JP2009125050A - Pretreatment method for enzymatic hydrolysis of herbaceous biomass, ethanol production method using herbaceous biomass as raw material and ethanol production method using palm hollow bunch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pretreatment method performed before enzymatic hydrolysis of herbaceous biomass, wherein the pretreatment for enzymatic hydrolysis of herbaceous biomass suppresses excessive decomposition of sugar generated by the pretreatment, requires no high pressure device and for obtaining the sugar at a low cost and a good yield, to provide an ethanol production method using herbaceous biomass as the raw material, and to provide an ethanol production method using palm hollow bunch as the raw material. <P>SOLUTION: The pretreatment method performed before enzymatic hydrolysis of herbaceous biomass comprises an alkali treatment step for alkali-treating with a hydroxide aqueous solution containing a hydroxide of sodium hydroxide, potassium hydroxide or calcium hydroxide, whose concentration is ≥0.2 wt.% but <1 wt.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pretreatment method for enzymatic hydrolysis of herbaceous biomass, an ethanol production method using herbaceous biomass as a raw material, and an ethanol production method using palm palm empty fruit bunch as a raw material.

  Biomass, which is an organic resource derived from living organisms, is a resource that can be renewed continuously because living organisms produce it from water and carbon dioxide using solar energy. Biomass ethanol produced from the biomass is a renewable natural energy, and its potential as an energy source is expected from the point that it does not increase the amount of carbon dioxide in the atmosphere by its combustion.

  Therefore, attempts to produce ethanol from biomass such as bagasse (fiber residue obtained by squeezing sugar solution from sugarcane), rice straw, wood chips, etc., and to use it as energy and chemical raw materials are being promoted inside and outside Japan. Although various biomass is used as a raw material, lignocellulosic biomass such as woody biomass that can be used as a useful resource in the future has been attracting attention. Lignocellulose is the main component of plant stems and leaves, and is mainly composed of cellulose, hemicellulose and lignin, and fiber cells based on cellulose and hemicellulose are bound by an intercellular layer based on lignin. ing.

  Cellulose is a relatively stable polymer in which a large number of monosaccharides such as glucose are bonded in a straight chain, and has strong crystallinity. Hemicellulose is also a polymer in which a large number of monosaccharides are bonded in a straight chain, but the bond is not regular like cellulose and is easily decomposed. Lignin is an amorphous polymer mainly having a benzene nucleus.

  In order to produce monosaccharides from lignocellulose and ferment them to produce ethanol, it is necessary to decompose (saccharify) cellulose and hemicellulose to monosaccharides. Cellulose and hemicellulose are surrounded by a strong structure such as lignin, and since the crystallinity of cellulose is strong, it is not easy to decompose lignocellulose, and various decomposition saccharification methods have been studied. As one of the decomposition saccharification methods of lignocellulose, there is a sulfuric acid method. The sulfuric acid method is a method of obtaining glucose from lignocellulose by hydrolyzing cellulose using concentrated sulfuric acid or dilute sulfuric acid. However, sulfuric acid not only decomposes cellulose and hemicellulose into monosaccharides such as glucose, but also excessively decomposes the produced monosaccharides, so that there is a problem that the yield of the final sugar is lowered.

  As a method for degrading saccharification of lignocellulose other than the sulfuric acid method, there is an enzyme hydrolysis method. This is a method of hydrolyzing and saccharifying cellulose or the like with an enzyme such as cellulase under mild conditions, and can suppress the excessive decomposition of monosaccharides. In the enzymatic hydrolysis method, a pretreatment is required to effectively react the enzyme with cellulose or hemicellulose. That is, it is necessary to perform a pretreatment for decomposing and removing lignin binding cellulose and hemicellulose from lignocellulose and weakening the crystallinity of cellulose.

