WO2011130725A2 - Production of organic acids from xylose rich hydrolysate by bacterial fermentation - Google Patents
Production of organic acids from xylose rich hydrolysate by bacterial fermentation Download PDFInfo
- Publication number
- WO2011130725A2 WO2011130725A2 PCT/US2011/032803 US2011032803W WO2011130725A2 WO 2011130725 A2 WO2011130725 A2 WO 2011130725A2 US 2011032803 W US2011032803 W US 2011032803W WO 2011130725 A2 WO2011130725 A2 WO 2011130725A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- bacterial cell
- mutation
- gene
- acid
- xylose
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07K—PEPTIDES
- C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
- C07K14/195—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from bacteria
- C07K14/24—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from bacteria from Enterobacteriaceae (F), e.g. Citrobacter, Serratia, Proteus, Providencia, Morganella, Yersinia
- C07K14/245—Escherichia (G)
-
- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
- C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
- C12N9/10—Transferases (2.)
- C12N9/12—Transferases (2.) transferring phosphorus containing groups, e.g. kinases (2.7)
- C12N9/1205—Phosphotransferases with an alcohol group as acceptor (2.7.1), e.g. protein kinases
-
- 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
- C12P13/00—Preparation of nitrogen-containing organic compounds
- C12P13/04—Alpha- or beta- amino acids
- C12P13/14—Glutamic acid; Glutamine
-
- 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
- C12P13/00—Preparation of nitrogen-containing organic compounds
- C12P13/04—Alpha- or beta- amino acids
- C12P13/20—Aspartic acid; Asparagine
-
- 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
- C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
-
- 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
- C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
- C12P7/42—Hydroxy-carboxylic acids
-
- 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
- C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
- C12P7/44—Polycarboxylic acids
- C12P7/46—Dicarboxylic acids having four or less carbon atoms, e.g. fumaric acid, maleic acid
-
- 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
- C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
- C12P7/56—Lactic acid
-
- 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
- C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
- C12P7/58—Aldonic, ketoaldonic or saccharic acids
Definitions
- a 2004 U.S. Department of Energy report entitled “Top value added chemicals from biomass” has identified twelve building block chemicals that can be produced from renewable feedstocks.
- the twelve sugar-based building blocks are 1,4-diacids (succinic, fumaric and maleic), 2,5-furan dicarboxylic acid, 3-hydroxy propionic acid, aspartic acid, glucaric acid, glutamic acid, itaconic acid, levulinic acid, 3-hydroxybutyrolactone, glycerol, sorbitol, and xylitol/arabinitol.
- Building block chemicals are molecules with multiple functional groups that possess the potential to be transformed into new families of useful molecules. These twelve building blocks can be subsequently converted to a number of high-value bio-based chemicals or materials.
- Lignocellulosic biomass can be obtained from a number of sources including agricultural residues, food processing wastes, wood, and wastes from the paper and pulp industry.
- Biomass consists of roughly 40-50% of hexose sugars (sugars with six carbon atoms) and 10-30%) of pentose sugars (sugars with five carbon atoms).
- the hexose sugars are known in the art as C6 sugars.
- the pentose sugars are known in the art as C5 sugars.
- the lignocellulosic materials When hydrolyzed, the lignocellulosic materials yield a mixture of C5 and C6 sugars that includes glucose, xylose, arabinose, mannose and galactose.
- a number of fermentation processes for the production of industrial chemicals have been developed with pure glucose as a source of carbon for their growth and metabolism.
- the E. coli strain described in U.S. Patent No. 7,223,567 uses a rich medium supplemented with glucose as the source of carbon.
- the E. coli strain KJ122 useful for the production of succinic acid described by Jantama et al (2008a; 2008b) and in the published PCT Patent Applications Nos.
- WO/2008/021141A2 and WO2010/115067A2 can grow on a minimal medium but still requires glucose as the source of carbon. It would be ideal if these organisms with the ability to produce industrial chemicals at high efficiency could be grown in a mixture of sugars derived from hydrolysis of lignocellulose.
- a method to make the microorganisms co -utilize the different sugars such as C5 and C6 sugars through a relief of catabolite repression during the production of industrial chemicals in a commercial scale would be critical to lowering the cost of industrial chemicals produced by fermentation.
- Microorganisms take up sugars through transporter proteins located in the cytoplasmic membrane.
- the microbial sugar transporters fall within three major categories.
- the largest group of sugar transporters in bacteria is known as ATP binding cassette (ABC) transporters.
- ABC transporters require a molecule of ATP for every molecule of sugar transported into the bacterial cell.
- XylFGH is an ABC transporter for the transport of xylose, a pentose sugar, into the cell.
- AraFGH is an ABC transporter for the transport of arabinose, yet another pentose sugar.
- MFS Facilitator Super family
- H + - linked symporters Na + - linked symporters- antiporters
- uniporters are simple facilitators for the sugar transport and do not require a molecule of ATP for every molecule of sugar transported into the cell.
- the trans-membrane protein Glf in Zymononas mobilis is an example of a facilitator.
- the H + - symporters require an extracellular proton for every sugar molecule transported into the cell.
- GalP galactose
- GalP a very well characterized symporter with 12 trans-membrane loops. GalP is also reported to have the ability to transport glucose across the cell membrane.
- AraE is a proton-linked symporter for the transport of arabinose across the cell membrane.
- XylE protein is a proton-linked symporter for the transport of xylose.
- the third sugar transporter primarily responsible for the uptake of hexose sugars such as glucose is known as the phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS).
- PTS carbohydrate phosphotransferase system
- the other two sugar transport systems ABSC transporters and members of MFS transporters
- non-PTS sugar transporters Transfer of the phosphoryl group from phosphoenolpyruvate (PEP) catalyzed by the PTS drives the transport and phosphorylation of glucose and other sugars and results in the formation of phosphorylated sugars and pyruvic acid inside the cell.
- PTS generated pyruvic acid is apparently not recycled to PEP under aerobic culture conditions where glucose is the sole source of carbon. Rather, pyruvate is oxidized by way of the tricarboxylic acid cycle to carbon dioxide. Thus, for the transport of every single molecule of glucose, a molecule of PEP is consumed. In terms of cellular bioenergetics, the transport of sugars through PTS is an energy intensive process. Therefore in cells growing anaerobically, where there is a need to conserve the phosphoenolpyruvate content within the cells for the production of industrially useful chemicals, it is desirable to replace the PTS with other non-PTS sugar transporters not requiring a molecule of PEP for every molecule of sugar transported into the cell.
- the PTS is comprised of two cytoplasmic components named El and HPr and a membrane -bound component EII.
- E. coli contains at least 15 different EII complexes. Each EII component is specific to a sugar type to be transported and contains two hydrophobic integral membrane domains (C and D) and two hydrophilic domains (A and B). These four domains together are responsible for the transport and phosphorylation of the sugar molecules.
- EI protein transfers the phosphate group from PEP to HPr protein.
- EII protein transfers the phosphate group from phosphorylated HPr protein to the sugar molecule.
- EI is encoded by the ptsl gene.
- HPr is encoded by the ptsH gene.
- the glucose-specific EII complex of enteric bacteria consists of two distinct proteins namely, EIIA Glc encoded by the gene err and the membrane-associated protein EIICB Glc encoded by the gene ptsG.
- the PTS mediated sugar transport can be inhibited by means of mutating one of these genes coding for the proteins associated with PTS.
- Functional replacement of PTS by alternative phosphoenolpyruvate -independent uptake and phosphorylation activities (non-PTS) has resulted in significant improvements in product yield from glucose and productivity for several classes of metabolites.
- GalP mediated glucose uptake is evidenced by the fact that the inactivation of galP gene in the pts mutant is found to prevent growth on glucose (Yi et al., 2003). In the absence of a PTS, Glk is necessary to achieve the phosporylation of the glucose molecule before it can enter into glycolysis.
- the expression of the GalP protein in a pts stain can be achieved either by expressing the galP gene under a constitutive promoter or by means of relieving the repression of the galP gene expression through mutations in genes coding for the repressor of the galP gene such as galS and galR.
- the use of lignocellulosic biomass derived from agricultural and forest residue as feedstock in the production of value-added chemicals involves one or more pretreatment steps in order to release free sugar monomers from the lignocellulose matrix.
- the dilute-acid pretreatment method efficiently hydrolyzes hemicellulose to arabinose, xylose, and glucose besides enabling enzymatic digestion of cellulose to glucose.
- One problem associated with the dilute-acid pretreatment process is that it also releases a number of toxic compounds including furan derivatives, phenolic compounds, and acetate which are toxic to biocatalysts used in the fermentative production of value-added chemicals.
- Bioabatement is yet another approach used to remove inhibitors form biomass-derived sugar hydrolysates.
