JP2010136686A - Method for saccharifying wood-based biomass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for pre-treating bark and a method for saccharifying the pre-treated bark, enabling a high yield saccharification by the enzyme treatment of cellulose and hemicellulose contained in the bark of an arboreous plant. <P>SOLUTION: The method for saccharifying wood-based biomass is provided with that the bark of the arboreous plant is pre-treated by immersing it in an aqueous alkaline solution of ≥pH 7.5, containing 2 to 10 mass% sulfite salt or hydrogen sulfite salt and also 1 to 5 mass% alkaline pH-adjusting assistant for a fixed time. Fibers obtained by the solid liquid separation of the pre-treated liquid and loosening of the pre-treated material are decomposed by a polysaccharide degradative enzyme to saccharify the bark of the arboreous plant. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pretreatment method for woody biomass and a novel saccharification method using a pretreated product subjected to the pretreatment method as a raw material. In particular, the present invention relates to a pretreatment method for using bark of a woody plant as a saccharification raw material, and a saccharification method of the pretreated product.

  As one of the carbon dioxide emission reduction measures for suppressing global warming, bioenergy development obtained by converting biomass into energy is being carried out. As a method of biomass conversion, as shown in many books (Non-Patent Documents 1 to 4), pyrolysis, gasification, anaerobic fermentation, etc. are widely performed. Methods for obtaining ethanol by fermenting saccharides are widely studied.

  Ethanol can be used as a liquid fuel, particularly as a transportation fuel. In the United States and Brazil, a process for producing bioethanol using starch or sugar obtained from corn or sugar cane as a raw material has already been put into practical use. It has been pointed out that when the price of gasoline rises with these raw materials, corn, sugar cane, etc. that should have been originally produced for food are used as bioethanol raw materials. Therefore, bioethanol production using raw biomass that does not compete with food is required.

Unused biomass includes herbaceous biomass such as rice straw and bagasse, and woody biomass such as forest residue and thinned wood. Among these, herbaceous biomass such as rice straw and bagasse is generally single-year, has a short annual available period, and has a low weight per unit volume (hereinafter also referred to as bulk weight) (150 or more, 300 kg / kg). m < ³ ). On the other hand, since woody biomass is generally perennial, it can be said that it is characterized by being available throughout the year and having a high bulk weight (300 kg / m ³ or more). Furthermore, while herbaceous biomass requires a yard for stocking raw materials that are discharged in a short period of time, woody biomass does not have this concern, and the bulk weight is high, so the transportation cost of raw materials is kept low. It is thought that it can be done.

On the other hand, business planting for the purpose of using pulp and building materials is being actively carried out, and it is said that the area of overseas plantation carried out by domestic companies reaches 400,000 ha. Among them, eucalyptus planted as a pulp material accounts for the majority. Eucalyptus grows quickly and can be harvested in about 10 years, so pulp has already been produced in Japan through logging and chipping.
A tree is divided into an inner xylem and an outer bark with a formation layer where cell division is active as a boundary. In young eucalyptus, the bark has a relatively low lignin content compared to the xylem and is soft with many soluble components.

In addition, the bark is divided into an outer bark of dead tissue and an inner bark of living tissue.
The outer bark mainly consists of pericytes or cork layers, which protects the wood tissue from mechanical damage and reduces fluctuations in temperature and humidity.
The inner bark consists of mentor elements, parenchyma cells and thick-walled cells. The mentor elements have the function of transporting liquids and nutrients, and the parenchyma has a function of storing nutrients such as starch and is interposed between the mentor elements of the inner bark. . Thick wall cells function as a supporting tissue, are observed in layers like the xylem rings, and are differentiated into bast fibers and scleroids by shape.

Bark tissue is roughly divided into fine substances including fibers, cork cells, and parenchyma cells. Bark fibers are chemically similar to xylem fibers and are composed of cellulose, hemicellulose and lignin. A fine substance containing cork cells and parenchyma contains a large amount of extracted components, and the cork cell walls are rich in suberins and the fine substance fraction is rich in polyphenols. Thus, bark, unlike xylem, contains many useful soluble components, the amount of which reaches 20-40% of the dry mass, and the fiber fraction has the same fiber as xylem. Has excellent properties.
However, bark is not used in timber applications and can be returned to the soil as a fertilizer in the plantation along with branches and roots when pulping in the papermaking process to reduce pulp quality even if mixed slightly. They are peeled and incinerated at lumber mills or chip mills and are not effectively used as woody biomass.

