WO2021049363A1 - Method for producing organic solvent-soluble lignin - Google Patents

Abstract

A method for producing an organic solvent-soluble lignin includes a pretreatment step of pretreating a herbaceous biomass by a dilute sulfuric acid digestion method, a saccharification step of saccharifying the pretreated herbaceous biomass obtained in the pretreatment step with an enzyme, a solid-liquid separation step of performing solid-liquid separation of the saccharification treatment product obtained in the saccharification step to obtain a saccharification residue, and an extraction step of adding an organic solvent to the saccharification residue to extract an organic solvent-soluble lignin, wherein in the pretreatment step, the treatment intensity by the dilute sulfuric acid digestion method is controlled so that the β-O-4 bond content, weight average molecular weight, molecular weight distribution, and hydroxyl group content of the obtained organic solvent-soluble lignin are within predetermined ranges.

Description

Method for producing organic solvent-soluble lignin

The present invention relates to a method for producing an organic solvent-soluble lignin.
The present application claims priority based on Japanese Patent Application No. 2019-165546 filed in Japan on September 11, 2019, the contents of which are incorporated herein by reference.

In recent years, the use of biomass made from plant resources has been attracting attention from the viewpoint of global warming countermeasures and effective utilization of waste. In general, sugars such as sugar cane and starches such as corn are often used as raw materials for producing compounds such as ethanol from biomass. However, these raw materials are originally used as food or feed, and if they are used as industrial resources for a long period of time, there is a risk of causing competition with food or feed use and causing a rise in raw material prices.

Therefore, technological development is underway to utilize non-edible biomass as an energy resource. Non-edible biomass includes cellulose, which is the most abundant on the earth, but most of it exists as lignocellulose, which is a complex with aromatic polymers lignin and hemicellulose.

In ethanol production using lignocellulose-based biomass as a raw material, it was obtained in a pretreatment step of thermochemically pretreating the biomass raw material, a saccharification step of enzymatically treating the biomass after the pretreatment step to produce a saccharified solution, and a saccharification step. It comprises a fermentation step of adding a microbial culture solution to a saccharified solution to perform ethanol fermentation, and a purification step of separating ethanol from the fermented solution obtained in the fermentation step by distillation or the like. In this ethanol production, since lignin remains as a solid, there is a problem that a large amount of fermentation residue is generated. This fermentation residue is generally processed by a boiler in an annexed factory, methane fermentation, etc., and is not effectively used at present.

Similarly, in the papermaking process using non-edible biomass as a raw material, lignin-based products (black liquor, lignin sulfonate) are generated as residues, and technology for effective utilization has been developed for many years. However, in the process of chemically decomposing biomass, lignin is affected by sulfonation or chloride, so that it is difficult to use, and most of them are limited to fuel use as a boiler heat source.

On the other hand, when lignin is decomposed, a phenol derivative or the like is obtained, so that it can be used as a raw material for chemical industrial products such as resin raw materials, composite materials and surfactants. Therefore, it is desired to develop a method for efficiently producing a decomposition product of lignin.

Patent Document 1 discloses a method for producing a lignin decomposition product by treating a lignin-containing biomass with a mixed solvent having a molar ratio of water to alcohol of 1/1 to 20/1. Patent Document 2 discloses a method for producing low molecular weight lignin by heating lignin-containing biomass in the presence of an acid catalyst in a mixed solvent of hydrocarbon and alcohol. In Patent Document 3, lignin-containing biomass is pretreated by combining hydrothermal treatment and pulverization treatment, and the enzymatic saccharification residue generated when the pretreated biomass is enzymatically saccharified is further hydrothermally treated by autoclave, and the treated product thereof. Disclosed is a method for producing a lignin decomposition product by dissolving the solid substance in an organic solvent after obtaining the solid substance from the solid-liquid separation of the above. In Patent Document 4, a lignin-containing biomass is saccharified with an enzyme to obtain a saccharified residue, and the saccharified residue is heated in a mixed solvent containing water and an organic solvent having a solubility in water at 20 ° C. of 90 g / L or more. A method for producing a lignin decomposition product by treating to obtain a heat treatment liquid containing a lignin decomposition product and then solid-liquid separation of the heat treatment liquid to remove insoluble matter is disclosed.

Japanese Patent Application Laid-Open No. 2014-015439 Japanese Patent Application Laid-Open No. 2016-050200 Japanese Patent Application Laid-Open No. 2015-157792 Japanese Patent Application Laid-Open No. 2013-241391

The lignin contained in the biomass raw material has a complicated structure, and its characteristics change randomly depending on various conditions in the method for producing the lignin decomposition product. Therefore, the methods described in Patent Documents 1 to 4 and the like cannot obtain lignin having specific properties. Moreover, in order to obtain lignin having a specific property, various conditions in the production method thereof have not been controlled so far.

The present invention has been made in view of the above circumstances, and provides a method for producing an organic solvent-soluble lignin having specific properties.

That is, the present invention includes the following aspects.
(1) Pretreatment step of pretreating herbaceous biomass by dilute sulfuric acid steaming method and
A saccharification step of enzymatically saccharifying the pretreated herbaceous biomass obtained in the pretreatment step, and a saccharification step.
A solid-liquid separation step of solid-liquid separation of the saccharification treatment product obtained in the saccharification step to obtain a saccharification residue, and a solid-liquid separation step.
An extraction step of adding an organic solvent to the saccharified residue to extract organic solvent-soluble lignin, and
Including
In the pretreatment step, a dilute sulfuric acid cooking method is performed so that the β-O-4 bond content, weight average molecular weight and molecular weight distribution, and hydroxyl group content of the obtained organic solvent-soluble lignin are within predetermined ranges. A method for producing an organic solvent-soluble lignin, which controls the treatment intensity of the lignin.
(2) In the pretreatment step, the content of the thioacidrysis monomer of the organic solvent-soluble lignin quantified by the thioacidrysis method as the content of the β-O-4 bond is in the range of 95 μmol / g or more and 248 μmol / g or less. The method for producing an organic solvent-soluble lignin according to (1), wherein the treatment intensity by the dilute sulfuric acid cooking method is controlled so as to be.
(3) In the pretreatment step, the treatment intensity by the dilute sulfuric acid cooking method is controlled so that the weight average molecular weight of the organic solvent-soluble lignin quantified by the gel permeation chromatograph method is in the range of 2400 or more and 4200 or less. , (1). The method for producing an organic solvent-soluble lignin.
(4) In the pretreatment step, the treatment intensity by the dilute sulfuric acid cooking method so that the molecular weight distribution of the organic solvent-soluble lignin quantified by the gel permeation chromatograph method is in the range of 1.0 or more and 2.0 or less. The method for producing an organic solvent-soluble lignin according to (1).
(5) In the pretreatment step, the content of the phenolic hydroxyl group of the organic solvent-soluble lignin quantified by phosphorifying the hydroxyl group as the content of the hydroxyl group by phosphorus 31 nuclear magnetic resonance spectroscopy is 7 mmol / g or more and 32 mmol /. The organic solvent according to claim 1, wherein the treatment intensity by the dilute sulfuric acid cooking method is controlled so that the treatment intensity is in the range of g or less and the content of alcoholic hydroxyl groups is in the range of 6 mmol / g or more and 196 mmol / g or less. Method for producing soluble lignin.
(6) In the pretreatment step, any one of (1) to (4), wherein the treatment intensity by the dilute sulfuric acid steaming method is 1.0 or more and 3.0 or less in terms of CSI represented by the following formula (I). The method for producing an organic solvent-soluble lignin according to one.