- microorganisms with the known ability to metabolize furfural and 5-hydroxymethylfurfural are used to detoxify the biomass-derived sugar hydrolysate.
- Coniochaeta ligniaria NRRL30616 has been reported to be useful in the removal of inhibitors from hydrolysate.
- Efforts have been made to incorporate bioabatement into a model scheme for production of ethanol from lignocellulosic biomass.
- the detoxified lignocellulosic hydrolysate is derived from the crude lignocellulosic hydrolysate by means of removing toxic chemicals which are known to be inhibitory to the growth of the microorganisms and their ability to produce organic acids in commercially significant quantities.
- the detoxification process used to remove toxic chemicals from the crude lignocellulosic hydrolysate is a lengthy process and could add up to the cost of the organic carbon source derived from the lignocellulosic hydrolysate.
- biocatalysts that can tolerate the inhibitory toxic chemicals present in the crude lignocellulosic hydrolysate. With the availability of biocatalysts capable of utilizing non- detoxified lignocellulosic hydrolysate the cost of the production of value-added chemicals through fermentative process can be significantly reduced.
- the objective of the present invention is to metabolically evolve microorganisms capable of using non-detoxified lignocellulosic hydrolysate in the production of high levels of organic acids.
- the inventors have surprisingly identified a process for metabolically evolving microorganisms to use C5 and C6 sugars simultaneously besides introducing the ability to use non-detoxified lignocellulosic hydrolysate as source of carbon. This process of metabolic evolution allows the cells to acquire the ability to use non-detoxified lignocellulosic hydrolysate without having any effects on any of its original characteristics such as rapid growth, and the ability to produce specific organic acid at commercially significant quantities.
- a feature of the invention is the utilization of the process of metabolic evolution to enable the microorganisms genetically modified and optimized for producing organic acids from glucose to acquire the ability to use hexose and pentose sugars simultaneously.
- an E. coli bacterium capable of producing an organic acid in a medium with glucose as a source of carbon is metabolically evolved to use additional types of sugar as a source of carbon while maintaining the same rate of organic acid production and retaining the capability to use glucose as a source of carbon.
- the present invention provides an E. coli bacterium capable producing organic acid in a minimal growth medium simultaneously using more than one type of sugar.
- the present invention provides an E. coli bacterium capable of producing organic acid in a minimal growth medium using plant hydrolysate including lignocellulosic hydrolysate as the source of carbon. (030) In a preferred embodiment, the present invention provides a bacterial cell capable of producing organic acid in a minimal growth medium using non-detoxified lignocelluloses hydrolysate as the source of organic carbon.
- an E. coli bacterium producing succinic acid using glucose and xylose simultaneously is provided.
- an E. coli bacterium producing succinic acid in a minimal growth medium using plant hydrolysate including lignocellulosic hydrolysate is provided.
- the present invention is especially useful for producing highly purified organic acids in a very cost-effective manner through biological fermentative process using non-detoxified lignocellulosic materials.
- the present invention provides a method for making a microorganism which uses multiple sugars simultaneously by means of mutating the genes coding for non-PTS transporter proteins in addition to reducing the activity of a gene coding for a protein associated with a PTS sugar transporter.
- a microorganism having PTS sugar transporter with reduced activity and a mutated form of galactose symporter is provided.
- FIG. 1 Fermentation profile for KJ122 strain of E. coli in mineral salts medium supplemented with 8% xylose. Fermentation was carried out for a total period of 168 hours.
- the xylose utilization shown in solid circles started around 96 hours accompanied by an increase in the bacterial cell density measured in terms of an increase in optical density at 550 nm shown in open circles.
- the increase in succinate concentration (mM) shown in solid squares began around 96 hours and leveled off after 168 hours. Also shown in the figure are the changes in the concentration of acetate, pyruvate and malate (mM) in the medium during the course of 168 hours of fermentation.
- FIG. 2 Fermentation profile for KJ122 strain of E. coli adapted to metabolize xylose in minimum mineral salt medium supplemented with 8% xylose. Fermentation was carried out for a total period of 168 hours.
- the xylose utilization shown in solid circles started around 72 hours accompanied by an increase in the bacterial cell density measured in terms of an increase in optical density at 550 nm shown in open circles.
- the increase in succinate concentration (mM) shown in solid squares occurred around 72 hours. Also shown in the figure are the changes in the concentration of acetate, pyruvate and malate (mM) in the medium during the course of 168 hours of fermentation.
- FIG. 3 Fermentation profile for TG400 strain of E. coli in minimum mineral salt medium supplemented with 8% xylose. The fermentation profile was monitored for a period of 120 hours.
- the xylose utilization shown in solid circles started around 30 hours accompanied by an increase in the bacterial cell density measured in terms of an increase in optical density at 550 nm shown in open circles.
- the increase in succinate concentration (mM) shown in solid squares occurred around 30 hours. Also shown in the figure are the changes in the concentration of acetate, pyruvate, and malate (mM) in the medium during the course of 120 hours of fermentation.
- FIG. 4 Profile of mixed sugar fermentation in minimum mineral salt medium by KJ122 and TG400 strains of E. coli.
- the fermentation was monitored for a total period of 144 hours.
- the fermentation medium contained both glucose and xylose.
- the glucose utilization as shown by a decrease in glucose concentration (mM) is shown by open squares.
- the xylose utilization as shown by a decrease in xylose concentration (mM) is shown by solid circles.
- the increase in the succinate concentration (mM) in the fermentation medium is shown by solid squares.
- the change in the cell density as measured by optical density at 550 nm during the course of 144 hours of fermentation is shown by open circles.
- Also shown in figures are the changes in the concentration of acetate, pyruvate and malate (mM) during the course of 144 hours of fermentation.
- FIG. 5 Profile of fermentation of detoxified concentrated bagasse hemicelluloses C5 hydro lysate supplemented with 2.5% (w/v) corn steep liquor by TG400 strain of E. coli. The fermentation was carried out for a period of 168 hours.
- the xylose utilization as measured by a decrease in the concentration of xylose (mM) is shown in solid circles.
- the increase in succinate concentration (mM) in the fermentation medium is shown by solid squares.
- Also shown in the figure are the changes in the concentration of pyruvate, acetate, malate and lactate (mM) in the medium during the course of 168 hours of fermentation.
- FIG. 6 Fermentation profile of WG37 strain of E. coli in a medium containing both glucose and xylose. Fermentation was carried out for a period of 120 hours.
- the glucose utilization as measured by a decrease in the glucose concentration (mM) in the medium is shown in open squares.
- the xylose utilization as measured by a decrease in the xylose concentration (mM) in the medium is shown in solid circles.
- the change in the bacterial cell density as measured by optical density at 550 nm during the course of 120 hours of fermentation is shown by open circles.
- the increase in the succinate concentration (mM) is shown in sold squares. Also shown in the figure are the changes in the concentration of acetic acid, pyruvic acid and malic acid (mM) during the course of 120 hours of fermentation.
- FIG. 7 Side -by-side comparison of succinic acid production by TG400, WG37 and KJ122 strains of bacteria grown in mineral salts medium containing 4% xylose and 7% glucose. The fermentation was carried out for a period of 120 hours. The increase in the concentration of succinic acid (mM) in the fermentation medium with TG400 (solid circles), KJ122 (solid triangle), and WG37 (inverted triangle) strains of E. coli was monitored for a period of 120 hours.
- mM succinic acid
- FIG. 8 Side -by-side comparison of succinic acid production by TG400, WG37 and KJ122 strains of bacteria grown in mineral salts medium containing only 10% xylose. The fermentation was carried out for a period of 120 hours. The increase in the concentration of succinic acid (mM) in the fermentation medium with TG400 (solid circles), KJ122 (inverted triangle), and WG37 (triangle) strains of E. coli was monitored for a period of 120 hours.
- mM succinic acid
- FIG. 9 Side -by-side comparison of succinic acid production by TG400, WG37 and KJ122 strains of bacteria gown in a mineral salts medium containing only 10% glucose. The fermentation was carried out for a period of 120 hours. The increase in the concentration of succinic acid (mM) in the fermentation medium with TG400 (solid circles), KJ122 (triangle), and WG37 (inverted triangle) strains of E. coli was monitored for a period of 120 hours. (046) FIG. 10. Growth Profile KJ122 and SI014 strains of E. coli in a growth medium containing xylose as the sole source of carbon. The bacterial growth was monitored in terms of optical density at 600 nm for a total period 97 hours. KJ122 strain of (solid circles) showed only a very slow growth. On the other hand, SI014 strain (solid squares) showed a fast growth within 27 hours followed by a slow decrease in the cell density.
- FIG. 11 Profile for xylose utilization and succinate production by KJ122 and SI014 strains of E. coli in a medium containing xylose as the sole source of carbon.
