WO2013103111A1

WO2013103111A1 - Method and apparatus for producing ethanol

Info

Publication number: WO2013103111A1
Application number: PCT/JP2012/083561
Authority: WO
Inventors: 佐藤　健治; 北野　誠; 典充金子; 健太郎成相; 伊藤　浩史; 矢野　伸一; 遠藤　貴士
Original assignee: 株式会社Ihi; 独立行政法人産業技術総合研究所
Priority date: 2012-01-06
Filing date: 2012-12-26
Publication date: 2013-07-11
Also published as: JP2015084650A

Abstract

Provided are a method and apparatus that efficiently saccharify and ferment hemicellulose contained in woody materials and the like and produce ethanol that can be converted into biomass ethanol. Pressurized hot water is caused to act on a biomass, the hemicellulose contained in the biomass is selectively degraded, a solid acid catalyst is caused to act on the degradation product at a temperature of 90-110°C, and a saccharified product containing xylose is obtained. Microorganisms having the ability to ferment xylose are caused to act on the resulting saccharified product, and ethanol is produced.

Description

Ethanol production method and production apparatus

The present invention relates to a method and apparatus for producing ethanol, and in particular, a method for producing ethanol that produces biomass ethanol by saccharification of lignocellulosic material and microbial fermentation using plant waste such as wood and wheat straw as biomass, and It relates to a manufacturing apparatus.

Recently, as a solution to the depletion of petroleum resources, biomass ethanol, which produces ethanol by fermentation of microorganisms using plant matter, has attracted attention, and various processes have been announced as its production technology. For example, Non-Patent Document 1 below discloses a process for producing ethanol by saccharifying cellulose in biomass into glucose using cellulase, which is widely known as a saccharifying enzyme, and fermenting the obtained glucose. . Patent Document 1 listed below describes a method for producing ethanol in which fine bark that has been subjected to treatment with an alkali solution of bark raw material and refined by mechanical treatment is prepared into a slurry having an appropriate pH and then subjected to concurrent saccharification and fermentation. .

Moreover, the following patent document 2 describes the treatment of biomass having a step of decomposing hemicellulose by treating cellulosic biomass with pressurized hot water, and the following patent document 3 uses pressurized hot water treatment. Have proposed a biomass processing apparatus for saccharifying cellulose and hemicellulose of cellulosic biomass.

On the other hand, in order to improve the efficiency of ethanol production from cellulosic biomass, development of microorganisms with high fermentation efficiency has been promoted, and various genetically modified yeasts have been proposed (for example, Non-Patent Document 2 below).

JP 2011-152067 A JP 2011-144337 A JP 2011-68578 A

Cellulose contained in the wood material used as lignocellulosic biomass is saccharified to glucose using cellulase and converted to ethanol by fermentation with yeast, etc., but the monosaccharide obtained from hemicellulose contained in the wood material is In addition, the conversion efficiency to ethanol in fermentation by natural yeast or the like is not so high, and there is a problem of alcohol resistance. Although the proportion of hemicellulose in the wood depends on the type of plant, it is generally around 30% and is not negligible. Therefore, in order to efficiently produce biomass ethanol at low cost, it is necessary to be able to efficiently perform hemicellulose saccharification and fermentation.

The problem to be solved by the present invention is to solve the above-mentioned problems and to provide a method for producing ethanol, which has high conversion efficiency in saccharification / fermentation of hemicellulose and can efficiently purify biomass ethanol.

In order to solve the above-mentioned problems, the present inventors have conducted extensive research. As a result, in the saccharification / fermentation of hemicellulose, an efficient method for producing biomass ethanol using xylose ethanol fermentation by genetically modified yeast is proposed. The present inventors have found that it can be configured and completed the present invention.

According to one aspect of the present invention, a method for producing ethanol includes a pressurized hot water reaction step of selectively decomposing hemicellulose contained in biomass by causing pressurized hot water to act on the biomass, and the pressurized hot water. A solid acid catalyst reaction step for obtaining a saccharification product containing xylose by allowing a solid acid catalyst to act on the decomposition product of the reaction step at a temperature of 90 to 110 ° C., and a saccharification product obtained in the solid acid catalyst reaction step The gist of the invention is to have a fermentation process in which a microorganism having xylose fermentability is allowed to act to produce ethanol.

Moreover, according to one aspect of the present invention, the ethanol production apparatus comprises a pressurized hot water reactor that selectively decomposes hemicellulose contained in biomass by causing pressurized hot water to act on the biomass, and the pressurized heat. The decomposition product of the water reactor is heated to 90 to 110 ° C. to act on a solid acid catalyst to obtain a saccharification product containing xylose, and the saccharification product obtained by the catalyst reaction device is subjected to xylose. The gist of the present invention is to have a fermentation apparatus that produces ethanol by causing a microorganism having fermentation ability to act.

According to the present invention, by introducing specific saccharification conditions in introducing yeast having good fermentation efficiency of xylose into the individual saccharification process of cellulose and hemicellulose, cellulose and hemicellulose contained in lignocellulosic biomass can be efficiently saccharified, respectively. -An ethanol production method and production apparatus capable of producing biomass ethanol by fermentation are provided, and the establishment and spread of a biomass ethanol production system is facilitated. Therefore, it is economically advantageous, the use of plant waste as biomass is promoted, and it is useful for solving energy resource problems and waste disposal problems.

The schematic block diagram which shows one Embodiment of the ethanol manufacturing apparatus which concerns on this invention. The graph which shows the relationship between the xylose ratio at the time of fermenting the mixture of xylose and glucose, and an ethanol yield. Graphs (a) to (f) showing temporal changes in the amounts of sugar and ethanol produced by the enzyme reaction in the samples (1) to (6) of the plots constituting the graph of FIG.