Examples of the pretreatment method for enzymatic hydrolysis include an alkali method (see Patent Document 1) and a pressurized hot water method (see Patent Document 2). Patent Document 1 discloses pretreatment of waste mushroom beds mainly composed of wood sawdust with an alkaline solution having a concentration of 1% or more as an alkali method. Patent Document 2 discloses a pretreatment for steaming or steaming waste building materials as a pressurized hot water method.
JP2006-20603 JP 2004-89016 A

  Lignocellulosic biomass is divided into woody biomass and herbaceous biomass, and the constituents are different. Woody biomass such as wood chips and waste wood is composed of about 50% cellulose, about 15% hemicellulose, and about 30% lignin, and the ratio of lignin is large, so how to decompose and remove the lignin. This is the point of pretreatment for enzymatic hydrolysis. On the other hand, herbaceous biomass such as bagasse, rice straw, rice husk, palm palm empty fruit bunch (empty fruit bunch with palm palm fruit, EFB) is composed of about 50% cellulose, about 30% hemicellulose, lignin Since it is about 15% and there is little lignin and the hemicellulose content is high, making the hemicellulose available efficiently is the point of pretreatment for enzymatic hydrolysis.

  The pretreatment methods of Patent Documents 1 and 2 are woody biomass pretreatment methods, and the following problems arise when applied to herbaceous biomass.

  When sugar is produced from herbaceous biomass such as palm palm empty fruit bunches, rice straw, bagasse, etc. by enzymatic hydrolysis, it is important to effectively use hemicellulose whose content is as high as 30% as described above. . Hemicellulose has weaker crystallinity and different degradability than cellulose. Hemicellulose, which is more easily decomposed than cellulose, decomposes hemicellulose under the pretreatment conditions in which woody biomass is decomposed with an alkaline solution having a concentration of 1% or more. Since the sugar produced | generated by this will be excessively decomposed | disassembled, the recovery rate of the whole sugar will become low. On the other hand, if the pretreatment conditions are too gentle, the degradation of lignin and embrittlement of the crystallinity of cellulose remain insufficient, and thus there is a problem that enzymatic hydrolysis saccharification after pretreatment does not proceed.

  Moreover, in the pretreatment of steaming or steaming of Patent Document 2, a high pressure device is required for treatment at high temperature and high pressure, and there is a problem that equipment costs and operating costs for the pretreatment are increased.

  The present invention has been made in view of such circumstances, and is a pretreatment method performed before enzymatic hydrolysis of a herbaceous biomass, which suppresses excessive decomposition of sugars produced from hemicellulose by pretreatment, and has a high pressure. A pretreatment method for enzymatic hydrolysis of herbaceous biomass to obtain sugar with high yield at low cost without using an apparatus, a method for producing ethanol using herbaceous biomass as raw material, and ethanol production using palm palm empty fruit bunch as raw material It is an object to provide a method.

According to the present invention, the above-mentioned problems are related to a pretreatment method for enzymatic hydrolysis of herbaceous biomass, an ethanol production method using herbaceous biomass as a raw material, and an ethanol production method using palm palm empty fruit bunch as a raw material as follows. Achieved.

<Pretreatment method for enzymatic hydrolysis of herbaceous biomass>
According to the present invention, the above-mentioned problem relates to a pretreatment method performed before the enzymatic hydrolysis treatment of herbaceous biomass, which contains any one hydroxide of sodium hydroxide, potassium hydroxide, and calcium hydroxide. Is achieved by having an alkali treatment step of alkali treatment with an aqueous hydroxide solution containing 0.2 wt% or more and less than 1 wt%.

  In the present invention, by adjusting the concentration of the aqueous hydroxide solution to 0.2 wt% or more and less than 1 wt%, lignin is decomposed and the crystallinity of cellulose is appropriately weakened. The reason for setting the concentration of the aqueous hydroxide solution in this range is that decomposition of the lignin and embrittlement of the crystallinity of the cellulose do not proceed when the aqueous hydroxide solution concentration is less than 0.2% by weight. This is because the sugar produced by the decomposition of is excessively decomposed and becomes inappropriate.

<Ethanol production method using herbaceous biomass>
According to the present invention, regarding the ethanol production method using herbaceous biomass as a raw material, the above-described problem is a pretreatment step performed by the above-described pretreatment method, and a solid-liquid separation step of solid-liquid separation of the reaction product of the pretreatment step. And an enzyme hydrolysis step for producing a sugar by enzymatic hydrolysis of a solid separated by solid-liquid separation, and a fermentation step for producing ethanol by fermenting the sugar produced by the enzyme hydrolysis. Achieved.