- the xylose utilization was measured in terms of a decrease in the xylose concentration (mM) in the medium for a period of 97 hours, Xylose utilization with SI014 strain (solid squares) was much faster when compared to the xylose utilization by KJ122 strain (solid circle).
- the succinic production (mM) with SI014 strain (open squares) was much faster when compared to the succinic acid production by KJ122 strain (open circles).
- FIG.12 Profile of xylose utilization and succinic acid production in TG400 and four different strains of E. coli namely WH1, WH2, WH3, and WH4 isolated based on their ability to consistently grow in non-detoxified sugarcane bagasse hydrolysate.
- the xylose utilization and the succinic acid production kinetics were measured in the cultures growing in AMI minimal mineral salt medium containing 10% xylose. The cultures were inoculated at an initial optical density of 0.5 at 550 nm. The xylose utilization and succinic acid production were measured during the course of 144 hours.
- FIG.13 Profile of xylose utilization and succinic acid production in WH3 strain of E. coli in media containing different concentration of corn steep liquor. Shown in the figure are sugar consumption and succinic acid production kinetics in media containing non-detoxified bagasse hydrolysate and 0.5% corn steep liquor or only non-detoxified bagasse hydrolysate without any corn steep liquor. The xylose utilization and the succinic acid production kinetics were measured in terms of the changes in the concentration of xylose and succinic acid in the growth medium.
- FIG. 14 Profiles of growth and succinic acid production by KJ122, TG400, WH3 strains of E. coli in AMI medium containing 10% xylose. The growth was measured in terms of change in the optical density at 550 nm. The kinetics of succinic acid production was measured in terms of the change in the concentration of succinic acid (mM) in the growth medium.
- FIG.15 Kinetics of utilization of glucose and xylose by KJ122, TG400, WG37 and WH3 strains of E. coli in AMI medium containing 4% xylose and 6% glucose. Glucose and xylose utilization was measured in terms of decrease in their respective concentration (mM) in the growth medium.
- FIG. 16 Kinetics of growth and succinic acid production in KJ122, TG400, WG37 and WH3 strains of E. coli in AMI medium containing 4% xylose and 6% glucose. The growth was measured in terms of optical density at 550 mM. The succinic acid production (mM) was measured in terms of change in the concentration of succinic acid in the growth medium.
- the present invention provides a process for the production of organic acids in commercially significant quantities from the fermentation of carbon compounds by recombinant microorganisms. More specifically, this present invention provides the microorganisms suitable for the production of organic acid through fermentative process.
- the microorganisms of the present invention possess the ability to use multiple sugars in the fermentative process for the production of commercially significant quantities of organic acid and an ability to use the non-detoxified lignocellulosic hydrolysate as the source of organic carbon.
- a number of industrially useful chemicals can be manufactured using the present invention. Examples of such chemicals include, but are not limited to, ethanol, butanols, lactate, succinate, fumarate, malate, threonine, methionine and lysine.
- organic acids can exist both as free acids and as salts (for example, but not limited to, salts of sodium, potassium, magnesium, calcium, ammonium, chloride, sulfate, carbonate, bicarbonate, etc), chemical names such as succinic acid, fumaric acid, malic acid, aspartic acid, threonine, methionine, and lysine shall be meant to include both the free acid and any salt thereof.
- any salt, such as succinate, fumarate, malate, aspartate, etc. shall be meant to include the free acid as well.
- the present invention combines the technique of specific genetic modifications with the process of metabolic evolution to obtain strains showing high yield, titer and volumetric productivity for succinic acid production under anaerobic growth condition in the mineral salt medium with a carbohydrate substrate.
- the carbohydrate substrate used by the biocatalysts of the present invention can be derived from either purified carbohydrates such as glucose or xylose or detoxified or non- detoxified lignocellulosic hydrolysate.
- the lignocellulosic hydrolysate is derived from the hydrolysis of lignocellulosic biomass / feedstock.
- lignocellulosic biomass or lignocelluosic feedstocks means non-edible plant material composed primarily of the polysaccharides cellulose, hemicellulose and lignin, a phenolic polymer that provides structural strength.
- Lignocellulosic biomass materials include, but not limited to, crop residues such as corn stover, wheat straw, rice straw, sugarcane bagasse, woody residues from forest thinning and paper production, grasses such as switch grass and fescue, and crops such as sorghum.
- a number of processes based on the application of enzymes for recovering organic carbon source from lignocellulosic biomass suitable for fermentative production of value- added chemicals are known in the art.
- pretreatment of the biomass is required to hydro lyze the hemicelluloses, and make the cellulose more accessible to the enzymes.
- An efficient pretreatment system is crucial to the enzymatic hydrolysis. Dilute -acid hydrolysis, steam explosion, liquid hot water extraction, alkaline hydrolysis, and ammonia treatment have been used for pretreatment.
- the dilute-acid hydrolysis and the steam explosion techniques are commonly used.
- the above described inhibitory compounds inhibit the efficiency of fermentation and therefore several detoxification methods have been attempted to improve the efficiency of utilization of carbon sources in the lignocellulosic hydrolysate during the fermentation.
- the list of detoxification processes which are currently under use includes neutralization, over liming, ion-exchange, electrodialysis, stream stripping, evaporation, membrane extraction, treatment with activated carbon or wood charcoal, treatment with microbials, and enzymatic treatment with laccase, and peroxidase.
- Laccase is a copper-containing blue oxidase that catalyzes the oxidation of phenolic units in lignin and aromatic amines to radicals with molecular oxygen as the electron acceptor that is reduced to water.
- the lignocellulosic hydrolysate obtained directly from the lignocellulosic biomass without any detoxification processes is referred as the non-detoxified lignocellulosic hydrolysate.
- the detoxified lignocellulosic hydrolysate is obtained.
- titer means the molar concentration of particular compound in the fermentation broth.
- a succinic acid titer of 100 mM would mean that the fermentation broth at the time of measurement contained 100 mmoles of succinic acid per liter of the fermentation broth.
- yield refers to the moles of particular compound produced per mole of the feedstock consumed during the fermentation process.
- yield refers to the number of moles of succinic acid produced per mole of glucose consumed.
- volumetric productivity refers to the amount of particular compound in grams produced per unit volume per unit time.
- a volumetric productivity value of 0.9 g L ⁇ l K l for succinic acid would mean that 0.9 gram succinic acid is accumulated in one liter of fermentation broth during an hour of growth.
- the term "gene” includes the open reading frame of the gene as well as the upstream and downstream regulatory sequences.
- the upstream regulatory region is also referred as the promoter region of the gene.
- the downstream regulatory region is also referred as the terminator sequence region.
- the phrase "functionally similar” means broadly any wild type or mutated DNA sequence, gene, enzyme, protein, from any organism, that has a biological function that is equivalent or similar to any wild type or mutated DNA sequence, gene, enzyme, protein that is found in the same or a different organism by the methods disclosed herein. Functionally similarity need not require sequence homology. Allele is one of two or more forms of DNA sequence of a particular gene. Each gene has different alleles. A gene without any mutation is referred as a wild type allele when compared to a corresponding gene that has a mutation.
- a homolog is a gene related to a second gene by descent from a common ancestral DNA sequence.
- the term, homolog may apply to the relationship between genes separated by the event of speciation or to the relationship between genes separated by the event of genetic duplication.
- Orthologs are genes in different species that evolved from a common ancestral gene by speciation. Normally, orthologs retain the same function in the course of evolution. Identification of orthologs is critical for reliable prediction of gene function in newly sequenced genomes. Speciation is the origin of a new species capable of making a living in a new way from the species from which it arose. As part of this process it has also acquired some barrier to genetic exchange with the parent species.
- Paralogs are genes related by duplication within a genome. Orthologs retain the same function in the course of evolution, whereas paralogs evolve new function, even if these are related to the original one.
- a gene or protein with "altered activity” is broadly defined as gene or protein that produces a measurable difference in a measurable property when compared to the relevant wild type gene or protein.
- the altered activity could manifest itself in a general way by increasing or decreasing the growth rate or efficiency of succinate production of the strain containing the altered gene or protein.
- Other measurable properties include, but are not limited to enzyme activity, substrate specificity of an enzyme, kinetic parameters of an enzyme such as affinity for a substrate or rate, stability of an enzyme, regulatory properties of an enzyme, gene expression level, regulation of gene expression under various conditions, etc.
- the term mutation refers to genetic modifications done to the gene including the open reading frame, upstream regulatory region or downstream regulatory region.
- the gene mutations may result either in an up regulation or a down regulation or complete inhibition of the transcription of the open reading frame of the gene.