In the production of biomass ethanol using plant waste (lignocellulosic biomass), saccharified products obtained by hydrolysis of cellulose and hemicellulose are ethanol fermented. In the present invention, saccharification of lignocellulosic biomass, that is, hydrolysis, is carried out in three types of processes: a pressurized hydrothermal reaction, a saccharifying enzyme reaction, and a solid acid catalytic reaction. In the pressurized hot water reaction, selective hydrolysis of hemicellulose proceeds, and in the saccharification enzyme reaction, hydrolysis of cellulose, which is a residue of pressurized hot water reaction, proceeds. ~ Partially decomposed polysaccharide is produced, and part of it is monosaccharide (primary saccharification). By subjecting the primary saccharified solution resulting from the hydrolysis reaction to a solid acid catalytic reaction, it is sufficiently saccharified to produce monosaccharides such as glucose and xylose (secondary saccharification). Monosaccharides obtained by such a saccharification process are fermented to produce ethanol.

Glucose fermentation proceeds easily with conventionally known fermentation microorganisms such as natural yeast, but the microorganisms that can be used for fermentation of hemicellulose-derived xylose are limited, and the yield of ethanol is low. In the present invention, a saccharification condition of hemicellulose is set so that a saccharified product suitable for the fermentation can be obtained by utilizing a recently developed microorganism having excellent xylose fermentability.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of an ethanol production apparatus according to the present invention. The ethanol production apparatus A is a monosaccharide production apparatus that saccharifies biomass B to produce a monosaccharide, a fermentation apparatus that ferments a saccharification product to produce ethanol, and distills the fermentation product to purify ethanol E. And a distillation apparatus 9. The monosaccharide production apparatus includes a pressurized hot water reaction apparatus 1, a solid-liquid separator 2, a cooler 3, an enzyme reaction apparatus 4, a first catalytic reaction apparatus 5, and a second catalytic reaction apparatus 7, and the first catalytic reaction. The device 5 hydrolyzes (saccharifies) a partially saccharified product derived from cellulose, and the second catalytic reaction device 7 hydrolyzes (saccharifies) a partially saccharified product derived from hemicellulose. The fermentation apparatus includes a first fermentation apparatus 6 that ferments a saccharified product derived from cellulose to produce ethanol, and a second fermentation apparatus 8 that ferments a saccharified product derived from hemicellulose to produce ethanol, which are generated from each. The fermentation products F1 and F2 are distilled by the distillation apparatus 9 to separate and purify ethanol.

The pressurized hot water reactor 1 includes a pump 1a, a heater 1b, a water amount adjusting valve 1c, a pressure-resistant reaction tank 1d, and a control device 1e. The pump 1a pressurizes and heats water supplied from the outside. To device 1b. The heater 1b heats the pressurized water flowing from the pump 1a to 150 to 230 ° C., preferably about 200 to 230 ° C., in accordance with a temperature control signal input from the control device 1e, and pressurizes hot water W ′ (pressure Hot water in a subcritical state of about 0.47 to 2.8 MPa, preferably about 1.6 to 2.8 MPa), which is supplied to the reaction tank 1d containing the biomass via the water amount adjusting valve 1c. . The water amount adjusting valve 1c is an electronic control valve whose opening degree can be adjusted in accordance with a flow rate control signal input from the control device 1e, and the flow rate of the pressurized hot water W ′ supplied from the heater 1b to the reaction tank 1d. Adjust appropriately. The control device 1e adjusts the temperature and flow rate of the pressurized hot water W ′ supplied to the reaction tank 1d by the temperature control signal output to the heater 1b and the water amount control signal output to the water amount adjustment valve 1c. The biomass hydrolysis conditions in the reaction tank 1d are controlled as described above. The hydrolysis conditions are, for example, the ratio K (= Q / V) between the supply amount Q (ml) of pressurized hot water W ′ and the biomass supply amount V (g), and the temperature T (° C. of pressurized hot water W ′. ) Can be set. Energy efficiency can be improved by providing a heat exchanger that recovers the thermal energy of hot water discharged from the reaction tank 1d and supplies it to the water supplied to the heater 1b.

The reaction tank 1d accommodates a certain amount of biomass supplied as a raw material from the outside, and adds and acts on the pressurized hot water W ′ supplied through the water amount adjusting valve 1c to the biomass, so that hemicellulose contained in the biomass is selected. It is hydrolyzed and solubilized. Compared to the fact that cellulose requires a temperature of about 240 to 300 ° C. when hydrolyzed with pressurized hot water, hemicellulose is easily decomposed and solubilized at about 230 ° C. or lower, which is lower than that of cellulose. By treating the biomass in the water reactor 1 at 150 to 230 ° C., preferably 200 to 230 ° C., the hemicellulose contained in the biomass is selectively partially decomposed and solubilized to become a hydrous liquid of polysaccharides containing oligosaccharides. The reaction product is a mixture of a water-containing liquid containing oligosaccharides derived from hemicellulose and a solid residue containing cellulose and lignin that do not decompose. The supply form of pressurized hot water in the reaction tank 1d may be a continuous water supply system or a batch system, but is configured so that the pressurized hot water can stay in the tank for about 5 to 120 minutes. If pressurized hot water of about 120 to 200 ° C. is supplied before the above-mentioned pressurized hot water is supplied, lignin can be easily separated.

The reaction product discharged from the pressurized hot water reactor 1 is supplied to the solid-liquid separator 2 and separated into a liquid saccharified portion of the hemicellulose-derived decomposition product and a solid residue S containing cellulose and lignin. The solid residue S is processed by the enzyme reaction device 4 and the first catalytic reaction device 5 after being supplied to the cooler 3. The liquid saccharified product part is supplied to the second catalytic reactor 7 as the primary saccharified solution H1 of hemicellulose.

The cooler 3 cools the high-temperature solid residue S after the pressurized hot water reaction, adjusts it to a temperature suitable for the subsequent enzyme reaction, and generally cools it to about 50 to 100 ° C. Energy efficiency is improved by providing a heat exchanger that recovers thermal energy from the refrigerant used in the cooler 3 and makes it available for heating water in the pressurized hot water reactor 1.

