocessing may be used to break down coal, oil shale, lignite, coal derivatives and similar structures to release more organic matter, or to make them more susceptible to degradation into smaller organic compounds.
  • coal and water at about a 1 :2 weight ratio are loaded into a mill with steel media. The duration of milling may be in the range from about 60 to about 90 minutes. After milling, the coal slurry may be used as an input to the oxidizing step 100.
  • the solubilizing agent used in the oxidizing step 100 may be selected from mineral acids or mineral bases.
  • Preferred bases include Group I (alkali metals) and Group II (alkaline earth) oxides, hydroxides, carbonates, borates, or halogenates.
  • sodium, potassium, calcium, and magnesium compounds are preferred.
  • the solubilizing agents include sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate. Naturally occurring minerals of some of these materials are also appropriate for use in this process.
  • the low value carbon source, oxidizing agent, and optionally a solubilizing agent, and a solvent such as water are mixed and fed to the oxidizing step 100.
  • Mineral bases generally comprise no more than about 15 wt% of the mixture provided to the oxidizing step 100, and preferably comprise below 10 about wt% and most preferably at or below about 6 wt% of the mixture provided to the oxidizing step 100.
  • the mineral base comprises at least about 1 wt% or at least about 3 wt% or at least about 5 wt% of the mixture provided to the oxidizing step 100.
  • the solubilizing agent may be a mineral acid, such as phosphoric acid, nitric acid, boric acid, hydrochloric acid, and sulfuric acid.
  • the low value carbon source may be mixed with the solubilizing agent provided in an aqueous solution to provide the mixture fed to the oxidizing step 100.
  • the low value carbon source may be combined with steam or water vapor containing solubilizing agent. In these embodiments, the vapor or steam may be blown onto the low value carbon source.
  • the low value carbon source is dispersed in an aqueous solution of the solubilizing agent to make the mixture.
  • the amount of low value carbon source dispersed in the aqueous solution is limited by the average size of the monomer molecules that may be oxidatively reformed from the low value carbon source and their solubility in water based on their functional groups, their degree of ionization in water, and physical and chemical attributes of the aqueous system, such as temperature, pH, pressure, activity coefficient, and other considerations.
  • Solution viscosity also increases with higher low value carbon source loading in the slurry-like mixture and is a limitation that may reduce mass transfer and mixing between the solid and liquid.
  • the low value carbon source content in the mixture may be less than about 40% by weight.
  • the low value carbon source content of the mixture may be at or below about 30% by weight, or at or below about 25% by weight.
  • the low value carbon source may be heated in a reaction vessel in the presence of at least one oxidizing agent.
  • the oxidizing step 100 may comprise raising the temperature of the low value carbon source to a desired temperature by any suitable means and/or subjecting the mixture to a pressure at or above the steam saturation pressure. Multiple reactions may occur during the oxidizing step 100, including oxidization, depolymerization, reforming and solubilization. In a reforming process, the molecular structure of high molecular weight carbonaceous molecules such as hydrocarbons is rearranged to produce smaller, lower molecular weight molecules that may be used effectively as nutrients for the microorganisms.
  • the oxidizing agent may be selected from air, oxygen enriched air, ozone, sulfuric acid, permanganates, carbon dioxide, nitrous oxide, nitric acid, chromates, perchlorates, persulfates, superoxides, chlorates, peroxides, hypochlorites, Fenton's reagent and nitrates in which the cations may comprise metal cations, hydrogen ions and/or ammonium ions.
  • Oxidizing agents may be ranked by their strength. See Holleman et al. "Inorganic Chemistry," Academic Press, 2001, page 208. A skilled person will appreciate that, to prevent over-oxidation of the low value carbon source, the conditions in the oxidizing step may be adjusted according to the strength of the oxidizing agent used. For example, when a strong oxidizing agent is used, one or more of temperature, pressure, and duration of the oxidizing step 100 may be reduced to prevent over-oxidation and/or ensure that the desired degree of conversion is not exceeded. On the other hand, when a weak oxidizing agent is used, one or more of temperature, pressure, and duration of the oxidizing step 100 may be increased to ensure that the desired degree of oxidation and/or conversion is achieved. When the oxidizing agent is gaseous, the pressure in the reaction vessel for the oxidizing step 100 is important for ensuring the desired degree of oxidation and/or conversion.
  • oxygen is used as the oxidizing agent.
  • oxygen can be delivered to the reaction vessel as air.
  • oxygen-enriched air can be used depending on the susceptibility of the low value carbon source to oxidation. Suitable enrichment percentages can be from an oxygen concentration slightly above that of atmospheric air to substantially pure oxygen.
  • a mineral acid may be used to provide more acidic conditions for carrying out the oxidation reaction.
  • suitable mineral acids include phosphoric acid, nitric acid, boric acid, hydrochloric acid, and sulfuric acid.
  • At least one catalyst may optionally be added to the mixture fed to the oxidizing step 100.
  • the catalyst may catalyze the oxidation reaction by, for example, causing or enhancing formation of peroxides and superoxides, which may enhance the rate of oxygen insertion into the large carbonaceous molecules, leading to a more complete breakdown of the large carbonaceous molecules in the low value carbon source relative to oxidation of the same low value carbon source in the absence of such catalysts.
  • the catalyst may be selected from water insoluble metals, transition metals, and precious metals. Examples of these metals include nickel, cobalt, platinum, palladium, rhenium, copper, vanadium and ruthenium.
  • the catalyst may be unsupported or may be supported on an inert or active matrix material such as clay, alumina, silica, silica alumina, zeolites, activated carbon, diatomaceous earth, titania, zirconia, molybdena, ceramics, and the like.
  • Such catalysts can enhance rates of oxygen insertion and reforming of high molecular weight carbonaceous molecules as well as being able to enhance the degree of relative oxidation.
  • the catalysts include metal oxides, mixed metal oxides, hydroxides, and carbonates, of ceria, lanthanum, mixed rare earths, brucite, hydrotalcite, iron, clays, copper, tin, and vanadium.
  • the reaction vessel in which the oxidizing step 100 is conducted is not limited to any particular reactor design, but may be any sealable reaction vessel that can tolerate the temperature and pressure required for the present invention.
  • the mixture is fed to a reaction vessel, which has been pre-heated to the desired temperature. Then, air or oxygen enriched air is slowly added to the reaction vessel until the desired pressure is reached. The temperature and pressure in the reaction vessel may be monitored to ensure a desired level of oxidization of the low value carbon sources during the filling of air or oxygen enriched air, as well as during the oxidizing step 100.
  • the mixture in the reaction vessel including the low value carbon source, an oxidizing agent, and optionally a solubilizing agent, a catalyst, and solvent such as water, is heated to a temperature below about 300 °C (572 °F), or below about 220 °C (428 °F), or below about 150 °C (302 °F).
  • a positive pressure in the reaction vessel is maintained at saturated steam pressure or slightly higher, for example below about 1230 psig, or below about 322 psig, or below about 54 psig respectively.
  • a minimum temperature is approximately 130 °C and a respective minimum pressure is approximately 24 psig.
  • the mixture in the reaction vessel has at least two phases: a liquid phase (water/solubilizing agent/oxidizing agent) and a solid phase (low value carbon source).
  • a liquid phase water/solubilizing agent/oxidizing agent
  • a solid phase low value carbon source
  • the mixture may be subjected to mechanical agitation.
  • the reaction vessel may include structural features to facilitate interactions among the phases. For example, an unstirred reaction vessel with gas dispersion features, a reaction vessel with mechanical agitation devices as well as reaction vessels with gas entrainment devices or combinations thereof may be used.
  • Exemplary reaction vessels include a co-current flow tubular reactor with gas dispersion, a counter-current flow tubular reactor with gas dispersion, and a flowing tubular reactor with static mixers.
  • the duration of the oxidizing step 100 may be determined, for example, by the oxidative stress induced in the mixture and the desired product. As a general rule, a higher oxidative stress requires a shorter duration oxidizing step 100. In addition, if the desired products are generated by more complete oxidization of the low value carbon source, e.g. via a series of sequential reaction steps, a longer duration for the oxidizing step 100 may be required.
  • the duration of the oxidizing step 100 can vary from a few seconds to several hours, depending on the degree of conversion required, the reduction in molecular weight desired, the reactivity of the low value carbon source, process economics, the amount of carbon dioxide, carbon monoxide, and hydrogen generated, and other constraints.
  • the low value carbon source is coal and the reaction time is in the range from about 0.02 to about 4 hours, or about 0.2 to about 4 hours, or about 0.5 to about 4 hours, or about 1 to about 3 hours, or about 1.5 to about 2.5 hours.
  • the reaction conditions including temperature, pressure and reaction time may also depend on molecular and elemental characteristics of the particular low value carbon source.
  • the characteristics of the low value carbon source which may be taken into consideration are the degree of aromaticity, the hydrogen to carbon ratio, oxygen to carbon ratio, nitrogen to carbon ratio, sulfur to carbon ratio, mineral or ash content, and other factors.
  • a blend of low value carbon sources of different characteristics may enhance the efficiency of the pretreatment method by adjusting one or more of these characteristics.
  • blending a highly aromatic, more difficult to react, carbon source, such as coal, with a more acyclic carbonaceous material, such as agricultural waste or synthetic polymer waste may result in an oxidized product stream that is more biodegradable and will support greater microbial population densities, as well as increasing the rate and depth of conversion of the less reactive large molecules in these low value carbon sources.
  • the extent of conversion can be controlled by using different reaction conditions to yield different types and amounts of, for example, partial oxidation products.