  In addition, regarding the ethanol production method using herbaceous biomass as a raw material, after pulverizing the reaction product of herbaceous biomass after the pre-grinding step of pulverizing herbaceous biomass before the pre-treatment step described above or after the pre-treatment step described above. It is also achieved by having a grinding step.

  In addition, regarding the ethanol production method using herbaceous biomass as a raw material, the pretreatment and pulverization step in which the pretreatment performed by the pretreatment method described above and the pulverization treatment for pulverizing the herbaceous biomass are performed simultaneously, and the reaction product of the pretreatment step A solid-liquid separation process for solid-liquid separation, an enzymatic hydrolysis process for enzymatically hydrolyzing the solid matter separated by solid-liquid separation, and fermenting the sugar produced by enzymatic hydrolysis to produce ethanol. It is also achieved by having a fermentation process to produce.

<Ethanol production method using palm palm empty fruit bunch>
Furthermore, according to the present invention, the above-mentioned problem relates to an ethanol production method using palm palm empty fruit bunches as a raw material, an ethanol production method using palm palm empty fruit bunches as a raw material, and a steaming step of steaming palm palm fruit bunches; A pretreatment performed by the pretreatment method according to any one of claims 1 to 3, and a step of extracting palm fruit from the palm palm fruit bunch after the steaming step to obtain a palm palm empty fruit bunch, a step of crushing the palm palm empty fruit bunch, or A pretreatment process for pretreatment at 60 to 100 ° C., a solid-liquid separation process for solid-liquid separation of the reaction product in the pretreatment process, and a enzyme obtained by enzymatic hydrolysis of the solid material separated by solid-liquid separation. This is achieved by having an enzymatic hydrolysis step to be produced and a fermentation step for producing ethanol by fermenting the sugar produced by the enzymatic hydrolysis.

  In the present invention, in the pretreatment stage, a hydroxide containing any one of sodium hydroxide, potassium hydroxide and calcium hydroxide and having a concentration of 0.2 wt% or more and less than 1 wt% is used. By performing the alkali treatment with an aqueous solution, the pretreatment is performed under mild conditions. This degrades lignin, weakens the crystallinity of cellulose, suppresses the excessive decomposition of hemicellulose, which is a large amount of lignocellulose in herbaceous biomass, and improves the yield of sugar in enzymatic hydrolysis. It is possible to achieve an improvement in ethanol yield in the subsequent fermentation.

  In addition, since the present invention performs pretreatment using a low-concentration hydroxide aqueous solution, it does not require heating and pressurization that are necessary in steaming treatment, so there is no need for expensive equipment and high running costs, Cost can be reduced. Furthermore, according to the present invention, in the production process of herbaceous biomass, particularly palm palm empty fruit bunches, the pretreatment of the enzyme hydrolysis treatment can be performed under mild conditions, so that the hemicellulose overdegradation can be achieved at low energy and low drug cost. This makes it possible to produce sugars with suppressed ethanol and to obtain ethanol at a low cost.

  The pretreatment method for the enzymatic hydrolysis of the herbaceous biomass of the present invention comprises an alkaline treatment step of decomposing the herbaceous biomass raw material with an aqueous solution of any one of sodium hydroxide, potassium hydroxide and calcium hydroxide. The concentration of the aqueous hydroxide solution is preferably 0.2% by weight or more and less than 1% by weight. This avoids excessive decomposition of sugar produced by decomposition of hemicellulose, which is abundant in herbaceous biomass, decomposes lignin, weakens the crystallinity of cellulose appropriately, and recovers sugar after enzymatic hydrolysis. The rate can be increased.

  In this embodiment, a method for producing ethanol including herbaceous biomass as a raw material and including the pretreatment method of the present invention will be described. The production method includes a pulverization step for pulverizing herbaceous biomass raw material, a pretreatment step performed by the above pretreatment method, a solid-liquid separation step for solid-liquid separation of the reaction product of the pretreatment step, and a solid substance separated by solid-liquid separation as an enzyme. It has an enzymatic hydrolysis step for producing sugar by hydrolysis, and a fermentation step for producing ethanol by fermenting the sugar produced by enzymatic hydrolysis.