The solid residue S adjusted to an appropriate temperature by the cooler 3 is supplied to the enzyme reaction device 4. The enzyme reaction apparatus 4 is equipped with a stirrer and a temperature control mechanism, and cellulase, which is a saccharifying enzyme, is added to and mixed with the solid residue S whose water content has been adjusted so that stirring is possible as necessary, so that the enzyme is activated at a temperature. By maintaining and stirring, cellulose in the solid residue S is hydrolyzed by the action of cellulase, and a degradation product mainly composed of a suspended polysaccharide or cellobiose (a dimer of glucose) that is a partial saccharified product of cellulose. Is obtained as the primary saccharified solution C1. Cellulase is generally known as an assembly of a plurality of types of saccharifying enzymes, and contains β-glucanase as a main component. β-glucanase is known as a saccharifying enzyme that hydrolyzes cellulose into insoluble suspended polysaccharide (having a higher degree of polymerization than water-soluble oligosaccharide) and water-soluble oligosaccharide (glucose dimer to hexamer). . The primary saccharified liquid C1 contains a water-soluble oligosaccharide (mainly cellobiose) and a water-insoluble suspended polysaccharide, and is a fluid liquid in which the suspended polysaccharide is dispersed in a water-containing liquid of the water-soluble oligosaccharide. The suspended polysaccharide is a partially decomposed product of cellulose, specifically, suspended particles containing cellohexaose crystals that are a glucose polymer having a polymerization degree of 7 or more and a hexamer of glucose. It can be decomposed into glucose by a catalytic reaction. The temperature of the enzyme reaction apparatus 4 is appropriately adjusted within the optimum pH and the optimum temperature range of about 40 to 90 ° C. so as to obtain an appropriate enzyme activity according to the saccharifying enzyme to be used. In order to facilitate the temperature adjustment of the enzyme reaction apparatus 4, it is preferable that the temperature of the solid residue S introduced into the enzyme reaction apparatus 4 is about 90 to 100 ° C., and the temperature is appropriately adjusted by the cooler 3 in the previous stage. . When a thermostable enzyme is used, the cooling capacity of the cooler can be reduced.

If the solid residue S before being supplied to the enzyme reaction apparatus 4 is subjected to beating and defibration / softening, the specific surface area of the solid residue increases and the saccharification of the saccharifying enzyme is facilitated. The amount used can be reduced, and the saccharification efficiency in the cellulosic saccharification process including the subsequent solid acid catalysis is improved.

The primary saccharified solution C1 of cellulose produced in the enzyme reaction apparatus 4 is supplied to the first catalytic reaction apparatus 5. If necessary, a separation device such as a belt press may be provided in front of the first catalytic reactor 5 as a means for removing solid residues (lignin and the like) that may remain in the primary saccharified liquid C1. The first catalytic reaction device 5 includes a first mixing device 5a having a temperature control mechanism and a first solid-liquid separation device 5b, and the primary saccharified solution C1 is 90 ° C. or higher and lower than 120 ° C. in the first mixing device 5a. Mix and stir with solid acid catalyst X at temperature. The oligosaccharide and the suspended polysaccharide of the primary saccharified liquid C1 are hydrolyzed by the action of the solid acid catalyst X to produce glucose (monosaccharide constituting cellulose), and the reaction product contains glucose as a main component. A mixture of the secondary saccharified solution C2 and the solid acid catalyst X is obtained.

The reaction product that has finished the hydrolysis reaction in the first mixing device 5a is charged into the first solid-liquid separation device 5b and separated into solid and liquid. Thereby, the secondary saccharified solution C2 containing glucose as a main component is separated as a supernatant and sent to the first fermentation apparatus 6. The solid acid catalyst X that has settled and separated is recovered and then returned to the first mixing device 5a to be used again. The 1st solid-liquid separation apparatus 5b should just be what can generally be used as a sedimentation tank.

The secondary saccharified solution C2 supplied from the first solid-liquid separation device 5b to the first fermentation device 6 is appropriately adjusted in water content and pH so as to be in a condition suitable for fermentation, and inoculated with fermenting microorganisms, and the fermentation stock solution The glucose is converted into ethanol by the action of the fermentation microorganism. As a fermentation microorganism used for ethanol fermentation, an ethanol fermentation microorganism having a known glucose fermentation ability such as yeast can be used. It is preferable to add a nutrient source necessary for the propagation and activity of fermenting microorganisms. If necessary, a temperature control mechanism for maintaining the temperature at which fermentation is likely to proceed may be provided.

The purified product F1 discharged from the first fermentation apparatus 6 is supplied to the distillation apparatus 9 and distilled to recover purified ethanol. The fermentation product F1 contains a solid substance, and may be distilled as it is without removing it. If necessary, if a filtration device for removing solids (lignin, fermentation microorganisms, etc.) from the fermentation product F1 is provided, only the liquid product can be distilled. The solid matter separated from the fermentation product F1 by filtration or the like may be introduced into the biomass saccharification step.

On the other hand, the hemicellulose-derived primary saccharified solution H1 separated by the solid-liquid separator 2 is supplied to the second catalytic reaction device 7. If necessary, a separation device for removing a solid dispersion (such as lignin) that may be mixed in the primary saccharified solution H1 may be provided in the front stage of the second catalytic reaction device 7. The second catalytic reaction device 7 includes a second mixing device 7a having a temperature control mechanism and a second solid-liquid separation device 7b, and the primary saccharified solution H1 is 90 ° C. or higher and lower than 120 ° C. in the second mixing device 7a. Mix and stir with solid acid catalyst X at temperature. The hemicellulose-derived oligosaccharides in the primary saccharified solution H1 are hydrolyzed by the action of the solid acid catalyst X to produce monosaccharides including xylose, arabinose (pentose sugar constituting hemicellulose), etc., and secondary saccharification including these Since the liquid H2 is obtained, the reaction product is a mixture of the secondary saccharified liquid H2 containing xylose and the solid acid catalyst X. The solid acid catalyst X used in the second catalytic reactor 7 may be appropriately selected from the same or different from those usable in the first catalytic reactor 5.

