WO2013146540A1 - エタノールの生産方法 - Google Patents
エタノールの生産方法 Download PDFInfo
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- WO2013146540A1 WO2013146540A1 PCT/JP2013/058106 JP2013058106W WO2013146540A1 WO 2013146540 A1 WO2013146540 A1 WO 2013146540A1 JP 2013058106 W JP2013058106 W JP 2013058106W WO 2013146540 A1 WO2013146540 A1 WO 2013146540A1
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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
- C12P7/02—Preparation of oxygen-containing organic compounds containing a hydroxy group
- C12P7/04—Preparation of oxygen-containing organic compounds containing a hydroxy group acyclic
- C12P7/06—Ethanol, i.e. non-beverage
- C12P7/08—Ethanol, i.e. non-beverage produced as by-product or from waste or cellulosic material substrate
- C12P7/10—Ethanol, i.e. non-beverage produced as by-product or from waste or cellulosic material substrate substrate containing cellulosic material
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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
- C12P7/02—Preparation of oxygen-containing organic compounds containing a hydroxy group
- C12P7/04—Preparation of oxygen-containing organic compounds containing a hydroxy group acyclic
- C12P7/06—Ethanol, i.e. non-beverage
- C12P7/14—Multiple stages of fermentation; Multiple types of microorganisms or re-use of microorganisms
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/10—Biofuels, e.g. bio-diesel
Definitions
- the present invention relates to a method for producing ethanol. More specifically, the present invention relates to a method for producing ethanol from biomass.
- biomass is a renewable resource, exists in large quantities on the earth, and does not increase carbon dioxide in the atmosphere even if it is used (carbon neutral), and can contribute to the prevention of global warming.
- bioethanol is mainly made from corn and sugarcane, and competition with food is a problem. Therefore, in the future, production of bioethanol using lignocellulosic biomass such as rice straw, wheat straw and waste wood that does not compete with food will be required.
- Lignocellulosic biomass is mainly composed of three types of components: cellulose, hemicellulose, and lignin.
- cellulose can be used for ethanol fermentation by yeasts such as Saccharomyces cerevisiae that can assimilate glucose when it is degraded (saccharified) to glucose by hydrolysis.
- cellulose hydrolase such as cellulase is usually used.
- cellulose is separated from biomass and exposed before the enzymatic reaction. Is pre-processed.
- hydrothermal decomposition methods, acid treatment methods, and alkali treatment methods are known as pretreatment methods.
- acid treatment method a method using a dilute acid at a high temperature (200 ° C. or higher) and a method using concentrated sulfuric acid are known.
- the hydrothermal decomposition method and acid treatment method partially decompose cellulose under extreme conditions, resulting in excessive decomposition products (by-products), low glucose yield (saccharification rate), and ethanol fermentation. The problem is that it can also produce inhibiting substances.
- the pretreated product of lignocellulosic biomass is subjected to enzyme treatment.
- the enzyme treatment the cellulose component and hemicellulose component constituting the pretreated product are hydrolyzed to generate oligosaccharides and monosaccharides.
- the commercially available enzyme used for saccharification has a low titer, a large amount of enzyme is required for sufficient saccharification, which increases the cost.
- a cell surface presentation technique is used as such a biotechnological technique.
- an enzyme group that hydrolyzes cellulose that is, a yeast that surface-displays endoglucanase, cellobiohydrolase, ⁇ -glucosidase, and the like has been produced by a cell surface display technique (Patent Document 1).
- An object of the present invention is to provide a method for producing ethanol from lignocellulosic biomass at low cost using yeast.
- the inventors of the present invention can produce ethanol from lignocellulosic biomass at low cost by efficiently separating yeast that can reuse the fermented product after fermentation by using a combination of solid-liquid separation processes.
- the present invention has been completed by finding out what can be done.
- the present invention provides a method for producing ethanol from lignocellulosic biomass, the method comprising (1) a step of pretreating lignocellulosic biomass and (2) a cellulose fraction obtained in step (1).
- the step of treating with cellulose hydrolase, (3) the step of mixing the saccharified biomass obtained in step (2) and yeast, and the ethanol fermentation, and (4) the fermented product obtained in step (3) are solidified.
- the cycle consisting of steps (1), (2), (3) and (4) is repeated twice or more, and the yeast obtained in step (4) is added to the next cycle step ( Used as all or part of the yeast of 3).
- the step (4) includes (a) a step of removing 30% by mass of the solid from 5% by mass of the fermented product, and (b) the remaining 5% of mass obtained in the step (a). Recovering 30% by mass of the solid part.
- the concentration of yeast cells in the fermented product is 10 7 cells / mL or more.
- the yeast is a yeast transformed to express one or two enzymes selected from the group consisting of ferulic acid esterase, ⁇ -glucosidase, ⁇ -galactosidase, and pectinase.
- the enzyme is displayed on the surface.
- the present invention provides a yeast-containing composition for the production of ethanol from lignocellulosic biomass, wherein the yeast consists of ferulic acid esterase, ⁇ -glucosidase, ⁇ -galactosidase, and pectinase. It has been transformed to express one or two more selected enzymes.
- the enzyme is displayed on the surface.
- a certain amount of residue containing yeast is used for fermentation in the next cycle, whereby the yeast cell concentration
- the fermentation can be repeated over a long period of time without supplying new yeast, while maintaining a constant range from about 10 6 pieces / mL to about 10 7 pieces / mL to 10 7 pieces / mL or more. Since yeast is constantly growing, there is no problem that the freshness is lowered. Since the cost for newly preparing yeast can be reduced, ethanol can be produced at low cost. Moreover, the fermentation inhibition by a residue with a large specific gravity can also be suppressed.
- a step of pretreating lignocellulosic biomass (2) a cellulose fraction obtained in step (1) is treated with a cellulose hydrolase.
- Biomass refers to a carbohydrate material derived from biological resources. Examples thereof include starch obtained from corn and the like, and molasses (waste molasses) obtained from sugarcane and the like.
- Lignocellulosic biomass refers to biomass composed mainly of three types of components, cellulose, hemicellulose, and lignin. Among these, cellulose is a fibrous polymer in which glucopyranose (glucose) is linked by ⁇ -1,4-glucoside bonds, and glucose obtained by hydrolysis is used as a fermentation substrate for yeast and the like.
- lignocellulosic biomass Use of lignocellulosic biomass is preferable because it does not compete with food.
- lignocellulosic biomass include wastes generated when processing biological materials such as rice, wheat, corn, sugarcane, wood (pulp), and napiergrass.
- biological materials such as rice, wheat, corn, sugarcane, wood (pulp), and napiergrass.
- rice straw, wheat straw, bagasse (residue after sugarcane juice), and waste materials For example, rice straw, wheat straw, bagasse (residue after sugarcane juice), and waste materials.