(In formula (I), X is time, Y is temperature, and Z is pH.)

(7) In the pretreatment step, the CSI was controlled to approach 1.0 in order to increase the β-O-4 bond content of the organic solvent-soluble lignin, while the organic solvent-soluble lignin was used. The method for producing an organic solvent-soluble lignin according to (6), wherein the CSI is controlled to approach 3.0 in order to reduce the content of β-O-4 bond.
(8) In the pretreatment step, the CSI is controlled to approach 1.0 in order to reduce the weight average molecular weight and molecular weight distribution of the organic solvent-soluble lignin, while the weight average molecular weight of the organic solvent-soluble lignin. The method for producing an organic solvent-soluble lignin according to (6), wherein the CSI is controlled to approach 3.0 in order to increase the molecular weight distribution.
(9) In the pretreatment step, in order to increase the hydroxyl content of the organic solvent-soluble lignin, the CSI is controlled to approach 1.0, while the hydroxyl content of the organic solvent-soluble lignin is adjusted. The method for producing an organic solvent-soluble lignin according to (6), wherein the CSI is controlled to approach 3.0 in order to reduce the amount.

According to the production method of the above aspect, it is possible to provide a production method of an organic solvent-soluble lignin having specific properties.

Thioacidrysis quantified by the thioacidrysis method for organic solvent-soluble lignin obtained using napier grass pretreated under the conditions of CSI of 1.27, 1.57, 2.35 and 2.95 in Example 1. It is a graph which shows the content of a monomer. Gel permeation chromatograph of organic solvent-soluble lignin obtained using napier glass pretreated under the conditions of CSI of 1.27, 1.87, 2.35, 2.65 and 2.95 in Example 1. It is a chromatogram obtained by measuring by the (GPC) method. It is a graph which shows the measured value of the weight average molecular weight of the peak which has the largest weight average molecular weight among the peaks of the chromatogram of FIG. 2A. The hydroxyl groups of the organic solvent-soluble lignin obtained using napier glass pretreated under the conditions of CSI of 1.27, 1.57, 1.87, 2.35 and 2.95 in Example 1 were phosphorylated. ³¹ It is a graph which shows the total content of the phenolic hydroxyl group and the alcoholic hydroxyl group quantified by the P-NMR method.

Hereinafter, the method for producing an organic solvent-soluble lignin according to the embodiment of the present invention (hereinafter, may be abbreviated as “the method for producing the present embodiment”) will be described in detail. In the present specification and claims, the meanings of various terms are defined as follows.

<Grass-based biomass>
In the production method of this embodiment, herbaceous biomass is used as a raw material. Further, instead of the herbaceous biomass, a residue generated in the process of producing bioethanol, biobutanol, a biochemical product or the like from cellulose and hemicellulose in the herbaceous biomass may be used. As the herbaceous biomass used as a raw material, crushed biomass can be used, and any shape such as a block, a chip, or a powder may be used. In the following, herbaceous biomass may be simply referred to as "biomass".

Herbaceous biomass includes bamboo, palm tree trunks and bunches, palm palm fruit fibers and seeds; bagasse (sorghum and high biomass sorghum), rice straw, straw, corn cob, foliage and residues (corn stover) , Corn cob, corn hull), sorghum (including sweet sorghum) residue, obtained from grasses such as switchgrass, erianthus, napiergrass; Residues and the like to be used can be mentioned. Among them, as the herbaceous biomass, one obtained from a gramineous plant is preferable, and bagasse or napier grass is more preferable, from the viewpoint of availability and compatibility with the production method of the present embodiment.

<Cellulose and hemicellulose>
As used herein, "cellulose" includes hexoses having six carbons as constituent units. Therefore, when cellulose is hydrolyzed, it produces a hexose monosaccharide (glucose or the like) composed of 6 carbons or a hexose oligosaccharide (for example, cellobiose or the like) in which a plurality of the monosaccharides are linked.

"Hemicellulose" includes pentose (C5 sugar) having five carbons such as xylose and six carbons such as mannose, arabinose, and 4-O-methylglucuronic acid as constituent units (hexose). Complex polysaccharides such as glucomannan and glucuronoxylan composed of C6 sugar) are included. Therefore, when hemicellulose is hydrolyzed, it is a monosaccharide of pentasaccharide consisting of 5 carbons, an oligosaccharide of pentasaccharide in which a plurality of monosaccharides are linked, a monosaccharide of hexasaccharide consisting of 6 carbons, and the like. A plurality of monosaccharides linked to each other produce an oligosaccharide of hexacarbonate, and an oligosaccharide in which a plurality of monosaccharides of pentasaccharide and a plurality of monosaccharides of hexasaccharide are linked.

Generally, the composition ratio and the amount of monosaccharide or oligosaccharide produced from hemicellulose or cellulose differ depending on the pretreatment method and the type of herbaceous biomass used as a raw material.

<Lignin>
In general, lignin is a natural polymer that is one of the three major principal components of herbaceous biomass. Among herbaceous biomass, bagasse contains 5% by mass or more and 30% by mass or less of lignin.

The basic skeleton of lignin is composed of aromatic nuclei (benzene nuclei), and lignin is classified into G nuclei, S nuclei and H nuclei based on its structure. The G nucleus has one methoxy group (-OCH ₃ ) at the ortho position of the phenol skeleton portion, the S nucleus has two methoxy groups at the ortho position, and the H nucleus is It does not have a methoxy group at the ortho position. In addition, lignin in herbaceous biomass such as bagasse contains all of H nucleus, G nucleus and S nucleus as a basic skeleton. Among the lignins derived from woody biomass, the lignin derived from coniferous trees has a G nucleus as a basic skeleton, and the lignin derived from broad-leaved trees has a G nucleus and an S nucleus as a basic skeleton.

Lignin has various intermolecular binding modes, but the most abundant among them is β-O-4 binding, which is about 50 mol% or more and 70 mol% or less of the total binding mode in the lignin molecule. It is an ether bond that occupies. The β-O-4 bond is a bond mode represented by the following formula (II) and forms a linear structure of lignin. In the process of polymerizing lignin in plant cells, the β-position of the side chain of the monomer and the 4-position of the aroma nucleus of the adjacent monomer are continuously linked to polymerize.

