JP2015139380A - Method for producing sugars from herbaceous biomass or woody biomass and method for producing ethanol from sugars - Google Patents

Abstract

A sugar component contained in a herbaceous biomass or a woody biomass that can be used as a raw material for ethanol production is used sufficiently effectively. An alkaline treatment step in which a herbaceous biomass and / or a woody biomass is contacted with an alkali solution, a step of adjusting pH by adding an acid to a solution or slurry after the alkali treatment step, a solution after pH adjustment, or It includes an amylase treatment step in which amylase is allowed to act on the slurry to hydrolyze the solution or starch contained in the slurry. [Selection] Figure 1

Description

  The present invention relates to a method for producing sugar from herbaceous biomass or woody biomass and a method for producing ethanol from the produced sugar.

  In recent years, bioethanol has attracted attention as a carbon-neutral liquid fuel that does not depend on fossil resources, and ethanol production technologies for various biomass have been proposed.

  When ethanol is produced from cellulose in biomass, cellulose and hemicellulose contained in biomass are hydrolyzed to saccharify into monosaccharides and oligosaccharides. As a saccharification method for cellulose and hemicellulose contained in herbaceous / woody biomass, an enzymatic method using a hydrolase such as cellulase is known. In the enzymatic method, before the cellulose or hemicellulose contained in the herbaceous / woody biomass is hydrolyzed by the enzyme, a treatment (alkali treatment) of immersing the herbaceous / woody biomass in an alkaline solution may be performed. According to this alkali treatment, the structure of herbaceous / woody biomass is relaxed and hydrolyzing enzymes effectively act on cellulose and hemicellulose contained in herbaceous / woody biomass to improve saccharification efficiency. be able to.

  For example, JP 2012-85544 A (Patent Document 1) discloses an alkali treatment step in which herbaceous biomass such as rice straw is pelletized and the pelletized herbaceous biomass is mixed with an alkali solution such as sodium hydroxide. An ethanol production method using biomass as a raw material is disclosed. In this method, in the alkali treatment, the amount of herbaceous biomass pellets with respect to the amount of the alkaline solution is set to 5 to 20%. In this method, after alkali treatment, an acid such as sulfuric acid is added to neutralize an alkaline solution containing herbaceous biomass, and then a hydrolase such as cellulase is allowed to act on the cellulose in the herbaceous biomass. Even sugar is broken down.

  In JP 2012-85544 A (Patent Document 1), prior to neutralization of an alkaline solution with an acid, the alkaline solution is solid-liquid separated to recover a solid component, and then the solid component is immersed in an acidic solution. And may be neutralized. Further, JP 2012-85544 A (Patent Document 1) discloses that cellulase-producing bacteria and ethanol-fermenting bacteria act in the same system using herbaceous biomass after alkali treatment as a raw material, and saccharification and ethanol by cellulase-producing bacteria. It is disclosed that ethanol may be produced by carrying out simultaneously with ethanol production by fermenting bacteria (also called simultaneous saccharification and fermentation).

  Further, for example, in Japanese Patent Application Laid-Open No. 2011-4730 (Patent Document 2), a slurry is prepared by mixing pulverized lignocellulosic biomass with a calcium hydroxide solution to perform alkali treatment, and then carbon dioxide is aerated. And / or pressurizing to neutralize and lower the pH to 5-7. JP 2011-4730 (Patent Document 2) uses carbon dioxide when neutralizing calcium hydroxide used for alkali treatment, so the solubility of calcium carbonate produced by neutralization is extremely low. It has been pointed out that even if it remains in the reaction system, it does not easily cause salt inhibition during enzyme reaction or microbial fermentation.

  Furthermore, JP 2013-515484 A (Patent Document 3) discloses a method of simultaneously saccharifying and fermenting biomass pretreated with ammonia with a saccharifying enzyme such as cellulase or amylase and an ethanol-producing bacterium such as Zymomonas microorganism. Has been.

JP 2012-85544 A JP 2011-4730 A Special table 2013-515484 gazette

  However, in the conventionally known technology as described above, among the various sugar components constituting the biomass, the sugar component that can be used as a raw material for ethanol production is not sufficiently utilized, and the amount of ethanol produced per biomass amount is small. There was a problem. Therefore, the present invention significantly increases the ethanol production amount (ethanol yield) per biomass amount by sufficiently effectively using the sugar component that can be used as a raw material for ethanol production contained in herbaceous biomass or woody biomass. The purpose is to improve.