As methods for converting woody biomass to bioethanol, various methods have been studied, as shown in many books (Non-patent Document 1, Non-patent Document 2, Non-patent Document 3). Among them, methods for obtaining ethanol by fermentation after mono-saccharification by acid saccharification method or enzymatic saccharification method are widely studied.
The acid saccharification method is a method of hydrolyzing woody biomass with an inorganic acid such as sulfuric acid to obtain sugar, and a dilute acid method and a concentrated acid method have been proposed depending on the concentration (Patent Documents 1 and 2). In the dilute acid method, both the temperature and the pressure are high, and the device is corroded by the added acid. Furthermore, there is a problem that it is difficult to separate the produced saccharide and acid and there is no economically effective acid recovery method. Moreover, since the concentrated acid method has a relatively low temperature and pressure, an inexpensive reactor material can be used, and the yield of glucose is high. However, there is a problem that a large amount of waste acid is generated because there is no economically effective method for separating and recovering acid from saccharides produced in the same manner as the diluted acid method.

  Enzymatic saccharification is a method in which lignocellulose is saccharified with enzymes such as cellulase and hemicellulase, and saccharification is possible under milder conditions than acid saccharification, so there are no restrictions on the equipment materials and the treatment of effluent. Convenient. However, since the cellulose in lignocellulose is covered with lignin and hemicellulose and the enzyme cannot easily contact the cellulose, the saccharification rate is generally low. Therefore, physical pretreatments such as fine pulverization, pressurized hot water treatment, steaming / explosion treatment, and chemical pretreatment with chemicals such as acids and alkalis have been mainly studied in order to improve the enzyme saccharification rate.

Among the physical pretreatments, pulverization is intended to promote saccharification by exfoliating part of lignin and hemicellulose covering cellulose by pulverization and increasing the frequency with which the enzyme contacts cellulose. This is a pre-processing method.
The pressurized hot water treatment is a method in which lignin and hemicellulose are softened and separated from cellulose by hot hot water. Furthermore, there is also known a method of performing saccharification with an enzyme on a processed product that has been subjected to mechanical grinding after being softened by pressurized hot water treatment (see Patent Document 3).
Also, in the steaming / explosive treatment method in which biomass is released immediately under atmospheric pressure or near low temperature and low pressure conditions after high-temperature and high-pressure treatment, the enzyme is produced by causing cracks in the lignin and hemicellulose covering the cellulose. It becomes possible to contact cellulose (see Patent Document 4).

  The chemical pretreatment is a pretreatment that enables enzymatic saccharification by removing lignin and hemicellulose covering cellulose by softening or dissolving them with chemicals and exposing the cellulose to the surface. Alkaline treatment as in Patent Document 5 is a typical chemical pretreatment, but polysaccharide degrading enzymes such as cellulase and hemicellulase must be treated in a neutral to weakly acidic region, so that chemical removal is required before saccharification. Or the process of adjusting pH may be needed.

The method of Patent Document 3 requires a large energy cost, and the method of Patent Document 4 similarly requires an energy cost and can only perform batch processing. As described above, Patent Document 5 has drawbacks such as requiring a neutralization step.
JP 2006-75007 A JP 2006-246711 A JP 2006-136263 A JP 59-204997 A JP 2008-092910 A Edited by The Wood Society of Japan, “Wood Biomass Utilization Technology” p19-61, Bunnendo Publishing, July 1997 Hideaki Yukawa et al. “Latest Biomass Energy Utilization”, Chapter II-1, CMC Publishing, August 2001 Keisuke Iizuka et al. “Latest Technology of Wood Chemicals” p6-34, published by CMC, October 2001 Funaoka et al. “New Development of Woody Organic Resources” Chapter 5-2, CMC Publishing, published in January 2005

  Enzymatic saccharification treatment does not have a sufficient saccharification yield even when pretreatment as described above is performed. An object of the present invention is to provide a simple pretreatment method necessary for saccharifying cellulose and hemicellulose contained in woody biomass by enzymatic treatment, and improving the saccharification yield. Moreover, even if it eliminates the process of neutralizing for an enzyme process after a pre-processing, or provides the process of neutralizing, it makes it a subject to reduce a chemical | medical agent as much as possible.

  As a result of intensive studies to solve the above problems, the present inventors have specialized in raw materials for bark and, as a pretreatment, low concentration sulfite in which an alkaline pH adjusting aid is mixed with the bark. Alternatively, it has been found that the enzyme saccharification yield can be improved by immersing with an aqueous solution of bisulfite. That is, the present invention is selected from the following methods.