- Pretreatment refers to, for example, in order to hydrolyze cellulose to glucose, before it is treated with a cellulose hydrolase such as cellulase, in order to facilitate the action of the enzyme on cellulose, The process of separating from biomass and exposing it.
- the pretreatment method is not particularly limited. Examples include hydrothermal decomposition methods and pressing and steaming methods.
- lignocellulosic biomass is pulverized as necessary, and mixed with water so as to have a content of, for example, about 20% by mass (dry mass), and this mixture is heat-treated.
- the heat treatment is performed at 120 ° C. to 300 ° C., preferably 150 ° C. to 280 ° C., more preferably 180 ° C. to 250 ° C., for 15 seconds to 1 hour.
- the treatment temperature and time can vary depending on the biomass used, and increasing the treatment temperature can shorten the treatment time. In addition, you may pressurize during heat processing.
- the lignocellulosic biomass is pressed and steamed.
- the order of pressing and steaming is not particularly limited, and can be appropriately set by those skilled in the art.
- a pressing method For example, the method of pressing lignocellulosic biomass with a hydraulic press, a screw press, a meat mining machine, a press dehydrator, a centrifuge, etc. is mentioned.
- a steaming method For example, the method of steaming lignocellulosic biomass with high temperature steam is mentioned.
- the conditions for the steaming are not particularly limited.
- the lignocellulosic biomass is impregnated with 1% by mass to 5% by mass of sulfuric acid, and 180 ° C. under a pressure of 1.0 Mpa to 1.6 Mpa.
- the conditions include steaming at 200 ° C. for 5 to 30 minutes.
- a water-soluble hemicellulose fraction and a water-insoluble cellulose fraction are separated.
- the water-insoluble cellulose fraction can be easily separated as a solid content by a centrifugal separation method or the like.
- a cellulose fraction can be obtained from lignocellulosic biomass.
- it does not specifically limit as solid content which a cellulose fraction contains, Preferably, it is 100 g dry mass / L or more, More preferably, it is 200 g dry mass / L or more.
- step (2) Treatment of cellulose fraction obtained in step (1) with cellulose hydrolase (step (2)) Cellulose hydrolase hydrolyzes the ⁇ -1,4-glucoside bond of cellulose to produce glucose. This process is called saccharification.
- the cellulose hydrolase include, but are not limited to, endo ⁇ -1,4-glucanase (hereinafter simply referred to as “endoglucanase”), cellobiohydrolase, and ⁇ -glucosidase.
- Endoglucanase is an enzyme called cellulase that cleaves cellulose from the inside of the molecule, and glucose, cellobiose, and cellooligosaccharide (degree of polymerization is 3 or more, and usually 10 or less, but is not limited thereto) ) Is generated.
- Endoglucanase is highly reactive to low crystallinity or amorphous cellulose, such as non-crystallized cellulose, soluble cellooligosaccharides, and cellulose derivatives such as carboxymethylcellulose (CMC), but has a crystalline structure Reactivity to cellulose microfibrils is low.
- Endoglucanase is an example of an enzyme that hydrolyzes amorphous cellulose. Examples of endoglucanase include, but are not limited to, Trichoderma reesei-derived endoglucanase (particularly EGII).
- Cellobiohydrolase decomposes from either the reducing end or non-reducing end of cellulose to release cellobiose.
- Cellobiohydrolase degrades crystalline cellulose such as cellulose microfibrils with a crystalline structure, but is not reactive to low crystallinity or amorphous cellulose such as cellulose derivatives such as carboxymethylcellulose (CMC).
- CMC carboxymethylcellulose
- Cellobiohydrolase is an example of an enzyme that hydrolyzes crystalline cellulose. Hydrolysis of crystalline cellulose by cellobiohydrolase is slower than hydrolysis of amorphous cellulose by endoglucanase due to the strong structure due to the intermolecular and intramolecular dense hydrogen bonds of crystalline cellulose. .
- cellobiohydrolase 1 There are two types of cellobiohydrolase, which are called cellobiohydrolase 1 and cellobiohydrolase 2, respectively.
- Examples of cellobiohydrolase include, but are not limited to, Trichoderma reesei cellobiohydrolase (particularly CBH2).
- ⁇ -glucosidase is an exo-type hydrolase that separates glucose units from non-reducing ends in cellulose.
- ⁇ -glucosidase cleaves a ⁇ 1,4-glucoside bond between an aglycon or sugar chain and ⁇ -D-glucose, and hydrolyzes cellobiose or cellooligosaccharide to produce glucose.
- ⁇ -glucosidase is an example of an enzyme that hydrolyzes cellobiose or cellooligosaccharide.
- One type of ⁇ -glucosidase is currently known and is referred to as ⁇ -glucosidase 1.
- Examples of ⁇ -glucosidase include, but are not limited to, Aspergillus acreatas-derived ⁇ -glucosidase (particularly BGL1).
- the cellulose hydrolase preparation is not particularly limited as long as it is a preparation containing the cellulose hydrolase. Commercially available enzyme preparations or those prepared by culturing enzyme-producing microorganisms may be used.
- the activity of cellulose hydrolase is expressed as the amount of enzyme (1 FPU) that liberates 1 ⁇ mol of glucose from filter paper (for example, Filter Paper: No. 1 filter manufactured by Whatman) per minute.
- the treatment concentration of the cellulose hydrolase is not particularly limited, but is preferably 4 FPU to 20 FPU / g cellulose fraction.
- the treatment time for cellulose hydrolase is not particularly limited, but is preferably 0.5 hours to 10 hours, more preferably 0.5 hours to 8 hours, and further preferably 0.5 hours to 6 hours.
- the treatment temperature of the cellulose hydrolase is not particularly limited as long as the enzyme works. Preferably, it is 40 ° C to 80 ° C.
- Saccharified biomass can be obtained from the cellulose fraction by this step.
- the saccharified biomass refers to biomass obtained by saccharification treatment, and includes, for example, glucose (monosaccharide) generated by hydrolysis of cellulose as a main component. Although it does not specifically limit as a shape of saccharified biomass, For example, a slurry form is mentioned.
- a nutrient source for yeast may be added.
- a nutrient source of yeast for example, YP (contains yeast extract 10g / L and polypeptone 20g / L), corn steep liquor (CSL), and these combination are mentioned
- YP contains yeast extract 10g / L and polypeptone 20g / L
- corn steep liquor CSL
- corn steep It is a liquor. Since corn steep liquor is inexpensive, the cost required for ethanol fermentation can be reduced.
- the amount of yeast nutrient source added is not particularly limited. For example, when YP is added, it may be 1 ⁇ YP to 10 ⁇ YP, and the total amount of the enzyme-treated solution is about 48 mL.