  As a result of intensive studies by the present inventors in order to achieve the above-mentioned object, after the herbaceous biomass or woody biomass is alkali-treated with an alkaline solution, the solution contains gelatinized starch. It has been found that it can be effectively used for ethanol production, and the present invention has been completed.

  In the method for producing sugar or ethanol according to the present invention, the pH is adjusted by adding an acid to the alkali treatment step in which the herbaceous biomass and / or the woody biomass is brought into contact with the alkali solution, and the solution or slurry after the alkali treatment step. The step includes an amylase treatment step in which amylase is allowed to act on the solution or slurry after pH adjustment to hydrolyze starch contained in the solution or the slurry.

  In the method for producing sugar or ethanol according to the present invention, the pH may be adjusted by adding an acid to the solution obtained by solid-liquid separation after the alkali treatment step, or solid-liquid separation after the alkali treatment step. Alternatively, the pH may be adjusted by adding an acid to the slurry. In the method for producing sugar or ethanol according to the present invention, the solution obtained by solid-liquid separation after the alkali treatment step is repeatedly used as the alkali solution in the alkali treatment step, and used at a predetermined number of repetitions. The pH may be adjusted by adding an acid to the solution. At this time, it is preferable that the solution obtained by solid-liquid separation after the alkali treatment step is supplemented with alkali, and the solution supplemented with alkali is used in the next alkali treatment step.

  In the amylase treatment step, any of the solutions, slurries, and solutions used at a predetermined number of repetitions that have undergone the above pH adjustment can be subjected to amylase to hydrolyze starch to obtain sugar.

  Moreover, in the manufacturing method of the saccharide | sugar or ethanol which concerns on this invention, the process of making the solid content after the said alkali treatment process contact cellulase and obtaining the saccharide | sugar component derived from the said solid content may be further included. At this time, acid may be added to the solid content obtained by solid-liquid separation after the alkali treatment step to adjust the pH, and then the cellulase may be contacted to obtain a sugar component, or solid-liquid separation after the alkali treatment step. Without adjusting the pH, the sugar component may be obtained by contacting the cellulase after adjusting the pH.

  On the other hand, the sugar or ethanol production method according to the present invention may further include a fermentation step of producing ethanol by alcohol fermentation using the sugar component obtained in the amylase treatment step. In addition, in the fermentation process which produces | generates this ethanol, the saccharide | sugar component obtained by hydrolyzing the solid component after the said alkali treatment process with a cellulase can also be used as the raw material of alcohol fermentation.

  In particular, in the method for producing sugar or ethanol according to the present invention, a cellulase treatment step for hydrolyzing a solid component after the alkali treatment step with cellulase, a sugar component obtained by the cellulase treatment, and the amylase treatment step. The fermentation process using the obtained sugar component can be performed simultaneously (in other words, in the same reaction system) to produce ethanol. Furthermore, in the method for producing sugar or ethanol according to the present invention, the cellulase treatment step for hydrolyzing the solid component after the alkali treatment step with cellulase, the amylase treatment step, the sugar component obtained by the cellulase treatment, and the above The fermentation process using the sugar component obtained in the amylase treatment process can be performed simultaneously (in other words, in the same reaction system) to produce ethanol.

  In the method for producing sugar or ethanol according to the present invention, lignin, starch, oligosaccharides and the like are eluted in the alkaline solution used for the alkaline treatment of herbaceous biomass or woody biomass, and the alkaline solution is subjected to alkaline treatment. The greater the number of recycles, the higher the concentration of lignin, starch, oligosaccharide, etc. in the alkaline solution. Lignin can be used as a fuel, and starch and oligosaccharides can be used as raw materials for ethanol production by microorganisms such as yeast by breaking down into monosaccharides. However, when lignin is present, it is difficult to decompose oligosaccharides into monosaccharides that can be easily used by microorganisms such as yeast by cellulase, but according to a preferred embodiment of the present invention, recycling to an alkali treatment step, An acid is added to an alkali solution used for alkali treatment of herbaceous biomass or woody biomass over a predetermined number of times, for example, pH is adjusted to 6 or less, acid-insoluble lignin is precipitated and separated, and lignin is recovered. ing.