In the present specification, the "water-soluble lignin" is a lignin that is soluble in water, and specifically, a saccharification product after a saccharification step, a fermentation product after a fermentation step, and a purification step, which will be described later. Indicates the lignin contained in the liquid component when the waste liquid of the above is solid-liquid separated. Since the number average molecular weight of water-soluble lignin is relatively small, about 1000 or less, it is presumed that water-soluble lignin is soluble in water.

The "water-insoluble lignin" is a lignin that is insoluble in water, and specifically, a solid solution of a saccharification product after a saccharification step, a fermentation product after a fermentation step, and a waste liquid after a purification step, which will be described later. When separated, it shows the lignin contained in the solid components (ie, saccharification residue, fermentation residue and solid residue). Since the water-insoluble lignin has a relatively large number average molecular weight of more than 1,000 and less than 10,000, it is presumed that it is insoluble in water.

The "saccharification product" referred to here includes a saccharified solution which is a liquid component and a saccharified residue which is a solid component, the saccharified solution contains water-soluble lignin, and the saccharified residue contains water-insoluble lignin. included. The "fermentation product" contains a fermentation broth which is a liquid component and a fermentation residue which is a solid component, the fermentation broth contains water-soluble lignin, and the fermentation residue contains water-insoluble lignin. The waste liquid contains a liquid residue which is a liquid component and a solid residue which is a solid component, the liquid residue contains water-soluble lignin, and the solid residue contains water-insoluble lignin.

The "organic solvent-soluble lignin" is a lignin that is soluble in an organic solvent. Specifically, in the extraction step described later, water-insoluble lignin is added to the organic solvent, mixed, and then stirred. Shows the lignin contained in the liquid component when solid-liquid separated. Since the number average molecular weight of the organic solvent-soluble lignin is about 1000 or more and 3000 or less, it is presumed that the organic solvent-soluble lignin is insoluble in water while being soluble in the organic solvent.

"Organic solvent-insoluble lignin" refers to lignin contained in a solid component when water-insoluble lignin is added to an organic solvent, mixed, stirred, and then solid-liquid separated in an extraction step described later. Since the organic solvent-insoluble lignin has a relatively large number average molecular weight of more than 3000 and 10000 or less, it is presumed that it is insoluble in water and organic solvents.

The number average molecular weight of each lignin can be measured by gel permeation chromatography (GPC).

<Saccharifying enzyme>
In the present specification, examples of the "saccharifying enzyme" include cellulase that decomposes cellulose, hemicellulose that decomposes hemicellulose, and amylase that decomposes starch.

The cellulase may be any cellulase that decomposes cellulose into monosaccharides such as glucose or oligosaccharides, for example, endoglucanase (EG), cellobiohydrolase (CBH), and β-glucosidase (β). -Glucosidase; BGL) has at least one activity of each activity, and an enzyme mixture having each of these activities is preferable from the viewpoint of enzyme activity.

The hemicellulase may be any one that decomposes hemicellulose into monosaccharides such as xylose or oligosaccharides, and for example, at least one activity of each activity of xylanase, xylosidase, mannanase, galactosidase, glucuronidase, and arabinofuranosidase. From the viewpoint of enzyme activity, it is preferable that the enzyme mixture has each of these activities.

The origin of these saccharifying enzymes such as cellulase and hemicellulase is not limited, and for example, Trichoderma, Acremonium, Aspergillus, Bacillus, Pseudomonas. Saccharifying enzymes such as cellulases and hemicellulase derived from microorganisms such as the genus Penicillium, Aeromonus, Irpex, Sporotichum, and Humicola can be used.

<Manufacturing method of organic solvent-soluble lignin>
The manufacturing method of this embodiment includes the following steps.
Pretreatment step of pretreating herbaceous biomass by dilute sulfuric acid steaming method;
A saccharification step of enzymatically saccharifying the pretreated herbaceous biomass obtained in the pretreatment step;
Solid-liquid separation step of solid-liquid separation of the saccharification treatment product obtained in the saccharification step to obtain a saccharification residue;
Extraction step of adding an organic solvent to the saccharified residue to extract an organic solvent-soluble lignin

In the production method of the present embodiment, the β-O-4 bond content, weight average molecular weight and molecular weight distribution, and hydroxyl group content of the obtained organic solvent-soluble lignin in the pretreatment step are each within a predetermined range. As described above, the treatment intensity by the dilute sulfuric acid cooking method is controlled.

As shown in Examples described later, the inventors have determined the treatment strength by the dilute sulfuric acid steaming method in the pretreatment step, the content of β-O-4 bond, the weight average molecular weight and the molecular weight distribution, and the content of hydroxyl group. The present invention was developed by controlling the treatment intensity by the dilute sulfuric acid steaming method in the pretreatment step in order to obtain an organic solvent-soluble lignin whose characteristics are within a predetermined range. It came to be completed.

The β-O-4 bond content of the organic solvent-soluble lignin obtained in the production method of the present embodiment can be expressed by the content of the thioacidrysis monomer of the organic solvent-soluble lignin quantified by the thioacidlysis method. According to the production method of the present embodiment, the content of the thioacidrysis monomer is 95 μmol / g or more and 248 μmol / g or less, preferably 173 μmol / g or more and 248 μmol / g or less, and more preferably 201 μmol / g or more and 248 μmol / g or less. It is possible to produce an organic solvent-soluble lignin in the range of.

The content of the thioacidlysis monomer can be quantified by the thioacidlysis method, and specifically, it can be measured by using the method shown in Examples described later.

In the production method of the present embodiment, it is possible to produce an organic solvent-soluble lignin in which the weight average molecular weight of the organic solvent-soluble lignin quantified by the gel permeation chromatography (GPC) method is in the range of 2400 or more and 4200 or less. As for the weight average molecular weight whose numerical range is defined here, as shown in Examples described later, the weight average molecular weight is the largest among the peaks of the chromatogram obtained by measuring the organic solvent-soluble lignin by the GPC method. It is a measured value of the weight average molecular weight of a certain peak.

The weight average molecular weight can be quantified by the GPC method, and specifically, it can be measured by using the method shown in Examples described later.

In the production method of the present embodiment, it is possible to produce an organic solvent-soluble lignin in which the molecular weight distribution of the organic solvent-soluble lignin quantified by the GPC method is in the range of 1.0 or more and 2.0 or less. As for the molecular weight distribution in which the numerical range is defined here, as shown in Examples described later, the weight average molecular weight is the largest among the peaks of the chromatogram obtained by measuring the organic solvent-soluble lignin by the GPC method. It is a value obtained by dividing the measured value of the peak weight average molecular weight Mw by the measured value of the number average molecular weight Mn.

The molecular weight distribution can be calculated by measuring the number average molecular weight Mn and the weight average molecular weight Mw by the GPC method and dividing the obtained weight average molecular weight Mw by the number average molecular weight Mn. Specifically, it can be calculated by using the method shown in Examples described later.