- corn steep liquor for example, corn steep liquor with respect to the total amount (mL) of the enzyme treatment solution prepared when the cellulose fraction is treated with cellulose hydrolase.
- the content of is, for example, 0.05% by mass to 2% by mass, preferably 0.0625% by mass to 1% by mass, and more preferably 0.125% by mass to 0.5% by mass. is there.
- it does not specifically limit as a time which adds the nutrient source of yeast It may be before or after processing a cellulose fraction with a cellulose hydrolase, or during a process.
- step (3) Ethanol fermentation by mixing saccharified biomass and yeast obtained in step (2) (step (3))
- the yeast is not particularly limited as long as ethanol fermentation can be performed using glucose as a substrate. It may be a wild-type yeast or a transformed yeast.
- the transformed yeast is appropriately prepared by a method commonly used by those skilled in the art.
- Saccharomyces cerevisiae strains include, for example, Saccharomyces cerevisiae TJ14 strain (Moucamnerd et al., Appl. Microbiol. Biotechnol., 2010, Vol. 88, p. 87-94), and Saccharomyces cerevisiae KF-7 strain (Ting Et al., Process Biochem., 2006, Vol. 41, pp. 909-914).
- the transformed yeast can be, for example, a yeast in which an enzyme for promoting saccharification of lignocellulosic biomass by the cellulose hydrolase preparation in step (2) is expressed.
- an enzyme for promoting saccharification of lignocellulosic biomass by the cellulose hydrolase preparation in step (2) is expressed.
- an enzyme for promoting saccharification of lignocellulosic biomass by the cellulose hydrolase preparation in step (2) is expressed.
- examples of such an enzyme include, but are not limited to, ferulic acid esterase, ⁇ -glucosidase, ⁇ -galactosidase, pectinase, and one or two combinations thereof.
- Preferred is a yeast transformed to express ferulic acid esterase.
- Ferulic acid esterase refers to an enzyme that causes an esterification reaction between ferulic acid and glycerol. Ferulic acid esterase has an action of hydrolyzing ferulic acid that connects lignin and polysaccharide in lignocellulosic biomass. By this action, the structure of lignocellulosic biomass is relaxed (that is, part of the structure of lignocellulosic biomass is decomposed), whereby saccharification by the cellulose hydrolase preparation can be promoted.
- the ferulic acid esterase is not particularly limited.
- Aspergillus genus for example, Aspergillus niger
- Penicillium for example, Penicillium chrysogenum and Penicillium chrysogenum
- ferulic acid esterase derived from Talamomyces funiculosus
- Examples of the gene encoding ferulic acid esterase include a gene derived from Talamomyces funiculosus (FaeA: GenBank Accession Number: AJ31296).
- Pectinase is a generic term for a group of enzymes that degrade pectin contained in the cell walls of higher plants.
- the pectinase is not particularly limited, and examples thereof include bacteria belonging to the genus Bacillus, Trichosporon, Endomyces, Endomycopsis, Saccharomyces saccharomyces, Genus (Schizosaccharomyces), Pichia (Pichia), Hansenula (Hansenula), Debaryomyces (Debaryomyces), Hansenia spora (Hansenispora), Candida genus (Tulopsis) Yeasts belonging to, and Aspergillus Examples include pectinases derived from filamentous fungi belonging to the genus Aspergillus and Rhizopus.
- the ⁇ -glucosidase described above can be used as the ⁇ -glucosidase.
- ⁇ -galactosidase refers to an enzyme that decomposes lactose into galactose and glucose.
- ⁇ -galactosidase has an action of decomposing galactan in pectin and relaxing the structure of the plant cell wall (ie, decomposing part of the structure of lignocellulosic biomass). This is expected to soften lignocellulosic biomass and promote saccharification by cellulose hydrolase preparations.
- ⁇ -galactosidase is not particularly limited, and examples thereof include, for example, Bacillus (for example, Bacillus circulans) and Aspergillus (for example, Aspergillus oryzae). And ⁇ -galactosidase.
- the gene encoding the enzyme is amplified by polymerase chain reaction (PCR) using, for example, a genomic DNA or cDNA prepared from the organism from which the enzyme is derived as a template, and a primer pair prepared based on the sequence information of the structural gene. And get.
- PCR polymerase chain reaction
- the enzyme may be secreted from yeast or expressed so as to be presented on the surface of the yeast.
- a method known to those skilled in the art can be employed as a method for causing the enzyme to be displayed on the cell surface of yeast.
- a GPI anchor of a cell surface localized protein JP-A-11-290078
- a sugar chain A binding domain WO 02/085935
- cell surface localized proteins used in these methods include ⁇ - or a-agglutinin (yeast aggregating protein), FLO proteins (eg, FLO1, FLO2, FLO4, FLO5, FLO9, FLO10 and FLO11), And alkaline phosphatase.
- Examples of a method for presenting an enzyme on the cell surface using a GPI anchor include a method using a recombinant DNA comprising a DNA encoding a secretory signal sequence, a target gene, and a DNA encoding a GPI anchor adhesion recognition signal.
- Glucoamylase expressed from this recombinant DNA and secreted outside the cell membrane can bind to the GPI anchor of the cell membrane via a GPI anchor attachment recognition signal.
- the GPI anchor attachment recognition signal sequence for example, a GPI anchor attachment recognition signal sequence present in a 320 amino acid sequence counted from the C-terminus of yeast ⁇ -agglutinin can be used.
- the enzyme is N-terminal side, C-terminal side, or N-terminal side and C-terminal side of a cell surface localized protein (aggregation functional domain).
- aggregation functional domain a cell surface localized protein
- the enzyme expressed from this recombinant DNA and secreted outside the cell membrane can remain on the cell surface layer when a plurality of sugar chains of the sugar chain binding domain interact with sugar chains in the cell wall.
- the aggregation functional domain include sugar chain binding sites such as a lectin and a lectin-like protein, and typically include an aggregation functional domain of a GPI anchor protein.
- the secretion signal sequence used for the recombinant DNA is not particularly limited, and may be an enzyme secretion signal, a cell surface localized protein secretion signal sequence, or leading the enzyme to the outside of the cell. Other secretory signal sequences can be used. If the enzyme activity is not affected, a part or all of the secretory signal sequence and pro-sequence may remain at the N-terminus after cell surface display.
- the method for secreting an enzyme from yeast is carried out, for example, by introducing into the yeast a recombinant DNA in which a gene encoding the target enzyme is linked downstream of the DNA encoding the secretory signal sequence. obtain.
- the synthesis and binding of the recombinant DNA can be performed, for example, by a method commonly used by those skilled in the art.
- the recombinant DNA may be incorporated into an expression vector.