  • the reaction conditions may also be adjusted to convert substantially all of the solids of the low value carbon source, other than inorganics concentrated in an ash stream, without significant loss of carbonaceous compounds to C0 2 production.
  • a portion of the gaseous phase in the reaction vessel may optionally be continuously or periodically withdrawn and replaced.
  • Carbon dioxide formed during the reaction has several roles, including acting as an excess base neutralizer and forming a carbonate buffering system in the water.
  • a carbonate buffered system is a desirable feature for subsequent conversion of the treatment product by the genetically engineered microorganisms.
  • microorganisms prefer a system at or around pH 7.
  • the C0 2 produced in the pretreatment reacts with excess base and reduces or eliminates the need to adjust the pH of the product stream resulting from depolymerization by the addition of acid, thereby lowering costs. Any excess carbon dioxide formed during the reaction is preferably removed from the reaction vessel.
  • gas is withdrawn from the reaction vessel, the carbon dioxide content of the withdrawn gas is reduced and the gas with the reduced carbon dioxide content is optionally resupplied back to the reaction vessel, with or without being enriched with oxygen.
  • This embodiment may also be used for maintaining a desired partial pressure of oxygen in the reaction vessel during the pretreatment method.
  • samples of the gas phase in the reaction vessel may be taken periodically in order to monitor the progress of pretreatment.
  • the gas sample may be analyzed by, for example, a gas chromatograph to identify the content of one or more components to provide an indication of the progress of the pretreatment.
  • the oxidizing step 100 may be terminated. Carbon dioxide may be withdrawn or oxygen may be periodically or continuously added to the reaction vessel to maintain the desired level of oxidant.
  • the oxidizing step 100 can be conducted in batch mode, semi-batch mode, or continuously.
  • at least a portion of the carbonaceous material in the low value carbon source may be oxidized by the oxidizing step 100.
  • the carbonaceous material may be oxidized to organic acids, such as oxalic acid, mellitic acid, benzoic acid and acetic acid.
  • high molecular weight carbonaceous molecules may be depolymerized/reformed to lower molecular weight carbonaceous molecules.
  • mineral bases are used to increase the pH of the mixture to a caustic alkaline pH of greater than about 7, greater than about 9 or greater than about 10.
  • the formed organic acids will be present in salt form due to the presence of the mineral base.
  • Such salts may be recovered from the products of the oxidizing step 100 by filtering off the solid material and extracting the oxalic acid therefrom with dilute hydrochloric or sulfuric acid.
  • the salts of mellitic acid and like acids can be isolated from the filtrate by acidifying, warming, and filtering the warm liquid, while acetic acid can be recovered from the residual liquid by, for example, steam distillation.
  • the products of the oxidizing step 100 may include minerals, chemicals and low- molecular weight carbonaceous compounds. After optionally extracting the minerals and high- value chemicals, the remainder of the product may be used as a feedstock for the genetically engineered microorganisms. This portion of the product includes solubilized carbonaceous compounds, and possibly some solid high molecular weight carbonaceous molecules.
  • the product may be used for fermentation by the genetically engineered microorganisms to produce PHAs, where the carbonaceous molecules, especially the low- molecular weight carbonaceous molecules produced by oxidation and depolymerization, are used as feedstock for the genetically engineered microorganisms to produce acetyl-CoA and eventually PHAs.
  • the conditions of the oxidizing step 100 are selected on the basis of producing modified, partially solubilized low value carbon source that may include larger quantities of biodegradable materials and/or may exhibit an enhanced rate of biodegradation or an enhanced tendency to biodegrade.
  • the oxidizing step 100 is part of pretreatment process schematically represented in Figure 7.
  • the low value carbon source carbonaceous raw material
  • the reagents include at least one oxidizing agent, and optionally at least one solubilizing agent or a catalyst.
  • the oxidizing step 100 comprises heating the mixture to a suitable temperature and at a suitable pressure.
  • two or more sequential heating stages may be conducted under different conditions using the product of a prior heating stage as the feed to the following heating stage. The reaction conditions at each heating stage are adjusted to favor different reactions, rates of reaction, degrees of conversion, etc.
  • the oxidizing step 100 is used to treat black liquor in a reactor, which is the liquor resulting from the cooking of pulpwood in an alkaline solution in a soda or sulfate, such as a Kraft, paper making process by removing lignin, hemicelluloses, tall oil, and other extractives from the wood to free the cellulose fibers.
  • a reactor which is the liquor resulting from the cooking of pulpwood in an alkaline solution in a soda or sulfate, such as a Kraft, paper making process by removing lignin, hemicelluloses, tall oil, and other extractives from the wood to free the cellulose fibers.
  • a soda or sulfate such as a Kraft, paper making process by removing lignin, hemicelluloses, tall oil, and other extractives from the wood to free the cellulose fibers.
  • the black liquor and an oxidizing agent are fed into a reactor, along with optional additional reagents, and heated under pressure.
  • the reaction within the reactor creates a reaction mixture, which can then be treated and/or separated by chemical, physical or microbial means, to yield organic compounds.
  • These organic compounds include organic compounds comprising from about 2 to about 20 carbon atoms that are suitable as nutrients for the genetically engineered microorganisms.
  • the black liquor is separated, or fractionated, into various components prior to the oxidizing step 100 in a reactor.
  • One possible embodiment is exemplified in Figure 9.
  • the black liquor is separated by a chemical, a physical or a microbial process, selected organic polymers are recovered as an economically valuable commodity, and the balance of the black liquor is a black liquor component reactor feedstock.
  • This black liquor component reactor feedstock is fed, along with an oxidizing agent and optional additional reagents, into the reactor, and is heated under pressure.
  • the reaction within the reactor creates a reaction mixture, which can then be treated and/or separated by chemical, physical or microbial means, to yield organic compounds.
  • These organic compounds include organic compounds comprising from about 2 to about 20 carbon atoms that are suitable as nutrients for the genetically engineered microorganisms.
  • the black liquor is separated, or fractionated, into various components prior to the oxidizing step 100 in a reactor, as exemplified in Figure 10.
  • the black liquor from the pulp line (“raw black liquor”) is separated by a chemical, physical or microbial process, to obtain the black liquor component reactor feedstock, and a residue.
  • the black liquor component reactor feedstock is fed, along with an oxidizing agent and optional additional reagents, into the reactor, and is heated under pressure.
  • the reaction within the reactor creates a reaction mixture, which can then be treated and/or separated by chemical, physical or microbial means, to yield organic compounds.
  • These organic compounds include organic compounds comprising from about 2 to about 20 carbon atoms that are suitable as nutrients for the genetically engineered microorganisms.
  • the residue from the separation of raw black liquor is further dewatered, and burned in a recovery boiler to produce energy.
  • the black liquor is separated, or
  • the black liquor is separated by a chemical, physical or microbial process, to obtain the selected organic polymers, the black liquor component reactor feedstock, and the residue.
  • the black liquor component reactor feedstock is fed, along with an oxidizing agent and optional additional reagents, into the reactor, and is heated under pressure.
  • the reaction within the reactor creates a reaction mixture, which can then be treated and/or separated by chemical, physical or microbial means, to yield organic compounds.
  • These organic compounds include organic compounds comprising from about 2 to about 20 carbon atoms that are suitable as nutrients for the genetically engineered microorganisms.
  • the residue from the separation of raw black liquor is further dewatered, and burned in a recovery boiler to produce energy.
  • Such separation of components from the raw black liquor may decrease the concentration of some components, and thus increase the relative concentration of other components.
  • removal of soaps and/or tall oils will increase the concentration of the lignin.
  • the concentration of lignin is increased from about 35 to about 45 wt with respect to the total organics to at least about 55 wt .
  • the concentration is increased to at least about 65 wt .
  • the concentration is increased to at least about 75 wt .
  • the black liquor may be heated in a reaction vessel in the presence of at least one oxidizing agent.
  • the oxidizing step 100 may comprise raising the temperature of the mixture to a desired temperature by any suitable means and/or subjecting the mixture to a pressure at or above the steam saturation pressure. Multiple reactions may occur during the pretreatment step, including oxidization, depolymerization, reforming and solubilization. In a reforming process, the molecular structure of a hydrocarbon is rearranged. Without being bound by theory, it is believe that the pretreatment step of the present invention may oxidatively crack wood polymers to provide small organic compounds.
  • the black liquor stream as generated by the pulping process is typically very caustic. Such a caustic environment is typically sufficient to allow oxidative breaking down of wood polymers to generate one or more small organic compounds comprising from about 2 to about 20 carbon atoms that are suitable as nutrients for the genetically engineered microorganisms. However, in some cases, the black liquor stream may have a lower pH that does not readily allow for acceptable oxidative breaking down of wood polymers. Under such circumstances, a mineral base may be added to the black liquor. Exemplary bases that may be used include Group I (alkali metal) and Group II (alkaline earth) oxides, hydroxides, carbonates, borates, and halogenates. In particular, sodium, potassium, calcium, and magnesium compounds are preferred. Examples of suitable bases include sodium hydroxide and potassium hydroxide.
  • the oxidizing 100 of black liquor occurs at a temperature sufficient to oxidize components of the black liquor to generate one or more organic compounds comprising from about 2 to about 20 carbon atoms that are suitable as nutrients for the genetically engineered microorganisms. This temperature has been found to be up to about 300 °C, or between about 150 °C and about 250 °C.
  • the treatment of the black liquor occurs at a temperature between about 150 °C and about 220 °C.
  • the pretreatment of the black liquor occurs at a temperature below about 150 °C.