The reaction product that has finished the hydrolysis reaction in the second mixing device 7a is charged into the second solid-liquid separation device 7b, and the solid acid catalyst X in the charged reaction product is allowed to settle, so that The secondary saccharified liquid H2 is separated and sent to the second fermentation apparatus 8. The solid acid catalyst X that has settled and separated is recovered and then returned to the second mixing device 7a to be used again. The second solid-liquid separator 7b may be anything that can generally be used as a precipitation tank.

The secondary saccharified solution H2 supplied from the second solid-liquid separation device 7b to the second fermentation device 8 is appropriately adjusted in water content and pH so as to be in a condition suitable for fermentation, inoculated with fermenting microorganisms, and the fermentation stock solution And xylose or the like is converted into ethanol by the action of the fermentation microorganism. The fermentation microorganism used is a microorganism having xylose fermentation ability. It is preferable to add a nutrient source necessary for the propagation and activity of fermenting microorganisms. If necessary, a temperature control mechanism for maintaining the temperature at which fermentation is likely to proceed may be provided.

The purified product F2 discharged from the second fermentation apparatus 8 is supplied to the distillation apparatus 9 and distilled to recover purified ethanol. Fermentation product F2 contains a solid substance and may be distilled as it is without removing it. If necessary, if a filtration device for removing solids (lignin, fermentation microorganisms, etc.) from the fermentation product F2 is provided, only the liquid product can be distilled. The solid matter separated from the fermentation product F2 by filtration or the like may be introduced into the biomass saccharification step. The distillation of the fermentation product F2 can be performed together with the fermentation product F1 obtained from the first fermentation apparatus 5 or individually.

Blow water is discharged from the reaction tank 1 d of the pressurized hot water reactor 1. Further, water generated in the process of ethanol fermentation is discharged from the first fermentation apparatus 6 and the second fermentation apparatus 8. The waste water D is supplied to the waste water treatment apparatus 10 and appropriately subjected to purification treatment, and then discharged to the outside.

A method for producing ethanol performed in the ethanol production apparatus configured as described above will be described below.

The biomass B used as a raw material may be any lignocellulosic material, for example, woody materials such as wood, thinned wood, bark, herbs such as rice straw, wheat straw, rice husk, pulp, waste paper, cotton cloth, linen And fiber materials such as artificial cellulose materials, and in particular, plant materials such as wood materials containing hemicellulose can be efficiently saccharified and fermented. From the viewpoint of reaction efficiency, it is preferable to pulverize such biomass B into a granular or powder form in advance, and it is preferable to prepare particles having a particle diameter of about 5 mm or less.

In the pressurized hot water reactor 1, a certain amount of biomass supplied as a raw material from the outside is accommodated in the reaction tank 1d, the heater 1b is adjusted by a temperature control signal input from the controller 1e, and the pump 1a The pressurized water flowing in from is heated to about 150 to 230 ° C., preferably about 190 to 210 ° C., to form pressurized hot water W ′ (for example, subcritical hot water having a pressure of about 1.3 to 1.9 MPa). It is supplied to the reaction tank 1d containing the biomass through the regulating valve 1c. The flow rate of the pressurized hot water W 'supplied from the heater 1b to the reaction tank 1d is adjusted appropriately by adjusting the opening of the water amount adjusting valve 1c by a flow rate control signal input from the control device 1e. When pressurized hot water is added to and acted on biomass, hemicellulose contained in the biomass is selectively hydrolyzed and solubilized and liquefied. The woody material is lignocellulosic biomass containing cellulose as the main component and containing hemicellulose and lignin. When hydrolyzed with pressurized hot water, cellulose is hemicellulose compared with the case where it requires a temperature of about 240 to 300 ° C. Is easily decomposed and solubilized at about 150 to 230 ° C., which is lower than that of cellulose. Therefore, a reaction product obtained by treating a wooden material with a pressurized hydrothermal reactor contains a xylooligosaccharide partially decomposed and solubilized from hemicellulose. A solid-liquid mixture containing a saccharide-containing liquid and a solid residue of cellulose and lignin that does not decompose is obtained. Pressurized hot water may be supplied either continuously or batchwise. However, in the case of continuous water flow, the water flow rate should be set so that the residence time in the tank is 5 to 120 minutes. Adjust and react for about 10 to 120 minutes.

The reaction product of the pressurized hot water reactor 1 is supplied to the solid-liquid separator 2 and separated into the liquid portion of the hemicellulose decomposition product and the solid residue S containing cellulose and lignin. The liquid part is supplied to the second catalytic reactor 7, and the solid residue S is supplied to the cooler 3.

In the cooler 3, the solid residue S supplied from the solid-liquid separator 2 is cooled and adjusted to a temperature suitable for the subsequent enzyme reaction. In order to easily control the temperature of the enzyme reaction apparatus 4, it is preferable that the temperature of the solid residue S introduced into the enzyme reaction apparatus 4 is about 50 to 100 ° C. Adjust as appropriate. When a thermostable enzyme is used, the cooling capacity of the cooler can be reduced.

The solid residue S whose temperature has been adjusted by the cooler 3 is supplied to the enzyme reaction apparatus 4, and an aqueous liquid containing cellulase, which is a saccharifying enzyme, is added and mixed to maintain the enzyme at an active temperature. The cellulose in the solid residue S is decomposed by the action of cellulase, and as a primary saccharified solution C1 of cellulose, a decomposition product mainly containing cellobiose (a dimer of glucose) which is a water-soluble oligosaccharide is obtained. Cellulase is generally known as an assembly of a plurality of types of saccharifying enzymes, and contains β-glucanase as a main component. β-glucanase is known as a saccharification enzyme that hydrolyzes cellulose into water-soluble oligosaccharides (glucose dimer to hexamer). Cellobiose, which is a part of the water-soluble oligosaccharide, is decomposed into glucose by β-glucosidase contained in cellulase. The primary saccharified liquid C1 contains a water-soluble oligosaccharide and a water-insoluble suspended polysaccharide, and is a fluid liquid in which the suspended polysaccharide is dispersed in a water-containing liquid of the water-soluble oligosaccharide. Suspended polysaccharide is a partial degradation product of cellulose, and is a cellulohexaose crystal, which is a glucose polymer with a polymerization degree of 7 to 3000 and glucose hexamer, and is decomposed into glucose by the subsequent solid acid catalyzed reaction. Is possible.