- the gene mutations may be achieved either by deleting the entire coding region of the gene or a portion of the coding nucleotide sequence or by introducing a frame shift mutation, a missense mutation, an insertion, or by introducing a stop codon or combinations thereof. Mutations may occur in the structural genes coding for the proteins directly involved in the biological functions such as enzyme reactions or transport of the organic molecules across the cell membrane.
- regulatory genes may occur in the regulatory genes coding for the proteins which control the expression of the genes coding for the proteins directly involved in the biological functions.
- the proteins which control the expression of the other genes are referred as regulatory proteins and the genes coding for these regulatory proteins are referred as regulatory genes.
- “Mutation” shall also include any change in a DNA sequence relative to that of the relevant wild type organism.
- a mutation found in strain KJ122 is any change in a DNA sequence that can be found when the DNA sequence of the mutated region is compared to that of the parent wild type strain, E. coli C, also known as ATCC 8739.
- a mutation can be an insertion of additional DNA of any number of base pairs or a deletion of DNA of any number of base pairs.
- a particular type of insertion mutation is gene duplication.
- a gene can be duplicated by a spontaneous mutational event, in which the second copy of the gene can be located adjacent to the original copy, or a gene can be duplicated by genetic engineering, in which the second copy of the gene can be located at a site in the genome that is distant from the original copy.
- a mutation can be a change from one base type to another base type, for example a change from an adenine to a guanine base.
- a mutation can be a missense (which changes the amino acid coded for by a codon), a nonsense (which changes a codon into stop codon), a frame shift (which is an insertion or deletion of a number of bases that is not a multiple of three and which changes the reading frame and alters the amino acid sequence that is encoded downstream from the mutation, and often introduces a stop codon downstream from the mutation), or an inversion (which results from a DNA sequence being switched in polarity but not deleted).
- a "null mutation” is a mutation that confers a phenotype that is substantially identical to that of a deletion of an entire open reading frame of the relevant gene, or that removes all measurable activity of the relevant gene.
- a “mutant” is a microorganism whose genome contains one or more mutations.
- exogenous is intended to mean that a molecule or an activity derived from outside of a cell is introduced into the host microbial organism.
- the introduced nucleic acid may exist as an independent plasmid or may get integrated into the host chromosomal DNA.
- the exogenous nucleic acid coding for a protein may be introduced into the microbial cell in an expressible form with its own regulatory sequences such as promoter and terminator sequences.
- the exogenous nucleic acid molecule may get integrated into the host chromosomal DNA and may be under the control of the host regulatory sequences.
- the term “endogenous” refers to the molecules and activity that are present within the host cell.
- the term “exogenous” refers to an activity that is introduced into the host reference organism.
- the source can be, for example, a homologous or heterologous encoding nucleic acid sequence that expresses the referenced activity following introduction into the host microbial organism. If the nucleic acid sequence coding for a protein is obtained from the same species of the microbial organism, it is referred as homologous DNA. If the nucleic acid derived from a different microbial species, it is referred as heterologous DNA.
- exogenous expression of an encoding nucleic acid of the invention can utilize either or both heterologous and homologous encoding nucleic acid.
- a cell that "utilizes C5 and C6 sugars simultaneously" means a cell that consumes at a measurable rate, and without any substantial delay at the beginning of an inoculation of said cell into a medium, both a C5 sugar, such as xylose, arabinose, ribose, etc., and a C6 sugar, such as glucose, fructose, galactose, etc., when the cell is grown in a medium that contains a substantial concentration of both a C5 and a C6 sugar.
- the medium containing both a C5 and a C6 sugar can be made from purified sugars, or it can be derived from a biomass hydro lysate.
- a number of microorganisms including Escherichia coli, Citrobactor freundii, Gluconobacter oxydans, Gluconobacter asaii, Achromobacter delmarvae, Achromobacter viscosus, Achromobacter lacticum, Agrobacterium tumefaciens, Agrobacterium radiobacter, Alcaligenes faecalis, Arthrobacter citreus, Arthrobacter tumescens, Arthrobacter parqffineus, Arthrobacter hydrocarboglutamicus, Arthrobacter oxydans, Aureobacterium saperdae, Azotobacter indicus, Brevibacterium ammoniagenes, divaricatum, Brevibacterium lactofermentum, Brevibacterium flavum, Brevibacterium globosum, Brevibacterium fuscum, Brevibacterium ketoglutamicum, Brevibacterium helcolum, Brevibacterium pusillum, Brevibacterium testace
- the recombinant microorganisms most suitable for this present invention are derived preferably from the Enterobacteriaceae family.
- the preferred microorganisms are selected form the genera Escherichia, Erwinia, Providencia, Klebsiella, Citrobacter and Serratia.
- the genus Escherichia is most preferred. Within the genus Escherichia, the species Escherichia coli is particularly preferred.
- E. coli strains capable of producing organic acids in significant quantities are well known in the art.
- the U. S. Patent Application Publication No. 2009/0148914 provides strains of E. coli as a biocatalyst for the production of chemically pure acetate and/or pyruvate.
- the U. S. Patent No. 7,629, 162 provides derivatives of E. coli K01 1 strain constructed for the production of lactic acid.
- International Patent Applications published under the Patent Cooperation Treaty Nos. WO 2008/1 15958 and WO 2010/1 15067 provide microorganism engineered to produce succinate and malate in a minimal mineral salt medium containing glucose as a source of carbon in a pH-controlled batch fermentation.
- the wild type E. coli strains obtained from culture collections such as the ATCC can be genetically engineered and subsequently metabolically evolved to obtain a strain with an enhanced ability to produce one more organic acid in commercially significant amounts.
- genomic engineered or “genetic engineering” as used herein refers to the practice of altering the expression of one or more enzymes in the microorganisms through manipulating the genomic DNA or a plasmid of the microorganism.
- the genomic manipulations involve either altering, adding or removing specific DNA sequences from the genomic DNA.
- the genetic manipulations also involve the insertion of a foreign DNA sequence into the genomic DNA sequence of the microorganism. In the most preferred embodiments of the present invention, the genetic manipulations are accomplished by means of removing specific DNA sequences from the genomic DNA of the microorganisms without introducing any foreign DNA.
- Patent Application 2009/0148914 and the International patent applications published under the Patent Cooperation Treaty with International Publication Numbers WO 2008/1 15958 and WO 2010/1 15067 also describe the genetic engineering techniques useful in practicing various embodiments of this present invention.
- These scientific publications as well as patent documents are herein incorporated by reference for the purpose of providing the details for genetic engineering techniques useful for the present invention.
- microorganisms suitable for the practice of present invention can be grown aerobically (in the presence of oxygen) or anaerobically (in the complete absence of oxygen) or micro aerobically (with a low rate of oxygen supply).
- the microorganisms suitable for the present invention can be grown in a dual -phase growth regime, wherein the microorganism is initially grown in aerobic growth condition to reach a certain level of cell growth before transferring it to anaerobic growth condition to achieve the production of desired organic acids in commercially significant quantities.
- the metabolic pathways are genetically engineered so that a microorganism produces a particular organic acid of our choice.
- the microorganisms are capable of synthesizing a number of organic acids including lactic acid, acetic acid, and succinic acid.
- the list of the enzymes that are active in the microbial fermentative pathway which can be manipulated using the known genetic engineering techniques includes, but is not limited to, isocitrate synthetase (aceA), malate synthase (aceB), the glyoxylate shunt operon (aceBAK), acetate kinase- phosphotransacetylase (ackA-pta); aconitase hydratase 1 and 2 (acnA and acnB); acetyl- CoA synthetase (acs); alcohol dehydrogenase (adhE); citrate synthase (citZ); fumarate reductase ifrd); lactate dehydrogenases (Idh); malate dehydrogenaase (mdh); aceBAK operon repressor (iclR); phosphoenol pyruvate carboxlase (pepC); pyruvate formate lyas
- genetic manipulation of the genes involved in the uptake of carbon compounds useful as a source of energy for the synthesis of organic acid can also be manipulated either to enhance the carbon uptake or to enhance the efficiency of energy utilization in organic acid production.
- a decrease in the glucose uptake by a phosphotransferase system (PTS) could help in reducing the energy spent on glucose uptake into the microbial cell.
- PTS phosphotransferase system
- the phosphotransferase system genes ptsH and ptsG can be manipulated to conserve the energy in glucose uptake and thereby improve the efficiency of organic acid production by microorganism. Thus by mining the data available in the area of microbial metabolic pathways, one can delete a set of genes so as to block most of the metabolic pathways and channel the carbon flow to the production of a particular organic acid.
- carboxylating enzymes within the bacterial cells can also be manipulated to improve the fermentative production of organic acid.
- the role of carboxylating enzymes in the fermentative production of value-added organic chemicals is now well established.
- At least four different types of carboxylating enzymes are known to be functional within bacterial cells.