Examples of the hydroxyl group of the organic solvent-soluble lignin include an alcoholic hydroxyl group bonded to an aliphatic hydrocarbon group (including a modifying group of a sugar or a related compound) and a hydroxyl group bonded to an aromatic hydrocarbon group (phenol). Various hydroxyl groups such as (sexual hydroxyl group, etc.) and OH group at the end of the carboxy group can be mentioned. Among them, from the viewpoint of applying various modifications to the obtained organic solvent-soluble lignin, it may have many phenolic hydroxyl groups and alcoholic hydroxyl groups. preferable. The phenolic hydroxyl group also includes a hydroxyl group bonded to the benzene ring of syringyl and guaiacyl.
In the production method of the present embodiment, the total content of the phenolic hydroxyl group and the alcoholic hydroxyl group of the organic solvent-soluble lignin quantified by ^{phosphorus 31 nuclear magnetic resonance spectroscopy (31 P-NMR method) by phosphorifying the hydroxyl group is 13 mmol /} An organic solvent-soluble lignin in the range of g or more and 228 mmol / g or less can be produced.
Further, in the production method of the present embodiment, the phenolic hydroxyl group content of the organic solvent-soluble lignin quantified by ^{phosphorus 31 nuclear magnetic resonance spectroscopy (31 P-NMR method) by phosphorifying the hydroxyl group is 7 mmol / g or more and 32 mmol.} It is possible to produce an organic solvent-soluble lignin having a range of / g or less and an alcoholic hydroxyl group content of 6 mmol / g or more and 196 mmol / g or less.

According to the production method of the present embodiment, an organic solvent-soluble lignin having a β-O-4 bond content, a weight average molecular weight and a molecular weight distribution, and a hydroxyl group content within the above ranges can be obtained.
Next, each step of the manufacturing method of the present embodiment will be described in detail below.

[Pretreatment process]
In the pretreatment step, herbaceous biomass is pretreated by the dilute sulfuric acid steaming method.

The dilute sulfuric acid cooking method is a method of heating and pressurizing in the presence of dilute sulfuric acid. The dilute sulfuric acid to be used can be added, for example, so that the pH of the pretreatment solution containing herbaceous biomass is about 0.8 or more and 6.7 or less.

In the pretreatment step, lignin undergoes a polycondensation reaction as well as a decomposition reaction, and its structure changes depending on the pretreatment conditions. Therefore, since the chemical structure and degree of shrinkage of lignin change depending on the pretreatment conditions, the water-soluble lignin and water-insoluble content contained in the liquid fraction (saccharified liquid) and solid fraction (saccharified residue) in the solid-liquid separation step. The proportion of lignin, as well as the proportion of organic solvent-soluble lignin and organic solvent-insoluble lignin contained in the liquid fraction (extract) and solid fraction (extraction residue) in the extraction step, also changes.

Further, the strength of the pretreatment, that is, the strength of decomposing lignin, cellulose and hemicellulose can be controlled by three parameters of temperature, time and pH. From this, the processing intensity can be evaluated by the CSI (Combined Severity Index) represented by the following formula (I) with the above three parameters as variables. The larger the CSI value, the higher the decomposition strength of biomass tends to be, and the smaller the CSI value, the lower the decomposition strength of biomass tends to be. By setting the pretreatment conditions so that the CSI, which is a numerical value calculated from the formula (I), is within a predetermined range, the desired decomposition strength can be achieved.

(In formula (I), X is time, Y is temperature, and Z is pH.)

As shown in Examples described later, there is a correlation between the β-O-4 bond content, weight average molecular weight and molecular weight distribution of the obtained organic solvent-soluble lignin, and the hydroxyl group content and the CSI value. There is a relationship. Therefore, the CSI value is controlled so that the β-O-4 bond content, the weight average molecular weight and the molecular weight distribution, and the hydroxyl group content of the organic solvent-soluble lignin are within the above ranges.

Further, the larger the CSI value, the higher the decomposition strength of the biomass. On the other hand, if the CSI value is too large, the β-O-4 bond content and the hydroxyl group content will be shown in Examples described later. The amount tends to decrease, the weight average molecular weight is relatively large, and the width of the molecular weight distribution tends to increase. This is because the β-O-4 bond decreases and the side chain increases as the decomposition strength of the biomass increases, the polycondensation reaction becomes more significant than the decomposition reaction and the molecular weight increases, and the modification progresses. It is presumed that this is due to the decrease in phenolic hydroxyl groups and alcoholic hydroxyl groups.

When the content of β-O-4 bond is within the desired range, for example, in order to increase the content of the thioacidrysis monomer of the organic solvent-soluble lignin quantified by the thioacidlysis method, the CSI value is set. In order to reduce the content of the thioacidrysis monomer, the CSI value is controlled to be large.

When the weight average molecular weight and the molecular weight distribution are within the desired ranges, for example, in order to reduce the weight average molecular weight and the molecular weight distribution of the organic solvent-soluble lignin, the CSI value is controlled to be small, while the CSI value is controlled to be small. In order to increase the weight average molecular weight and the molecular weight distribution of the organic solvent-soluble lignin, the CSI value is controlled to be large.

When the hydroxyl group content is within the desired range, for example, to increase the total content of phenolic hydroxyl groups and alcoholic hydroxyl groups of the organic solvent-soluble lignin quantified by the ^{31 P-NMR method by phosphorylating the hydroxyl groups.} In order to reduce the total content of the phenolic hydroxyl group and the alcoholic hydroxyl group, the CSI value is controlled to be large.

From these facts, the content of the thioacidrysis monomer is 95 μmol / g or more and 248 μmol / g or less, the weight average molecular weight is 2400 or more and 4200 or less, the molecular weight distribution is 1.0 or more and 2.0 or less, and The total content of phenolic hydroxyl groups and alcoholic hydroxyl groups is 13 mmol / g or more and 228 mmol / g or less (specifically, the content of phenolic hydroxyl groups is 7 mmol / g or more and 32 mmol / g or less, and alcoholic. In order to produce an organic solvent-soluble lignin (which has a hydroxyl group content of 6 mmol / g or more and 196 mmol / g or less), the CSI is preferably 1.0 or more and 3.0 or less, more preferably 1.2 or more and 2.8 or less. It is preferable, 1.5 or more and 2.7 or less is more preferable, and 1.5 or more and 2.5 or less is particularly preferable. When the CSI is within the above range, an organic solvent-soluble lignin having a β-O-4 bond content, a weight average molecular weight and a molecular weight distribution, and a hydroxyl group content within the above range can be produced.

In the pretreatment step, as specific treatment conditions within the range of the above CSI, the pH is preferably 0.8 or more and less than 1.5, more preferably 0.8 or more and 1.4 or less, and 0.8. More than 1.2 or less is more preferable.

The temperature can be, for example, 100 ° C. or higher and 250 ° C. or lower, 120 ° C. or higher and 200 ° C. or lower, and 150 ° C. or higher and 180 ° C. or lower.