As the saccharifying enzyme used in the enzyme reaction apparatus 4, a commercially available saccharifying enzyme can be used, and a commercially available saccharifying enzyme can also be used. The normal saccharifying enzyme has the maximum enzyme activity at about 40 to 50 ° C., and the thermostable enzyme has the maximum enzyme activity at about 70 to 90 ° C. Therefore, the temperature of the enzyme reaction apparatus 4 depends on the saccharifying enzyme used. Depending on the conditions, appropriate adjustments may be made to obtain an appropriate enzyme activity. When a thermostable enzyme is used, the cooling capacity of the cooler can be reduced, and the temperature of the enzyme reaction device 4 and the temperature of the first mixing device 5a can be brought close to each other. Can improve.

The amount of saccharifying enzyme used in the enzyme reaction apparatus 4 is set at a rate of 0.025 to 0.15 g / g, preferably 0.5 to 0.1 g / g, based on the mass (dry) of the solid residue S. Unreacted cellulose can be substantially exhausted by the reaction for 12 to 72 hours, preferably 24 to 48 hours. When the solid residue before the enzyme reaction is subjected to beating treatment and defibration and softening, the enzyme reaction can be completed within about 12 hours using a small amount of enzyme of 0.25 g or less per gram of cellulose. The amount of monosaccharide from the suspended polysaccharide of the primary saccharified solution C1 is increased by the subsequent solid acid catalyzed reaction, and the monosaccharide recovery rate is increased.

When the primary saccharified liquid C1 produced in the enzyme reaction apparatus 4 is mixed and stirred with the solid acid catalyst X at a temperature of 90 ° C. or higher and lower than 120 ° C. in the first mixing apparatus 5a, the oligosaccharide and suspension of the primary saccharified liquid C1 are mixed. The polysaccharide is hydrolyzed satisfactorily by the action of the solid acid catalyst X to produce glucose (a monosaccharide constituting cellulose), and a secondary saccharified solution C2 containing glucose as a main component is obtained. Examples of the solid acid catalyst X to be used include inorganic solid acids such as zeolite, alumina and silica, and those in which acidic groups are introduced by sulfonation treatment of organic materials such as resins. A powdered or particulate solid acid catalyst is used. In the present invention, a sulfonated carbon type obtained by carbonizing an organic carbon material and then sulfonated is preferable. The sulfonated carbon-based solid acid catalyst is an amorphous black solid (carbide) obtained by heat-treating organic carbon materials such as woods or herbs in an inert gas atmosphere such as nitrogen. It is obtained by heat treatment in order to add a sulfone group to the carbide skeleton and washing with hot water. Carbonization and sulfonation may be performed at the same time, and the treatment temperature for carbonization and sulfonation is appropriately selected depending on the type of organic substance used. The amount of the solid acid catalyst X used is preferably 5 to 30% by mass with respect to the primary saccharified liquid C1. The reaction time may generally be about 2 to 10 hours.

The reaction product that has finished the hydrolysis reaction in the first mixing device 5a is supplied to the first solid-liquid separation device 5b, and the solid acid catalyst X in the reaction product is precipitated. The secondary saccharified solution C2 mainly composed of glucose is separated as a supernatant, sent to the first fermentation apparatus 6, and the solid acid catalyst X separated by settling is recovered and then returned to the first mixing apparatus 5a to be used again. The

The secondary saccharified solution C2 supplied from the first solid-liquid separation device 5b to the first fermentation device 6 is appropriately adjusted in water content and pH so as to be in a condition suitable for fermentation, and inoculated with fermenting microorganisms, and the fermentation stock solution The glucose is converted into ethanol by the action of the fermentation microorganism. As a fermentation microorganism used for ethanol fermentation, known ethanol fermentation microorganisms such as yeast can be used. Examples include Zymomonas mobilis and Kluyveromyces marxianus. Moreover, you may utilize the bacterium which introduce | transduced the enzyme gene which has the conversion ability to ethanol by gene recombination. The use of flocculent yeast is advantageous in solid-liquid separation after fermentation because of good sedimentation, and it is advantageous for yeast to use amino acids and the like degraded by hydrolyzing enzymes of surrounding microorganisms as nutrient sources. Since it is also a form, it is useful for improving fermentation efficiency. During fermentation, it is preferable to add a nutrient source necessary for the propagation and activity of the fermenting microorganisms and adjust to an optimum pH. In order for yeast to be active and proliferating, essential nutrients such as phosphorus, nitrogen and vitamins, and required trace elements such as Co, Ni, and Zn are necessary, and yeast used for the production of biomass ethanol is The ability to synthesize vitamins or amino acids may be low or lacking. As a nutrient source for fermentation microorganisms to which such necessary components are added from the outside, yeast extract, polypeptone and the like can be generally used. Alternatively, plant waste such as tea husk and coffee husk and algal crushed material may be used, and components contained in these cell protoplasts can be used as the nutrient source.

The saccharified product (glucose) concentration in the fermentation stock solution is adjusted to be about 1 to 20% by mass, preferably about 10% by mass. The addition amount of the nutrient source for microorganisms (in terms of dry matter) is appropriately adjusted according to the type of fermenting microorganism, and is generally set to about 0.1 to 1% by mass, preferably about 0.2 to 0.5% by mass. Good. The pH of the fermentation stock solution is adjusted to about 2.5 to 5.5, preferably about 3.0 to 5.5, inoculated with fermenting microorganisms at a rate of about 1 to 30 g / L, and a temperature of 30 to 37 ° C. The fermentation proceeds by holding for about 2 to 48 hours. For example, ethanol can be produced at a rate of about 20 to 25 g-ethanol / (L · h) using a fermentation stock solution having a glucose concentration of about 10% by mass.