(1) The bark of a woody plant is contained in an alkaline aqueous solution having a pH of 7.5 or more containing 2 to 10% by mass of sulfite or bisulfite and 1 to 5% by mass of an alkaline pH adjusting aid. A method for saccharifying a bark of a woody plant, characterized by decomposing a fiber obtained by soaking for a certain period of time, followed by solid-liquid separation and fibrillation with a polysaccharide-degrading enzyme.
(2) The method according to (1) above, wherein the pH of the liquid after the immersion treatment is 7.5 to 11.0, wherein the bark of the woody plant is saccharified.
(3) A method for saccharifying bark of a woody plant, wherein the sulfite or bisulfite is a sodium salt in the method according to (1) or (2) above.
(4) In the method according to any one of (1) to (3), the pH adjuster is an alkali carbonate, an alkali hydrogen carbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide. A method for saccharifying bark of a woody plant, characterized in that it is at least one selected from the group consisting of sodium carbonate and sodium hydrogen carbonate.
(5) In the method described in (4) above, when the pH adjusting aid is a salt of a weak acid such as an alkali carbonate or an alkali hydrogen carbonate, the mass of the sulfite or the bisulfite is 1 / A method for saccharifying bark of a woody plant, comprising blending in an amount of 2 or more and 2 or less.
(6) The method according to any one of (1) to (5) above, wherein the temperature of the dipping treatment is 130 ° C. or lower, and the method for saccharifying a bark of a woody plant.
(7) In the method according to any one of (1) to (6) above, the immersion treatment time is 5 to 60 minutes when the treatment temperature exceeds 100 ° C, and the treatment temperature is 100 ° C or less. Is a method for saccharifying bark of a woody plant, characterized in that it is 10 to 120 minutes.
(8) In the method according to any one of (1) to (7) above, the bark saccharification of a woody plant is characterized in that the mass ratio of the alkaline aqueous solution to the dry mass 1 of the bark is in the range of 5 or less. Method.
(9) In the method according to any one of the above (1) to (8), the woody plant belongs to the genus Eucalyptus, preferably a Grandis species, a globulous species, a nitens species, It is at least one selected from the species of camaldulensis, degrapta, viminalis, Urophylla, dunnii and their hybrids To saccharify the bark of woody plants.
(10) The method for saccharifying a bark of a woody plant according to any one of (1) to (9) above, comprising the method of immersing the bark of a woody plant in an alkaline aqueous solution for a certain time. A method for producing raw materials used in the method for saccharification of bark.

  According to the method of the present invention, as a pretreatment for enzymatic saccharification, the use of a low concentration of chemicals reduces the environmental burden, enables a pretreatment in a short time and with less input energy, and also improves the saccharification yield. It has become possible.

  The lignocellulose targeted in the present invention is the bark of a woody plant. The bark to be used is not particularly limited, but is preferably a genus Eucalyptus, more preferably a grandis, a globulus, a nitens, a camaldulensis, a degrapta ) Species, Viminalis species, Urophylla species, Dunnii and their hybrids.

The bark raw material can be used as a raw material in an available state. Usually, it is preferable to treat the material as it is if it is in a state of being cut or pulverized into several cm ² in consideration of handling property at the time of conveyance. The smaller the size of the bark raw material, the easier it is to treat. However, in the method of the present invention, the bark treated in the pretreatment process can be easily refined with less energy cost by defibrating treatment, so the dried bark raw material is excessively refined It is preferable to avoid processing.

Below, the process of this invention is demonstrated in order.
First, a so-called pretreatment process will be described in which the bark is held for a certain period of time in a state of being immersed in a low concentration sulfite solution mixed with an alkaline pH adjusting aid.
The sulfite or bisulfite used in the pretreatment step is not particularly limited as long as it softens the bark. For example, a solution containing at least one sulfite from sulfite water, ammonium sulfite, calcium sulfite, magnesium sulfite, sodium sulfite, ammonium hydrogen sulfite, calcium hydrogen sulfite, magnesium hydrogen sulfite, sodium hydrogen sulfite can be used, preferably Sodium sulfite can be used.
It is necessary to use 2 to 10% by mass of sulfite or bisulfite as a solution concentration. If it is less than 2% by mass, the effect as a pretreatment is insufficient, and even if it exceeds 10% by mass, the effect reaches a peak. It becomes.