- an expression vector is, for example, in the form of a plasmid.
- a plasmid having a replication origin (Ori) of 2 ⁇ m plasmid of yeast and a replication origin of ColE1 is preferably used.
- the plasmid preferably has a selection marker and a replication gene for Escherichia coli in terms of facilitating preparation of the plasmid and detection of the transformant.
- selectable markers include drug resistance genes and auxotrophic genes.
- the drug resistance gene include, but are not limited to, an ampicillin resistance gene (Ampr) and a kanamycin resistance gene (Kanr).
- auxotrophic genes include N- (5′-phosphoribosyl) anthranilate isomerase (TRP1) gene, tryptophan synthase (TRP5) gene, malate ⁇ -isopropyl dehydrogenase (LEU2) gene, imidazole glycerol phosphate dehydration
- TRP1 N- (5′-phosphoribosyl) anthranilate isomerase
- TRP5 tryptophan synthase
- LEU2 malate ⁇ -isopropyl dehydrogenase
- imidazole glycerol phosphate dehydration Specific examples include, but are not limited to, the elementary enzyme (HIS3) gene, the histidinol dehydrogenase (HIS4) gene, the dihydroorotic acid dehydrogenase (URA1) gene, and the orotidine-5-phosphate decarboxylase (URA3) gene.
- a replication gene for yeast is selected as necessary.
- the expression vector preferably has an appropriate promoter and terminator for expressing a gene encoding the target enzyme in yeast.
- promoters and terminators include GAPDH (glyceraldehyde 3′-phosphate dehydrogenase), PGK (phosphoglycerate kinase), PYK (pyruvate kinase), TPI (triose phosphate isomerase) promoters and terminators.
- GAPDH glycose
- PGK phosphoglycerate kinase
- PYK pyruvate kinase
- TPI triose phosphate isomerase
- the method for introducing recombinant DNA into yeast is not particularly limited. Examples thereof include a lithium acetate method, an electroporation method, and a protoplast method.
- the introduced recombinant DNA may exist, for example, in the form of a plasmid, or may exist in a form inserted into a yeast chromosome or a form integrated into a yeast chromosome by homologous recombination.
- Yeast into which the recombinant DNA has been introduced is selected by a selectable marker and selected by measuring the activity of the expressed enzyme. That the target enzyme is presented on the cell surface can be confirmed, for example, using an antibody against the enzyme.
- the yeast cell concentration at the start of the first fermentation is not particularly limited. Preferably, it is about 2 to 20 g wet weight / L (1 ⁇ 10 7 pieces / mL to 1 ⁇ 10 8 pieces / mL).
- Yeast culture conditions are not particularly limited. Usually, it may be the conditions for ethanol fermentation using glucose as a substrate.
- the culture temperature is, for example, 30 ° C. to 37 ° C.
- the culture pH is, for example, 4-8.
- the culture time is usually 2 days to 3 days.
- the end of the fermentation is determined based on, for example, the fact that the amount of generated carbon dioxide gas is 1/10 or less of that at the start of fermentation.
- the fermented material after completion of fermentation contains solids such as lignin and ash derived from raw materials, in addition to the yeast and ethanol of the fermentation product. That is, a slurry containing a solid is also included.
- the cell concentration of yeast in the fermented product after completion of fermentation is not particularly limited. For example, the cell concentration at the start of the first fermentation is about 1 ⁇ 10 7 cells / mL to 5 ⁇ 10 8 cells / mL.
- yeast is efficiently recovered from this fermented product and reused.
- the combination of the solid-liquid separation step is not particularly limited, but preferably (a) a step of removing a solid part of 5% by mass to 30% by mass of the fermented product (step (4) (a)), and (b) This is a combination of the steps (steps (4) and (b)) of recovering the solid portion of 5 to 30% by mass of the remainder obtained in the step (4) (a).
- step (4) A step of removing a solid part of 5% by mass to 30% by mass of the fermented product (step (4) (a))
- the yeast is recovered in the liquid part.
- the solid part of 5% by mass to 30% by mass, preferably 5% by mass to 20% by mass, of the fermented product obtained in the step (3) is removed.
- the means for removing the solid part is not particularly limited, but preferably includes 100G to 1000G centrifugation, hydra sieve, and decanter. In this step, most of ligrin and ash are removed as a solid part.
- the yeast is recovered in the solid part.
- the solid part of 5 to 30% by mass, preferably 20 to 30% by mass of the remainder obtained in the step (4) (a) is recovered.
- the means for recovering the solid part is not particularly limited, but preferably includes a centrifugal separation of 1200 G to 5000 G, a filter press, and an Oliver filter. In this process, most of the fermentation product ethanol is recovered as a liquid part.
- the yeast recovery rate in step (4) is not particularly limited, but is preferably 50% or more.
- the percentage of residual bands such as lignin and ash is not particularly limited, but is preferably 10% or less.
- the cycle comprising the above steps (1) to (4) is repeated twice or more, preferably 6 times or more.
- the yeast obtained at the said process (4) is utilized as all or one part of the yeast of the process (3) of the next cycle.
- the proportion of yeast obtained in step (4) is 50% by mass to 100% by mass, preferably 80% by mass to 100% by mass.
- Example 1 Ethanol fermentation 1 using rice straw
- Process 1 Hydrothermal treatment of rice straw
- Rice straw is mixed with water to a content of about 20% by mass (dry mass), and this is mixed into a hydrothermal treatment apparatus (manufactured by Mitsubishi Heavy Industries, Ltd.) at about 180 ° C. and about 3 MPa for 5 minutes to 20 minutes. Processed. Subsequently, solid content was isolate
- Step 2 Enzyme treatment
- the composition is shown in Table 1.
- This enzyme treatment solution is put into a 50 mL plastic test tube (Corning), and the enzyme treatment is performed at 50 ° C. and a rotation speed of 35 rpm using a thermoblock rotator (Nisshin Rika Co., Ltd., SN-06BN). went.
- Yeast Saccharomyces cerevisiae TJ14 strain (Moucamnerd et al., Appl. Microbiol. Biotechnol., 2010, Vol. 88, p. 87-94) was used for fermentation.
- yeast seed culture is performed overnight in a tester containing 5 mL of YPD liquid medium (yeast extract 10 g / L, polypeptone 20 g / L, glucose 20 g / L), and then the culture solution is a flask containing 500 mL of YPD liquid medium.
- the main culture was performed for 2 days. This culture solution was centrifuged (3000 rpm, 4 ° C., 10 minutes), and the yeast cells were washed twice with sterile distilled water and then suspended in sterile distilled water so that the cell concentration was 100 g wet weight / L. .
- the ethanol concentration produced in the fermentation broth was quantified over time by HPLC (High performance liquid chromatography system; Hitachi High-Tech Fielding, LaChrom Elite).