The fermentation product F1 that has undergone fermentation in the first fermentation apparatus 6 as described above is subjected to distillation apparatus 9 after removing solids (lignin, fermentation microorganisms, etc.) from the fermentation product F1 as necessary, by filtration or the like. The ethanol is recovered by distillation at You may distill as it is, without removing solid content from fermentation product F1. You may introduce | transduce into the biomass saccharification process the solid substance isolate | separated from the fermentation product F1.

On the other hand, the hemicellulose-derived primary saccharified liquid H1 separated by the solid-liquid separator 2 is supplied to the second catalytic reactor 7 and the solid acid catalyst X and the primary acid catalyst X at a temperature of 90 ° C. or higher and lower than 120 ° C. in the second mixing device 7a. Mix and stir. The hemicellulose-derived oligosaccharide of the primary saccharified solution H1 and the polysaccharide which is a partial decomposition product are hydrolyzed by the action of the solid acid catalyst X to produce monosaccharides including xylose and arabinose (pentose sugar constituting hemicellulose). A secondary saccharified solution H2 containing these is obtained. In order to suppress a decrease in ethanol production efficiency in the subsequent fermentation in the second fermentation apparatus 8, it is preferable to perform the solid acid catalytic reaction at a temperature of 90 to 110 ° C, particularly around 100 ° C. At temperatures of 120 ° C. or higher, xylose decomposition tends to proceed. The solid acid catalyst X used in the second catalytic reactor 7 can be appropriately selected from the same or different from those that can be used in the first catalytic reactor 5, and after the carbonization treatment of the woods or herbs, the sulfonation treatment is performed. Use of the resulting sulfonated carbon material is preferred. The amount of the solid acid catalyst X to be used is preferably 5 to 30% by mass with respect to the primary saccharified liquid H1 as in the first catalytic reactor 5, and the reaction time may be generally about 1 to 5 hours.

The reaction product that has finished the hydrolysis reaction in the second mixing device 7a is charged into the second solid-liquid separation device 7b, where the solid acid catalyst X in the reaction product is allowed to settle, and the secondary saccharified solution H2 is used as a supernatant. To be separated. This is sent to the second fermentation apparatus 8. The solid acid catalyst X that has settled and separated is recovered and then returned to the second mixing device 7a to be used again. The secondary saccharified liquid H2 is a monosaccharide liquid mainly composed of xylose.

The secondary saccharified solution H2 supplied from the second solid-liquid separation device 7b to the second fermentation device 8 is appropriately adjusted in water content and pH so as to be in a condition suitable for fermentation, inoculated with fermenting microorganisms, and the fermentation stock solution And xylose or the like is converted into ethanol by the action of the fermentation microorganism. Examples of microorganisms having xylose fermentability include Pichia and Rhizopus oryzae. Xylose-fermenting yeast tends to decrease the fermentation rate of xylose in the presence of glucose, but the use of a genetically modified yeast having xylose-fermenting ability can improve the efficiency of producing ethanol from semi-herulose secondary saccharified solution H2. In particular, XR genes (genes encoding enzymes that catalyze the conversion reaction from xylose to xylitol), XDH genes (genes encoding enzymes that catalyze the conversion reaction from xylitol to xylulose) and XK genes (xylose and A genetically modified yeast introduced with a gene encoding an enzyme that catalyzes the conversion reaction from ATP to xylulose 5-phosphate and ADP can ferment xylose well in the presence of glucose. Such genetically modified yeasts include, for example, industrial strain IR-2 (FERM BP-754), Type-II (baker yeast) and shochu 3 (association yeast), experimental strain D452-2, It is obtained by transforming the host organism using a vector in which the above gene is incorporated according to a general molecular biological technique, using yeast such as INVSc1 strain as the host organism (see US Patent Publication No. 2011 / 0027847A1), Alternatively, it can be obtained as a genetically modified yeast (N-WT strain, N-ARSdR strain, R-WT strain, R-ARSdR strain, MA-R4 strain) provided by the National Institute of Advanced Industrial Science and Technology. Saccharomyces yeast 424A (LNH-ST) (according to Dr. Ho et al., Purdue University) also ferments xylose well in the presence of glucose. The use of flocculent yeast is advantageous in solid-liquid separation after fermentation because of good sedimentation, and it is advantageous for yeast to use amino acids and the like degraded by hydrolyzing enzymes of surrounding microorganisms as nutrient sources. Since it is also a form, it is useful for improving fermentation efficiency.

In the fermentation reaction of the secondary saccharified solution H2, the concentration of xylose in the fermentation stock solution is adjusted to 0.1 to 20%, preferably about 0.5 to 10%, and the pH is 3.0 to 7.6, preferably 5 The temperature is adjusted to about 0.0 to 6.0, and it is performed under anaerobic conditions at a temperature of about 25 to 38 ° C., preferably about 27 to 33 ° C. Yeast extract, polypeptone, or the like may be appropriately used as necessary as a nutrient source for fermentation microorganisms added from the outside as described above, and it is preferable to add about 1% yeast extract. The fermentation reaction is completed in about 48 hours or more. The fermentation time varies depending on the type of yeast and breeding conditions.