  • the oxidizing of black liquor occurs at a pressure sufficient to oxidize components of the black liquor to generate one or more organic compounds comprising from about 2 to about 20 carbon atoms that are suitable as nutrients for the genetically engineered microorganisms.
  • This pressure has been found to be below about 1230 psig or about 322 psig. In another embodiment, this pressure has been found to be below about 54 psig. In certain embodiments, this pressure ranges from atmospheric pressure to about 1230 psig, or about 322 psig or about 54 psig.
  • the oxidizing conditions including temperature, pressure and reaction time may also depend on the molecular and elemental characteristics of the particular black liquor feedstock. Different species of wood may result in differing compositions of the black liquor.
  • the characteristics of the black liquor used in the pulping process that may affect pretreatment include the degree of aromaticity, the hydrogen to carbon ratio, the oxygen to carbon ratio, the nitrogen to carbon ratio, the sulfur to carbon ratio, and the mineral or ash content, as well as other factors.
  • the product of the oxidizing step 100 is a modified, partially solubilized low value carbon source that may be cooled to a temperature suitable for the growth of wild-type microorganisms and genetically engineered microorganisms.
  • a suitable growth temperature for yeast is about 28 °C and many bacteria grow at a temperature of about 37 °C.
  • a suitable growth temperature for the wild-type microorganisms and the genetically engineered microorganisms may be established by a person skilled in the art.
  • the product of oxidizing step 100 may be subjected to one or more additional optional steps to prepare the modified, partially solubilized low value carbon source to be used by the genetically engineered microorganism to produce PHAs.
  • One optional step involves adding one or more microorganisms to the modified, partially solubilized low value carbon source to convert one or more components in the modified, partially solubilized low value carbon source to intermediate products that can be more efficiently metabolized by the genetically engineered microorganisms to produce acetyl-CoA and/or PHAs.
  • Another optional step involves adding at least one nutrient to the modified, partially solubilized low value carbon source in order to enhance growth of the microorganism involved in the biosynthesis of PHAs.
  • the nutrient may be selected from substances upon which the genetically engineered microorganisms are dependent or substances that can be converted in situ to another product upon which the genetically engineered microorganisms are dependent.
  • Suitable nutrients may include ammonium, ascorbic acid, biotin, calcium, calcium pantothenate, chlorine, cobalt, copper, folic acid, iron, K 2 HP0 4 , KNO 3 , magnesium, manganese, molybdenum, Na 2 HP0 4 , NaN0 3 , NH 4 C1, NH 4 NO 3 , nickel, nicotinic acid, p-aminobenzoic acid, biotin, lipoic acid, mercaptoethanesulfonic acid, nicotinic acid, phosphorus, potassium, pyridoxine HC1, riboflavin, selenium, sodium, thiamine, thioctic acid, tungsten, vitamin B6, vitamin B2, vitamin B l, vitamin B12, vitamin K, yeast extract, zinc and mixtures of one or more of these nutrients.
  • Yet another optional step involves adding at least one enzyme to the modified, partially solubilized low value carbon source to increase the yield of, and/or selectivity for, PHA biosynthesis, for example, to enhance utilization of the modified, partially solubilized low value carbon source by the genetically engineered microorganism.
  • an enzyme may be used to assist in converting one or more components of the low value carbon source to intermediate(s) that may be more effectively used by the genetically engineered microorganism.
  • enzymes may be used to further to enhance the yield and/or selectivity of the biosynthesis of PHAs.
  • Enzymes suitable for the present invention may include Acetyl xylan esterase, Alcohol oxidases, Allophanate hydrolase, Alpha amylase, Alpha mannosidase, Alpha-L- arabinofuranosidase, Alpha-L-rhamnosidases, Ammoniamonooxygenase, Amylases, Amylo- alpha-l,6-lucosidase, Arylesterase, Bacterial alpha-L-rhamnosidase, Bacterial pullanases, Beta-galactosidase, Beta-glucosidase, Carboxylases, Carboxylesterase, Carboxymuconolactone decarboxylase, Catalases, Catechol dioxygenase, Cellulases, Chitobiase/beta-hexo-aminidase, CO dehydrogenase, CoA ligase, Dexarboxylases,
  • Dienelactone hydrolase Dioxygenases, Dismutases, Dopa 4,5-dioxygenase, Esterases, Family 4 glycosylhydrolases, Glucanaeses, Glucodextranases, Glucosidases, Glutathione S- transferase, Glycosyl hydrolases, Hyaluronidases, Hydratases/decarboxylases, Hydrogenases, Hydrolases, Isoamylases, Laccases, Levansucrases/Invertases, Mandelate racemases, Mannosyl oligosaccharide glucosidases, Melibiases, Methanomicrobialesopterin S- me thy transferases, Methenyl tetrahydro-methanopterin cyclohydrolases, Methyl-coenzyme M reductase, Methylmuconolactone methyl-isomerase, Monooxygenases
  • Oxygenases Pectinesterases, Periplasmic pectate lyase, Peroxidases, Phenol hydroxylase, Phenol oxidases, Phenolic acid decarboxylase, Phytanoyl-CoA dioxygenase, Polysaccharide deacetylase, Pullanases, Reductases, Tetrahydromethan- opterin S-methyltransferase, Thermotoga glucanotransferase and Tryptophan 2,3-dioxygenase.
  • the modified, partially solubilized low value carbon source comprises nutrients that may be used by the genetically engineered microorganism to produce acetyl CoA, which may then be used to produce PIIAs.
  • Oxygenated organic compounds that may be present in the modified, partially solubilized low value carbon source include oxygenated hydrocarbons, carboxylic acids, and oxygenated compounds comprising additional heteroatoms.
  • Oxygenated organic compounds are organic compounds that comprise at least one oxygen atom.
  • Heteroatom means any atom besides hydrogen or carbon. Examples of heteroatoms other than oxygen include nitrogen, phosphorus, sulfur, fluorine, and chlorine.
  • oxygenated hydrocarbons examples include alcohols, aldehydes, carboxylic acids, salts of carboxylic acids, esters, ethers, anhydrides, and like.
  • Oxygenated compounds may be monofunctional, difunctional, trifunctional, or polyfunctional. Included in the definition of oxygenated hydrocarbons are also compounds with more than one functional group, such as polyols, dicarboxylic acids, triacids, polyesters, polyethers, aldehydic acids, and the like. Also included in the definition of oxygenated hydrocarbons are compounds in which there is more than one type of functional group.
  • carboxylic acids include compounds of the formula R-COOH, wherein R is an alkyl group.
  • Particular examples include formic acid, methanoic acid, acetic acid, ethanoic acid, propionic acid, butyric acid, butanoic acid, valeric acid, pentanoic acid, caproic acid, hexanoic acid, enanthic acid, heptanoic acid, caprylic acid, octanoic acid, pelargonic acid, nonanoic acid, capric acid, decanoic acid, undecylic acid, undecanoic acid, lauric acid, dodecanoic acid, tridecylic acid, tridecanoic acid, myristic acid, tetradecanoic acid, pentadecanoic acid, palmitic acid, hexadecanoic acid, margaric acid, heptadecanoic acid, stearic acid, octadecanoic acid,
  • Dicarboxylic acids of the present invention are organic compounds that contain two carboxylic acid groups. Such dicarboxylic acids may comprise additional heteroatoms, such as oxygen, nitrogen, or sulfur. Dicarboxylic acids may be aliphatic or aromatic. Aside from the two -COOH groups, dicarboxylic acids may be saturated or unsaturated.
  • the dicarboxylic acids may be represented by the formula HOOC-R-COOH, wherein R is a difunctional organic group, such as alkylene, alkenylene, alkynylene, arylene, and any of the preceding modified by a one or more heteroatoms.
  • dicarboxylic acids include compounds such as alkylene dicarboxylic acids, having the general formula HOOC-(CH 2 ) consult-COOH wherein n is 0 to about 12; mono- unsaturated forms thereof; di-unsaturated forms thereof; tri-unsaturated forms thereof; and polyunsaturated forms thereof.
  • dicarboxylic acids also include oxalic acid, ethanedioic acid, malonic acid, propanedioic acid, succinic acid, butanedioic acid, glutaric acid, pentanedioic acid, adipic acid, hexanedioic acid, pimelic acid, heptanedioic acid, suberic acid, octanedioic acid, azelaic acid, nonanedioic acid, sebacic acid, decanedioic acid, undecanedioic acid, and dodecanedioic acid.
  • oxalic acid ethanedioic acid
  • malonic acid propanedioic acid
  • succinic acid propanedioic acid
  • butanedioic acid glutaric acid
  • pentanedioic acid adipic acid
  • hexanedioic acid pimelic acid
  • aromatic dicarboxylic acids include phthalic acid, benzene- 1 ,2- dicarboxylic acid, o-phthalic acid, isophthalic acid, benzene-l,3-dicarboxylic acid, m-phthalic acid, terephthalic acid, benzene- 1,4-dicarboxylic acid, and p-phthalic acid.
  • Examples of monounsaturated acids include maleic acid, (Z)-butenedioic acid, fumaric acid, (E)-butenedioic acid, glutaconic acid, pent-2-enedioic acid, traumatic acid, and dodec-2-enedioic acid.
  • Examples of di-unsaturated acids include the three isomeric forms of muconic acid, and (2E,4E)-hexa-2,4-dienedioic acid.
  • the modified, partially solubilized low value carbon source comprises primarily alcohols and ethers. In another embodiment, involving more complete oxidation, the modified, partially solubilized low value carbon source comprises greater relative amounts of aldehydes. By increasing the degree of oxidation further, the modified, partially solubilized low value carbon source may comprise greater relative amounts of carboxylic acids and esters. The alcohols, ethers, aldehydes, esters, and carboxylic acids may be monofunctional, or polyfunctional.
