WO2021153585A1

WO2021153585A1 - Production method for sugar solution

Info

Publication number: WO2021153585A1
Application number: PCT/JP2021/002757
Authority: WO
Inventors: 舩田茂行; 日笠雅史; 山田勝成
Original assignee: 東レ株式会社
Priority date: 2020-01-28
Filing date: 2021-01-27
Publication date: 2021-08-05
Also published as: JPWO2021153585A1; CN115023507A

Abstract

This production method for a sugar solution comprises steps (1)-(4), and enables production of a sugar solution in which fermentation-inhibiting substances such as organic acids and aromatic compounds are reduced. Step (1): a step for pulverizing cellulose-containing biomass such that the proportion of particles that do not pass through a sieve having a mesh opening size of 1 mm is at most 50% in terms of dry weight. Step (2): a step for obtaining pretreated biomass by bringing the pulverized biomass obtained in step (1) into contact with an alkaline aqueous medium. Step (3): a step for adding water to the pretreated biomass obtained in step (2) for solid-liquid separation, to obtain cellulose-containing solid. Step (4): a step for hydrolyzing the cellulose solid obtained in step (3) to obtain a sugar solution.

Description

Manufacturing method of sugar solution

The present invention relates to a method for producing a sugar solution that can be used as a fermentation raw material from cellulose-containing biomass.

The fermentation production process for chemicals made from sugar is used for the production of various industrial raw materials. Currently, sugars derived from edible raw materials such as sugar beet, starch, and sugar beet are industrially used as sugars as raw materials for fermentation. From the ethical aspect of competition, renewable non-edible resources, that is, the process of more efficiently producing sugar solution from cellulose-containing biomass, or the obtained sugar solution is efficiently converted into industrial raw material as a fermentation raw material. The construction of the process to do so is an issue for the future.

The sugar in the cellulose-containing biomass raw material is embedded in the cell wall that has a complicated structure. Therefore, in order for the enzyme to act efficiently, it is preferable to apply an alkali treatment to the biomass raw material prior to the enzymatic hydrolysis.

For example, in order to improve the enzymatic hydrolysis rate of cellulol, an alkaline treatment is performed in which a cellulose-containing substance and an alkaline aqueous solution are brought into contact with each other, and a specific pretreatment that repeatedly uses an alkaline filtrate is applied to the cellulose-containing biomass to obtain a sugar solution. Is disclosed to contain sugar with high purity (Patent Document 1).

Further, the cellulose-containing plant biomass raw material is treated with a treatment agent containing ammonia and immersed in water at 40 to 100 ° C. to elute the polysaccharide in water to obtain a raw material for enzymatic saccharification to be used in the enzymatic saccharification step. Is disclosed. According to the present invention, enzymatic saccharification can be efficiently performed, and therefore, it is used in a method for producing sugar with improved sugar production efficiency (Patent Document 2).

However, there is a quality problem that fermentation-inhibiting substances such as organic acids and aromatic compounds generated during alkaline treatment are mixed in the sugar solution, and a method for producing a cellulose sugar solution in which fermentation-inhibiting substances are reduced is still required.

WO2017 / 170552 WO2012 / 096236

An object of the present invention is to provide a method for reducing fermentation inhibitors such as organic acids and aromatic compounds generated by alkaline treatment of cellulose-containing biomass when producing a sugar solution from cellulose-containing biomass.

The present inventor has now crushed cellulose-containing biomass to a specific degree of crushing, brought it into contact with an alkaline aqueous medium to add water, solid-liquid separated the pretreated biomass to which water was added, and hydrolyzed the pretreated biomass. Then, it was found that the sugar solution in which the fermentation inhibitor was reduced could be efficiently obtained.

The present invention is based on such findings, and is composed of the following [1] to [10].
[1] A method for producing a sugar solution using cellulose-containing biomass as a raw material. Step (1): The cellulose-containing biomass is crushed so that the weight ratio that does not pass through a sieve having an opening of 1 mm is 50% or less in terms of dry weight. Process,
Step (2): A step of contacting the crushed biomass obtained in the step (1) with an alkaline aqueous medium to obtain a pretreated biomass.
Step (3): Water is added to the pretreated biomass obtained in step (2) and solid-liquid separation is performed to obtain a cellulose-containing solid content, and step (4): cellulose obtained in step (3). The process of hydrolyzing the contained solids to obtain a sugar solution,
Including methods.
[2] The method for producing a sugar solution according to [1], wherein the step (2) is a step of passing an alkaline medium through the crushed biomass obtained in the step (1) to obtain a pretreated biomass.
[3] The step (2) is a step of supplying the crushed biomass and the alkaline medium obtained in the step (1) to a filter and passing the crushed biomass and the alkaline medium through the filter. The method for producing a sugar solution according to [1] or [2].
[4] The method for producing a sugar solution according to any one of [1] to [3], wherein the alkaline aqueous medium of the step (2) is an aqueous medium containing sodium hydroxide and / or potassium hydroxide.
[5] The method for producing a sugar solution according to any one of [1] to [4], wherein the solid-liquid separation in the step (3) is pressing.
[6] The method for producing a sugar solution according to any one of [1] to [5], wherein the cellulose-containing biomass is bagasse.
[7] Step (5): The sugar solution obtained in step (4) is filtered through a nanofiltration membrane or a reverse osmosis membrane, the sugar solution is recovered as a non-permeate solution, and the permeate solution is used in step (3). The process of reusing water to be added to pretreated biomass,
The method for producing a sugar solution according to any one of [1] to [6], further comprising.
[8] Cellulose-containing solid containing pulverized cellulose-containing biomass and an alkaline aqueous medium having a dry weight of 50% or less and having a water content of 50% by weight or more and less than 70% by weight. Minutes.
[9] The cellulose-containing solid content according to [8], wherein the cellulose-containing biomass is bagasse.
[10] Biomass containing crushed cellulose having a dry weight of 40 to 50% that does not pass through a sieve having an opening of 1 mm.