The yield of ethanol in fermentation with yeast having xylose fermentation ability is higher from glucose than that from xylose (see FIG. 2), and the fermentation rate is also related to the consumption rate of xylose than the consumption rate of glucose. However, if it is pure xylose, it will be completed in about several hours, and will be somewhat slower due to the coexistence of glucose. There are other by-products in the hemicellulose-based saccharified liquid produced from cellulosic biomass, and if the amount is large, the xylose fermentation rate is further reduced and the fermentation by-products are increased. By setting the conditions in the hydrothermal reaction and the solid acid catalyzed reaction as described above, an increase in by-products due to xylose decomposition or the like is prevented, and a decrease in speed due to inhibition of xylose fermentation is suppressed. Moreover, when the yeast previously cultured under the selective pressure containing secondary saccharified liquid H2 is used for fermentation, fermentation efficiency will improve. That is, by culturing yeast in an environment containing the secondary saccharified solution H2, yeast having resistance to the inhibitor contained in the secondary saccharified solution H2 grows and propagates, and a yeast having such resistance is selected. Can be obtained. Specifically, when the yeast is cultured using a medium containing a low-concentration diluted solution of the secondary saccharified liquid H2, the secondary saccharified liquid concentration of the medium is gradually increased when the propagated yeast is taken out and repeated. By this, the tolerance of the cultured yeast is gradually strengthened.

The fermentation product F2 that has undergone fermentation in the second fermentation apparatus 8 as described above is subjected to distillation apparatus 9 after removing solids (lignin, fermentation microorganisms, etc.) from the fermentation product F2 as necessary, by filtration or the like. Purified ethanol is recovered by distillation in You may distill as it is, without removing solid content from fermentation product F2. The solid separated from the fermentation product F2 may be introduced into the biomass saccharification step. The distillation of the fermentation product F2 can be performed together with or separately from the fermentation product F1 obtained from the first fermentation apparatus 6.

Solid acid catalysts include powders and pellets. When pellets are used in the first catalyst reaction device 5 and the second catalyst reaction device 7, the solid acid catalyst may be made of a mesh or the like through which the liquid flows easily. The solid acid catalyst can be held in the permeable container and fixed in the primary saccharified liquids H1 and C1, and the primary saccharified liquid can be flowed between the solid acid catalyst pellets by flowing the primary saccharified liquid. . By adopting such a fixed bed type solid acid catalyst, it is possible to simplify the apparatus configuration relating to solid-liquid separation in the first catalytic reaction apparatus and the second catalytic reaction apparatus.

Regarding the relationship between the xylose production rate constant and the xylose decomposition rate constant in solid acid catalyzed reaction and temperature, the xylose production rate constant increases rapidly at about 80 ° C or higher, and the solid acid catalytic reaction proceeds well at about 90 ° C or higher. To do. On the other hand, the xylose decomposition rate constant starts to gradually increase when the temperature exceeds 100 ° C. For this reason, in order to suppress decomposition | disassembly of xylose and to suppress the fermentation inhibition by a by-product, the temperature setting of a solid catalytic reaction is important.

Moreover, in each of the first fermentation apparatus 6 and the second fermentation apparatus 8, when microorganisms such as Clostridium acetobutylicum, Clostridium begerinki, Clostridium auranticylicum, Clostridium tetanomorphum are used as fermentation microorganisms, butanol or the like is obtained by fermentation. Can be produced, and can be applied to the production of useful alcohols and ketones other than ethanol. Similarly, it can be applied to the production of hydroxymethylfurfural and furfural.

(Pressurized hot water reaction of herbaceous biomass)
As herbaceous biomass, prepared by finely pulverizing 300 g of sweet sorghum bagasse (water content: 30% by mass), charged in a batch-type pressurized hot water reactor (OML-5 manufactured by OM Labtech Co., Ltd.), and heated to 200 ° C. 3 L of pressurized hot water (pressure: 1.56 MPa, saturated vapor pressure) was supplied and reacted for 20 minutes. The reaction product was taken out from the pressurized hot water reactor and centrifuged at 15 minutes by applying a centrifugal force of 3000 G, so that 2134 g of hemicellulose-derived primary saccharified solution and cellulose-containing solid residue (water content 84.32% by mass) were obtained. ) To 127.55 g.

(Solid acid catalyzed reaction of primary saccharified solution)
75 g of a carbon-based solid acid catalyst obtained by sulfonating amorphous carbide was prepared, and the temperature was maintained at 90 to 100 ° C. in addition to 500 g of the primary saccharified solution obtained by performing the above-mentioned pressurized hot water reaction. The solid acid catalyst reaction was carried out for 2 hours by using and stirring at a speed of 10 rpm. The solid acid catalyst was removed by sedimentation to obtain 400 g of a secondary saccharified solution derived from hemicellulose. When xylose and glucose contained in the secondary saccharified solution were quantified by HPLC analysis, the xylose concentration was 0.75% by mass and the glucose concentration was 0.36% by mass.

(Fermentation reaction of secondary saccharified solution)
Water is added to the secondary saccharified solution obtained above to adjust the concentration of xylose to about 10%, the pH is adjusted to 6.0, and yeast of the genus Saccharomyces (see US Patent Publication 2011 / 0027847A1) as a fermentation microorganism. The strain MA-2, in which the gene for the enzyme with improved coenzyme specificity was introduced, was inoculated into the IR-2 strain, and the fermentation was carried out for 48 hours while maintaining at about 30 ° C. in a nitrogen atmosphere.

When solids containing microorganisms were removed from the liquid after fermentation and xylose, glucose and ethanol contained in the liquid were quantified by HPLC analysis, the xylose concentration was 0 mass%, the glucose concentration was 0 mass%, and the ethanol concentration was It was 0.4 mass%.

(Progress during fermentation)
In the fermentation reaction of the above secondary saccharified solution, the fermentation solution was sampled 12 hours after the start of fermentation, and when xylose, glucose and ethanol were quantified, xylose concentration: 0.25% by mass, glucose concentration: 0% by mass, Ethanol concentration: 0.36% by mass.

The relationship between the xylose ratio of the fermentation stock solution and the ethanol yield after fermentation shown in FIG. 2 is obtained according to the following operation.

According to the same operation as in Example 1, a hemicellulose-derived secondary saccharified solution was prepared from herbaceous biomass, and the ratio of xylose and glucose contained was examined. Sample (1) was 0.67, and sample (2) was 0.66 and sample (3) were 0.47.