- the phosphoenol pyruvate carboxylase (PEPcase or PPC) carboxylates phosphoenol pyruvate leading to the formation of oxaloacetic acid.
- the malic enzymes carboxylate pyruvic acid leading to the formation of malic acid and requires reduced cofactors such as NADH or NADPH.
- PCK phosphoenolpyruvate carboxykinase
- Any one of these carboxylating enzyme can also be manipulated appropriately in the bacterial strains with the ability to utilize hexose and pentose sugars simultaneously to improve the fermentative production of industrially useful chemicals.
- the phosphoenolpyruvate carboxykinase (pck) can be genetically manipulated to improve the flow of carbon into the tricarboxylic acid cycle.
- the advantage in improving the activity of pck lies in the fact that this enzyme while carboxylating phosphoenol pyruvate to oxaloacetate, results in the production of a molecule of ATP for every molecule of oxaloacetate produced. An increase in the ATP yield would increase the growth rate of the cells.
- the recruitment of the native pck for fermentative succinate production can be achieved by any mutation that positively affects the transcription of the pck gene.
- An increase in the level of PCK activity can be achieved by means of expressing the pck gene in a multicopy plasmid with a native promoter or any other promoter sequence which is known to increase the gene's expression.
- Another way to increase the expression of the pck gene within the cell is to integrate additional copies of the pck gene using transposons.
- the native promoter of the pck gene can be replaced by some other promoter elements known to enhance the level of activity.
- An increased expression of pck gene can also be achieved either by mutation in the promoter region of the gene or by genetic manipulation of the regulatory elements that are known to interact with the promoter region of the pck gene.
- the gene coding for a regulator protein of the pck gene can be mutated or deleted or overexpressed in some way in order to increase the expression of pck gene.
- a single point mutation (G to A transition at position - 64 relative to the ATG start codon of pck gene) could increase the transcription of the pck gene accompanied by a corresponding increase in the phosphoenol pyruvate carboxykinase enzyme activity.
- a similar increase in the pck gene expression can also be achieved by genetically manipulating the genes coding for the proteins known to regulate the expression of pck gene.
- the production of the organic acid by the genetically engineered microorganism can be confirmed and quantified by using appropriate techniques well known in the art.
- HPLC techniques can be used to measure the quantity of the organic acid produced by the selected clone.
- the HPLC technology is also helpful in determining the purity of the organic acid produced by the selected clones.
- the microbial organism of the present invention can be grown in a number of different culture media well known in the field of microbiology.
- the wild type and mutant strains of E. coli are grown in Luria-Bertani (LB) medium containing 1% (w/v) tryptone, 0.5% (w/v) yeast extract, and 0.5% (w/v) NaCl.
- LB Luria-Bertani
- a minimal mineral salt medium supplemented with a carbon source is preferred.
- the use of a minimal mineral salt medium as opposed to a rich medium like LB medium reduces the cost for the production of organic acids in a commercial scale.
- the minimal mineral mediums suitable for the present invention include NBS medium (Causey et al., 2007) and AMI medium (Martinez et al., 2007).
- the NBS medium contains 1 mM betaine, 25.72 mM KH 2 P0 4 , 28.71 mM K 2 HP0 4 , 26.50 mM (NH 4 ) 2 HP0 4 , 1 mM MgS0 4 .7H 2 0, 0.1 mM CaCl 2 .2H 2 0, 0.15 mM Thiamine HC1, 5.92 ⁇ FeCl 3 .6H 2 0, 0.84 ⁇ CoCl 2 .6H20, 0.59 ⁇ CuCl 2 .2H 2 0, 1.47 ⁇ ZnCl 2 , 0.83 ⁇ Na 2 Mo0 4 .2H 2 0, and 0.81 ⁇ H 3 B0 3 .
- the AMI medium contains 1 mM betaine, 19.92 mM (NH 4 ) 2 HP0 4 , 7.56 mM NH 4 H 2 P0 4 , 1 .5 mM MgS0 4 .7H20, 1.0 mM Betaine-KCl, 8.88 ⁇ FeCl 3 .6H 2 0, 1.26 ⁇ CoCl 2 .6H 2 0, 0.88 ⁇ CuCl 2 .2H 2 0, 2.20 ⁇ ZnCl 2 , 1.24 ⁇ Na 2 Mo0 4 2H 2 0, 1.21 ⁇ H 3 B0 3 and 2.50 ⁇ MnCl 2 .4H 2 0.
- the pH of the culture vessel can be continuously monitored using a H probe, and appropriate base can be added to maintain the pH of the growth medium around neutral pH.
- the bases suitable for maintaining the pH of the microbial culture includes, NaOH, KOH, NH4HCO3, Na 2 C0 3 , NaHC0 3 , K 2 C0 3 , KHCO3, Ca(OH) 2 (lime) and (NH 4 ) 2 C0 3 .
- the bases suitable for this purpose can be used alone or in combination.
- the mineral medium for microbial growth is supplemented with a carbon source.
- the carbon sources useful in the production of value-added organic chemicals include but are not limited to pentose sugars like xylose, and hexose sugars like glucose, fructose, and galactose.
- the carbon source can also be satisfied by providing a combination of different sugars such as a combination of glucose and xylose.
- the carbon source can also be derived from a hydrolysis of starch or lignocellulose. The hydrolysis of complex carbohydrates such as starch and lignocelluloses can be achieved either by using thermo-chemical conversion processes or enzymatic methods well known in the art.
- the preferred carbon source for the industrial production of organic acid using microbial fermentation is lignocellulosic hydrolysate derived from the hydrolysis of agricultural or forestry wastes.
- the lignocellulosic hydrolysate may further be fractionated to yield a hexose-enriched and a pentose-enriched fraction and those fractions can serve as the source of carbon for the commercial production of the organic acids using microbial fermentation process.
- the lignocellulosic hydrolysate can further be detoxified to remove certain chemicals such as furfural which are found to be toxic to a number of microbial organisms above certain concentrations.
- the microbial strains obtained from genetic engineering have the expected genotype for the production of organic acids. However, their growth rate in the minimal mineral salt medium or the their ability to produce specific organic acid at the required rate or their ability to tolerate certain chemicals in the carbon source derived from lignocellulosic hydrolysate may not be suitable for using these genetically modified microorganism as a biocatalyst for the commercial production of organic acid through large scale fermentation process. Genetically modified microbial strains obtained from gene deletions are subsequently selected for the best representative clone via metabolic adaptation or evolution.
- the selected culture is repeatedly transferred into fresh minimal medium for a period of time to achieve a clone in which one or more spontaneous mutations that occurred during selection results in a phenotype that exhibits fast cell growth, rapid consumption of different carbon sources, ability to use multiple sugars simultaneously, ability to tolerate toxic chemicals in the carbon source and high production yield and productivity of the desired organic acid, but low production of other organic acids.
- attention is paid to select the clone with the desirable phenotypes.
- a microbial organism genetically engineered to produce a particular organic acid may not have a commercially attractive growth rate and consequently may not show the expected yield of that particular organic acid.
- Metabolic evolution can be followed to evolve a strain which shows a significant growth accompanied by an increased rate for the production of that particular organic acid.
- a clone resulting from the metabolic evolution showing a very good growth rate in mineral medium supplemented with a carbon source but that has not improved in the yield of the desired organic acid is not a desirable clone.
- KJ122 strain of E. coli is used in the preferred embodiment of the present invention.
- KJ122 was derived from the wild type E. coli C strain through multiple stages involving a combination of both genetic engineering and metabolic evolution.
- twelve different genes including lactate hydrogenase ⁇ IdhA), alcohol dehydrogenase ⁇ adhE), formate transporter (focA), acetate kinase ⁇ ackA), pyruvate-formate lyase (pflB), methylglyoxal synthase ⁇ msgA), pyruvate oxidase ⁇ poxB), propionate kinase with acetate kinase activity ⁇ tdcD), a-ketobutryate formate lyase ⁇ tdcE), citrate lyase ⁇ citF), aspartate aminotransferase ⁇ aspC), and malic enzyme ⁇ sfcA) were
- Metabolic evolution accompanied by a certain genetic change is desirable.
- the microorganism acquiring a stable genetic change during metabolic evolution can be easily identified by means of growing the microorganism in the original growth medium without any selection pressure for some time before transferring it to the fresh medium with the selection pressure. If these organisms are able to show good growth and the expected phenotype without any lag period, the organism is considered to have acquired a changed genotype during metabolic evolution.
- the basis of genetic change gained during the metabolic evolution can be determined by sequencing the chromosomal DNA of the organism and comparing the sequence data with that of the parent strain.
- the genomic sequence data can be obtained by means of following the techniques well known in the art.
- the parent stain KJ122 obtained from E. coli strain ATCC 8739 can be subjected to metabolic evolution to obtain a strain with a desirable new phenotype.