- HPLC High performance liquid chromatography system; Hitachi High-Tech Fielding, LaChrom Elite.
- ULTON PS-80H (Shinwa Kako Co., Ltd., 300 mm (L) ⁇ 8 mm (ID)) was used as the HPLC separation column, and ultrapure water (purified water using Milli-Q manufactured by Millipore Japan) was used as the mobile phase.
- a refractive index detector was used as the detector.
- the HPLC conditions were a liquid feed rate of 0.9 mL / min and a column temperature of 50 ° C.
- yeast cell concentration in the fermentation broth to a YPD agar medium (YPD liquid medium with 20 g / L agar added), culturing at 30 ° C. for 2 days, and counting the number of colonies Quantified over time.
- YPD agar medium YPD liquid medium with 20 g / L agar added
- the yeast cell concentration was 1.5 g wet weight / L (7.6 ⁇ 10 6 cells / mL: at the start of the second cycle of ethanol fermentation).
- fermentation was started at 37 ° C. in the same manner as in Step 3 above.
- the ethanol concentration and the yeast cell concentration in the fermentation broth were quantified over time.
- the yeast cell concentration at the end of the second cycle of ethanol fermentation was 6.4 g wet weight / L (3.2 ⁇ 10 7 cells / mL), which was increased from the start of fermentation.
- FIG. 1 shows the results of quantifying the ethanol concentration produced in the fermentation broth and the yeast cell concentration over time.
- ethanol fermentation could be continued without any problems even if the yeast was reused and the fermentation was repeated 4 to 6 times. It was not necessary to add additional yeast prepared separately.
- the solid part containing yeast after the end of each fermentation cycle is charged at a rate of 10% by mass to 20% by mass with respect to the fermentation liquid of the next cycle, so that the yeast cell concentration in the fermentation liquid is constant (each fermentation It was found that ethanol fermentation can be performed for a long period of time while being maintained at about 10 6 pieces / mL to about 10 7 pieces / mL at the start of the cycle and 10 7 pieces / mL or more at the end.
- Example 2 Ethanol fermentation 2 using rice straw
- Step 4 of Example 1 filtration was performed using a hydra sieve (manufactured by Toyo Screen Industry Co., Ltd .; 0.1 mm screen) instead of centrifuging at a low rotation speed (100 G) using a centrifuge.
- the experiment was conducted in the same manner as in Example 1 except that.
- the collected filtrate (liquid part) was 85% by mass.
- Example 3 Ethanol fermentation 3 using rice straw
- Step 4 of Example 1 instead of centrifuging at a low rotation speed (100 G) using a centrifuge, a microseparator (TSK-80 basket type centrifuge; ⁇ : 31 m 2 , bowl capacity: 7 L
- Disc-type centrifuge instead of centrifuging at a liquid flow rate of 50 L / H using a solid space: 4.8 L
- the experiment was conducted.
- the supernatant (liquid part) recovered by the first centrifugation was 83% by mass.
- the precipitate (solid part) recovered by the second centrifugation was 25% by mass.
- Table 3 shows the yeast cell concentration
- the yeast cell concentration in the supernatant (liquid part) collected from the microseparator was 6.4 ⁇ 10 6 cells / mL, and the supernatant collected from the disk-type centrifuge ( There was almost no yeast in the liquid part) and a large amount of yeast (5.7 ⁇ 10 7 / mL) in the precipitate (solid part).
- the yeast cell concentration in this solid part is capable of ethanol fermentation even when the solid part is charged at a rate of 10% by mass to 20% by mass with respect to the fermentation liquid of the next cycle. Cell density. Accordingly, it was found that ethanol fermentation can be performed for a long period of time by reusing the yeast separated by the solid-liquid separation method of the above Examples.
- Example 4 Ethanol fermentation 4 using rice straw
- Step 2 of Example 1 instead of 5.0 mL of 10 ⁇ YP, corn steep liquor (CSL) was added to 0.0625% by mass with respect to the total amount (mL) of the enzyme treatment solution. Then, ethanol fermentation was performed in the same manner as in Example 1 except that the enzyme treatment solution was prepared.
- CSL corn steep liquor
- Example 5 Ethanol fermentation 5 using rice straw
- Ethanol fermentation was performed in the same manner as in Example 4 except that the enzyme treatment solution was prepared by adding corn steep liquor to 0.125% by mass with respect to the total amount (mL) of the enzyme treatment solution. It was.
- the results of quantifying the ethanol concentration produced in the fermentation broth over time are shown in FIG.
- Example 6 Ethanol fermentation 6 using rice straw
- Ethanol fermentation was performed in the same manner as in Example 4 except that the enzyme treatment solution was prepared by adding corn steep liquor to 0.25 mass% with respect to the total amount (mL) of the enzyme treatment solution. It was. The results of quantifying the ethanol concentration produced in the fermentation broth over time are shown in FIG.
- Example 7 Ethanol fermentation 7 using rice straw
- Ethanol fermentation was carried out in the same manner as in Example 4 except that the corn steep liquor was added to 0.5% by mass with respect to the total amount (mL) of the enzyme-treated solution to prepare the enzyme-treated solution. It was.
- the results of quantifying the ethanol concentration produced in the fermentation broth over time are shown in FIG.
- corn steep liquor was 0.125% by mass (Example 5), 0.25% by mass (Example 6) and 0. 0% with respect to the total amount (mL) of the enzyme-treated solution. When it added so that it might become 5 mass% (Example 7), even if it repeated a fermentation cycle, it was able to perform ethanol fermentation stably.
- corn steep liquor was added to 0.0625% by mass (Example 4) with respect to the total amount (mL) of the enzyme-treated solution, the ethanol concentration decreased after the third and fourth fermentation cycles. However, no decrease was observed in the ethanol concentration after the end of the first and second fermentation cycles. From this, it can be seen that ethanol fermentation was sufficiently performed even when an inexpensive nutrient source such as corn steep liquor was used instead of an expensive nutrient source such as YP.
- Example 8 Ethanol fermentation 1 using bagasse
- Step 1 of Example 1 instead of rice straw as a raw material, bagasse was used.
- Step 2 instead of 5.0 mL of 10 ⁇ YP in the enzyme treatment solution, corn steep liquor was used as a whole solution of the enzyme treatment solution.
- Ethanol fermentation was carried out in the same manner as in Example 1 except that the enzyme treatment solution was prepared by adding 0.25 mass% with respect to the amount (mL). The results of quantifying the ethanol concentration produced in the fermentation broth over time are shown in FIG.
- Example 9 Ethanol fermentation 2 using bagasse
- Ethanol fermentation was carried out in the same manner as in Example 8 except that corn steep liquor was added to 0.5% by mass with respect to the total amount (mL) of the enzyme-treated solution to prepare the enzyme-treated solution. It was.