  • the modified, partially solubilized low value carbon source is used as the feedstock for the genetically engineered microorganisms of the present invention.
  • the composition of the modified, partially solubilized low value carbon source obtained from the oxidizing step 100 may affect one or both of the yield and selectivity of PHA biosynthesis.
  • the conditions of the oxidizing step 100 are selected based on producing a modified, partially solubilized low value carbon source that may include larger quantities of biodegradable materials and/or may exhibit an enhanced yield and/or selectivity in the process for biosynthesis of PHAs.
  • the modified, partially solubilized low value carbon source is placed in contact with the genetically engineered microorganism.
  • the genetically engineered microorganism of the present invention may be derived from a wild- type microorganism that comprises the PHA biosynthesis pathway as shown in Figure 2A. Such a wild-type microorganism is capable of producing PHAs, though typically at low levels that are not viable for commercial production. Genetic engineering of the wild-type microorganism can significantly enhance the yield and/or selectivity of a process for producing a PHA using the genetically engineered microorganism.
  • the wild-type microorganism is screened from
  • the environmental samples may be soil samples collected from different geographic locations with different climate conditions.
  • the microorganisms in the environmental samples may be cultured in a medium that is carbon rich and low in other essential nutrients such as nitrogen.
  • the modified, partially solubilized low value carbon source of the present invention is carbon rich and low in other essential nutrients, thus ideal for production of PHAs by microorganisms.
  • Such carbon-rich medium is used for screening wild-type microorganisms from environmental samples that can produce PHAs at a relatively high level, in one embodiment, the microorganisms from an environmental sample axe cultured in the modified, partially solubilized low value carbon source of the present invention.
  • microorganism cells are then extracted and stained with a PHA specific stain, Nile Blue, and examined with a fluorescence microscope.
  • the microorganism cells with the most fluorescence are those that produce the most PHAs, thus may be selected as the wild- type microorganism for further genetic engineering as shown in Figure 16.
  • the wild-type microorganism is capable of growing on a particular class of a modified, partially solubilized Sow value carbon source as described herein.
  • Different types of low value carbon sources can yield different modified, partially solubilized low value carbon sources that may support a different spectrum of
  • the same low value carbon source oxidized under different conditions or using different procedures may yield different modified, partially solubilized low value carbon sources that support different microorganisms.
  • the present invention may involve selection of a suitable wild-type microorganism depending on the characteristics of the modified, partially solubilized low value carbon source from the oxidizing step 100 that is to be used as a feedstock for the PHA production process.
  • a simple test may be employed to select a suitable wild-type microorganism.
  • One option involves measuring the growth potential of the wild-type microorganism in the modified, partially solubilized low value carbon source. Wild-type microorganisms showing good growth potential in the modified, partially solubilized low value carbon source may be selected for further genetic engineering.
  • a suitable wild-type microorganism may also need to have the ability to be transformed by exogenous nucleic acids (vectors) to generate a genetically engineered microorganism.
  • Gene transformation may be accomplished by techniques known in the art, such as electroporation, conjugation, transduction, or natural transformation,
  • the wild-type microorganisms include Thermoto gales, Cytophaga group, Azospirillum group, Paracoccus subgroup, Sphingomonas group,
  • Nitrosomonas group Azoarcus group, Acidovorax subgroup, Oxalobacter group,
  • Rhodococcus group Thiobacillus group, Xanthomonas group, Oceanospirillum group, Pseudomonas and relatives, Marinobacter hydrocarbonoclaticus group, Pseudoalteromonas group, Vibrio subgroup, Aeromonas group, Desulfovibrio group, Desulfuromonas group, Desulfobulbus assemblage, Campylobacter group, Acidimicrobium group, Frankia subgroup, Arthrobacter and relatives, Nocardiodes subgroup, Thermoanaerobacter and relatives, Bacillus megaterium group, Carnobacterium group, Clostridium and relatives, and archaea such as Archaeo glob ales, Methanobacteriales, Methanomicrobacteria and relatives, Methanopy rales, and Methanococcales.
  • Suitable microorganisms may preferably be selected from a genus such as Escherichia (and particularly E. coli), Corynebacterium, Clostridium, Zymonomas, Salmonella, Rhodococcus, Pseudomonas, Bacillus, Lactobacillus, Enterococcus, Alcaligenes, Klesiella, Paenibacillus, Arthrobacter, Brevibacterium, Pichia, Candida, Hansenula, Synechococcus, Synechocystis, Anabaena, Ralstonia, Lactococcus, or Saccharomyces.
  • the wild-type microorganism is selected from the Rhodococcus genus.
  • the wild-type microorganisms may be a strain selected from strains of Pseudomonas oleovornas subsp. lubricantis DSM 21016, Rhodococcus opacus DSM 43251, Rhodococcus ruber DSM 44190, Rhodococcus ruber DSM 45332,
  • the genetically engineered microorganism of the present invention may comprise at least one genetically modified enzyme in the PHA biosynthesis pathway with an increased enzymatic activity in comparison with the wild-type microorganism.
  • the increase/decrease of enzymatic activity or expression level in the genetically engineered microorganism is in comparison with the corresponding enzymatic activity of the wild-type microorganism from which the genetically engineered microorganism is derived.
  • the increased enzymatic activity of at least one enzyme in the PHA biosynthesis pathway can enhance the yield and/or selectivity of PHA biosynthesis process.
  • These enzymes functioning in the PHA biosynthesis pathway include thioesterase, acyl-CoA synthase, acetyl-CoA carboxylase, malonyl-CoAiACP acyl transferase, ⁇ -ketoacyl- ACP synthase, ⁇ -ketoacyl-ACP reductase, ⁇ -hydroxyacyl-ACP dehydratase, enoyl-ACP reductase, CoA:ACP acyltransferase, ⁇ -ketothilase, 2-ketoacyl-CoA reductase, 2,3-enoyl- CoA hydrase and PHA polymerase.
  • an exogenous PHA polymerase is introduced into the genetically engineered microorganism.
  • the exogenous PHA polymerase may be a PHA polymerase preferentially or specifically producing short chain PHAs, medium chain PHAs or long chain PHAs,
  • the PHA polymerase may have substrate specificity for monomers with a 3-hydroxacyl group of a short chain length (C3 -C j, a medium chain length (C& -CM), or a long chain length (C 15 or longer).
  • the exogenous PHA polymerase may be optimized to produce PHAs with a weight average molecular weight of at least 400,000 Da, or a weight average molecular weight of at least 700,000 Da, or a weight average molecular weight of at least 1,000,000 Da, or a weight average molecular weight of at least 2,000,000 Da, or a weight average molecular weight of at least 4,000,000 Da, or a weight average molecular weight of at least 6,000,000 Da.
  • the exogenous PHA polymerase may be naturally occurring or non-naturally occurring.
  • a non-naturally occurring PHA polymerase is a PHA polymerase mutated from a naturally occurring polymerase by modification with any technique known to a skilled person that results in addition, deletion, modification, or mutation of one or more amino acids in the enzyme polypeptide sequence, as long as the catalytic activity of the enzyme is not eliminated. Examples of non-naturally occurring PHA polymerases and methods for making them can be found in U.S. Patent No. 6,143,952 (incorporated herein by reference).
  • the non- naturally occurring PHA polymerases may have different substrate (monomer) specificity in comparison with the wild-type PHA polymerase.
  • the non-naturally occurring PHA polymerase may even be capable of polymerizing monomers that are not known to be polymerized by natural occurring PHA polymerases.
  • the genetically engineered microorganism may have an improved secretory system in comparison with the wild-type microorganism.
  • one or more components in the type I secretory system or type ⁇ secretory system may be overexpressed in the genetically engineered microorganism.
  • the genes encoding the one or more components may be selected from hlyB, hlyD, tolC, torD and secYEG.
  • the increase or decrease in the enzymatic activity of a particular enzyme may be measured by incubating the enzyme with a substrate for the enzyme.
  • the product of the enzyme produced in a unit of time under a set of specific conditions or in a specific environment, preferably a set of conditions or an environment suitable for growing the genetically engineered microorganism, is a measurement of the enzymatic activity of the enzyme.
  • the enzymatic activity of the enzyme in the genetically engineered microorganism and the wild-type microorganism measured under the same conditions or in the same environment can be compared to determine the increase or decrease in the enzymatic activity of the particular enzyme as described in the present application.
  • the genetically engineered microorganism is Rhodococcus erythropolh DSM-312 transformed with plasmid pCE43 which contains a PHA polymerase gene from Thauera sp. MZ1T (SEQ ID NO:l) or from Rhodococcus opacus (SEQ ID NO:2).
  • Aeyl-CoA may exit the PHA biosynthesis pathway through fatty acid ⁇ -oxidation pathway as shown in Figure 2D, which degrades acyl-CoA.
  • This pathway is also referred to as fatty acid degradation pathway (fatty acid degradation pathway and fatty acid ⁇ -oxidation pathway are used herein interchangeably).
  • this fatty acid degradation pathway should be eliminated or inhibited by reducing or eliminating the enzymatic activity of one or more enzymes involved in the fatty- acid degradation pathway, as shown in Figure 2C. These enzymes include acyl-CoA
  • the genetically engineered microorganism has a decreased enzymatic activity for PHA depolymerasse.
  • PHA may be degraded by PHA depolymerase as shown in step (3) of Figure 2A. Attenuating or eliminating the PHA polymerase activity in the genetically engineered microorganism can enhance the yield and/or selectivity of the PHA biosynthesis process.