  In a further preferred embodiment of the present invention, the solution obtained by separating the precipitated lignin and then eluting the starch and oligosaccharide is supplied to a saccharification tank to which the enzyme is supplied, and the starch and oligosaccharide are monosaccharideized. To the fermenter in which the yeast is present and fermented to produce ethanol, or to the simultaneous saccharification and fermenter in which the enzyme and the yeast are present to monosaccharide, ferment, and ethanol Is configured to generate

  In the present invention, the alkaline substance is not particularly limited, and other alkaline substances such as sodium hydroxide and calcium hydroxide can be used.

  According to the present invention, the amount of ethanol produced per biomass (ethanol yield) can be greatly increased by sufficiently effectively using the sugar component that can be used as a raw material for ethanol production contained in herbaceous biomass or woody biomass. It becomes possible to improve.

It is a lineblock diagram showing typically one form of the system to which the manufacturing method of sugar or ethanol concerning the present invention is applied. It is a block diagram which shows typically the other form of the system to which the manufacturing method of the saccharide | sugar or ethanol which concerns on this invention is applied. It is a block diagram which shows typically the further another form of the system to which the manufacturing method of the saccharide | sugar or ethanol which concerns on this invention is applied. It is a characteristic view which shows a time-dependent change of the glucose concentration in the saccharification test performed in the present Example.

  The method for producing sugar or ethanol according to the present invention is to produce sugar from herbaceous biomass or woody biomass (hereinafter sometimes simply referred to as biomass), or from herbaceous biomass or woody biomass as a raw material. It means to include a method for producing ethanol from the produced sugar. A system to which the method for producing sugar or ethanol according to the present invention is applied is schematically shown in FIG. As shown in FIG. 1, this system includes an alkali treatment tank 1 that performs an alkali treatment on biomass, a solid-liquid separation device 2 that performs solid-liquid separation on biomass that has been alkali-treated in the alkali treatment tank 1, and a solid-liquid separation. A pH adjusting tank 3 that adds acid to the liquid (solution) separated by the apparatus 2 to a predetermined pH, and an amylase processing tank that performs an amylase treatment on the solution adjusted to a predetermined pH in the pH adjusting tank 3 4, a pH adjustment tank 5 in which acid is added to the solid content separated by the solid-liquid separator 2 to obtain a slurry having a predetermined pH, and the slurry adjusted to a predetermined pH in the pH adjustment tank 5 and the amylase treatment tank 4. And a simultaneous saccharification and fermentation tank 6 that performs saccharification and alcohol fermentation using cellulase and a microorganism having alcohol fermentation ability.

  In particular, in the system shown in FIG. 1, the solution separated by the solid-liquid separator 2 can be returned to the alkali treatment tank 1 and used again for the alkali treatment in the alkali treatment tank 1. In other words, in the system shown in FIG. 1, the liquid (solution) obtained in a given batch is reused in a batch after the given batch in the alkali treatment and subsequent solid-liquid separation that are normally performed in the batch process. Can be used. When the liquid obtained by solid-liquid separation is reused, the alkali can be replenished so as to have a desired alkali concentration, and the alkali replenished liquid is supplied to the alkali treatment tank 1 for alkali treatment. be able to. In addition, the frequency | count of reuse of the liquid obtained by solid-liquid separation is not specifically limited.

  Here, the herbaceous biomass means a material mainly composed of herbs as a raw material. The herbaceous biomass is not particularly limited, and examples thereof include herbs themselves, a part of herbs, processed herbs, and herb-derived products. More specifically, examples of herbaceous biomass include rice, wheat, bagasse, bamboo, corn stover, switch grass, turf, rice husk, various weeds, soybean hulls, and the like. The herbaceous biomass may be composed of one kind of herb or a plurality of kinds of herb. In addition, as herbaceous biomass, you may use the pellet shape | molded by applying desired pressure with respect to the grass which is a raw material.

  In addition, woody biomass is not particularly limited as long as it is a woody resource. For example, construction waste wood, waste packing materials, logging materials, sawdust, thinned wood, wood chips, rice straw, bark, forest land residue, Use trees, backboards, etc. The woody biomass may be composed of one kind of woody resource, or may be composed of a plurality of kinds of woody resources.