- the results of quantifying the ethanol concentration produced in the fermentation broth over time are shown in FIG.
- Example 10 Ethanol fermentation 3 using bagasse
- Ethanol fermentation was performed in the same manner as in Example 8 except that the enzyme treatment liquid was prepared by adding corn steep liquor to 1% by mass with respect to the total amount (mL) of the enzyme treatment liquid.
- the results of quantifying the ethanol concentration produced in the fermentation broth over time are shown in FIG.
- Examples 11 to 14 ethanol fermentation using napier grass
- Step 1 Napiergrass pressing and steaming
- Napiergrass is squeezed with a uniaxial extruder under conditions of 79.7 N ⁇ m to remove unnecessary liquid in advance, impregnated with 1% by mass of sulfuric acid to the residue, and at 180 ° C. under a pressure of 1.0 Mpa. Steamed for 30 minutes. Subsequently, solid content was isolate
- Step 2 Enzyme treatment
- corn steep liquor 1.0 mass% or 0.1 mass% (concentration with respect to the total volume of the enzyme treatment liquid) or water as a nutrient source in the enzyme treatment liquid, obtained in step 1.
- About 48 mL of four kinds of enzyme-treated liquids containing pressed napiergrass and steamed solids were prepared (Examples 11 to 14). The composition is shown in Table 4.
- PGK406AG Japanese Patent Laid-Open No. 2011-142879
- PGK406AG Japanese Patent Laid-Open No. 2011-142879
- genomic DNA was extracted from cultured cells of Talamomyces funiculosus.
- a primer SalI-ssFaeA-Fw (SEQ ID NO: 1) containing a secretory signal sequence of a glucoamylase gene derived from Rhizopus oryzae and a primer SalI-FaeA-Rv (SEQ ID NO: 2) PCR was performed.
- the gene fragment thus obtained was digested with SalI and inserted into the SalI site of pGK406AG to construct plasmid pGK406-ssFaeA-AG.
- PAUR101 (Takara Bio Inc.) was used as a vector to be introduced into yeast.
- the primer pAuR101-SphI-Fw was used with pGK406-ssFaeA-AG as a template. PCR was performed using (SEQ ID NO: 3) and primer pAuR101-SphI-Rv (SEQ ID NO: 4).
- This gene fragment was inserted into pAUR101 cleaved with SphI using In-Fusion HD Cloning Kit (manufactured by Takara Bio Inc.) to construct a plasmid pAUR101-pGK-ssFaeA-AG for display on the surface of FaeA yeast.
- This pAUR101-pGK-ssFaeA-AG was digested with StuI and transformed into yeast (Saccharomyces cerevisiae TJ14 strain) using YAST MAKER yeast transformation system (Clontech Laboratories, Palo Alto, California, USA), A (Aureobasidin A) resistant strain was obtained, and FaeA surface display yeast was obtained.
- the obtained FaeA surface display yeast was used in Examples 15 and 16 below.
- Example 15 Ethanol Fermentation 1 Using FaeA Surface Display Yeast (Process 1: Bagasse Hydrothermal Treatment) Bagasse is mixed with water to a content of about 20% by mass (dry mass), and this is put into a hydrothermal treatment apparatus (manufactured by Mitsubishi Heavy Industries, Ltd.) and treated at about 180 ° C. and about 3 MPa for 5 to 20 minutes did. Subsequently, solid content was isolate
- a hydrothermal treatment apparatus manufactured by Mitsubishi Heavy Industries, Ltd.
- Step 2 Enzyme treatment
- the composition is shown in Table 5.
- This enzyme treatment solution is put into a 50 mL plastic test tube (Corning), and the enzyme treatment is performed at 50 ° C. and a rotation speed of 35 rpm using a thermoblock rotator (Nisshin Rika Co., Ltd., SN-06BN). went.
- the yeast is seeded overnight in a test tube containing 5 mL of YPD liquid medium (liquid medium containing 10 g / L of yeast extract, 20 g / L of polypeptone and 20 g / L of glucose), and then the culture is treated with 500 mL of YPD. It moved to the flask containing a liquid medium, and main culture was performed for 2 days. This culture solution was centrifuged (3000 rpm, 4 ° C., 10 minutes), and the precipitated yeast cells were washed twice with sterilized distilled water.
- YPD liquid medium liquid medium containing 10 g / L of yeast extract, 20 g / L of polypeptone and 20 g / L of glucose
- the ethanol concentration produced in the fermentation broth was quantified over time by HPLC (Hitachi High-Tech Fielding, LaChrom Elite).
- HPLC Hakachi High-Tech Fielding, LaChrom Elite
- ULTON PS-80H (Shinwa Kako Co., Ltd., 300 mm (L) ⁇ 8 mm (ID)) was used as the HPLC separation column, and ultrapure water (purified water using Milli-Q manufactured by Millipore Japan) was used as the mobile phase.
- a refractive index detector was used as the detector.
- the HPLC conditions were a liquid feed rate of 0.9 mL / min and a column temperature of 50 ° C.
- yeast cell concentration in the fermentation broth to a YPD agar medium (YPD liquid medium with 20 g / L agar added), culturing at 30 ° C. for 2 days, and counting the number of colonies Quantified over time.
- YPD agar medium YPD liquid medium with 20 g / L agar added
- the precipitate was recovered and added to 48 mL of the enzyme treatment solution obtained in the same manner as in Step 2 above.
- yeast addition fermentation was started at 37 ° C. in the same manner as in Step 3 above.
- the ethanol concentration and the yeast cell concentration in the fermentation broth were quantified over time.
- Example 16 Ethanol fermentation using FaeA surface display yeast 2
- the FaeA surface display yeast and the control were the same as in Example 15 except that the enzyme-treated solution was prepared (Table 5) by adding the hydrothermal solid content of bagasse to 150 g / L (dry weight basis).
- Ethanol fermentation was performed using (yeast Saccharomyces cerevisiae TJ14 strain).
- FIG. 6 shows the results of quantifying the ethanol concentration produced in the fermentation broth and the yeast cell concentration over time.
- bagasse hydrothermally treated product was used at 200 g / L (Example 15) and 150 g / L (Example 16) on a dry weight basis.
- more ethanol was stably produced as compared with the wild yeast TJ14 strain.
- the yeast displaying the ferulic acid esterase on the surface promoted saccharification by cellulase of the bagasse hydrothermally treated product and showed higher ethanol production than the wild yeast TJ14 strain.
- ethanol fermentation is performed for a long period of time while maintaining the yeast cell concentration in the fermentation broth at a constant level (approximately 10 6 cells / mL to 10 7 cells / mL at the start of each fermentation cycle and 10 7 cells / mL or more at the end). I understand that I was able to.