  Furthermore, the alkaline pH adjusting aid is preferably at least one selected from alkali carbonates, alkali hydrogen carbonates, sodium hydroxide, magnesium hydroxide, and potassium hydroxide. By mixing the pH adjusting aid, the enzyme reaction in the subsequent process is promoted. These pH adjustment aids not only promote the reaction but also have an effect of keeping the pH in the vicinity of neutrality, so that removal of chemicals and pH adjustment can be omitted in the enzyme reaction step.

  The alkaline pH adjustment aid needs to be used in an amount of 1 to 5% by mass as the solution concentration. If it is less than 5% by mass, the pH adjustment effect is insufficient, and even if it exceeds 5% by mass, the effect reaches a peak. At the same time, the alkalinity becomes too strong. In any case, the pH of the treatment solution before immersion needs to be alkaline of 7.5 or more, and when it is less than 7.5, the effect of improving the sugar yield is not perfect. In consideration of the upper limit of pH, the treatment solution pH before immersion is preferably 7.5 to 13.6, more preferably 8.0 to 12.5. When the pH is high, the sugar yield increases, but the pH after the treatment increases, and a lot of chemicals required for neutralization are required.

When the pH adjustment aid is an alkali metal or alkaline earth metal hydroxide, the pH adjustment aid is equal to or less than the mass of sulfite or bisulfite, and the solution concentration is 2.5. It should be blended at a mass% or less, and if this amount is exceeded, the pH after the treatment becomes high, and a neutralization treatment before the enzyme treatment is required.
When the pH adjusting aid is a salt of a weak acid such as alkali carbonate or alkali hydrogen carbonate, it may be blended in an amount of 1/2 or more and 2 or less times the mass of sulfite or bisulfite. preferable. If it is this range, since the pH after a process is not so high, it can enter into an enzyme treatment process, without neutralizing, and the effect which maintains the pH in a system stably can be exhibited.

Another object of the present invention is to eliminate the neutralization step after the pretreatment step or to reduce the chemical for neutralization as much as possible. The immersion treatment is preferably carried out with an alkaline pH of 7.5 or higher, and the higher the pH, the higher the yield of subsequent saccharification treatment. However, many enzymes used for saccharification are highly active in the neutral or acidic region. In order to reduce the neutralizing chemical as much as possible, the pH after the immersion treatment needs to be 11.0 or less.
There are alkaline and saccharifying enzymes, but even in that case, the conditions are preferably pH 10.0 or less. Therefore, if the pH after the immersion treatment is 10.0 or less, the neutralization step can be omitted. Therefore, it is preferable that the mixture of sulfite or bisulfite and an alkaline pH adjuster has a pH close to neutral after immersing the bark, and in particular, the pH after the immersing is 10.0 or less. Such a blending ratio is preferable.

  The above-mentioned mass proportions of the respective drugs take into account this point. However, depending on the combination of the drugs, even if the mass proportion is blended, a preferable pH range may not be obtained. In such a case, it is preferable to determine the blending ratio by prior experiments. As a standard, in order to set the pH after the immersion treatment to 7.5 to 11.0, the pH is set to 8.0 to 13.5, preferably 8.0 to 13 in the state before the treatment.

The mass ratio of the aqueous solution to the dry mass 1 of the bark can be selected within a range of 5 or less. If the amount ratio of the aqueous solution is high, the energy required for heating increases, which is expensive. When the remaining liquid fraction obtained by separating the solid content after the treatment is treated as a waste liquid, the treatment cost increases as the amount ratio of the solution increases.
The temperature of the immersion treatment can be selected in the range of 50 ° C. to 130 ° C., and may be pressurized. Considering the effect of softening the bark and the evaporation of water, implementation at 100 ° C. or lower is preferable. The heating time is selected in the range of 5 to 60 minutes under the condition of exceeding 100 ° C, and in the range of 10 to 120 minutes in the case of 100 ° C or less.

  The bark treated by immersing in a sulfite solution may be subjected to a defibrating process as it is, or may be subjected to a defibrating process by separating the solid and liquid components by solid-liquid separation. As solid-liquid separation means, filtration under normal pressure using a filter or the like, pressure filtration, suction filtration, or centrifugal separation means can be used.

Next, the defibrating process will be described.
The machine used for the defibrating process varies depending on the degree of the pretreatment described above, and when the lignin is sufficiently dissolved, it can be defibrated by a disintegrator that disaggregates pulp or a refiner that beats pulp. Further, when the degree of lignin dissolution in the pretreatment is low, it is ground and defibrated using a grinder or a refiner used when producing mechanical pulp from wood. As the grinder, a stone grinder that presses and grinds a lignocellulosic material against a stone roll is preferable. For example, a pocket grinder pressed by a cylinder or a chain grinder pressed by a chain can be used. As the stone, natural stone, cement stone, ceramic stone and the like can be used. A stone mill grinder can also be used.