  By the way, the method for producing sugar or ethanol according to the present invention can be a system as schematically shown in FIG. In the system shown in FIG. 2, an acid is added to the solid content in the pH adjusting tank 5 to obtain a slurry having a predetermined pH, and then the obtained slurry is subjected to solid-liquid separation. That is, the system shown in FIG. 2 includes a solid-liquid separation device 7 that performs solid-liquid separation on the slurry after pH adjustment in the pH adjustment tank 5. In the system shown in FIG. 2, the solid content separated by the solid-liquid separation device 7 is supplied to the simultaneous saccharification and fermentation tank 6, and the liquid content separated by the solid-liquid separation device 7 is returned to the pH adjustment tank 5 and reused. .

  As described above, in the system configured as shown in FIG. 1 or FIG. 2, the starch contained in the liquid is hydrolyzed by amylase after the herbaceous biomass and / or the woody biomass is alkali-treated. . That is, according to this system, the saccharide | sugar derived from starch can be utilized effectively by saccharifying the starch contained in the raw material biomass. In this system, since starch contained in biomass is gelatinized by alkali treatment, starch can be hydrolyzed without requiring heat treatment or the like for gelatinization.

  As described above, in the system configured as shown in FIG. 1 or FIG. 2, simultaneous saccharification and fermentation can be performed using sugar derived from starch, that is, α-glucose as a carbon source. Thereby, the sugar concentration at the time of simultaneous saccharification and fermentation start becomes high, and the start-up of fermentation by the microorganisms having alcohol fermentability can be accelerated. Moreover, in the system comprised as shown in FIG. 1 or FIG. 2, in addition to the saccharide | sugar derived from a cellulose, the saccharide | sugar derived from a starch can be utilized as a carbon source of alcohol fermentation. As a result, simultaneous saccharification and fermentation can be performed in a short time, and the ethanol yield per unit weight of biomass is also improved, so that the cost of ethanol production can be greatly reduced.

  Further, in the system configured as shown in FIG. 1 or FIG. 2, the liquid (alkali solution) is reused by solid-liquid separation after the alkali treatment. Thus, the starch component contained in a liquid component can be concentrated by reusing the liquid component obtained by solid-liquid separation after an alkali treatment. At this time, the alkali concentration contained in the liquid component solid-liquid separated by the solid-liquid separation device 2 is lower than the concentration necessary for performing the alkali treatment in the alkali treatment tank 1, and the amount of the solution itself is small. Therefore, in this system, the liquid to be recycled is replenished with alkali so that the amount and / or alkali concentration necessary for the alkali treatment is obtained. Thereby, the amount of alkali used when the biomass is alkali-treated can be reduced as compared with the conventional method in which the alkaline solution is not reused.

  By the way, as shown in FIGS. 1 and 2, the method for producing sugar or ethanol according to the present invention is not limited to the one that solid-liquid separates the biomass after alkali treatment into a liquid component and a solid component. That is, for example, as shown in FIG. 3, the method for producing sugar or ethanol according to the present invention comprises an alkali treatment tank 1, an alkali treatment in the alkali treatment tank 1, and then a biomass as a solid and an alkali solution as a liquid. PH adjusting tank 8 for adjusting the pH of the slurry containing sucrose, and slurry having a predetermined pH in the pH adjusting tank 8 are charged, and saccharification is performed by cellulase and amylase (microorganism having alcohol fermentation ability in the case of simultaneous saccharification and fermentation). It is good also as a system provided with the enzyme saccharification tank 9 (in the case of simultaneous saccharification fermentation, simultaneous saccharification fermentation tank 9) to perform (alcohol fermentation in the case of simultaneous saccharification fermentation).

  Even in the system shown in FIG. 3, the starch contained in the liquid is hydrolyzed by amylase after the herbaceous biomass and / or the woody biomass is alkali-treated. That is, according to the system shown in FIG. 3, sugar derived from starch can be effectively used by saccharifying starch contained in raw material biomass. Also in the system shown in FIG. 3, since starch contained in biomass is gelatinized by alkali treatment, starch can be hydrolyzed without requiring heat treatment or the like for gelatinization. Therefore, the system configured as shown in FIG. 3 can also use sugar derived from starch as a carbon source for alcohol fermentation in addition to sugar derived from cellulose. As a result, since the ethanol yield per unit weight of biomass is also improved, the cost of ethanol production can be greatly reduced. In the system shown in FIG. 3, the alkali treatment tank 1, the pH adjustment tank 8, and the enzyme saccharification tank (simultaneous saccharification and fermentation tank) 9 are used in the same tank, alkali treatment, pH adjustment, enzyme saccharification (simultaneous saccharification). Each step of (fermentation) may be performed sequentially.