Samples of the secondary saccharified solutions (1) to (3) obtained above and purified monosaccharides are commercially available glucose reagent (sample (4)), xylose reagent (sample (5)), and glucose. A mixture (sample (6)) in which the ratio of xylose obtained by mixing the reagent and the xylose reagent was 0.68 was prepared.

For each of samples (1) to (6), water was added to adjust the monosaccharide concentration to about 10%, and the pH was adjusted to 6.0 to obtain a fermentation stock solution. The fermentation was carried out for 48 hours. During this time, the liquid during the fermentation was sampled, and xylose, glucose and ethanol contained in the liquid were quantified by HPLC analysis, and the change with time of each component amount was examined. The results are shown in (a) to (f) of FIG. FIG. 2 is a graph showing the relationship between the xylose ratio of the fermentation stock solution of each sample and the ethanol yield at the end of fermentation using these results.

The present invention uses a resource that can efficiently saccharify and ferment hemicellulose contained in wood and other materials to produce ethanol when producing biomass ethanol using plant waste as biomass, and there is no risk of food price increases. Therefore, it can be treated economically and rationally, contributing to waste treatment and resource production, and can contribute to promoting recycling, protecting the environment, and solving energy problems.

Claims

A pressurized hot water reaction step in which pressurized hot water is allowed to act on the biomass to selectively decompose hemicellulose contained in the biomass;
A solid acid catalyst reaction step of obtaining a saccharification product containing xylose by allowing a solid acid catalyst to act on the decomposition product of the pressurized hot water reaction step at a temperature of 90 to 110 ° C .;
A method for producing ethanol comprising a fermentation step in which a microorganism having xylose fermentation ability is allowed to act on a saccharification product obtained in the solid acid catalyst reaction step to produce ethanol.
The method for producing ethanol according to claim 1, wherein the temperature of the pressurized hot water in the pressurized hot water reaction step is 150 to 230 ° C, and the pressure is 0.47 to 2.8 MPa.
The microorganism in the fermentation step includes a gene encoding an enzyme that catalyzes a conversion reaction from xylose to xylitol, a gene encoding an enzyme that catalyzes a conversion reaction from xylitol to xylulose, and xylulose and ATP to xylulose pentaphosphate and The method for producing ethanol according to claim 1 or 2, which is a genetically modified yeast into which a gene encoding an enzyme that catalyzes a conversion reaction to ADP is introduced by chromosomal integration.
Further, a saccharifying enzyme is allowed to act on the solid residue after the pressurized hot water reaction step to decompose cellulose contained in the solid residue, thereby producing a liquid containing a suspended polysaccharide having a degree of polymerization of 7 to 3000. The method for producing ethanol according to any one of claims 1 to 3, further comprising a primary saccharification step.
The ethanol according to claim 4, further comprising a secondary saccharification step of cellulose in which a product of the cellulose in the primary saccharification step is allowed to act on a solid acid catalyst to decompose the suspended polysaccharide to produce glucose as a monosaccharide. Manufacturing method.
The method for producing ethanol according to any one of claims 1 to 5, further comprising a separation step of separating a decomposition product from the pressurized hot water reaction step from a solid residue.
The method for producing ethanol according to any one of claims 1 to 6, further comprising a purification step for purifying ethanol contained in the product after the fermentation step.
2. The method for producing ethanol according to claim 1, wherein a yeast having xylose fermentation ability, which has been cultured in advance under a selective pressure containing a saccharification product obtained in the solid acid catalytic reaction step, is used as the microorganism in the fermentation step.
A pressurized hot water reactor for selectively decomposing hemicellulose contained in biomass by applying pressurized hot water to the biomass;
A catalytic reaction apparatus for obtaining a saccharification product containing xylose by heating a decomposition product obtained by the pressurized hot water reaction apparatus to 90 to 110 ° C. to act a solid acid catalyst;
An ethanol production apparatus comprising: a fermentation apparatus that produces ethanol by allowing a microorganism having xylose fermentation ability to act on a saccharification product obtained by the catalytic reaction apparatus.
The ethanol production apparatus according to claim 9, further comprising a heating and pressurizing system for supplying pressurized hot water having a temperature of 150 to 230 ° C to the pressurized hot water reactor at a pressure of 0.47 to 2.8 MPa.
The fermentation apparatus comprises, as the microorganism, a gene encoding an enzyme that catalyzes a conversion reaction from xylose to xylitol, a gene encoding an enzyme that catalyzes a conversion reaction from xylitol to xylulose, and xylulose and ATP to xylulose 5-phosphorus The ethanol production apparatus according to claim 9 or 10, which accommodates a genetically modified yeast into which a gene encoding an enzyme that catalyzes a conversion reaction to acid and ADP is introduced by chromosomal integration.
The ethanol production apparatus according to any one of claims 9 to 11, further comprising a separation device for separating a decomposition product from the pressurized hot water reactor from a solid residue.
The ethanol production apparatus according to any one of claims 9 to 12, further comprising a distillation apparatus for purifying ethanol contained in the product of the fermentation apparatus.
The ethanol production apparatus according to any one of claims 9 to 13, further comprising an apparatus for separating and recovering the solid acid catalyst from the saccharification product of the catalytic reaction apparatus.
Furthermore, a saccharifying enzyme is allowed to act on the solid residue separated by the separation device, and the cellulose contained in the solid residue is decomposed to produce a liquid containing a suspended polysaccharide having a polymerization degree of 7 or more. Equipment,
A catalytic reaction device for cellulose that produces a glucose as a monosaccharide by causing a solid acid catalyst to act on the product of the enzyme reaction device for cellulose;
The ethanol production apparatus according to claim 12, further comprising: a cellulose-based fermentation apparatus that generates ethanol by causing a microorganism having glucose fermentation ability to act on a product of the catalytic reaction apparatus for cellulose.