  • the genetically engineered microorganism may further comprise an increased enzymatic activity for at least one enzyme that contributes to improved NAD(P)H regeneration activity.
  • NAD(P)H As discussed above, there are multiple steps in the PHA biosynthesis pathway use NAD(P)H as a co-factor.
  • the improved NAD(P)H regeneration activity may lead to a higher NAD(P)H concentration in the cytoplasm of genetically engineered microorganism, and thus a higher yield and/or selectivity of PHA biosynthesis.
  • the enzymatic activity contributing to regeneration of NAD(P)H may be a pyridine nucleotide transliydrogenase activity, for example, pntAB from E. coli and/or a giyceraldehyde-3-phosphate dehydrogenase activity (for example, gapN from S. mutans).
  • the genetically engineered microorganism may further have an increased pyridine nucleotide transhydrogenase enzymatic activity and/or a glyceraidehyde-3-phosphate dehydrogenase enzymatic activity.
  • the NAD(P)H concentration may thus be increased in the genetically engineered microorganism cells to achieve a higher yield of and/or selectivity for PHA biosynthesis.
  • the genetically engineered microorganism comprises at least one enzyme with increased enzymatic activity that enhances the production of acetyl- CoA, which is the starting material for the PHA biosynthesis pathway, as shown in Figures 2A-2B.
  • the microorganism grows on a modified, partially solubilized low value carbon source containing aromatic compounds and small carbohydrate molecules.
  • the enzymes that enhance production of acetyl-CoA in such a medium include enzymes in the beta-ketoadipate pathway.
  • Some examples of enzymes in the beta-ketoadipate pathway include catechol 1 ,2-dioxygenase (catA) E.G.
  • the genetically engineered microorganism may comprise at least one of these enzymes with enhanced enzymatic activity in order to enhance the production of acetyl-CoA.
  • the genetically engineered microorganism is derived from a wild -type microorganism that comprises a PHA biosynthetic pathway from acetyl-CoA to a PHA.
  • the technologies for deriving the genetically engineered microorganism from the wild-type microorganism are described in detail in this section. It is understand that one or a combination of the techniques described in this section may be used to genetically modify any enzymes in the wild-type microorganism that may be involved in the PHA biosynthesis pathway and/or the fatty acid degradation pathway, and thereby derive the genetically engi neered microorgani sm .
  • the target gene which is an enzyme that directly or indirectly affects the yield or selectivity of the PHA biosynthesis pathway, may have its enzymatic activity increased or decreased, depending on whether the enzyme contributes to or hinders the biosynthesis of PHAs, as discussed herein.
  • the target encodes an enzyme that contributes to the biosynthesis of PHAs
  • the present invention uses the genetic engineering technologies to increase the enzymatic activity of the enzyme.
  • the increase of an enzymatic activity of a target gene (encoding the enzyme) in a genetically engineered microorganism may be achieved in one of three ways: by either replacing the native enzyme with an exogenous enzyme which is more active than the native enzyme encoded by the target gene, or enhancing the expression level of the target gene, or both.
  • the exogenous enzyme may be an ortholog, a homolog, or an up-mutant of the target gene.
  • the enzyme encoded by the target gene is produced in larger quantity.
  • the genetically engineered microorganism will have increased enzymatic activity of the target gene.
  • the up-mutant can have point mutations, deletions or insertions.
  • the present invention uses the genetic engineering technologies to decrease the enzymatic activity of the enzyme.
  • the decrease of an enzymatic activity of a target gene (encoding the enzyme) in a genetically engineered microorganism may also be achieved in one of three ways: by either replacing the native enzyme with an exogenous enzyme which is less active than the native enzyme, deleting part or all of the target gene, suppressing the expression level of the target gene.
  • the exogenous enzyme may be an ortliolog, a homolog, or a down-mutant of the target gene.
  • the genetically engineered microorganism will have decreased enzymatic activity of the target gene in comparison with the wild-type microorganism.
  • the down-mutant can have point mutations, deletions or insertions. Partial or complete deletion of the target gene often causes complete loss of the enzymatic activity in the genetically engineered microorganism.
  • enzymatic activities may be increased/decreased by either random mutagenesis or by DNA shuffling of the coding sequence of the target gene.
  • the increase/decrease in enzymatic activity can be monitored in an enzyme specific fashion, depending on the characteristics of the enzyme. Enzymatic activity often can be measured by known methods such as a colorimetric/fiuorometric/spectrophotometric assay with a proper substrate or product which produces measurable signals.
  • the present invention uses vectors to introduce genetic materials (e.g. a gene, a promoter) into a wild-type microorganism to genetically engineer the microorganism to improve the yield and/or selectivity of PIIA biosynthesis.
  • the vectors can autonomously replicate and operate irrespecti ve of the host genome in the genetically engineered microorganism to create a stably transformed microorganism.
  • Such vectors include plasmids, cosmids, and bacteriophages.
  • the vectors are suicide vectors designed to cause homologous recombination between the microorganism modifications to the microorganism genome (e.g.
  • the suicide vectors are not capable of replicating in the genetically engineered microorganism. Plasmids are often used as suicide vectors to cause homologous recombination with the host microorganism genome.
  • a typical plasmid vector that can replicate autonomously comprises (a) an origin of replication functioning in the wild-type microorganism so that the vector can effectively replicate and result in several hundred copies of the plasmid vector in each microorganism host cell, (b) an antibiotic-resistance gene so that a microorganism host cell transformed with the plasmid vector can be identified, and (c) a sequence comprising at least one restriction enzyme site where an exogenous DNA fragment can be inserted into the vector.
  • a vector and the exogenous DNA fragment can easily be ligated by using a synthetic oligonucleotide adaptor or a linker according to conventional methods known in the art.
  • the vector can express the gene in the vector thus to produce the protein (en enzyme in the present invention) encoded by the gene. This will result in increased enzymatic activity for the target gene.
  • This type of vectors commonly referred to as expression vectors, have an exogenous gene operably linked to expression control sequences (e.g. promoters) for control of transcription of the gene in the genetically engineered microorganism.
  • the expression vector is used for enhancing enzymatic activity for an enzyme in the genetically engineered microorganism.
  • the promoter and the exogenous gene are included in an expression vector together with a selection marker and a replication origin.
  • the exogenous genes that may be inserted into an expression vector include the enzymes in the PHA biosynthesis pathway, the enzymes contributing to regeneration of NADPH and enzymes enhancing production of acetyl-CoA.
  • the target gene may be overexpressed or underexpressed in the genetically engineered microorgamsm.
  • the present invention provides two methods for overexpressing a target gene in the genetically engineered microorganism: (a) introducing a strengthened promoter to replace the native promoter of the target gene, and (b) introducing an extra copy of the target gene.
  • the strengthened promoter is more active than the native promoter, thus can drive a higher expression level for the target gene in comparison with the wild- type microorgamsm.
  • an extra copy of the target gene in the genetically engineered microorganism means that the enzyme encoded by the target gene may be produced from both the native target gene and the introduced extra copy of the target gene, thus a significantly higher expression level for the target gene in the genetically engineered microorganism may be achieved, in comparison with the wild-type microorganism.
  • overexpression of the target gene may involve introducing a homolog of the target gene that encodes a protein with the same enzymatic activity.
  • the homolog will produce an enzyme to enhance the enzymatic activity of the target gene.
  • the methods for underexpressing a target gene in the genetically engineered microorganism may be (c) introducing a weakened promoter to replace the native promoter of the target gene, and (d) knock-out the target gene.
  • the weakened promoter is less active than the native promoter, thus producing a lower expression level for the target gene compared with the wild-type microorganism. Further, knock out of the target gene in the microorganism will completely diminish the expression of the target gene. Thus no functional product of the target gene will be produced in the genetically engineered microorganism.
  • the introduction of a strengthened promoter or a weakened promoter to replace the native promoter of the target gene, as well as introducing an extra copy of the target gene or its homolog may be accomplished by the knock-in technique.
  • the introduction of an extra copy of the target gene or its homolog may also be achieved by transforming the microorganism with a plasmid containing the target gene so long as the plasmid can independently and autonomously replicate in the transformed microorganism.
  • the introduced promoter may affect the expression of ail the genes in an operon to which the target gene belongs.
  • the genes in an operon are evolutionarily selected to carry out the same or related function. For example, genes in the same metabolic pathway are often organized in the same operon. Thus, replacing the promoter of an operon provides the potential of affecting multiple genes that enhance biosynthesis of PHAs in a coordinated fashion.
  • Knock-out and knock-in techniques are often used to affect the expression of ail the genes in an operon to which the target gene belongs.
  • Figure 4A represents an embodiment of knock-out technique where the target gene is completely deleted from the wild-type microorganism genome.
  • Figure 4B shows an embodiment of knock-in technique where a nati ve sequence (e.g. promoter, target gene) is replaced with an exogenous sequence.
  • Figure 4C represents an embodiment of knock-in technique where an exogenous sequence (target gene or its homolog) is inserted into the genome of microorganism.
  • the vectors used in the knock-out and knock-in techniques are preferably suicide vectors, which cannot replicate in the wild-type microorganism. The suicide vectors thus do not have a functional origin of replication in the microorganism and have the sole purpose of causing homologous recombination with the host genome.
  • a suicide vector for knock-out/knock-in in Rhodococcus is built using the backbone of a pUC57-Kan vector from E. coli that contains an origin of replication not functioning in the Rhodococcus species.
  • the sacB (levansucrase) gene from Bacillus subtilis is synthesized and inserted into the pUC57-Kan backbone.
  • the suicide vector further comprises an antibiotic resistance cassette.