  Hereinafter, each process of alkali treatment, cellulose saccharification treatment, starch saccharification treatment, and ethanol fermentation will be described in detail.

<Alkali treatment (pretreatment) process>
Here, the alkali solution used in the alkali treatment step means an aqueous solution of a hydroxide of an alkali metal or an alkaline earth metal (synonymous with the Group 2 element in the present invention). That is, the hydroxide contained in the alkaline solution includes lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, francium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, water Examples include strontium oxide, barium hydroxide, and radium hydroxide. Of these, sodium hydroxide, potassium hydroxide, and calcium hydroxide are preferably used from the viewpoint of the influence of inhibition in the subsequent fermentation process. In particular, sodium hydroxide is preferably used from the viewpoint of drug cost and solubility in water.

  When using herbaceous biomass as cellulosic biomass, the pH of the alkaline aqueous solution can be 9.5 to 13.5, and preferably 10 to 13. The herbaceous biomass amount (feed amount) with respect to the alkaline solution amount is not particularly limited, but is, for example, 5 to 20%, desirably 10 to 15%, based on the dry weight of the herbaceous biomass.

  The temperature conditions for the alkali treatment may be, for example, from room temperature to 160 ° C., preferably from room temperature to 121 ° C., for example, 80 ° C. The holding time can be set according to the temperature of the alkali treatment and the shape of the herbaceous biomass, and generally ranges from 15 minutes to 24 hours.

  In the alkali treatment step, the herbaceous biomass is infiltrated into the alkaline solution, and then neutralized by adding an acid such as sulfuric acid. The pH after adding the acid to the alkaline solution is preferably a pH suitable for the enzyme treatment described later. Note that the solid component may be recovered by solid-liquid separation before neutralization with an acid, and then the alkali impregnated in the herbaceous biomass may be neutralized by immersing the solid component in an acidic solution.

  When using woody biomass as cellulosic biomass, the pH of the alkaline aqueous solution can be 9.5 to 13.5, preferably 10 to 13, and more preferably pH 11 to 12.5. preferable. The addition amount of the alkaline solution is, for example, 2 to 30% by weight ratio per dry wood weight, and desirably 5 to 20%. The mixing ratio of the aqueous solution containing a predetermined amount of the alkali agent and the dry wood is preferably 5 to 50 wood weight with respect to 100 solution volume.

  In the alkali treatment, it may be present as an oxidizing agent. As the oxidizing agent, hydrogen peroxide, persulfate, percarbonate, peracetate, ozone, sodium peroxide, or the like can be used.

<Cellulose saccharification process>
In this step, cellulase enzyme treatment is performed on the solid content after the alkali treatment step described above, whereby cellulose contained in biomass is decomposed to glucose by cellulase. Cellulase is meant to include at least one enzyme selected from the group consisting of endoglucanase, cellobiohydrase, β-glucosidase and hemicellulase. In this step, hemicellulose contained in biomass may be saccharified to monosaccharides such as mannose, galactose, xylose, and arabinose. The cellulase used is not particularly limited as long as it can saccharify cellulose to hexose. The cellulase used is preferably one that can further saccharify hemicellulose to hexose and pentose. For example, the cellulase may be derived from plants or animals, and may be chemically modified or produced by genetic recombination. In addition, although the temperature, time, and quantity which make cellulase react depend on the kind of cellulase, those skilled in the art can select suitably according to the kind of cellulase to be used.

  In particular, in the case of the simultaneous saccharification and fermentation system shown in FIG. 1 and the like, it is preferable to use a cellulase having a pH optimum for a range in which a microorganism having alcohol fermentation ability is suitable for growth. For example, a cellulase having an optimum pH of 4.6 can be used.