- a certain amount of residue containing yeast is used for fermentation in the next cycle, whereby the yeast cell concentration
- the fermentation can be repeated over a long period of time without supplying new yeast, while maintaining a constant range from about 10 6 pieces / mL to about 10 7 pieces / mL to 10 7 pieces / mL or more. Since yeast is constantly growing, there is no problem that the freshness is lowered. Since the cost for newly preparing yeast can be reduced, ethanol can be produced at low cost. Moreover, the fermentation inhibition by a residue with a large specific gravity can also be suppressed.
Abstract
Description
バイオマスとは、生物資源に由来する糖質材料をいう。例えば、トウモロコシなどから得られるデンプン、サトウキビなどから得られる糖蜜(廃糖蜜)が挙げられる。リグノセルロース系バイオマスとは、主にセルロース、ヘミセルロースおよびリグニンの3種類の成分から構成されるバイオマスをいう。このうち、セルロースは、β-1,4-グルコシド結合によりグルコピラノース(グルコース)が連なった繊維状高分子であり、加水分解されて得られるグルコースが酵母などの発酵基質として利用される。
セルロース加水分解酵素は、セルロースのβ-1,4-グルコシド結合を加水分解してグルコースを生成する。この過程を糖化という。セルロース加水分解酵素としては、例えば、エンドβ-1,4-グルカナーゼ(以下、単に「エンドグルカナーゼ」という)、セロビオヒドロラーゼ、およびβ-グルコシダーゼが挙げられるが、これらに限定されない。
酵母としては、グルコースを基質としてエタノール発酵し得る限り、特に限定されない。野生株酵母であってもよいし、形質転換酵母であってもよい。形質転換酵母は、当業者が通常用いる方法により適宜作製される。
発酵終了後の発酵物は、酵母および発酵産物のエタノールのほか、原料に由来するリグニンおよび灰分などの固体も含む。すなわち、固体を含むスラリー状もまた包含される。発酵終了後の発酵物中の酵母の菌体濃度としては、特に限定されないが、例えば、最初の醗酵開始時の菌体濃度が1×107個/mL~5×108個/mL程度の場合、1×107個/mL~5×108個/mL、好ましくは、5×107個/mL~5×108個/mL、より好ましくは、1×108個/mL~5×108個/mLである。固液分離工程の組み合わせを用いて、この発酵物から酵母を効率よく回収して再利用する。固液分離工程の組み合わせとしては、特に限定されないが、好ましくは(a)発酵物の5質量%~30質量%の固体部を除去する工程(工程(4)(a))、および(b)当該工程(4)(a)で得られた残部の5質量%~30質量%の固体部を回収する工程(工程(4)(b))の組み合わせである。
この工程では、酵母を液体部に回収する。このため、工程(3)で得られた発酵物の5質量%~30質量%、好ましくは5質量%~20質量%の固体部を除去する。固体部を除去するための手段としては、特に限定されないが、好ましくは100G~1000Gの遠心分離、ハイドラシーブ、およびデカンターが挙げられる。この工程で、固体部としてリグリンおよび灰分の大半が除去される。
この工程では、酵母を固体部に回収する。工程(4)(a)で得られた残部の5質量%~30質量%、好ましくは20質量%~30質量%の固体部を回収する。固体部を回収するための手段としては、特に限定されないが、好ましくは1200G~5000Gの遠心分離、フィルタープレス、およびオリバーフィルターが挙げられる。この工程で、液体部として発酵産物のエタノールの大半が回収される。
(工程1:稲ワラの水熱処理)
稲ワラを約20質量%(乾燥質量)の含量となるように水と混合し、これを水熱処理装置(三菱重工業株式会社製)に入れ、約180℃および約3MPaにて5分間~20分間処理した。次いで、固形分を分離し、分離した固形分を発酵基質として用いた。
工程1で得られた稲ワラ水熱処理固形分を含む酵素処理液約48mLを調製した。その組成を表1に示す。
発酵には、酵母サッカロマイセス・セレビシエTJ14株(Moukamnerdら、Appl.Microbiol.Biotechnol.、2010年、第88巻、p.87-94)を用いた。
発酵開始から48時間後、発酵液を回収し、遠心分離機を用いて低回転数(100G)にて遠心分離した。20質量%の沈殿(固体部;リグニンおよび灰分を多量に含む)と80質量%の上澄み(液体部)とに分離された。次いで、上澄みを回収し、遠心分離機を用いて高回転数(1200G)にて遠心分離した。80質量%の上澄み(液体部;エタノールを含む)と20質量%の沈殿(固体部;酵母を多量に含む)とに分離された。発酵液の物質収支を表2に示す。
上記工程4を同様にさらに4回繰り返した。発酵液中に生産されたエタノール濃度および酵母の菌体濃度を経時的に定量した結果を図1に示す。
実施例1の工程4において、遠心分離機を用いて低回転数(100G)にて遠心分離したことに代えてハイドラシーブ(東洋スクリーン工業株式会社製;0.1mmスクリーン)を用いてろ過分離したこと以外は実施例1と同様に実験を行った。回収されたろ液(液体部)は85質量%であった。
実施例1の工程4において、遠心分離機を用いて低回転数(100G)にて遠心分離したことに代えてマイクロセパレータ(TSK-80バスケット型遠心分離機;Σ:31m2,ボウル容量:7L、ソリッドスペース:4.8L)を用いて通液量50L/Hにて遠心分離したこと、および遠心分離機を用いて高回転数(1200G)にて遠心分離したことに代えてディスク型遠心分離機(アルファ・ラバル社製LAPX404;Σ:5230m2,ボウル容量:2.2L,ソリッドスペース:1.1L)を用いて通液量100L/Hにて遠心分離したこと以外は実施例1と同様に実験を行った。最初の遠心分離で回収された上澄み(液体部)は83質量%であった。2回目の遠心分離で回収された沈殿(固体部)は25質量%であった。各画分中の酵母の菌体濃度を表3に示す。
実施例1の工程2において、5.0mLの10×YPに代えて、コーンスティープリカー(CSL)を酵素処理液の全体液量(mL)に対して0.0625質量%になるように添加して酵素処理液を調製したこと以外は、実施例1と同様にしてエタノール発酵を行った。
コーンスティープリカーを酵素処理液の全体液量(mL)に対して0.125質量%になるように添加して酵素処理液を調製したこと以外は、実施例4と同様にしてエタノール発酵を行った。発酵液中に生産されたエタノール濃度を経時的に定量した結果を図2に示す。