The time can be, for example, 3 minutes or more and 150 minutes or less, 5 minutes or more and 120 minutes or less, 7 minutes or more and 90 minutes or less, and 8 minutes or more and 40 minutes or less. ..

The reaction vessel used in the dilute sulfuric acid cooking method is not particularly limited as long as it is a steam supply type, but has a heating pressure device such as an autoclave having acid resistance, or a heating pressure vessel having acid resistance, and further has a screw. It is conceivable that the feeders are integrated and put into a device or the like capable of continuous processing for processing.

In the pretreatment step, the biomass may be crushed using a mill or the like before and after the treatment by the dilute sulfuric acid steaming method.

[Saccharification process]
In the saccharification step, the saccharification reaction is carried out using an enzyme using cellulose and hemicellulose contained in the pretreated herbaceous biomass obtained in the pretreatment step as substrates.

The enzyme referred to here is mainly a saccharifying enzyme, and those exemplified in the above "saccharifying enzyme" can be used.

The saccharification temperature is preferably 45 ° C. or higher and 70 ° C. or lower, more preferably 45 ° C. or higher and 55 ° C. or lower, and particularly preferably 50 ° C. The saccharification time is preferably 12 hours or more and 120 hours or less, more preferably 24 hours or more and 96 hours or less, and further preferably 24 hours or more and 72 hours or less.

The saccharification step is not particularly limited and can be carried out using a known saccharification apparatus. Specific examples thereof include saccharification devices such as a stirring type, a ventilation stirring type, a bubble tower type, a fluidized bed type, and a packed bed type.
Further, the saccharification device may be provided with a temperature control device such as a hot water circulation type jacket on the outside of the device in order to keep the temperature inside the device constant.

[Solid-liquid separation process]
In the solid-liquid separation step, the saccharification treatment product obtained in the saccharification step is solid-liquid separated and separated into a saccharification solution which is a liquid fraction and a saccharification residue which is a solid fraction to obtain a saccharification residue. This saccharified residue contains water-insoluble lignin.

As a method for solid-liquid separation, a known method for separating solid content and liquid content can be used. For example, a method of filtering with a filter, a vibrating sieve or the like, a centrifugal separation method, a separation method using a screw press, or the like can be used. These are, but are not limited to.

The saccharified solution obtained in the solid-liquid separation step may be refined by removing impurities from the saccharified solution and sold as molasses, or the saccharified solution may be used to produce useful components produced by microbial fermentation. You may. Details of the useful ingredient will be described later.

[Extraction process]
In the extraction step, an organic solvent is added to the saccharified residue obtained in the solid-liquid separation step to extract the organic solvent-soluble lignin.

As the organic solvent, one having an affinity for water (hydrophilicity) is preferable. Further, from the viewpoint of improving the extraction rate of the organic solvent-soluble lignin, the solubility in water at 20 ° C. is preferably 90 g / L or more, more preferably 100 g / L or more, still more preferably 120 g / L or more.

Further, the organic solvent preferably has an SP value of 8 or more and 23 or less, more preferably 8 or more and 16 or less, and further preferably 9 or more and 15 or less, from the viewpoint of improving the extraction rate of the organic solvent-soluble lignin.

Here, the "SP value" means a solubility parameter (SP value), and the method of Fedors (Reference 1: "Fedors RF," A Method for Estimating Both the Solubility Parameters and Molar Volumes ". of liquids ”, Polymer Engineering and Science, Vol. 14, No. 2, p147-154, 1974.”), and the value δ [(cal / cm ³ ) ^{1 / 2} ], which is obtained from the square root of the ratio of the total evaporation energy (Δei) of the atom or atomic group of the chemical structure of the compound to the total molar volume (Δvi).

Fedors formula: δ = (ΣΔei / ΣΔvi) ^1/2

Specific examples of such an organic solvent include alcohols, nitriles, ethers, and ketones. These organic solvents may be used alone or in combination of two or more.

Examples of alcohols include methanol, ethanol, diethylene glycol, n-propanol, isopropanol, 2-butanol, isobutanol, t-butyl alcohol and the like.

Examples of nitriles include acetonitrile and the like.

Examples of ethers include dioxane, tetrahydrofuran (THF) and the like.

Examples of ketones include acetone, methyl ethyl ketone and the like.

Among them, as the organic solvent, methanol, ethanol, THF, or acetone is preferable, and acetone is more preferable, because the extraction rate of the organic solvent-soluble lignin is excellent. Since these organic solvents have low solubility of biomass saccharified products such as glucose and xylose and do not dissolve cellulose, hemicellulose, etc., lignin can be efficiently extracted.

Further, in the extraction step, a mixed solvent of an organic solvent and water can be used. The ratio of water to the organic solvent is preferably more than 0/100 and 40/60 or less, more preferably 10/90 or more and 40/60 or less, and further preferably 20/80 or more and 40/60 or less in terms of mass ratio. When the ratio is within the above range, the organic solvent-soluble lignin can be extracted more efficiently.

Further, when a mixed solvent of an organic solvent and water is used, the water also contains water contained in the saccharified residue. For example, by adding 4 parts by mass or more and 5 parts by mass or less of an organic solvent (preferably acetone or ethanol) having a concentration of 90% by mass with respect to 1 part by mass of the saccharified residue having a water content of 60% by mass. , The extraction can be carried out under the conditions within the above range, which is the ratio of water to the organic solvent.

As an extraction method, for example, the saccharified residue and the organic solvent are mixed and stirred to dissolve the organic solvent-soluble lignin in the organic solvent. The extraction step can be performed using, for example, a known extraction device such as a rotocell type extraction device.

The amount of the solvent (organic solvent or mixed solvent of organic solvent and water) added can be 2 times or more and 40 times or less in terms of mass ratio with respect to the dry mass of the saccharified residue, and can be 2 times or more and 30 times or less. It can be 2 times or more and 20 times or less, and can be 5 times or more and 15 times or less, and is not limited to this.

The extraction time (time for mixing and stirring the saccharified residue and the organic solvent) can be, for example, 30 minutes or more and 240 minutes or less, and is not limited thereto. Further, in the extraction step, the temperature condition until the organic solvent-soluble lignin is dissolved in the organic solvent and the extract is obtained can be carried out under mild temperature conditions equal to or lower than the boiling point of the organic solvent used, for example, room temperature ( Specifically, it can be carried out under the condition of 15 ° C. or higher and 35 ° C. or lower). Other conditions such as the stirring speed can be appropriately set according to the mixing amount of the saccharified residue and the organic solvent.

Then, by solid-liquid separation of the stirred solution, an extract containing an organic solvent-soluble lignin can be obtained. Examples of the solid-liquid separation method include the same methods as those exemplified in the above-mentioned “solid-liquid separation step”. The organic solvent-soluble lignin contained in the extract can be obtained as a powdery organic solvent-soluble lignin by removing the organic solvent by a known method such as using a distillation column or the like.
At this time, it is preferable that the removed organic solvent is cooled, concentrated, recovered by using a condenser such as a capacitor, and reused.