- the genome of the metabolically evolved new strain along with the parent strain KJ122 can be sequenced and the mutations in the metabolically evolved strain accounting for the changed phenotype can be identified.
- the term mutation includes any change in the nucleotide sequence within the gene.
- a nucleotide change within a gene may be a single nucleotide change within a triplet codon leading to the replacement of one amino acid residue with another amino acid residue.
- a nucleotide change within an open reading frame of a gene may involve a deletion of a portion of the open reading frame or the entire open reading frame.
- a nucleotide change within an open reading frame can also include introduction of a stop codon and as a result, the open reading frame codes for a truncated protein instead of a full-length protein.
- the term mutation also includes changes in the nucleotide sequences in the upstream or downstream of the open reading frame.
- the regions upstream and downstream of an open reading frame contain several regulatory nucleotide sequences and are involved in the expression of the protein coded by the open reading frame.
- a mutation occurring in these regulatory regions can alter the gene expression leading either to an up-regulation or down-regulation of gene function.
- Another possibility is a nucleotide insertion or deletion resulting in a frames shift mutation. (094)
- the genetic modifications leading to the simultaneous utilization of pentose and hexose sugars can be carried out in any bacterial strain already genetically engineered for the production of one or more industrial chemicals using glucose as the source of carbon.
- the genetic modification required for the simultaneous utilization of hexose and pentose sugar can be carried out in any wild type bacterial strains and the wild type bacterial strain thus modified for simultaneous hexose and pentose sugar utilization can be subjected to further genetic modifications to develop a microorganism suitable for the production of industrial chemicals in a commercial scale.
- the knowledge gained on the genetic modifications that confer the ability to tolerate the toxic components present in the non-detoxified lignocellulosic hydrolysate can be used to develop new bacterial strains with the ability to use the non -detoxified lignocellulosic hydrolysate as the source of organic carbon.
- KJ122 E. coli C, AldhA, AadhE, AackA, AfocA- pflB, AmgsA, ApoxB, AtdcDE, AcitF, AaspC, AsfcA
- KJ122 was derived from E. coli C (ATCC 8739) strain through genetic modifications as described by Jantama et al (2008a; 2008b) and in the International Patent Applications published under Patent Cooperation Treaty with International Publication Nos. WO 2008/115958 and WO 2010/115067. All these documents are herein incorporated by reference.
- E. coli strain KJ122 is capable of fermenting 10% glucose in AMI mineral media to produce 88 g/L succinate, normalized for base addition, in 72 hours.
- AMI medium contains 2.63 g/L (NH 4 ) 2 HP0 4, 0.87 g/L NH 4 H 2 P0 4, 1.5 mM MgS0 4, 1.0 mM betaine, and 1.5 ml/L trace elements.
- the trace elements are prepared as a 1000X stock and contained the following components: 1.6 g/L FeCl 3, 0.2 g/L CoCl 2 » 6H 2 0, 0.1 g/L CuCl 2, 0.2 g/L ZnCl 2 » 4H 2 0, 0.2 g/L NaMo0 4 , 0.05 g/L H 3 B0 3 , and 0.33 g/L MnCl 2 » 4H 2 0.
- the pH of the fermentation broth is maintained at 7.0 with: 1 :4 (6 N KOH: 3 M K 2 C0 3 ) (1.2 N KOH, 2.4 M K 2 C0 3 ). (097)
- corn steep liquor was added. It is a byproduct from the corn wet-milling industry. When compared to the yeast extract and peptone, it is an inexpensive source of vitamins and trace elements.
- Fermentations were started by streaking on a fresh NBS-2% xylose plate from a glycerol stock of E. coli strain genetically engineered to produce succinic acid which was stored in the -80°C freezer. After 16 hours (37°C), cells from the plate were scraped off and inoculated directly into the fermentation vessel. The fermentation vessels have a working volume of 500 ml. This first fermentation was referred to as the "seed" culture, and was not used to accumulate data.
- the medium in all fermentations was traditional AMI medium supplemented with 0.03M KHCO 3 , 1 mM betaine and 8-10% xylose (unless otherwise noted) and neutralized with a base consisting of 1.2 N KOH and 2.4 M K 2 CO 3 .
- the fermentation vessels were maintained at a pH of 7.0, 37°C with 150 rpm stirring.
- the seed culture was used to inoculate a new culture (whether batch experiments or "transfers") to a starting OD550 of 0.05. With the exceptions of the daily transfers, all experiments were conducted in triplicate.
- the C5/C6 co-fermentation experiment included 4% xylose, and 6 or 7% glucose.
- the C5/C6 co-fermentation was also conducted with the mixture of 8% xylose and 1% glucose.
- Cell growth was estimated by measuring the optical density at 550 nm or 600 nm (OD 550 or OD 6 oo) using a Thermo Electronic Spectronic 20 spectrophotometer.
- Organic acid and sugar analysis The concentration of various organic acids and sugars were measured by HPLC. Succinic acid and other organic acids present in the fermentation broth were analyzed on Agilent 1200 HPLC apparatus with BioRad Aminex HPX-87H column. BioRad Microguard Cation H + was used as a guard column. The standards for HPLC analysis were prepared in 0.008N sulfuric acid. The HPLC column temperature was maintained at 50°C. Sulfuric acid at 0.008N concentration was used as a mobile phase at the flow rate of 0.6 ml/min. Quantification of various components was done by measuring their absorption at 210 nm.
- Metabolic evolution Cells from the pH controlled fermentations were serially transferred at 24 hours to encourage metabolic evolution though growth-based selection. The inoculum, approximately 1/100 of the volume of new media, was added directly to pre- warmed, fresh media to a starting OD 55 o of 0.05. Clones with improved fermentation characteristics were isolated. The metabolic evolution strategy was applied to improve xylose fermentation.
- the sugarcane bagasse is dried to a moisture content of about 10% and milled using a knife mill.
- the material is treated in steam reactors (Zipperclave & Parr) with dilute sulfuric acid at moderate temperatures.
- Typical pretreatment conditions for dilute acid pretreatment are 0.1-3% acid concentration, 100-200°C temperature, and 1-30 minutes residence time in the reactor.
- the optimal reactor conditions to achieve maximum xylose yield with minimal sugar degradation are about 0.5% acid concentration, 160°C, and 10 min resident time in the reactor.
- PCR and DNA sequencing A set of two galP specific primers BY38 and BY39 (Table 1), were used to obtain the galP gene from TG400, KJ122, and WG37 strains of E.coli.
- the PCR was carried out using the standard protocol using 2Phusion HF master mix kit from New England Biolabs.
- the PCR products were run on a 0.8% agarose gel to determine the size of the PCR products from each of these different strains of E. coli.
- the PCR products were also sequenced using the Sanger method by Tufts DNA sequencing core facility in Boston, MA, USA. The sequence data were analyzed using the Vector NTI software program.
- WG37 stain of E. coli was derived from KJ122 strain by deleting the entire coding region of the galP gene.
- the galP gene was deleted in two steps involving homologous recombination. In the first stage, the galP gene sequence was replaced by a cassette containing an antibiotic marker and sacB gene sequence. The recombinants were selected on a LB plate with antibiotic. In the second stage, the antibiotic cassette was removed from the chromosomal DNA and the recombinants were selected on a medium containing sucrose. The colonies growing on the sucrose containing plates are highly enriched for loss of the sacB cassette.
- a kan cassette was amplified by PCR using the primers 51a and 51b (Table 1) and Xmnl digested pGW162 plasmid as a template.
- the DNA fragment of kan-sacB cassette was introduced into KJ122 strain of E. coli.
- transformants were selected on a LB plate with kanamycin and were confirmed by PCR using the primers 49a, 49b (Table 1).
- This strain was designated as WG35.
- the galP gene and neighboring 300 bp regions were amplified using the primers 49a, 49b (Table 1) and cloned into pGEMT easy vector to produce plasmid pGW180.
- Escherichia coli strain KJ122 (E. coli C, AldhA, AadhE, AackA, AfocA-pflB, AmgsA, ApoxB, AtdcDE, AcitF, AaspC, AsfcA) was able to grow aerobically on glucose, xylose, and arabinose.
- the objective of the present invention was to grow the KJ122 strain of E. coli micro aerobically in a medium containing both hexose and other pentose sugars and to select an organism that is able to use both types of sugars simultaneously.
- a glycerol stock of this culture was prepared and stored at -80°C. Either the fresh culture at the end of the 216 hour growth period or the glycerol stock of the culture prepared at the end of 216 hour growth period was used to inoculate a fresh fermentation vessel with AMI mineral medium supplemented with 8% xylose. Irrespective of the source of inoculum, whether it was from a fresh culture or a glycerol stock, the culture in the second fermentation vessel grew without any lag period. The succinic acid production also accompanied the bacterial growth without any lag period. Thus three rounds of growth on a solid mineral medium with 2% xylose followed by a single growth cycle for 216 hour period resulted in the "adapted strain" of KJ122 which is able to grow micro aerobically on xylose containing medium.