  First, an outline of the present embodiment will be described. In this embodiment, sodium hydroxide is used as the hydroxide.

  First, in the pulverization step, the herbaceous biomass raw material is pulverized. As a result, the contact between the herbaceous biomass material and the aqueous sodium hydroxide solution is improved in the subsequent pretreatment step, and the decomposition reaction of the herbaceous biomass material is facilitated.

  Next, in the pretreatment step, lignin binding cellulose or hemicellulose in the lignocellulose of the herbaceous biomass raw material is decomposed by the aqueous sodium hydroxide solution, and the crystallinity of the cellulose is embrittled. Due to the decomposition of lignin and the crystalline embrittlement of cellulose, cellulose and hemicellulose are easily hydrolyzed in the subsequent enzymatic hydrolysis step. In the present embodiment, in the pretreatment step, the concentration of the sodium hydroxide aqueous solution is set to 0.2 wt% or more and less than 1 wt% so that the sugar produced by the decomposition of hemicellulose is not excessively decomposed.

  In the solid-liquid separation step, the solid is separated into a solid containing cellulose or hemicellulose and a liquid containing a lignin decomposition product. The solid is hydrolyzed to sugar in a subsequent enzymatic hydrolysis step. Furthermore, ethanol is produced from the sugar in the subsequent fermentation process.

  Next, each process of this embodiment is demonstrated.

<Crushing process>
Cellulose forms a structure in which fibrous substances are aggregated to form a crystal, and the crystallized structure gathers to form a microfibril. In addition, lignin is firmly bound to cellulose. For this reason, since the enzymatic hydrolysis of cellulose is difficult, it is necessary to reduce the degree of crystallization of cellulose. Therefore, the herbaceous biomass raw material is pulverized before the pretreatment of the enzyme hydrolysis to improve the contact between the herbaceous biomass raw material and the aqueous sodium hydroxide solution and to refine the cellulose to reduce the crystallinity. In the pretreatment step, the alkali decomposition reaction and the crystalline embrittlement reaction can be promoted, and the enzyme hydrolysis reaction can be further promoted.

In the pulverization step, the herbaceous biomass material is pulverized to a size of 30 mm or less, preferably 10 mm or less. The smaller the size after pulverization, the higher the efficiency of the pretreatment in the pretreatment step, but the smaller the pulverization size, the greater the energy required for pulverization. From this viewpoint, since an appropriate pulverization size exists, it is preferable to pulverize to the above pulverization size.

As the pulverization means, mechanical pulverization or mechanochemical treatment is effective, and specifically, a grounder, cutter mill, vibration ball mill, rotating ball mill, planetary ball mill, roll mill, disk mill, homomixer, etc. Any of them may be used.

  The pulverization step may be performed before the pretreatment with the alkaline agent or after the pretreatment step with the alkaline agent. Moreover, you may implement a grinding | pulverization process and pre-processing simultaneously by adding an alkaline agent at the time of a grinding | pulverization. When carrying out the pulverization treatment and the pretreatment at the same time, a powdered hydroxide may be added as an alkaline agent. By doing so, the pretreatment and the pulverization can be performed simultaneously without reducing the efficiency of the pulverization.

<Pretreatment process>
The ground herbaceous biomass raw material is alkali-treated in an aqueous sodium hydroxide solution. The weight of the sodium hydroxide aqueous solution is preferably 1 to 5 times the raw material weight. The concentration of the sodium hydroxide aqueous solution is 0.2% by weight or more and less than 1% by weight.

  If the sodium hydroxide aqueous solution concentration is less than 0.2% by weight, the decomposition of lignin and the crystallinity embrittlement of cellulose do not progress, and if it is 1% by weight or more, the sugar produced by the decomposition of hemicellulose is excessively decomposed. Therefore, concentrations below 0.2% by weight and concentrations above 1% by weight are unsuitable.