  As the refiner, various high-concentration refiner machines used for producing mechanical pulp from wood can be used. Refiner molds include a single disk refiner that is ground by a fixed disk and one rotating disk, a double disk refiner that is ground by two counter-rotating disks, and a disk that rotates on both sides of the fixed plate. A twin disc refiner can be used. Further, a conical refiner in which the rotating plate is not a flat plate but a conical shape can be used. In grinders and refiners, a grinding process is performed while preventing clogging in the grinding machine using a hot water shower or the like in order to maintain grinding efficiency.

Next, the enzymatic saccharification step will be described. In the enzymatic saccharification step, a cellulose-degrading enzyme and, if necessary, a hemicellulose-degrading enzyme are also added, and the bark after the defibrating treatment is enzymatically treated. At this time, the bark is in a state of a neutral or weak alkaline aqueous slurry in a state of pulp fibers. The bark concentration in the slurry is adjusted to 10 to 60% by mass, preferably about 30 to 50% by mass.
The cellulolytic enzyme used in the saccharification reaction step is an enzyme collectively called cellulase having cellobiohydrolase activity, endoglucanase activity, and betaglucosidase activity.
Another enzyme used as necessary in the saccharification and fermentation reaction step, hemicellulose-degrading enzyme is at least selected from a series of hemicellulose-degrading enzymes such as xylan-degrading enzyme, mannan-degrading enzyme, pectin-degrading enzyme, and arabinan-degrading enzyme. It is an enzyme.

Cellulose-degrading enzyme and hemicellulose-degrading enzyme may be added in appropriate amounts, respectively, but commercially available cellulase preparations have various cellulase activities as well as hemicellulase activity. There are many, and a commercially available cellulase preparation may be used.
Commercial cellulase preparations include Trichoderma, Acremonium, Aspergillus, Phanerocheet, Trametes, Humicola, and Humicola. There are cellulase preparations derived from the above. Examples of such commercially available cellulase preparations are all trade names, for example, cellulosin T2 (manufactured by HIPI), mecerase (manufactured by Meiji Seika Co., Ltd.), Novozyme 188 (manufactured by Novozyme), multifect CX10L (manufactured by Genencor) ) And the like.

  The amount of the cellulase preparation used relative to 100 parts by mass of the bark solid content is preferably 0.5 to 100 parts by mass, particularly preferably 1 to 50 parts by mass.

The reaction conditions are preferably as close to neutrality as possible. When the pH after the defibrating treatment is higher than the optimum pH of the enzyme to be selected, neutralization with an acid is preferable.
The temperature is preferably 25 to 50 ° C, more preferably 30 to 40 ° C. The saccharification and fermentation reaction is preferably a continuous type, but may be a batch type. The saccharification and fermentation reaction time varies depending on the enzyme concentration, but in the case of a batch type, it is 10 to 240 hours, more preferably 15 to 160 hours. Also in the case of a continuous type, the average residence time is 10 to 150 hours, more preferably 15 to 100 hours.

  EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to a following example. In each Example shown below,% is based on the total mass unless otherwise specified. For calculating the average degree of polymerization, the total sugar amount was calculated by the phenol-sulfuric acid method. For each quantification method, the “quantification method of reducing sugar” (Sakuzo Fukui Publishing Center) was referenced.

Example 1
Eucalyptus globulus bark was cut into approximately 1 cm square and used in the following tests.
The sample corresponding to 5 g of absolute dryness was immersed in a sulfite solution containing 20 ml of 5% sodium sulfite and 2.5% sodium hydrogen carbonate, and this mixture was heated at 120 ° C. for 1 hour for immersion treatment. It was 8.54 when the pH of the liquid was measured before the immersion treatment (5 minutes after the sample was immersed in the solution).
After the immersion treatment, the sample and the sulfite solution were separated using a fluororesin mesh. The pH of the separated liquid after cooling to 25 ° C. was measured to be 9.25.
The soaked bark was defibrated for 1 minute using a Waring blender [7012S type manufactured by Osaka Chemical Co., Ltd.]. After defibration, the extracted fiber is subjected to an enzymatic saccharification treatment at 50 ° C. for 18 hours under the condition in which 3 ml of commercially available cellulase (GC220 manufactured by Genencor) is added to 100 ml of 100 mM acetate buffer (pH 5.0). The amount of sugar in the subsequent saccharified solution was measured, and the sugar yield was calculated according to the following formula.