  • the suicide vector may contain a region that fuses the two regions (two arms) surrounding the target gene ( Figure 4A). For example, a 1.5kb DNA fragment is used for each "arm".
  • the two 1.5 kb DNA "arms” are fused and inserted into the suicide vector (pCE20, SEQ ID NO:5) by Gibson assembly (https://www.neb.com/applications/cloning- and-synthetic-biology/gibson-assembly-cloning).
  • the suicide vector may then be electroporated to the wild-type microorganism. Mutants containing integrated plasmid, caused by a single crossover are selected based on their antibiotic resistance and sucrose sensitivity, since the first round of recombination generates a chromosomal mutant which is sensitive to sucrose and resistant to antibiotics (Figure 4A).
  • a 2 nd recombination event is selected for lack of antibiotic resistance and no sucrose sensitivity, since the second round of recombination generates two possible mutants ( Figure 4A).
  • the intended one with a genomic deletion of the target gene, is selected based on its resistance to sucrose and antibiotic sensitivity.
  • a similar approach is used to insert a sequence
  • the electroporation process may be carried out as follows. Rhodococcus strains (either wild-type or containing a plasmid) are inoculated in LB (Luria- Bertani) broth (with appropriate antibiotic if containing plasmid) in a shaker at 28 °C until they reach mid- log phase. Cultures are cooled to 4 °C and cells are harvested by centrifugation at 3000 g for 10 minutes. Bacterial cells are washed twice with ice-cold water and centrifuged again at 3000 g for 10 minutes. In the final step, bacterial cells are resuspended in water containing 10% aliquoted glycerol solution. The treated bacterial cells can be used directly for electroporation or stored in a -80 °C freezer for later electroporation.
  • competent cells are thawed on ice if retrieved from the freezer. Plasmid DNA is added to the competent cells and incubated on ice for 30 minutes. Cells are then transferred to a pre-chilled 2 mm electroporation cuvette and electroporated with a single pulse at 2.5 kV followed by addition of 1 ml of super optimal broth with catabolite repression (SOC) medium and 3 hours recovery in a shaker at 28 °C. Cells are then plated in LB-Agar plates under the appropriate selection and grown for 2-3 days at 28 °C.
  • SOC catabolite repression
  • a strategy for gene knock-out/knock-m uses the phage ⁇ - Red Recombinase system.
  • ⁇ -Red Recombinase genes are amplified from pKD46 (Datsenko et al., 'One- step inactivation of chromosomal genes in Escherichia coli K-12 using PGR products," Proc. Nat, Acad, Sri,, vol. 97, pages 6640-5, 2000, incorporated herein by reference) and assembled to an expression vector (e.g. pCE17) capable of replicating in Rhodococcus which contains an inducible promoter (e.g. pTrc, SEQ ID:62).
  • the sacB counter-selectable marker is also inserted to cure from plasmid after recombination.
  • a wild-type Rhodococcus strain is first made electrocompetent by transforming with a ⁇ -Red Recombinase plasmid (e.g. pCE58). Successful transformation is verified by PGR amplification of the ⁇ -Red Recombinase cassette from bacterial colonies. Colonies positive for ⁇ -Red Recombinase are then grown overnight and after dilution with fresh media, induced for ⁇ -Red Recombinase expression (e.g. by addition of IPTG). The Rhodococcus cells are thus made electrocompetent.
  • a ⁇ -Red Recombinase plasmid e.g. pCE58.
  • Competent Rhodococcus cells expressing the ⁇ -Red Recombinase genes are transformed with PGR products obtained by amplification of an antibiotic cassette flanked by short DNA sequences homologous to the arms outside the region to be knocked-ouL in some cases antibiotic cassettes are also flanked by recombination sites (e.g. flippase recognition target (FRT) or Cre-LOX) to allow for removal of antibiotic marker if desired.
  • Transformants are selected based on their capability to grow under antibiotic selection and successful gene deletion is confirmed by colony PGR with primers designed to amplify the region of DNA knocked out or a combination of a primer that either amplifies the inserted antibiotic cassette or one of the flanking "arms”.
  • FRT flippase recognition target
  • Cre-LOX Cre-LOX
  • the expression level of a target gene is mostly controlled by the promoter of the target gene.
  • a strong promoter leads to a higher expression level for the target gene, while a weak promoter leads to a lower expression level for the target gene.
  • the present invention provides strengthened promoters and weakened promoters to increase or decrease the expression level of a target gene.
  • an exogenous promoter may be introduced into the microorganism genome to replace the native promoter of a target gene using the knock-in technique disclosed herein, thus the expression level of the target gene may be enhanced or suppres ed.
  • the strengthened promoter or weakened promoter is determined by comparison with the native promoter, if the exogenous promoter has a higher transcription initiation activity than the native promoter, the exogenous promoter is a strengthened promoter that may be used to replace the native promoter to drive overexpression of the target gene. Conversely, the weakened promoter has a lower transcription initiation activity than the native promoter, and thus may be used to replace the native promoter to drive underexpression of the target gene.
  • Examples include an SV40 promoter or the early and late promoters of adenovirus, the promoter of lac operon, the promoter of trp operon, the promoter of TAG or TRC system, T3 and T7 promoters, the major operator and promoter domain of phage lambda, the promoter of bacteriophage fd coat protein, the promoter of 3 -phosphoglycerat kinase or other glycolytic enzymes, the promoters of a phosphatase (e.g. Pho5), and the promoter of the yeast alpha- mating system.
  • SV40 promoter or the early and late promoters of adenovirus the promoter of lac operon, the promoter of trp operon, the promoter of TAG or TRC system, T3 and T7 promoters, the major operator and promoter domain of phage lambda, the promoter of bacteriophage fd coat protein, the promoter of 3 -phosphoglycerat
  • promoters there are numerous other promoters can be used in the present invention, depending on the level of expression desired for the target gene in the genetically engineered microorganism.
  • a skilled person can easily assess the strength of a promoter by making a construct with a reporter gene where the expression of the reporter gene is driven by the promoter.
  • a reporter gene may be green fluorescent protein gene or luciferase. The product of green fluorescent protein may be visible under blue light and the amount of luciferase expressed may be measured by simple enzymatic reaction. Thus, the strength of a promoter can be determined in this manner.
  • three promoter/terminator systems may be used. Two of them are based on the pTrc promoter made inducible or constitutive by the presence (inducible) or absence (constitutive) of a lacl gene. The third promoter is based on a Pnit promoter.
  • a ribosomal binding site (RBS) may be inserted into a promoter to enhance the binding of ribosomes, thus increasing expression of the downstream target gene.
  • Transcriptional terminators used are (rrnB Tl and T2, and Thca terminator as shown in Figure 5.
  • the three promoter/terminators systems are represented by SEQ ID NOS: 62-64.
  • the three promoter/terminator systems are also shown in Figures 6A- 6C.
  • Genes in microorganisms, especially in bacteria, are often organized in operons where transcription of the genes in the same operon is controlled by a common promoter. It is understood that transcription of an entire operon can be modified (i.e., increased, decreased, or eliminated) by modifying a common promoter. Alternatively, any gene or combination of genes in an operon can be modified to alter the function or activity of the encoded polypeptide (up-mutants or down-mutants). These modification can result in an increase or decrease in the activity of the encoded enzyme.
  • the weakened and strengthened promoters may be built by these skilled in the art with known techniques.
  • Baliga Promoter analysis by saturation mutagenesis
  • Biol. Proced. vol. 3, pages 64-69, 2001
  • Kagawa et al. Identification of a methanol-inducible promoter from Rhodococcus erythropolis PR4 and its use as an expression vector
  • /. Biosci. Bioeng. vol. 113, pages 596-603, 2012
  • the modified, partially solubilized low value carbon source may be at least partially solubilized after the oxidizing step 100.
  • the modified, partially solubilized low value carbon source is placed in contact with the genetically engineered microorganism, whereby the microorganism may utilize the solubilized carbonaceous materials as nutrients to first produce acetyi-CoA, which is then converted into PFIAs through the PHA biosynthesis pathway. This process is called fermentation where the genetically engineered
  • microorganisms are cultured under suitable conditions in a medium comprising the modified, partially solubilized low value carbon source in order to produce PIIAs.
  • the fermentation medium may comprise, in addition to the modified, partially solubilized low value carbon source, a suitable mineral, salt, enzymatic cofactor, buffer, and other components known to those skilled in the art which are suitable for stimulating the disclosed PHA biosynthesis pathway and/or for growth of the genetically engineered microorganism in the culture.
  • microorganism cells are grown at a temperature in the range of about 25 °C to about 40 °C.
  • a suitable pH for the fermentation is between about pH 5-0 to about pH 9.0. More specifically, the initial pll for culture and fermentation may be about pH 6.0 to about pH 8.0. Fermentation may be performed under aerobic or anaerobic conditions. In one embodiment, fermentation is performed under an anaerobic or microaerobic condition.
  • the fermentation process may be a batch fermentation process.
  • a classical batch fermentation is a closed system in which the composition of the medium is established at the beginning of the fermentation and not subjected to artificial alterations during the
  • the medium is inoculated with the desired organism, and the fermentation is permitted to occur without anything being added to or retrieved from the medium during the fermentation.
  • the batch fermentation is often not completely closed with respect to the addition of the modified, partially solubilized low value carbon source, as well as altering controlling factors such as pH and oxygen concentration during the fermentation.
  • the metabolite and carbon source composition of the system change constantly up to the time the fermentation is stopped.
  • cell growth proceeds through a static lag phase to an exponential growth (log) phase and finally to a stationary phase where the growth rate is decreased or stopped.