[Other processes]
The production method of the present embodiment may further include other steps in addition to the above steps.

The production method of the present embodiment may further include a fermentation step after the saccharification step.
In the fermentation step, microorganisms are added to the saccharified solution obtained in the saccharification step, and the fermentation reaction is carried out with stirring. In the fermentation reaction, when microorganisms ingest monosaccharides such as glucose and xylose and oligosaccharides in the saccharified solution, useful components different from organic solvent-soluble lignin are produced.

Further, the production method of the present embodiment may further include a fermentation step after the saccharification step and before the solid-liquid separation step. In this case, in the fermentation step, microorganisms are added to the saccharified products (saccharified liquid and saccharified residue) obtained in the saccharification step, and the fermentation reaction is carried out with stirring. Further, in the solid-liquid separation step, the fermentation product obtained in the fermentation step is solid-liquid separated to obtain a fermentation residue. Further, in the extraction step, an organic solvent is added to the fermentation residue to extract the organic solvent-soluble lignin.
Deterioration of the structure of lignin (change in chemical structure and degree of polycondensation) is hardly affected except in the above pretreatment step, and lignin is persistently decomposed. Therefore, it is presumed that the physical properties and yield of the obtained organic solvent-soluble lignin do not change even after the fermentation step and the purification step described later, and the fermentation residue separated from the fermentation product obtained after the fermentation step and after the purification step. The solid residue separated from the obtained waste liquid can be used as a raw material for extraction of the organic solvent-soluble lignin in the same manner as the saccharified residue.

The microorganism used in the fermentation step is not particularly limited as long as it can produce a useful component different from the target organic solvent-soluble lignin. Specific examples thereof include yeast and bacteria, and genetically modified microorganisms are also preferably used. Genetically modified microorganisms are microorganisms that do not have the enzyme genes required for conversion to useful components different from the target organic solvent-soluble lignin such as alcohol, and these genes are introduced by genetic engineering technology into alcohol and the like. It enables the production of useful components different from the target organic solvent-soluble lignin. Examples of the genetically modified microorganism include recombinant Escherichia coli having alcohol fermentability. Among them, yeast is preferable as the microorganism used in the production method of the present embodiment.

Further, as the microorganism, the culture solution containing the microorganism may be used as it is, or the culture solution containing the microorganism may be concentrated by centrifugation, or may be appropriately used.
The amount of microorganisms used may be calculated based on the growth rate of microorganisms, the size of the fermentation apparatus, the amount of saccharified solution used for fermentation, and the like.

Above all, in the fermentation step, it is preferable to ferment the saccharification product using yeast as a microorganism to produce alcohol such as ethanol as a useful component different from the organic solvent-soluble lignin.

The fermentation step may be appropriately performed based on the prior art. For example, the fermentation temperature is preferably 25 ° C. or higher and 50 ° C. or lower, more preferably 28 ° C. or higher and 35 ° C. or lower, and particularly preferably 32 ° C. The fermentation time is preferably 24 hours or more and 120 hours or less, more preferably 24 hours or more and 96 hours or less, and further preferably 24 hours or more and 72 hours or less.

The fermentation step is not particularly limited and can be carried out using a known fermentation apparatus. Specific examples thereof include, but are not limited to, a stirring type, a ventilation stirring type, a bubble tower type, a fluidized bed type, a packed bed type and the like.
Further, the fermentation apparatus may be provided with a temperature control device such as a hot water circulation type jacket on the outside of the apparatus in order to keep the temperature inside the apparatus constant.

The production method of the present embodiment may further include a purification step after the fermentation step.
In the purification step, useful components different from the organic solvent-soluble lignin are extracted from the fermentation product obtained in the fermentation step.

Further, the production method of the present embodiment may further include a purification step after the fermentation step and before the solid-liquid separation step. In this case, in the purification step, a useful component different from the organic solvent-soluble lignin is extracted from the fermentation product obtained in the fermentation step. As a result, the waste liquid is discharged after the useful components different from the organic solvent-soluble lignin are taken out. The waste liquid contains water-soluble lignin and water-insoluble lignin. Further, in the solid-liquid separation step, the waste liquid obtained in the purification step is solid-liquid separated to obtain a solid residue in the waste liquid. Further, in the extraction step, an organic solvent is added to the solid residue to extract the organic solvent-soluble lignin. As described above, alteration of the structure of lignin (change in chemical structure and degree of polycondensation) is hardly affected except in the above pretreatment step, and lignin exhibits persistent decomposability. Therefore, it is presumed that the physical properties and yield of the obtained organic solvent-soluble lignin do not change even after the purification step, and the solid residue separated from the waste liquid obtained after the purification step is used as a raw material for extraction of the organic solvent-soluble lignin. It can be used in the same manner as the above saccharified residue.

The useful component different from the organic solvent-soluble lignin means a compound produced by ingesting monosaccharides and oligosaccharides obtained by decomposing herbaceous biomass by microorganisms such as yeast. Specific examples of useful components include alcohols such as ethanol, butanol, 1,3-propanediol, 1,4-butanediol, and glycerol; pyruvic acid, succinic acid, malic acid, inosinic acid, citric acid, lactic acid, and the like. Organic acids; nucleosides such as inosin and guanosine; nucleotides such as inosinic acid and guanylate; diamine compounds such as cadaberine and the like. When the compound obtained by fermentation is a monomer such as lactic acid, it may be converted into a polymer by polymerization. Among them, ethanol is preferable as a useful component produced in the above-mentioned fermentation step.

When the herbaceous biomass compound is an alcohol, the purification method includes, for example, a method of distilling the fermentation broth (distillation method). When the herbaceous biomass compound is an amino acid, for example, an ion exchange method, a method for adsorbing and removing foreign substances using activated carbon, and the like can be mentioned. Above all, in the fermentation step, yeast is used as a microorganism to ferment the saccharification product to produce alcohol such as ethanol as a useful component, and then in the purification step, alcohol such as ethanol is produced from the fermentation product by a distillation method. It is preferable to take it out.

<Usage of organic solvent-soluble lignin>
Since the organic solvent-soluble lignin obtained by the production method of the present embodiment has a phenolic hydroxyl group, various modifications can be made. For example, an epoxy resin can be obtained by subjecting an organic solvent-soluble lignin to an addition reaction of epichlorogenohydrin (for example, epichlorohydrin or the like). Further, for example, a urethane resin can be obtained by reacting an organic solvent-soluble lignin with an isocyanate compound. Further, for example, a phenol resin can be obtained by performing a curing reaction of an organic solvent-soluble lignin using hexamine as a curing agent. Since organic solvent-soluble lignin contains an aromatic skeleton, it can be used as a raw material having excellent mechanical properties such as fire resistance, heat resistance, and hardness, and the above-mentioned various resins can be used as electric substrate materials, heat-resistant plastic materials, and the like. can do. Alternatively, since the organic solvent-soluble lignin has excellent dispersibility, it can be used as a surfactant, for example, by modifying the organic solvent-soluble lignin to introduce a long-chain hydrocarbon group or the like.