    Sugar yield (%) = [sugar amount in saccharified solution (%) / sample dry weight (%)] × 100

  When the sugar yield was calculated for this sample, a sugar equivalent to 44.2% of the bark mass could be obtained. When sugar is extracted from this sample by treatment with 70% sulfuric acid at 20 ° C. for 18 hours, sugar equivalent to 46.5% of the untreated bark can be obtained. The recovery rate is calculated to be 95.0%.

(Comparative Example 1)
Immersion treatment and saccharification were performed in the same manner as in Example 1 except that the xylem was used instead of the bark.
When the sugar yield was calculated for this sample, it was possible to obtain a sugar equivalent to 15.3% of the pre-treatment xylem. When sugar is extracted from this sample by treatment with 70% sulfuric acid at 20 ° C. for 18 hours, sugar equivalent to 55.0% of the xylem before treatment can be obtained. The sugar recovery rate is calculated as 27.8%.
In the case of xylem, the pH before and after the immersion treatment was measured in the same manner as in Example 1. The pH before treatment was 8.54, and the pH after treatment was 9.01, and there was no significant difference.
From the comparison between Example 1 and Comparative Example 1, it was found that in the case of the immersion treatment of the present invention, the sugar recovery rate of the bark was significantly higher than that of the xylem.

(Example 2)
Example 2-1 was obtained by performing immersion treatment and saccharification in the same manner as in Example 1 except that the immersion liquid was sulfite solution of 2.5% sodium sulfite and 2.5% sodium bicarbonate 20 ml. .
Moreover, except having changed the immersion liquid into what is shown in Table 1, what was carried out similarly to Example 2-1 was set to Example 2-2 to Example 2-4, and sugar yield was also described in Table 1.

(Comparative Example 2, Example 3)
Examples 3-1 to 3-3 and Comparative Example 2 were the same as in Example 1 except that sodium bisulfite and a pH adjusting aid were used as the immersion liquid, and the compositions described in Table 1 were used. The sugar yield is also listed in Table 1.

(Reference example)
Examples similar to those in Examples except that sulfites, hydrogen sulfites, and pH adjusting aids were used alone as immersion liquids are shown in Table 2 as reference examples. The concentration of each solution and the sugar yield are also shown in Table 2.
In Tables 1 and 2, A is sodium sulfite, B is sodium hydrogen sulfite, 1 is sodium hydrogen carbonate, 2 is sodium carbonate, and 3 is a system using sodium hydroxide.

  In each example, when NaOH is used as a pH adjustment aid, the sugar yield increases, but the pH after the treatment tends to increase. From the balance between the pH after treatment and the sugar yield, sodium sulfite is used, Most preferably, sodium carbonate or sodium bicarbonate is used as the pH adjuster.

Claims (7)

  The bark of a woody plant is immersed in an alkaline aqueous solution of pH 7.5 or higher containing 2 to 10% by mass of sulfite or bisulfite and 1 to 5% by mass of an alkaline pH adjusting aid for a certain period of time. A method for saccharifying a bark of a woody plant, characterized by decomposing a fiber obtained by solid-liquid separation and defibration after treatment with a polysaccharide-degrading enzyme.   The method for saccharifying bark of a woody plant according to claim 1, wherein the pH of the solution after immersion treatment in the alkaline aqueous solution for a certain time is 7.5 to 11.0.   The method for saccharifying bark of a woody plant according to claim 1 or 2, wherein the sulfite or bisulfite is a sodium salt.   The pH adjuster is at least one selected from the group consisting of alkali carbonate, alkali hydrogen carbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide and magnesium hydroxide. Item 4. A method for saccharifying bark of a woody plant according to any one of Items 1 to 3.   The method for saccharifying bark of a woody plant according to any one of claims 1 to 4, wherein the temperature of the immersion treatment is 130 ° C or lower.   The time of the immersion treatment is 5 to 60 minutes when the treatment temperature exceeds 100 ° C, and 10 to 120 minutes when the treatment temperature is 100 ° C or less. A method for saccharifying bark of a woody plant according to any one of the above.   The woody plant includes Eucalyptus genus grandis, globulus, nitens, camaldulensis, degrupta, viminalis, The saccharification of the bark of a woody plant according to any one of claims 1 to 6, characterized in that it is at least one selected from the species of Europhylla, Dunnii and hybrids thereof. Method.