  Alternatively, by fermenting cellulase-producing bacteria using biomass neutralized after alkali treatment as a raw material, cellulose in the biomass can be decomposed to monosaccharides by cellulase to obtain a secondary sugar solution. Such cellulase producing bacteria are known in the art, e.g. Aspergillus niger, A. foetidus, Alternaria alternata, Chaetomium thermophile, C. globosus, Fusarium solani, Irpex lacteus, Neurospora crassa, Cellulomonas fimi, C. uda, Erwinia chrysanthemi, Pseudomonas fluorescence, Streptmyces flavogriseus, etc. are mentioned, for example, "Cellulose resources-Technological development for advanced use and its basics", Tetsuo Koshijima, Japan Society for Publishing Press, 1991.

  In addition, as described above, the biomass after alkali treatment may be subjected to cellulase enzyme treatment, and it is also possible to produce ethanol by simultaneous fermentation of cellulase-producing bacteria and ethanol-fermenting bacteria using the biomass after alkali treatment as a raw material.

  The monosaccharide produced in this step can be used as a biorefinery as a fermentation raw material for microorganisms capable of producing ethanol, butanol and other chemical raw materials. In addition, by further enzymatic treatment of glucose obtained by saccharification of cellulosic biomass, it is a refreshing agent D-sorbitol, a sweetener D-fructose, an osmotic pressure regulator mannitol, a feed additive Useful substances such as mannose and other foods and pharmaceuticals can also be produced.

<Starch saccharification process>
In this step, the amylase enzyme treatment is performed on the liquid after the alkali treatment step described above (alkaline solution), whereby the starch contained in the liquid is decomposed to glucose by amylase. Here, amylase is meant to include at least one enzyme selected from the group consisting of pullulanase, α-amylase, glucoamylase and β-amylase.

  Although it does not specifically limit as amylase used at this process, It is preferable to set it as substantially the same pH (for example, pH 4.6) of the cellulase mentioned above. By using amylase having an optimum pH substantially the same as that of cellulase, the saccharified solution after the amylase treatment step can be used as it is for simultaneous saccharification and fermentation without adjusting the pH. Further, by using an amylase having an optimum pH substantially the same as the optimum pH of the cellulase, as shown in FIG. 3, the cellulase treatment step, the amylase treatment step (and the alcohol fermentation step) can be performed in the amylase treatment step. The subsequent saccharification solution can be carried out in the same tank without adjusting the pH.

<Ethanol production process>
Ethanol can be produced by performing alcoholic fermentation using the sugar obtained in the above saccharification step as a raw material. The sugar component obtained in the above-described saccharification step contains sugar derived from cellulose and sugar derived from starch contained in biomass. Moreover, when hemicellulose contained in biomass is saccharified, pentoses such as xylose and arabinose and hexoses such as glucose, galactose, and mannose are included as sugars derived from hemicellulose. Glucose which is sugar derived from cellulose and sugar derived from starch can be easily converted into ethanol by yeast or the like.

  Alcohol fermentation using glucose as a carbon source can be carried out using yeast or bacteria having a gene necessary for ethanol production by genetic recombination according to an ethanol production method known in the art. Ethanol fermentation of pentoses, for example, genetically modified Escherichia coli in which both pentose and hexoses are assimilated, but that does not produce ethanol, a gene derived from a microorganism that produces ethanol, and ethanol fermentation It can be carried out by using a genetically modified bacterium in which a pentose metabolic gene is introduced into a sexual Zymomonas bacterium (for example, JP-T-5-502366 and JP-A-6-504436) ). Alternatively, a method in which pentose and hexose are fermented with ethanol to recover ethanol and carbon dioxide may be used (Japanese Patent Laid-Open No. 2006-111593).

  Those skilled in the art can appropriately set conditions for ethanol fermentation according to the type of sugar used as a raw material, the type of ethanol-fermenting bacteria used, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, the technical scope of this invention is not limited to a following example.

[Example 1]
1. Purpose The starch contained in the liquid obtained by alkali treatment and solid-liquid separation of rice straw has been gelatinized into a form in which amylase can be decomposed by alkali treatment, and can be converted to glucose by amylase, or by cellulose degradation by cellulase and amylase Check if starch degradation can proceed simultaneously.

2. experimental method
1) Alkali treatment of rice straw Table 1 shows the alkali treatment conditions of rice straw.