In general, chemical synthetic raw materials are required to have (1) few steric hindrances (having many linear structures); (2) relatively small molecules; and (3) many hydroxyl groups. As described above, the organic solvent-soluble lignin obtained by the production method of the present embodiment has a β-O-4 bond content, a weight average molecular weight and a molecular weight distribution, and a hydroxyl group content within a predetermined range. Yes, it is possible to provide a lignin that can meet the above specifications.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to the following Examples.

[Example 1]
(Examination of conditions for dilute sulfuric acid cooking method)
Using napier grass, which is a herbaceous biomass, a dilute sulfuric acid cooking method was carried out under each condition shown in Table 1. Specifically, the treatment by the dilute sulfuric acid cooking method was carried out by adding dilute sulfuric acid to the napier glass so as to have the following pH conditions, and then using a steam supply type pressurized pretreatment apparatus.

In Table 1, CSI (Combined Safety Index) is a numerical value calculated using the following formula (I) with temperature, pH, and treatment time, which are parameters of the conditions of the dilute sulfuric acid cooking method, as variables. The larger the CSI value, the higher the decomposition strength of lignin, and the smaller the CSI value, the lower the decomposition strength of lignin.

(In formula (I), X is time, Y is temperature, and Z is pH.)

The napier grass pretreated under each of the above conditions was saccharified by adding saccharifying enzymes (cellulase and hemicellulase) to obtain a saccharified product. The obtained saccharification product was filtered to obtain a saccharification residue.

(Extraction of organic solvent-soluble lignin)
Then, the saccharified residue obtained in the above process was dried to obtain a dried saccharified residue. Using this dried saccharified residue, organic solvent-soluble lignin was extracted.
First, 1 g of the dried saccharified residue is added to 40 mL (31.1 g) of acetone, stirred at room temperature (20 ° C.) for 30 minutes, and then solid-liquid separated using a centrifuge to extract the extract and the extract residue. And got. The extract and the extract residue were dried, respectively, to obtain a dried extract and a dried extract residue.

(Physical characteristics of organic solvent-soluble lignin)
Various physical properties of the organic solvent-soluble lignin contained in the dried extract were investigated.

(1) Content of β-O-4 bond The content of β-O-4 bond in the organic solvent-soluble lignin was measured by using the thioacidlysis method. In the thioacidrysis method, a decomposition product containing a thioacidrysis monomer composed of syringyl and guaiacyl is produced by cleaving the β-O-4 bond, and by analyzing the decomposition product, β-O- contained in lignin is produced. Quantify 4 bonds. That is, the content of the thioacidrysis monomer is quantified as the content of β-O-4 bond. Specifically, first, 5 mg of each sample was added to a dioxane / ethanethiol (9: 1) solution, and heat treatment was performed at 100 ° C. for 4 hours. Next, the solution after the heat treatment was neutralized with sodium hydrogen carbonate, hydrochloric acid was added to precipitate sodium chloride, and the solution was filtered and desodium-treated. Methylene chloride was added to the filtrate to extract the monomer into the methylene chloride phase. The obtained extract was concentrated. A pyridine solution of N, O-Bis (trimethylsilyl) trifluoroacetamide (BSTFA) was added to the concentrate as a silylating agent, and the mixture was stirred at room temperature for 30 minutes or more and 60 minutes or less to prepare a derivatized sample. The derivatized sample was measured by gas chromatography-mass spectrometry (GC-MS) under the measurement conditions shown below, and the content of the thioacidrysis monomer composed of syringyl (S) and guaiacyl (G) was calculated. The results are shown in FIG. In FIG. 1, “thioacidrysis S + G” is the content (μmol / g) of the thioacidlysis monomer composed of syringyl (S) and guaiacyl (G).

(Measurement condition)
GC / MS device: Shimadzu GCMS-QP2010SE
Column: DB-5MS volume (30m x 0.25mm, id, 0.25μm film thickness)
Column temperature: 170 ° C, 3 min, 2 ° C / min, 30 min after temperature rise to 280 ° C Column flow rate: 1.0 mL / min
Injection port temperature: 250 ° C
Injection method: Split method Ion source temperature: 200 ° C
Interface temperature: 250 ° C
Ionization method: EI
Sample amount: 1.0 μL

From FIG. 1, there was a tendency that the content of the thioacidrysis monomer, that is, the content of β-O-4 bond, decreased as the CSI increased. It was speculated that this was due to the fact that the linear structure was decomposed and the side chains increased as the treatment strength by the dilute sulfuric acid cooking method increased.
Further, in the range of CSI of 1.27 or more and 2.95 or less, the content of the thioacidrysis monomer of the organic solvent-soluble lignin quantified by the thioacidrysis method as the content of β-O-4 bond is 95 μmol / g or more and 248 μmol. It was less than / g.
These facts suggest that the control of CSI is effective for obtaining the organic solvent-soluble lignin in which the content of the thioacidrysis monomer, that is, the content of the β-O-4 bond is in a specific range. It was.

(2) Weight average molecular weight and molecular weight distribution An organic solvent obtained using napier glass pretreated under the conditions of CSI of 1.27, 1.87, 2.36, 2.66 and 2.95 as a sample. Soluble lignin was used. The weight average molecular weight Mw and the number average molecular weight Mn of the organic solvent-soluble lignin were measured by GPC under the measurement conditions shown below. The molecular weight distribution Mw / Mn was obtained by dividing the weight average molecular weight Mw by the obtained number average molecular weight Mn.

(Measurement condition)
Equipment: Shimadzu Prominence System Column: TSKgel Supermultipore HZ-M 4.6 mm x 150 mm Triple Carrier: Tetrahydrofuran (THF, Stabilizer Free)
Detection method: UV 280 nm, absorption sample concentration: 4 mg / mL
Outflow: 0.35 mL / min
Column temperature: 40 ° C

FIG. 2A is a gel permeation chromatograph of organic solvent-soluble lignin obtained using napier glass pretreated under the conditions of CSI of 1.27, 1.87, 2.36, 2.66 and 2.95. It is a chromatogram obtained by measuring by the method. The weight average molecular weight Mw, the number average molecular weight Mn, and the molecular weight distribution Mw / Mn at each peak of each chromatogram shown in FIG. 2A are shown in Table 2 below.

FIG. 2B is a graph showing the measured values of the weight average molecular weight of the peak having the largest weight average molecular weight (peak 1 in Table 2 above) among the peaks of the chromatogram shown in FIG. 2A.