コーンスティープリカーを酵素処理液の全体液量(mL)に対して0.25質量%になるように添加して酵素処理液を調製したこと以外は、実施例4と同様にしてエタノール発酵を行った。発酵液中に生産されたエタノール濃度を経時的に定量した結果を図2に示す。
コーンスティープリカーを酵素処理液の全体液量(mL)に対して0.5質量%になるように添加して酵素処理液を調製したこと以外は、実施例4と同様にしてエタノール発酵を行った。発酵液中に生産されたエタノール濃度を経時的に定量した結果を図2に示す。
実施例1の工程1において、原料として稲ワラに代えてバガスを用い、かつ工程2において、酵素処理液中の5.0mLの10×YPに代えて、コーンスティープリカーを酵素処理液の全体液量(mL)に対して0.25質量%になるように添加して酵素処理液を調製したこと以外は、実施例1と同様にしてエタノール発酵を行った。発酵液中に生産されたエタノール濃度を経時的に定量した結果を図3に示す。
コーンスティープリカーを酵素処理液の全体液量(mL)に対して0.5質量%になるように添加して酵素処理液を調製したこと以外は、実施例8と同様にしてエタノール発酵を行った。発酵液中に生産されたエタノール濃度を経時的に定量した結果を図3に示す。
コーンスティープリカーを酵素処理液の全体液量(mL)に対して1質量%になるように添加して酵素処理液を調製したこと以外は、実施例8と同様にしてエタノール発酵を行った。発酵液中に生産されたエタノール濃度を経時的に定量した結果を図3に示す。
(工程1:ネピアグラスの圧搾および蒸煮)
ネピアグラスを一軸エクストルーダーによって79.7N・mの条件で圧搾して不要な液体分をあらかじめ取り除き、残渣に対して1質量%の硫酸を含浸させ、1.0Mpaの圧力下、180℃にて30分間蒸煮した。次いで、固形分を分離し、分離した固形分を発酵基質として用いた。
酵素処理液中の栄養源として、1×YP、コーンスティープリカー1.0質量%または0.1質量%(酵素処理液の全体液量に対する濃度)あるいは水を使用して、工程1で得られたネピアグラスの圧搾および蒸煮固形分を含む4種の酵素処理液約48mLをそれぞれ調製した(実施例11~14)。その組成を表4に示す。
遺伝子発現に必要なプロモーターとターミネーター、および酵母表層提示に必要なα-アグルチニン遺伝子を含むプラスミドとしてpGK406AG(特開2011-142879号公報)を用いた。FaeAをクローニングするために、タラモマイセス・フニクロサス(Talaromyces funiculosus)培養菌体からゲノムDNAを抽出した。このゲノムDNAを鋳型として、リゾプス・オリゼ(Rhizopus oryzae)由来グルコアミラーゼ遺伝子の分泌シグナル配列を含むプライマーSalI-ssFaeA-Fw(配列番号1)と、プライマーSalI-FaeA-Rv(配列番号2)とを用いてPCRを行った。これにより得られた遺伝子断片をSalIで消化し、pGK406AGのSalIサイトに挿入することでプラスミドpGK406-ssFaeA-AGを構築した。
(工程1:バガスの水熱処理)
バガスを約20質量%(乾燥質量)の含量となるように水と混合し、これを水熱処理装置(三菱重工業株式会社製)に入れ、約180℃および約3MPaにて5分間~20分間処理した。次いで、固形分を分離し、分離した固形分を発酵基質として用いた。
工程1で得られたバガス水熱処理固形分を含む酵素処理液約48mLを調製した。その組成を表5に示す。
発酵には、調製例1で得られたFaeA表層提示酵母を用いた。なお、コントロールとして、酵母サッカロマイセス・セレビシエTJ14株を用いてエタノール発酵を行った。
発酵開始から48時間後、発酵液を回収し、遠心分離機を用いて低回転数(100G)にて遠心分離した。20質量%の沈殿(固体部;リグニンおよび灰分を多量に含む)と80質量%の上澄み(液体部)とに分離された。次いで、上澄みを回収し、遠心分離機を用いて高回転数(1200G)にて遠心分離した。80質量%の上澄み(液体部;エタノールを含む)と20質量%の沈殿(固体部;酵母を多量に含む)とに分離した。
上記工程4を同様にさらに2回繰り返した。発酵液中に生産されたエタノール濃度およびの酵母の菌体濃度を経時的に定量した結果を図5に示す。
バガスの水熱処理固形分を150g/L(乾燥重量基準)になるように添加して酵素処理液を調製(表5)したこと以外は、実施例15と同様にして、FaeA表層提示酵母およびコントロール(酵母サッカロマイセス・セレビシエTJ14株)を用いてエタノール発酵を行った。発酵液中に生産されたエタノール濃度および酵母の菌体濃度を経時的に定量した結果を図6に示す。
Claims (7)
- リグノセルロース系バイオマスからのエタノールの生産方法であって、
(1)リグノセルロース系バイオマスを前処理する工程、
(2)工程(1)で得られたセルロース画分をセルロース加水分解酵素で処理する工程、
(3)工程(2)で得られた糖化バイオマスと酵母とを混合してエタノール発酵する工程、および
(4)工程(3)で得られた発酵物を固液分離する工程
を含み、
工程(1)、(2)、(3)および(4)からなるサイクルを2回以上繰り返し、そして
工程(4)で得られた酵母を、次のサイクルの工程(3)の酵母の全部または一部として用いる、方法。 - 前記工程(4)が、
(a)前記発酵物の5質量%から30質量%の固体部を除去する工程、および
(b)工程(a)で得られた残部の5質量%から30質量%の固体部を回収する工程
を含む、請求項1に記載の方法。 - 前記発酵物中の酵母の菌体濃度が、107個/mL以上である、請求項1または2に記載の方法。
- 前記酵母が、フェルラ酸エステラーゼ、β-グルコシダーゼ、β-ガラクトシダーゼ、およびペクチナーゼからなる群より選択される1または2種の酵素を発現するように形質転換された酵母である、請求項1から3のいずれかに記載の方法。
- 前記酵素が、表層提示されている、請求項4に記載の方法。
- リグノセルロース系バイオマスからのエタノールの生産のための、酵母を含有する組成物であって、
該酵母が、フェルラ酸エステラーゼ、β-グルコシダーゼ、β-ガラクトシダーゼ、およびペクチナーゼからなる群より選択される1または2種の酵素を発現するように形質転換されている、組成物。 - 前記酵素が、表層提示されている、請求項6に記載の組成物。
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CA3109239A1 (en) | 2018-08-15 | 2020-02-20 | Cambridge Glycoscience Ltd | Novel compositions, their use, and methods for their formation |
JP2022545650A (ja) | 2019-08-16 | 2022-10-28 | ケンブリッジ グリコサイエンス エルティーディー | バイオマスを処理してオリゴ糖および関連組成物を生成する方法 |
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