  Under the conditions shown in Table 1, alkali treatment was performed according to the following procedure. First, 25 kg of NaOH was dissolved in 919.2 L of water so that the solid-liquid ratio at the time of alkali treatment was 5% for 108.8 kg of rice straw with a moisture content of 8.1% (corresponding to a dry weight of 100 kg) and placed in a 4000 L capacity alkaline treatment tank. An alkaline solution was prepared. The above rice straw cut to 1 cm or less was put into this alkaline solution and subjected to alkali treatment for 18 hours while stirring at room temperature.

2) Solid-liquid separation after alkali treatment The slurry rice straw after the alkali treatment was separated into a solid content and a liquid content by a twin screw dehydrator. The solid content after solid-liquid separation was a wet weight of 206 kg-wet, a dry weight of 59 kg-dry, and a liquid content of 2,002 L.

3) Neutralization of solid content The solid content after alkali treatment and solid-liquid separation of 2) is immersed in a 4000L tank filled with water at a ratio of 3% to the solid-liquid ratio to the dry weight of the solid content. While stirring, sulfuric acid was added to adjust pH = 4.6. The slurry-like rice straw after pH adjustment was separated into a solid content and a liquid content by a twin screw type dehydrator, and the solid content was used for a saccharification test as a cellulose-based raw material. The rice straw recovered as a solid content had a wet weight of 142.1 kg-wet and a dry weight of 50.3 kg-dry.

4) Neutralization of liquid
The liquid after the alkali treatment and solid-liquid separation in 2) was adjusted to pH = 4.6 by adding sulfuric acid while stirring, and used in the saccharification test as a starch-based material.

5) Saccharification treatment In a 100 ml duran bottle under the conditions (1) to (4) shown in Table 2 so that the solid-liquid ratio at the time of treatment is 5% with respect to the solid content after neutralization treatment equivalent to 3 g of dry weight. After treatment, solids, 100 mM citrate buffer solution (pH = 4.6), neutralized alkaline solution, amylase, cellulase, and antibiotics (cycloheximide, chloramphenicol) were added to prevent the growth of bacteria. Enzymatic saccharification was performed by shaking for 72 hours in a constant-temperature shaking incubator.

6) Sampling and analysis The solution was sampled after 24, 48 and 72 hours from the start of the saccharification test, and the glucose concentration was measured.

3. Experimental Results The change in glucose concentration under each condition is shown in FIG. In FIG. 4, (1) is a reaction system of rice straw + neutralized alkaline solution + amylase + cellulase, (2) is a reaction system of rice straw + amylase + cellulase, and (3) rice straw + cellulase. (4) Rice straw + amylase. From the experimental conditions shown in Table 1, when each enzyme acts, in (1), glucose is produced from the starch in the neutralized alkaline solution and the cellulose and starch in the treated rice straw. Glucose is produced from cellulose and starch in the treated rice straw in (2), from cellulose in the treated rice straw in (3), and from starch in the treated rice straw in (4). The glucose concentration after 72 hours is (1): 31.1 g / L, (2): 26.8 g / L, (3): 25.2 g / L, (4): 1.3 g / L, and cellulose in rice straw Glucose derived from starch (3) 25.2g / L, Glucose derived from starch in rice straw is (4) 1.3g / L, Glucose derived from neutralized alkaline solution is (1)-(2) = 4.3g / L

  From the above experimental results, it was confirmed that the starch contained in the neutralized alkaline solution was gelatinized into a form in which amylase acts and was converted to glucose by amylase. It was also confirmed that starch degradation by amylase can be performed simultaneously with cellulose degradation by cellulase.

4). Trial calculation of ethanol yield improvement by using starch as raw material The yield of glucose production from rice straw in this experiment is calculated as follows.
2. Raw material straw 100kg-dry before alkali treatment, rice straw dry weight 50.3kg recovered after alkali treatment / neutralization treatment; From the result of the experiment, the glucose concentration derived from cellulose was 25.2 g / L, the saccharification experiment solution amount was 60 mL, and the rice straw dry weight after the alkali treatment and neutralization treatment used in the saccharification experiment was 3 g-dry.
[Cellulose-derived glucose yield per dry weight of raw rice straw] = 50.3 × (25.2 × 60/1000/3) /100=25.4% (1)