  • the microorganism cells in the stationary phase will eventually die.
  • microorganism cells in the log phase are involved in bulk-formation of the final product and/or any intermediates.
  • a modified version of the standard batch fermentation process is a called fed-batch fermentation process.
  • a fed-batch fermentation process is identical to a typical batch fermentation process except that a growth-limiting substrate is incrementally added as the fermentation progresses.
  • a fed-batch process is useful in various circumstances, such as when catabolite repression is apt to inhibit metabolic action in the cells or where it is desirable to have limited amounts of substrate in the medium, for example to control the reaction rate.
  • the actual substrate concentration is difficult to measure, and is therefore calculated based on the change in measurable factors such as pH, dissolved oxygen, or the partial pressure of a waste gas, such as C0 2 .
  • Batch and fed-batch is identical to a typical batch fermentation process except that a growth-limiting substrate is incrementally added as the fermentation progresses.
  • a fed-batch process is useful in various circumstances, such as when catabolite repression is apt to inhibit metabolic action in the cells or where it is desirable to have limited amounts of substrate in the medium, for example to control the reaction rate.
  • the fermentation process may also be a continuous fermentation process.
  • a continuous fermentation is carried out in an open system in which fresh fermentation medium or at least one of its components is added continuously to the reaction vessel and an equal amount of conditioned medium is removed simultaneously for processing.
  • Continuous fermentation permits microorganism cells to be maintained at a constant high density where the cells are mainly in log-phase growth.
  • Continuous fermentation processes allow for modulation of one or more factors that affect cell growth and/or yield/selectivity of PHA biosynthesis.
  • continuous fermentation allows maintaining a limiting nutrient such as the carbon source or nitrogen level at a fixed concentration while letting all other parameters moderate.
  • a number of factors affecting cell growth can be altered continuously while the ceil concentration, measured by medium turbidity, is kept constant.
  • Continuous fermentation systems strive to maintain steady- state growth conditions and thus the cell loss due to the medium being drawn off must be balanced against the cell growth rate during the
  • the fermentation process may present a challenge when recovering the genetically engineered microorganism cells from the medium is desirable.
  • the continuous fermentation process allows constant withdrawal of medium from the fermentation system whereby the microorganism cells are lost from the reaction vessel.
  • the microorganism cells in the medium may all be lost if not recovered from the medium. Though some old medium with the microorganism cells may be added to fresh medium for the next batch of fermentation, this may be undesirable when the old medium contains some substances that could hinder or slow the start of the next fermentation.
  • a technique making the microorganism cells in the fermentation medium easily- recoverable may present significant advantages in some embodiments.
  • the genetically engineered microorganism cells may be immobilized on a supporting structure, which is then placed in the reaction vessel in contact with the modified, partially solubilized low value carbon source. Therefore the withdrawal of medium from the reaction vessel causes no or minimal loss to the microorganism cells in the reaction vessel.
  • the supporting structure is an integral portion of the reaction vessel such that the microorganism cannot be easily washed out of the reaction vessel even if the fermentation medium is repeatedly retrieved from the reaction vessel.
  • Immobilization of the genetically engineered microorganism ceils can improve the yield, selectivity and/or reduce the cost of PHA production.
  • a traditional method of cell immobilization is the piercing method, in which a film-forming material containing microbial cells is immobilized by dripping into a liquid fixative.
  • a film-forming material containing microbial cells is immobilized by dripping into a liquid fixative.
  • a film-forming material containing microbial cells is immobilized by dripping into a liquid fixative.
  • sodium alginate is immobilized in CaCl 2 solution
  • polyvinyl alcohol is immobilized in boric acid solution.
  • the process is complex, with long immobilizing and washing times and low preparation efficiency, and difficult for large-scale production.
  • Microencapsulation is an immobilization method using natural or synthetic polymer materials to embed living microorganism cells, even with some liquid substances to form micro-particles with a semipermeable or sealed membrane.
  • the polymer materials may be agar, alginate, carrageenan, cellulose and its derivatives, collagen, gelatin, epoxy resin, photo cross- linkable resins, polyacrylamide, polyester, polystyrene and polyurethane.
  • the microencapsulation method encapsulates microorganism cells within a rigid polymeric network to prevent the cells from diffusing into surrounding medium while still allowing penetration of nutrients and substrates (Ramakrishna et al., "Microbial fermentations with immobilized cells," Current Science, vol. 77, pages 87-100, 1999).
  • Immobilization of the genetically engineered microorganism cells eliminates most of the constraints faced with free-cell fermentation systems.
  • a remarkable advantage of cell immobilization is the freedom to determine ceil density prior to fermentation, it also facilitates operation of microbial fermentation on continuous mode without cell washout, where the solubilized carbon source moves continuously through the reaction vessel, while the genetically engineered microorganism cells are almost completely retained in the reaction vessel during the continuous fermentation process.
  • a bacterial strain Rhodococcus erythropoUs DSM-312 is transformed with plasmid pCE43 which contains an exogenous PHA polymerase gene.
  • the exogenous PHA polymerase gene is derived from Thauera sp. ⁇ (SEQ ID NO: l).
  • the genetically engineered Rhodococcus erythropoUs DSM-312 will have increased enzymatic activity for PHA polymerase, which will lead to an increased yield/selectivit of polyhydroxyalkanoate production
  • Rhodococcus strains were transformed by vectors.
  • Two shuttle vectors, pCE7 and pCE8, were built using the backbone of the E. coli plasmid pACYC177 (containing the E. coli origin of replication and antibiotic resistance cassettes) and origins of replication of plasmid pRC4 from Rhodococcus rhodochrous DSM 43269 and plasmid pRE8424 from Rhodococcus erythropolis DSM 8424 respectively. Fragments were amplified by PCR and assembled by using the Gibson assembly reaction in E. coli (https://www.neb.com/applications/cloning-and-synthetic-biology/gibson-assembly- cloning).
  • Rhodococcus strains were made competent by standard molecular biology techniques, followed by transformation by the pCE7 and pCE8 plasmids using electroporation of the plasmids into the Rhodococcus cells. Strains were plated under kanamycin selective conditions. Of the ten Rhodococcus strains tested, five strains produced transformed colonies when transformed with pCE7 and three strains produced transformed colonies when transformed with pCE8 (Table 2 and Figure 12). Table 2. Ability of Rhodococcus strains being transformed by a plasmid
  • Plasmid DNA extracted from transformed E. coli was extracted from colonies, retransformed in E. coli, digested and compared with original pCE7 and pCE8 plasmids. Plasmid DNA extracted from transformed E. coli
  • Rhodococcus colonies was able to replicate in E. coli, indicating the presence of a functional origin of replication for these organisms.
  • the extracted plasmid DNA was indistinguishable from the original pCE7 and pCE8 plasmids as analyzed by restriction enzyme digestion. These results indicate successful transformation of Rhodococcus strains by the pCE7 and pCE8 plasmids. These two plasmids are potent vectors for genetic engineering of the Rhodococcus strains.
  • a suicide vector (pCE20, SEQ ID NO:5) was built using the backbone of a pUC57-Kan plasmid from E. coli that contains an origin of replication not functional in Rhodococcus species.
  • the sacB (levansucrase) gene from Bacillus subtilis was synthesized and inserted into the pUC57-Kan backbone (Gene synthesis was done by Genscript®).
  • the suicide vector pCE20 containing the SacB gene and an antibiotic resistance cassette, may be used as a backbone to build a vector for targeting a specific gene.
  • a knock-out vector based on pCE20 can be built by assembly of the two regions ("arms") surrounding a target gene to be deleted.
  • a 1.5kb DNA fragment is used for each "arm".
  • the two 1.5 kb DNA "arms” may be assembled to the pCE20 plasmid by Gibson assembly.
  • the knock-out plasmid may then be electroporated to Rhodococcus host cells.
  • Transformed cells containing integrated plasmid, caused by a single crossover may be selected based on their antibiotic resistance and sucrose sensitivity.
  • a 2 nd recombination event is selected for lack of antibiotic resistance and no sucrose sensitivity ( Figure 4A).
  • a vector pCE58 (SEQ ID NO:61) based on the phage ⁇ -Red Recombinase system was built for transformation of Rhodococcus strains.
  • the ⁇ -Red Recombinase genes were amplified from pKD46 (Datsenko et al., "One-step inactivation of chromosomal genes in Escherichia coli K-12 using PCR products," Proc. Nat. Acad. Sci., vol. 97, pages 6640-6645, 2000) and assembled to an expression vector pCE17 that is capable of replicating in
  • Rhodococcus cells The pCE58 vector contains an inducible promoter (e.g. pTrc, SEQ ID NO: 62).
  • the sacB counter-selectable marker was also inserted into the pCE58 vector to cure from plasmid after recombination.
  • the pCE58 vector can be used to make a Rhodococcus strain electrocompetent by transforming the bacteria with the vector. Successful transformation may be verified by PCR amplification of the ⁇ -Red Recombinase cassette from bacterial colonies. Transformed cells may then grow overnight. After dilution with fresh media, the bacterial cells can be induced for ⁇ -Red Recombinase expression (e.g. by addition of isopropyl ⁇ -D-l- thiogalactopyranoside (IPTG)) thus making the Rhodococcus cells electrocompetent.
  • IPTG isopropyl ⁇ -D-l- thiogalactopyranoside
  • Electrocompetent Rhodococcus ceils expressing the ⁇ -Red Recombinase cassette can be transformed with PCR products obtained by amplification of an antibiotic cassette flanked by short DNA sequences homologous to the "arms" outside the region to be knocked - out.