  The temperature of the sodium hydroxide aqueous solution in the pretreatment may be room temperature in terms of promoting the decomposition reaction of lignin and the crystalline embrittlement reaction of cellulose, but from 60 ° C. in order to further promote the decomposition reaction and the embrittlement reaction. It is preferable to set it as 100 degreeC. It has been confirmed that when the temperature of the aqueous sodium hydroxide solution is higher than 60 ° C., the lignin decomposition reaction and the cellulose crystal embrittlement reaction proceed significantly compared to the case of less than 60 ° C. In order to perform the pretreatment in a state where the temperature of the sodium hydroxide aqueous solution exceeds 100 ° C., a high-temperature / high-pressure treatment apparatus is required, which is unsuitable due to increased equipment costs and operation costs.

  The pretreatment time is preferably 10 minutes to 60 minutes. In less than 10 minutes, the pretreatment is insufficient and saccharification does not proceed in the subsequent enzyme hydrolysis step. Moreover, even if pretreatment for 60 minutes or more is performed, the degree of lignin decomposition or cellulose crystal embrittlement does not change, and pretreatment for 60 minutes or more is unsuitable because it requires processing costs.

  In the alkali treatment, as the alkali agent, in addition to sodium hydroxide, an alkali metal hydroxide such as potassium hydroxide may be used, or an alkaline earth metal hydroxide such as calcium hydroxide is used. May be.

  The concentration range of the alkali metal hydroxide or alkaline earth metal hydroxide solution is about the same as that of sodium hydroxide and is preferably in the range of 0.2 wt% to less than 1 wt%.

  Further, ammonia water, ammonium salts such as quaternary ammonium salts and ammonium carbonate may be used as alkali agents instead of hydroxides. In this case, the preferred concentration range is higher than the hydroxide.

<Solid-liquid separation process>
After the herbaceous biomass is pretreated, it is subjected to solid-liquid separation to separate into solids containing cellulose or hemicellulose whose crystallinity is embrittled and liquids containing lignin degradation products. As a result, impurities such as lignin degradation products can be removed, and cellulose and hemicellulose, which are embrittled crystallinity, can be extracted. Examples of the solid-liquid separation means include filtration methods such as natural filtration, suction filtration, pressure filtration, and centrifugal filtration, and centrifugal separation methods, and any means may be used. Before carrying out the enzyme hydrolysis step after the solid-liquid separation step, it is preferable to wash the solid and to make the pH weakly acidic suitable for the enzyme hydrolysis reaction.

<Enzyme hydrolysis step>
An enzyme is added to the liquid in which the solid obtained in the solid-liquid separation step is suspended, and the solid containing cellulose or hemicellulose is enzymatically hydrolyzed for saccharification. Since lignin is decomposed and removed by pretreatment and solid-liquid separation and the crystallinity of cellulose is embrittled, cellulose and hemicellulose in the solid matter are easily hydrolyzed by enzymes. In the enzyme hydrolysis step, a separately produced enzyme such as cellulase or hemicellulase may be used, or a microorganism such as mold producing the enzyme may be used. Specifically, for example, cellulase is added to a liquid in which a solid is suspended, and the reaction is performed, for example, at pH 4 to 6 and 30 to 60 ° C. for 10 to 120 hours with stirring. The liquid hydrolyzed by the cellulase contains glucose, which is a sugar derived from cellulose, and glucose, xylose, arabinose, galactose, mannose, etc., which are sugars derived from hemicellulose.

<Fermentation process>
A nutrient source containing nitrogen and phosphorus and an ethanol-fermenting microorganism are added to the hydrolyzed sugar solution to convert the sugar into ethanol. As the ethanol fermentation microorganism, either yeast or bacteria may be used. Examples of yeast include Saccharomyces cereviciae, Shizosaccharomyces pombe, Zygosaccharomyces rouxii, and Pichia stipitis. Examples of bacteria include Zymomonas mobilis.

  As described above, when the pretreatment method for herbaceous biomass according to this embodiment is used, it is possible to avoid excessive decomposition of sugar produced by the decomposition of hemicellulose contained in a large amount in herbaceous biomass, and to collect sugar after enzymatic hydrolysis. The rate can be increased. Therefore, the total sugar yield using herbaceous biomass as a raw material increases, and thereby the yield of ethanol produced by fermenting sugar can also be improved.