From FIGS. 2A and 2B, as the CSI increases, the weight average molecular weight increases, the width of the molecular weight distribution increases, and the weight average molecular weight of the entire organic solvent-soluble lignin is about 200 or less, which is a low molecular weight organic solvent. There was a tendency for the proportion of soluble lignin to decrease. Further, in the range of CSI of 1.27 or more and 2.95 or less, the measured value of the weight average molecular weight of the peak having the maximum weight average molecular weight Mw among the peaks of the chromatogram shown in FIG. 2A is 2453 or more and 4151 or less. The molecular weight distribution Mw / Mn was 1.32 or more and 1.86 or less.
These results suggest that control of CSI is effective for obtaining organic solvent-soluble lignin having a specific range of weight average molecular weight and molecular weight distribution.

(3) Hydroxy Group Content As a sample, organic solvent-soluble lignin obtained using napier grass pretreated under the conditions of CSI of 1.27, 1.57, 2.36 and 2.95 was used. The content of hydroxyl groups in the organic solvent-soluble lignin ^{was quantified by phosphorus 31 nuclear magnetic resonance spectroscopy (31} P-NMR method) after phosphorylation of the hydroxyl groups. Specifically, organic solvent-soluble lignin: 25 mg, 2-Chromium4,5,5-tetramethyl-1,3,2-dioxaphosphorane: 115 mg (100 μL: excess amount), and Tris (2,4-pentanedionato). -Chromium (III): 0.5 mg and N-Hydroxy-1,8-naphthalimide: 1.14 mg as an internal standard were added, and the mixture was reacted at 25 ° C. (room temperature) for 180 minutes. The obtained reaction solution was used as a sample ^{and subjected to 31} P-NMR. ³¹ The measurement conditions for P-NMR are as follows. ³¹ Of the hydroxyl groups quantified by P-NMR, the contents of phenolic hydroxyl groups (including hydroxyl groups bonded to the benzene rings of silingyl and guaiacyl) and alcoholic hydroxyl groups, and the total content of those hydroxyl groups are calculated. did. The results are shown in Table 3 and FIG.

(Measurement condition)
Measuring device: JEOL JNM-LA400MK
Observation frequency: 400MHz
Number of integrations: 409 6 times Measurement temperature: 16 ° C (room temperature)
Solvent used: Pyridine / deuterated chloroform mixture (mass ratio 8: 5)

From FIG. 3, as the CSI increased, the total content of phenolic hydroxyl groups (including hydroxyl groups bonded to the benzene rings of syringyl and guaiacyl) and alcoholic hydroxyl groups tended to decrease. It was speculated that this was due to the fact that the treatment strength by the dilute sulfuric acid cooking method was increased, the lignin was denatured, and the hydroxyl group content was reduced.
Further, in the range of CSI of 1.27 or more and 2.95 or less, the phenolic hydroxyl group of the organic solvent-soluble lignin (bonded to the benzene ring of syringyl and guaiacyl) quantified by the ^{31 P-NMR method as the hydroxyl group content.} The content of (including hydroxyl groups) was 7.03 mmol / g or more and 31.24 mmol / g or less. The content of alcoholic hydroxyl groups was 6.04 mmol / g or more and 195.7 mmol / g or less.
From these facts, it was suggested that the control of CSI is effective for obtaining the organic solvent-soluble lignin in which the content of hydroxyl groups, particularly the total content of phenolic hydroxyl groups and alcoholic hydroxyl groups, is in a specific range.

According to the production method of the present embodiment, an organic solvent-soluble lignin having specific properties can be produced.

Claims (9)

A pretreatment process for pretreating herbaceous biomass by the dilute sulfuric acid steaming method,
A saccharification step of enzymatically saccharifying the pretreated herbaceous biomass obtained in the pretreatment step, and a saccharification step.
A solid-liquid separation step of solid-liquid separation of the saccharification treatment product obtained in the saccharification step to obtain a saccharification residue, and a solid-liquid separation step.
An extraction step of adding an organic solvent to the saccharified residue to extract organic solvent-soluble lignin, and
Including
In the pretreatment step, a dilute sulfuric acid cooking method is performed so that the β-O-4 bond content, weight average molecular weight and molecular weight distribution, and hydroxyl group content of the obtained organic solvent-soluble lignin are within predetermined ranges. A method for producing an organic solvent-soluble lignin, which controls the treatment intensity of the lignin. In the pretreatment step, the content of the thioacidrysis monomer of the organic solvent-soluble lignin quantified by the thioacidlysis method as the content of the β-O-4 bond is in the range of 95 μmol / g or more and 248 μmol / g or less. The method for producing an organic solvent-soluble lignin according to claim 1, wherein the treatment intensity by the dilute sulfuric acid cooking method is controlled. The claim that the treatment intensity by the dilute sulfuric acid cooking method is controlled so that the weight average molecular weight of the organic solvent-soluble lignin quantified by the gel permeation chromatograph method in the pretreatment step is in the range of 2400 or more and 4200 or less. The method for producing an organic solvent-soluble lignin according to 1. In the pretreatment step, the treatment intensity by the dilute sulfuric acid cooking method is controlled so that the molecular weight distribution of the organic solvent-soluble lignin quantified by the gel permeation chromatograph method is in the range of 1.0 or more and 2.0 or less. The method for producing an organic solvent-soluble lignin according to claim 1. In the pretreatment step, the content of the phenolic hydroxyl group of the organic solvent-soluble lignin quantified by phosphorylation of the hydroxyl group as the content of the hydroxyl group by phosphorus 31 nuclear magnetic resonance spectroscopy is 7 mmol / g or more and 32 mmol / g or less. The organic solvent-soluble lignin according to claim 1, wherein the treatment intensity by the dilute sulfuric acid cooking method is controlled so that the content of the alcoholic hydroxyl group is in the range of 6 mmol / g or more and 196 mmol / g or less. Production method. The method according to any one of claims 1 to 4, wherein in the pretreatment step, the treatment intensity by the dilute sulfuric acid steaming method is 1.0 or more and 3.0 or less in terms of CSI represented by the following formula (I). A method for producing an organic solvent-soluble lignin.

(In formula (I), X is time, Y is temperature, and Z is pH.) In the pretreatment step, the CSI was controlled to approach 1.0 in order to increase the β-O-4 bond content of the organic solvent-soluble lignin, while β-O of the organic solvent-soluble lignin. -4. The method for producing an organic solvent-soluble lignin according to claim 6, wherein the CSI is controlled to approach 3.0 in order to reduce the content of the bond. In the pretreatment step, the CSI is controlled to approach 1.0 in order to reduce the weight average molecular weight and molecular weight distribution of the organic solvent-soluble lignin, while the weight average molecular weight and molecular weight distribution of the organic solvent-soluble lignin. The method for producing an organic solvent-soluble lignin according to claim 6, wherein the CSI is controlled to approach 3.0 in order to increase the amount of lignin. In the pretreatment step, in order to increase the hydroxyl group content of the organic solvent-soluble lignin, the CSI is controlled to approach 1.0, while the hydroxyl group content of the organic solvent-soluble lignin is decreased. The method for producing an organic solvent-soluble lignin according to claim 6, wherein the CSI is controlled to approach 3.0.

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