- the KJ122 strain was subjected to metabolic evolution.
- the KJ122 culture growing micro aerobically in a liquid AMI medium supplemented with xylose sugar was transferred to a fresh liquid AMI medium containing 8% xylose every 24 hours for a period of 2 weeks.
- the KJ122 strain was transferred to a fresh fermentor with AMI medium supplemented with 8% xylose.
- the anaerobic growth rate of KJ122 in the fermentor as well as the succinic acid production and the kinetics of xylose utilization were monitored.
- the succinic acid production in the fermentor started immediately without any lag period and also produced higher final titers and this strain is referred as a "metabolically evolved strain.” In our strain collection, this metabolically evolved strain has been designated as TG400.
- TG400 strain obtained through metabolic evolution was tested for its ability to use xylose derived from a hydrolysis of bagasse.
- the concentrated bagasse hydrolysate was detoxified by means of treating it with 50 grams of charcoal for every kilogram of bagasse hydrolysate at 35°C for 60 minutes in a rotary shaker at 200 rpm.
- the activated charcoal treated C5 enriched bagasse was pH adjusted, supplemented with AMI mineral salts, betaine and trace elements and then filter sterilized.
- the hydrolysate was comprised primarily of 8% (w/v) xylose (C5) and approximately 0.8% glucose (C6), 0.1% galactose (C6), 0.1%> mannose (C6) and 0.002% arabinose (C5).
- the entire genome of the parent strain KJ122 and the TG400 strain derived from KJ122 through metabolic evolution were sequenced using an Illumina Genome Analyzer II at the Tufts University Core Facility in Boston MA, USA.
- the Genome Analyzer II is provided by Illumina Sequencing Technology.
- the genomic data obtained for KJ122 and TG400 were compared to each other to identify the genetic changes accompanying the metabolic evolution of TG400 from KJ122.
- a comparative analysis of TG400 and KJ122 revealed a mutational change in the galP gene of TG400.
- the galP gene in TG400 showed a point mutation at the nucleotide position 889 of its open reading frame. The cytosine nucleotide at this position was changed to guanosine residue.
- galP* This mutation was the only difference between KJ122 and TG400 strains of bacteria at the nucleotide level.
- WG37 was able to use both glucose and xylose simultaneously during the course of 96 hours (Figure 6). Its growth kinetics as well as the sugar utilization patterns were similar to that of TG400 which has a mutated form of galP gene. In KJ122, the glucose was completely consumed within 72 hours while the xylose utilization showed an initial lag of 24 hours. Both in TG400 and in WG37, the glucose was not exhausted even after 96 hours of growth and a significant amount of glucose remained in the medium at 96 hours of growth. In addition, both in TG400 and WG37, the xylose utilization could be detected as early as 12 hours.
- Figures 7, 8 and 9 show the side-by-side comparison of kinetics of succinic acid production in all the three strains used in the present invention.
- all the strains showed a similar kinetics for succinic acid production irrespective of whether they had an intact galP gene sequence or not.
- TG400 showed a slightly higher rate for succinic acid production (Figure 7).
- WG35 KJ122 AgalP: :kan-sacB
- Plasmids pKD46 was then removed by growth at an elevated temperature (Datsenko and Waner, 2000).
- KJ122 was obtained off a MacConkey lactose plate.
- SI014 KJ122galP* was taken from an LB 2% glucose plate. Scrapes from the plates were used to inoculate 25 mis LB 2% glucose. Cultures were grown for 8 hours at 37°C, 150 rpm. Final OD 6 oo for these cultures was 0.71 for KJ 122 and 0.58 for SI014. 5 mis of each LB glucose culture was used to inoculate a 300 ml seed fermentor containing AMI 10% glucose medium. These fermentations were held at pH 7.0, 37°C for 24 hours. Final OD 6 oo for these cultures was 3.82 for KJ122 and 2.89 for SI014.
- the KJ122 strain of E. coli was subjected to metabolic evolution in the AMI minimal mineral salt medium as in Example 2 followed by a second metabolic evolution in a medium containing non-detoxified lignocellulosic hydro lysate derived from sugarcane bagasse.
- the non-detoxified sugarcane bagasse derived hydrolysate contained 2.57 g/L xylose, 2.28 g/L glucose, 1.59 g/L arabinose, 0.51 g/L mannose, 1.25 g/L furfural, 3.78 g/L acetic acid, 0.03 hydroxy methyl furfural, and 0.038 g/L pyruvic acid.
- the bacterial culture was transferred through the following series of mineral salt media with an increased concentration of hydrolyzate and decreasing levels of CSL: 90% (v/v) hydrolysate + 2.5% CSL; 90% (v/v) hydrolysate + 1% CSL; 90% (v/v) hydrolysate + 0.5% CSL; 90% (v/v) hydrolysate + 0.1% CSL; 90% (v/v) hydrolysate free of CSL. All these media contained a mineral composition which is comparable to that of AMI medium. The bacterial cultures were passed through each of these media for a period of one week and within each medium, the cultures were transferred to a fresh medium every 24 hours.
- Figures 12 compares the kinetics of growth and succinic acid production between TG400 and the four E. coli strains WHl, WH2, WH3, and WH4 metabolically evolved on non-detoxified lignocellulosic hydrolysate. These bacterial strains were grown on AMI minimal mineral salt medium supplemented with 10% xylose as the source of organic carbon. In the experiments reported in Figure 12, the cultures were inoculated at the initial optical density of 0.5 at 550 nm. As the results shown in Figure 12 indicate, with initial high cell density, the bacterial growth as well as the succinic acid production started without any lag period.
- the parental strain TG400 and the metabolically evolved WHl, WH2, WH3, and WH4 strains possess the same kinetics for growth and succinic acid production in the minimal mineral salt medium containing xylose as the source of organic carbon.
- WH3 strain showed better rates for growth and succinic acid production and was selected for further characterization.
- the WH3 strain of E. coli has the capacity to use xylose as the sole source of carbon in a minimal mineral salt medium, efforts were made to determine whether the WH3 strain of E. coli could make use of non-detoxified lignocellulosic hydrolysate as the sole source of organic carbon.
- the WH3 strain of E. coli was grown on a medium containing 90% (v/v) of non-detoxified lignocellulosic hydrolysate and different amounts of CSL ranging from 0.5% CSL to 0.0% CSL.
- the WH3 strain of E. coli has the ability to grow in a medium containing non-detoxified lignocellulosic hydrolysate as the only source of organic carbon.
- TG400 strain of E. coli has the ability to use both C6 and C5 sugars simultaneously.
- Figure 14 compares the kinetics of growth and succinic acid production in KJ122, TG400 and WH3 strains of E. coli in a minimal growth medium containing 10% xylose as the sole source of organic carbon. As the results in Figure 14 indicate, in a medium containing xylose, TG400, and WH3 strains of E. coli showed growth and succinic acid production without any lag period while the KJ122 strain of E. coli had a lag period of about 48 hours before showing any significant growth and succinic acid production.
- Figure 15 provides the kinetics of utilization of C6 and C5 sugars by KJ122, TG400, WG37 and WH3 strains of E. coli.
- the bacterial strains were grown in a minimal mineral salt medium with 4% xylose and 6% glucose.
- the utilization of glucose and xylose in the medium by each of these bacterial strains was determined by means of measuring the concentration of xylose and glucose remaining in the medium after specific periods of growth.
- KJ122 strain has a preference for glucose when compared to its preference for xylose as the source of carbon while the other three E. coli strains namely TG400, WH37 and WH3 showed the ability to use C6 and C5 sugars simultaneously.
- Figure 16 provides the kinetics of growth and succinic acid production for the bacterial strains KJ122, TG400, WG37 and WH3 when grown in a minimal mineral medium containing 4% xylose and 6% glucose. While there is a difference between KJ122 strain of E. coli and the other three E. coli strains namely TG400, WG37 and WH3 in terms of their ability to use C6 and C5 sugars, all the four E. coli strains showed the same kinetics for succinic acid production. These observations establish that the WH3 strains of E.
- the genomic sequence of WH3 strain of E. coli was obtained using the Illumina Genome Analyzer II at the Tufts University Core Facility in Boston MA, USA and the sequence of WH3 strain was compared with that of its parent strain KJ122 to identify the genetic changes that have occurred in WH3 strain during the process of metabolic evolution.
- This genomic analysis of WH3 strain revealed the following three genetic changes in WH3 strain when compared to that of its parental strain KJ122: (1) A frame shift mutation in galP gene sequence; (SEQ ID 11 and SEQ ID No. 12 provide the nucleic acid sequence of wild type galP gene and amino acid sequence of the wild type galP protein respectively.