<Ethanol production from palm palm empty fruit bunch>
Next, ethanol production when palm palm empty fruit bunch is used as herbaceous biomass will be described. Palm palm empty fruit bunches (EFB) are produced in large quantities when palm oil is produced, but the utilization as a biomass raw material has not been studied so far. When oil is extracted from palm palm, the palm palm bunch (FFB) is first steamed using steam. This is to facilitate the removal of palm fruit from FFB and at the same time inactivate enzymes such as lipase to prevent the degradation of palm oil. Next, the palm fruit taken from FFB is squeezed to squeeze palm oil. The palm fruit is separated from the FFB and discarded in the palm palm empty fruit bunch (EFB). Steamed EFB has a high moisture content of about 65% and is unsuitable for use as a fuel. Therefore, it has often been discarded without being effectively used.

  In the present invention, in cooperation with the palm oil production process, it was considered to assemble a process for producing ethanol by utilizing palm palm empty fruit bunches. The pretreatment step in this manufacturing process is preferably performed following the step of removing EFB when palm oil is produced from palm palm.

The manufacturing process is performed through the following steps.
(1) Steaming process of steaming palm palm bunch,
(2) The process of taking out a palm palm fruit from a palm palm fruit bunch after a steaming process, and obtaining a palm palm empty fruit bunch,
(3) a step of pulverizing palm palm empty fruit bunch,
(4) A pretreatment step of performing an alkali treatment with a 0.2 to 1% by weight sodium hydroxide aqueous solution (temperature: normal temperature or 60 to 100 ° C.) or a pretreatment of cooking at 60 to 100 ° C.,
(5) A solid-liquid separation step for solid-liquid separation of the reaction product in the pretreatment step,
(6) Enzymatic hydrolysis step for producing a sugar by enzymatic hydrolysis of solids separated by solid-liquid separation (7) Fermentation step for producing ethanol by fermenting the sugar produced by enzymatic hydrolysis In the oil extraction step Since the separated EFB has been cooked, the temperature is high, and further heating is unnecessary or less in the pretreatment step, so that energy for pretreatment can be saved. According to the above-described manufacturing process, EFB, which has been a waste material, can be used for enzymatic saccharification treatment for producing sugar, and ethanol can be further manufactured. Moreover, the heat energy used in the steaming process of steaming the palm palm fruit bunch can be effectively used as the heat energy for pretreatment.

  In this embodiment, although the sodium hydroxide aqueous solution was used as a pre-processing method, it may replace with it and you may pre-process using 60-100 degreeC warm water. As described above, by using warm water of 60 to 100 ° C., the rate of the lignin decomposition reaction and the cellulose embrittlement reaction is low as compared with the case of using the sodium hydroxide aqueous solution, but by pre-processing in an appropriate time, A low-cost pretreatment that does not require a high-temperature and high-pressure apparatus and a medicine can be performed.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely using an Example, this invention is not limited to these Examples.

  In this example, palm palm empty fruit bunches (EFB) are used as herbaceous biomass raw materials, pulverized to a size of 10 mm or less with a ball mill, and the concentration and temperature in an aqueous sodium hydroxide solution 5 times the weight of the raw materials. The pretreatment was carried out under different conditions, the pretreated reaction product was suction filtered, and the pretreated solid matter of the filtered residue was subjected to an enzymatic hydrolysis step. Enzymatic hydrolysis treatment was performed using a Meicelase solution as a cellulase enzyme and treated in 0.1 M acetate buffer (pH 4.5) at 40 ° C. for 24 hours. Then, the enzyme-hydrolyzed product was subjected to suction filtration, and the sugar in the filtrate was analyzed by the Sommoji Nelson method to determine the sugar yield per 100 g of EFB (dry matter) raw material.

  The concentration of the aqueous solution of sodium hydroxide is 0, 0.05, 0.1, 0.2, 0.4, 0.8, 0.9, 1 1.5 and 2 wt%, and the treatment temperature was 20 and 60 ° C.

  Table 1 shows the results of a test for producing sugar from the palm palm empty fruit bunches.

  When producing ethanol from herbaceous biomass, if the sugar yield per 100 g of raw material is 35 g or more, it is said to be an industrially efficient process, so the above test results will be evaluated based on this. .