  • the antibiotic cassette is also flanked by recombination sites (e.g. FRT or Cre-LOX) to allow for removal of antibiotic cassette if desired.
  • Transformed cells can be selected based on their capability to grow under antibiotic selection and successful gene deletion may be confirmed by colony PCR with primers designed to amplify the region of DNA knocked-out or a combination of a primer amplifying the inserted antibiotic cassette and another primer amplifying one of the flanking "arms".
  • a two-step process was used to knock-out a dihydroperoate synthase gene in a Rhodococcus strain CEBl (Rhodococcus erythropolis DSM-43066).
  • a knock-out plasmid is assembled by Gibson assembly from the following PCR fragments:
  • DNA fragments were generated by PCR amplification using Q5® Hot Start High-Fidelity 2X Master Mix (New England Biolabs) following the manufacturer' s instructions. DNA fragments were purified using a DNA Clean & ConcentratorTM- 5 kit from Zymo Research and assembled using the Gibson Assembly® Master Mix (New England Biolabs) according to the manufacturer's instructions. Assembled mix was used to transform New England Biolabs Turbo Competent E. coli. Transformation mixture was plated on LB- Kanamycin (50ug/ml) agarose plates.
  • plasmids were constructed.
  • One plasmid is for knocking-out of muconate cycloisomerase (catB) gene in Rhodococcus strain CEB2 (Rhodococcus erythropolis DSM-312), assembled by Gibson assembly.
  • the second plasmid is for knocking-in of an antibiotic resistance cassette to replace the catB gene in CEB2, flanked by recombination sites for later removal if desired, in place of the catB gene.
  • This approach can be applied for insertion of gene(s) and/or genetic elements to replace a gene or simply insert in any other location in the bacterial genome.
  • the knock-out plasmid pCE50 for deletion of catB was assembled using the following DNA fragments:
  • DNA fragments were generated by PCR amplification using Q5® Hot Start High- Fidelity 2X Master Mix (New England Biolabs) following the manufacturer' s instructions. DNA fragments were purified using a DNA Clean & ConcentratorTM- 5 kit from Zymo Research and assembled using the Gibson Assembly® Master Mix (New England Biolabs) according to the manufacturer's instructions. Assembled mix was used to transform NEB Turbo Competent E. coli (High Efficiency). Transformation mixture was plated on LB- Kanamycin (50ug/ml) agarose plates.
  • Colonies containing correct plasmid (pCE50, SEQ ID NO:33 or pCE57, SEQ ID NO: 34) were grown in LB-Kanamycin (50ug/ml) liquid media overnight and plasmid DNA was purified using a GeneJET Plasmid Miniprep Kit (Thermo Scientific). Purified pCE57 DNA was used to transform CEB-2 as described in example 2. After growing 2-3 days, colony PCR was performed using primers catB CEB002 KO Check Do, SEQ ID NO:27 and catB CEB002 KO Check Up, SEQ ID NO:28 to identify successful first single crossover, characterized by amplification of two bands. For second crossover, positive colonies were streaked on LB -Sucrose 20% agarose plates and checked by colony PCR to distinguish between reversion to the wild-type and generation of the knock-out mutant.
  • plasmids were constructed.
  • One plasmid was for knocking-out of protocatechuate 3,4-dioxygenase (pcaGH) in a Rhodococcus strain CEB2 (Rhodococcus erythropolis DSM-312), assembled by Gibson assembly.
  • the second plasmid is for knocking-in of an antibiotic resistance cassette to replace the pcaGH gene in CEB2, flanked by recombination sites for later removal if desired, in place of the deleted gene.
  • the knock-out plasmid pCE51 , SEQ ID NO:49 for deletion of pcaGH was assembled using the following DNA fragments:
  • DAN fragments were generated by PCR amplification using Q5® Hot Start High- Fidelity 2X Master Mix (New England Biolabs) following the manufacturer' s instructions and primers listed below. DNA fragments were purified using a DNA Clean & ConcentratorTM-5 kit from Zymo Research and assembled using the Gibson Assembly® Master Mix (New England Biolabs) according to the manufacturer's instructions. Assembled mix was used to transform NEB Turbo Competent E. coli (High Efficiency). Transformation mixture was plated on LB-Kanamycin (50ug/ml) agarose plates.
  • Colonies containing correct plasmid were grown overnight in LB-Kanamycin (50ug/ml) liquid media overnight and plasmid DNA was purified using a GeneJET Plasmid Miniprep Kit (Thermo Scientific). Purified pCE55 DNA was used to transform CEB-2 as described in Example 2. After growing 2-3 days, colony PCR was performed using primers pCE20-F, SEQ ID NO:6 and pCE20-R, SEQ ID NO:7 to confirm integration of the plasmid into the chromosome of CEB2. Gel electrophoresis ( Figure 15) shows analysis of different colonies after first recombination. The presence of a band of the size expected for pCE20 backbone indicates that the plasmid was successfully recombined. No band indicates either failed PCR or no integration of the plasmid.
  • a curable plasmid for adaptation of the ⁇ -red recombinase system to Rhodococcus was constructed.
  • An antibiotic cassette and a counterselectable marker were inserted into the inducible expression plasmid pCE17, SEQ ID NO:57, capable of replicating in both E. coli and Rhodococcus.
  • the following DNA fragments were used:
  • DNA fragments were generated by PCR amplification using Q5® Hot Start High- Fidelity 2X Master Mix (New England Biolabs) following the manufacturer' s instructions and primers listed below. DNA fragments were purified using a DNA Clean & ConcentratorTM-5 kit from Zymo Research and assembled using the Gibson Assembly® Master Mix (New England Biolabs) according to the manufacturer's instructions. Assembled mix was used to transform NEB Turbo Competent E. coli (High Efficiency). Transformation mixture was plated on LB-Kanamycin (50ug/ml) agarose plates.
  • Coal or another other low value carbon source was wet milled to provide an aqueous slurry with a median particle size of about 20 ⁇ .
  • the slurry was then fed to a continuous stirred-tank reactor (CSTR), operated in a batch or continuous mode.
  • An alkali base such as NaOH was added to the aqueous slurry.
  • 0 2 was introduced to the CSTR via pressurization of the headspace with compressed air or ( enriched air in batch mode, or via a continuous flow of air for continuous mode. Solids content, alkali base concentration, temperature, pressure, and stirring rate were adjusted to achieve various degrees of oxidative depolymerization of the low value carbon source.
  • Selected strains of Rhodococcus were cultured in a modified, partially solubilized low value carbon (e.g. pretreated coal) of the present invention.
  • the pretreated coal liquid was diluted to 3,000 mg/L dissolved organic carbon, pH adjusted to 7.0, centrifuged to remove large particles and then filtered through a 0.2 ⁇ filter.
  • the inoculum was prepared by growing the strains on agar plates, then carefully removing biomass from the plate, suspending the biomass in sterile PBS (phosphate buffered saline) and then adjusting the OD600 of the cell suspension to 0.5 with sterile PBS and using 200 ⁇ into 5 ml of the filtered pretreated coal liquid.
  • sterile PBS phosphate buffered saline
  • a bacterial strain Rhodococcus er thropol DSM-312 is transformed with plasmid pCE43 which contains an exogenous PHA polymerase gene.
  • polymerase gene is derived from Rhodococcus opacus B4 (SEQ ID NO:2).
  • the genetically engineered Rhodococcus erythropolis DSM-312 will have increased enzymatic activity for PHA polymerase, which will lead to an increased yield/selectivity of polyhydroxyalkanoate production.
  • a bacterial strain Rhodococcus rhodochrous ATCC 21198 is genetically engineered to have an increased enzymatic activity of acetyl-CoA carboxylase.
  • the expression of the gene is enhanced (overexpression) by introducing a strong promoter: SV40 promoter for the gene.
  • the position of the gene in the Rhodococcus rhodochrous ATCC 21198 genome may be found from GenBank Accession Number AZHI01000069.1.
  • the genetically engineered Rhodococcus rhodochrous ATCC 21198 bacteria have overexpressed acetyl- Co A carboxylase, which leads to increased enzymatic activity for acetyl-CoA carboxylase. This will lead to an increased yield/selectivi y of polyhydroxyalkanoate production.
  • a bacterial strain Rhodococcus equi 1038 is genetically engineered to have a decreased enzymatic activity of acyl-CoA dehydrogenase.
  • the acyl-CoA dehydrogenase gene in the Rhodococcus equi 103S may be found from GenBank Accession Number
  • Rhodococcus equi 103S The gene in Rhodococcus equi 103S is knocked out using a suicide vector pUC57-Kan from E. coli.
  • the genetically engineered Rhodococcus equi 1038 bacteria have a decreased enzymatic activity for acyl-CoA dehydrogenase. This will lead to an increased yield/selectivity of polyhydroxyalkanoate production.

Abstract

L'invention concerne un procédé de synthèse d'un polyhydroxyalcanoate à partir d'une source de carbone de faible valeur, comprenant les étapes consistant à oxyder la source de carbone de faible valeur avec au moins un agent oxydant pour produire une source de carbone de faible valeur modifiée, partiellement solubilisée ; et mettre en contact la source de carbone de faible valeur modifiée, partiellement solubilisée, avec un micro-organisme génétiquement modifié conçu pour croître dans la source de carbone de faible valeur, modifiée, partiellement solubilisée, qui est dérivé d'un micro-organisme de type sauvage comprenant une voie de biosynthèse de polyhydroxyalcanoate à partir de l'acétyl-CoA. Un micro-organisme génétiquement modifié du genre Rhodococcus est également décrit.
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