3. From the results of the experiment, the starch-derived glucose concentration in the neutralized alkaline solution was 4.3 g / L, the alkaline solution amount used in the saccharification experiment was 50 mL, and the saccharification experimental solution amount was 60 mL.
[Starch-derived glucose concentration in alkaline solution] = 4.3 g / L x 50/60 = 3.6 g / L (2)

Furthermore, from the value of the above (2) and the amount of solution after alkali treatment was from 2,002 L,
[Predicted production amount of glucose derived from starch in alkaline solution] = 2,002L × 3.6g / L = 7.2kg (3)

On the other hand, dry weight of rice straw recovered after alkali treatment / neutralization treatment is 50.3 kg. In the experimental results of the above, the starch-derived glucose concentration in rice straw was 1.3 g / L, the saccharification experimental solution amount was 60 mL, and the dry weight of rice straw was 3 g-dry after the alkali treatment and neutralization treatment used in the saccharification experiment.
[Predicted production of glucose derived from starch in rice straw after alkali treatment / neutralization treatment] = 50.3 × 1.3 × 60/1000/3 = 1.3 kg (4)

From the values of (3) and (4) above, the starch-derived glucose production yield per dry weight of rice straw is
[Production yield of starch-derived glucose per dry weight of rice straw] = (7.2 + 1.3) /100=8.5%
([Elution starch rate per dry weight of rice straw] = 7.2 / 100 = 7.2%, [Rate of solid starch per dry weight of rice straw] = 1.3 / 100 = 1.3%)

  From the above calculation results, it can be seen that the yield in the case of producing glucose from cellulose and starch is greatly improved to (25.4 + 8.5) = 33.9%, compared to the glucose yield of 25.4% in the case of cellulose alone. Considering that all the glucose produced is converted to ethanol, the ethanol yield per dry weight of rice straw is 182 L / t-dry when produced from cellulose alone, whereas it is derived from both cellulose and starch. When manufactured, it is 243 L / t-dry.

5. Concentration of starch by reuse of alkaline solution As mentioned above, the alkaline solution generated by alkali treatment and solid-liquid separation is 2,000 L, and the amount of straw solids recovered after alkali treatment and neutralization treatment is 50 kg-dry. . When the solid-liquid ratio at the start of simultaneous saccharification and fermentation is 10%, the liquid content required for a solid content of 50 kg-dry is 500 L. When an alkaline solution is added to the tank for simultaneous saccharification and fermentation, the alkaline solution is surplus because the generated alkaline solution is 2,000 L with respect to the required 500 L.

  Therefore, as in the system shown in FIGS. 1 and 2, the alkaline solution is reused multiple times, the alkaline solution after being reused multiple times is stored in a cushion tank, and the necessary amount is added to the simultaneous saccharification and fermentation tank. No surplus of alkaline solution occurs. The alkaline solution can be stored at a high pH to prevent the growth of various bacteria. In addition, by using 1 / X of the alkaline solution used X times for simultaneous saccharification and fermentation, ethanol can be produced from cellulose and starch in the same amount as that contained in rice straw for one alkali treatment.

DESCRIPTION OF SYMBOLS 1 Alkali processing tank 2 Solid-liquid separator 3 pH adjustment tank 4 Amylase processing tank 5 pH adjustment tank 6 Simultaneous saccharification fermentation tank 7 Solid-liquid separation apparatus 8 pH adjustment tank 9 Enzyme saccharification tank (simultaneous saccharification fermentation tank)

Claims (3)

An alkali treatment step of contacting herbaceous biomass and / or woody biomass with an alkaline solution;
A pH adjusting step of adjusting pH by adding an acid to the solution or slurry after the alkali treatment step;
A method for producing sugar or ethanol, comprising an amylase treatment step of allowing amylase to act on a solution or slurry after pH adjustment to hydrolyze starch contained in the solution or slurry. After the alkali treatment step and before the pH adjustment step, further comprising a solid-liquid separation step for solid-liquid separation of the slurry after the alkali treatment,
The method for producing sugar or ethanol according to claim 1, wherein the liquid obtained by the solid-liquid separation step is repeatedly used as an alkaline solution in the alkali treatment step.   2. The method for producing sugar or ethanol according to claim 1, wherein in the amylase treatment step, cellulase treatment for hydrolyzing the solid component after the alkali treatment step with cellulase is performed as the same reaction system.

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