  As shown in Table 1, at each temperature of 20 ° C. and 60 ° C., the sugar yield per 100 g of raw material was 35 g or more when the concentration of the sodium hydroxide aqueous solution was in the range of 0.2 wt% or more and less than 1 wt%. . If the amount is less than 0.2% by weight, the decomposition of lignin and the crystalline embrittlement of cellulose do not progress, and if the concentration is 1% by weight or more, the sugar produced by the decomposition of hemicellulose is excessively decomposed, and the sugar yield after enzymatic hydrolysis treatment Was confirmed to be low.

  Regarding the temperature, the sugar yield was slightly higher in the case of 60 ° C. than in the case of 20 ° C. However, as the treatment temperature of the aqueous sodium hydroxide solution increases, the excessive decomposition of the sugar produced by the decomposition of hemicellulose progresses, so the enzymatic hydrolysis treatment efficiency from cellulose increases due to lignin decomposition and cellulose embrittlement, but overall the sugar The yield of was not significantly increased.

  Similar results were obtained when pretreatment was performed using potassium hydroxide or calcium hydroxide instead of sodium hydroxide. The preferred concentration ranges of the aqueous potassium hydroxide solution and the aqueous calcium hydroxide solution are sodium hydroxide. The range is preferably 0.2% by weight or more and less than 1% by weight.

Claims (7)

It is a pretreatment method performed before the enzymatic hydrolysis treatment of herbaceous biomass,
Having an alkali treatment step of alkali treatment with a hydroxide aqueous solution containing any one hydroxide of sodium hydroxide, potassium hydroxide and calcium hydroxide and having a concentration of 0.2 wt% or more and less than 1 wt% A pretreatment method for enzymatic hydrolysis of herbaceous biomass characterized by   The pretreatment method for enzymatic hydrolysis of herbaceous biomass according to claim 1, wherein the temperature of the aqueous hydroxide solution is normal temperature.   2. The pretreatment method for enzymatic hydrolysis of herbaceous biomass according to claim 1, wherein the temperature of the aqueous hydroxide solution is 60 to 100 ° C. 3. A pretreatment step performed by the pretreatment method according to any one of claims 1 to 3;
A solid-liquid separation step for solid-liquid separation of the reaction product in the pretreatment step;
An enzymatic hydrolysis step of producing a sugar by enzymatic hydrolysis of the solid separated by solid-liquid separation;
A fermentation process for producing ethanol by fermenting sugar produced by enzymatic hydrolysis;
A method for producing ethanol using herbaceous biomass as a raw material.   The herbaceous biomass according to claim 4, further comprising a pre-grinding step of pulverizing the herbaceous biomass prior to the pretreatment step or a post-grinding step of pulverizing a reaction product of the herbaceous biomass after the pretreatment step. A method for producing ethanol as a raw material. A pretreatment and pulverization step for simultaneously performing the pretreatment performed by the pretreatment method according to any one of claims 1 to 3 and the pulverization treatment for pulverizing the herbaceous biomass;
A solid-liquid separation step for solid-liquid separation of the reaction product in the pretreatment step;
An enzymatic hydrolysis step of producing a sugar by enzymatic hydrolysis of the solid separated by solid-liquid separation;
A fermentation process for producing ethanol by fermenting sugar produced by enzymatic hydrolysis;
A method for producing ethanol using herbaceous biomass as a raw material. An ethanol production method using palm palm empty fruit bunch as a raw material,
Steaming process of palm palm bunch,
A step of removing palm fruits from the palm palm fruit bunch after the steaming process to obtain a palm palm empty fruit bunch;
Crushing palm palm empty fruit bunch;
A pretreatment step of performing a pretreatment performed by any of the pretreatment methods of claims 1 to 3 or a pretreatment of steaming at 60 to 100 ° C;
A solid-liquid separation step for solid-liquid separation of the reaction product in the pretreatment step;
An enzymatic hydrolysis step of producing a sugar by enzymatic hydrolysis of the solid separated by solid-liquid separation;
A fermentation process for producing ethanol by fermenting sugar produced by enzymatic hydrolysis;
An ethanol production method using palm palm empty fruit bunch as a raw material.