- SEQ ID 13 and SEQ ID 14 provide the nucleic acid sequence of galP gene in WH3 strain and amino acid sequence of galP protein in WH3 strain respectively)
- a point mutation (T- C) converting an isoleucine residue at position 221 in the phosphofructo kinase A (pfkA) enzyme into a valine residue;
- SEQ ID 15 and SEQ ID 16 provide the nucleic acid sequence of pfkA gene in WH3 strain and amino acid sequence of pfkA protein in WH3 strain respectively
- SEQ ID 17 and SEQ ID 18 provide the nucleic acid sequence of trkH gene in WH3 strain and amino acid sequence of trkH protein in WH3 strain respectively).
- a mutation in the galP gene is associated with the ability of the E. coli strain TG400 to utilize both C5 and C6 sugars.
- the frame shift mutation in galP gene sequence in WH3 could be attributable to the ability of this strain use C5 and C6 sugars simultaneously.
- the other two mutations in the WH3 strain of E.coli either alone or in combination among themselves or in combination with the mutation in galP gene could account for the ability of this E. coli strain to grow and produce succinic acid using non-detoxified lignocellulosic hydrolysate as the source of organic carbon.
- the importance of the genetic changes in the pfkA and trkH gene sequences can be established using reverse genetic analysis as it has been done with galP mutation in the Examples 7 and 8 above.
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Zoology (AREA)
- Wood Science & Technology (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Genetics & Genomics (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Bioinformatics & Cheminformatics (AREA)
- General Engineering & Computer Science (AREA)
- Microbiology (AREA)
- Biotechnology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Molecular Biology (AREA)
- Medicinal Chemistry (AREA)
- Gastroenterology & Hepatology (AREA)
- Proteomics, Peptides & Aminoacids (AREA)
- Biophysics (AREA)
- Biomedical Technology (AREA)
- Preparation Of Compounds By Using Micro-Organisms (AREA)
- Micro-Organisms Or Cultivation Processes Thereof (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
BR112012026539A BR112012026539A2 (en) | 2010-04-16 | 2011-04-16 | "production of organic acids from xylose-rich hydrolyzate by bacterial fermentation" |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US34269510P | 2010-04-16 | 2010-04-16 | |
US61/342,695 | 2010-04-16 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2011130725A2 true WO2011130725A2 (en) | 2011-10-20 |
WO2011130725A3 WO2011130725A3 (en) | 2012-04-19 |
Family
ID=44799374
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2011/032803 WO2011130725A2 (en) | 2010-04-16 | 2011-04-16 | Production of organic acids from xylose rich hydrolysate by bacterial fermentation |
Country Status (2)
Country | Link |
---|---|
BR (1) | BR112012026539A2 (en) |
WO (1) | WO2011130725A2 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN104046586A (en) * | 2014-07-02 | 2014-09-17 | 山东大学 | Genetically engineered bacteria and application of genetically engineered bacteria to production of (2R, 3R)-2,3-butanediol |
WO2015034948A1 (en) | 2013-09-03 | 2015-03-12 | Myriant Corporation | A process for manufacturing acrylic acid, acrylonitrile and 1,4-butanediol from 1,3-propanediol |
WO2016207147A1 (en) * | 2015-06-22 | 2016-12-29 | Dsm Ip Assets B.V. | Process for enzymatic hydrolysis of lignocellulosic material and fermentation of sugars |
CN109517776A (en) * | 2018-11-16 | 2019-03-26 | 河北科技师范学院 | A kind of Salmonella enteritidis icdA gene-deleted strain and its application |
CN111218408A (en) * | 2020-01-21 | 2020-06-02 | 天津科技大学 | Aspergillus niger strain for efficiently producing malic acid, construction method and application |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN104862321B (en) * | 2015-06-01 | 2018-03-13 | 大连理工大学 | Kalium ion transport GFP trkH, its encoding proteins and its application |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6962794B2 (en) * | 1995-05-05 | 2005-11-08 | Genecor International, Inc. | Application of glucose transport mutants for production of aromatic pathway compounds |
-
2011
- 2011-04-16 BR BR112012026539A patent/BR112012026539A2/en not_active IP Right Cessation
- 2011-04-16 WO PCT/US2011/032803 patent/WO2011130725A2/en active Application Filing
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6962794B2 (en) * | 1995-05-05 | 2005-11-08 | Genecor International, Inc. | Application of glucose transport mutants for production of aromatic pathway compounds |
Non-Patent Citations (4)
Title |
---|
ALMEIDA, J. R. ET AL.: 'Screening of Saccharomyces cerevisiae strains with respect to anaerobic growth in non-detoxified lignocellulose hydrolysate' BIORESOURCE TECHNOLOGY. vol. 100, no. 14, 28 March 2009, pages 3674 - 3677 * |
GROSSIORD, B. P. ET AL.: 'Characterization, expression, and mutation of the Lactococcus lactis gaIPMKTE genes, involved in galactose utilization via the Leloir pathway' JOURNAL OF BACTERIOLOGY. vol. 185, no. 3, February 2003, pages 870 - 878 * |
TIAN, S. ET AL.: 'Yeast strains for ethanol production from lignocellulosic hydrolysates during in situ detoxification' BIOTECHNOLOGY ADVANCES. vol. 27, no. 5, 22 April 2009, pages 656 - 660 * |
ZHANG, X. ET AL.: 'Metabolic evolution of energy-conserving pathways for succinate production in Escherichia coli' PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES vol. 106, no. 48, 16 November 2009, pages 20180 - 20185 * |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2015034948A1 (en) | 2013-09-03 | 2015-03-12 | Myriant Corporation | A process for manufacturing acrylic acid, acrylonitrile and 1,4-butanediol from 1,3-propanediol |
KR20160071376A (en) | 2013-09-03 | 2016-06-21 | 미리안트 코포레이션 | A process for manufacturing acrylic acid, acrylonitrile and 1,4-butanediol from 1,3-propanediol |
US10035749B2 (en) | 2013-09-03 | 2018-07-31 | Myriant Corporation | Process for manufacturing acrylic acid, acrylonitrile and 1,4-butanediol from 1,3-propanediol |
CN104046586A (en) * | 2014-07-02 | 2014-09-17 | 山东大学 | Genetically engineered bacteria and application of genetically engineered bacteria to production of (2R, 3R)-2,3-butanediol |
WO2016207147A1 (en) * | 2015-06-22 | 2016-12-29 | Dsm Ip Assets B.V. | Process for enzymatic hydrolysis of lignocellulosic material and fermentation of sugars |
CN109517776A (en) * | 2018-11-16 | 2019-03-26 | 河北科技师范学院 | A kind of Salmonella enteritidis icdA gene-deleted strain and its application |
CN111218408A (en) * | 2020-01-21 | 2020-06-02 | 天津科技大学 | Aspergillus niger strain for efficiently producing malic acid, construction method and application |
Also Published As
Publication number | Publication date |
---|---|
BR112012026539A2 (en) | 2015-09-22 |
WO2011130725A3 (en) | 2012-04-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8871489B2 (en) | Metabolic evolution of Escherichia coli strains that produce organic acids | |
KR101711308B1 (en) | Engineering the pathway for succinate production | |
US8076111B2 (en) | Method for producing an organic acid | |
US9017976B2 (en) | Engineering microbes for efficient production of chemicals | |
KR102266177B1 (en) | Method of Producing Succinic Acid and Other Chemicals Using Facilitated Diffusion for Sugar Import | |
WO2011130725A2 (en) | Production of organic acids from xylose rich hydrolysate by bacterial fermentation | |
EP3280794A1 (en) | A modified microorganism for the optimized production of 2,4-dihydroxyburyrate with enhanced 2,4-dihydroxybutyrate efflux | |
CA2809942C (en) | Novel succinic acid-producing mutant microorganism that utilizes sucrose and glycerol simultaneously and method for producing succinic acid using the same | |
US10017793B2 (en) | Metabolic evolution of Escherichia coli strains that produce organic acids | |
Grabar et al. | Metabolic evolution of Escherichia coli strains that produce organic acids | |
Fukui | Studies on Microbial Succinate Production |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 11769737 Country of ref document: EP Kind code of ref document: A2 |
|
NENP | Non-entry into the national phase in: |
Ref country code: DE |
|
REG | Reference to national code |
Ref country code: BR Ref legal event code: B01A Ref document number: 112012026539 Country of ref document: BR |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 11769737 Country of ref document: EP Kind code of ref document: A2 |
|
ENP | Entry into the national phase in: |
Ref document number: 112012026539 Country of ref document: BR Kind code of ref document: A2 Effective date: 20121016 |