According to the present invention, it is possible to obtain a high-purity sugar solution in which fermentation inhibitors derived from alkaline treatment of cellulose-containing biomass are reduced.

It is a process flow diagram which shows an example of the manufacturing method of the sugar solution of this invention.

The present invention is a method for producing a sugar solution using cellulose-containing biomass as a raw material. Step (1): The cellulose-containing biomass is crushed so that the ratio of non-passing through a sieve having an opening of 1 mm is 50% or less by dry weight. Step, Step (2): Step of contacting the crushed biomass with an alkaline aqueous medium to obtain pretreated biomass, Step (3): Add water to the pretreated biomass for solid-liquid separation to separate the cellulose-containing solids. Step and step (4): It is characterized by including a step of hydrolyzing a cellulose-containing solid content. An example of the process flow diagram of the present invention is shown in FIG. 1, but the flow of the present invention is not limited thereto.

It is known that the higher the degree of pulverization of powder, the more difficult it is to dehydrate in the treatment of wastewater in which powder is slurried (Table of J. Soc Power Technology, Japan, 38, 177-183 (2001)). See 2.). However, in the present invention, when the pretreated biomass obtained by alkali-treating the cellulose-containing biomass crushed to a certain degree of crushing is hydrolyzed and solid-liquid separated, it is surprisingly solid-liquid as compared with the case where such pulverization is not performed. A high-purity sugar solution can be obtained by reducing the water content after separation and thereby reducing the fermentation inhibitor derived from the pretreated biomass brought in during the subsequent hydrolysis.

Hereinafter, the present invention will be described step by step.

Cellulose-containing biomass refers to biological resources containing at least cellulose. Preferable examples of cellulose-containing biomass are herbaceous biomass such as bagasse, switchgrass, napiergrass, erianthus, corn stove, straw (rice straw, straw), chaff, or trees, wood chips, waste building materials. Woody biomass such as, aquatic environment-derived biomass such as algae and seaweed, corn husk, wheat husk, soy husk, rice husk, grain husk biomass such as residue after starch extraction from cassabaimo (cassaba lees), etc. Can be mentioned. Herbaceous biomass such as bagasse, rice straw, and oil palm empty fruit bunch is preferable.

The water content of the cellulose-containing biomass is not particularly limited, but the preferable range is, for example, about 3% or more, about 3% or more and about 60% or less, about 5% or more, about 5% or more and about 60% or less, about 5% or more. It is about 55% or less, about 5% or more and about 50% or less. The water content of the cellulose-containing biomass is measured by the method detailed in the examples.

In step (1), the cellulose-containing biomass is crushed to a specific degree of crushing to obtain crushed biomass. The pulverization means is not particularly limited, and the pulverization can be performed by using a machine commonly used for coarse pulverization of various materials such as a ball mill, a vibration mill, a cutter mill, a hammer mill, a willley mill, and a jet mill. This mechanical pulverization may be either dry or wet, but is preferably dry pulverization.

The degree of crushing of the crushed biomass obtained in the step (1) is such that the weight ratio (dry weight%) that does not pass through a sieve having a mesh size of 1 mm is crushed until the dry weight becomes about 50% or less, preferably about 40% or more. By pulverizing until about 50% or less, more preferably about 40% or more and about 45% or less, or about 45% or more and about 50% or less, the solid-liquid separation is unexpectedly compared with the case where such pulverization is not performed. The subsequent water content is reduced, which can reduce the fermentation inhibitors derived from the pretreated biomass brought in during the subsequent hydrolysis. The degree of crushing is evaluated by drying the crushed biomass to a water content of 20% or less, and then sieving the crushed biomass with an opening of 1 mm. In the present specification, if the weight ratio (dry weight%) of the crushed biomass that does not pass through the sieve having an opening of 1 mm is low, it may be expressed that the degree of crushing is high. The sieving method and conditions follow ISO 2591-1.

In step (2), the crushed biomass obtained in step (1) is brought into contact with an alkaline aqueous medium to obtain pretreated biomass. The pretreated biomass referred to here refers to those containing the solid content of the cellulose-containing biomass that has been subjected to alkali treatment so that the cellulose-containing biomass is efficiently hydrolyzed in the subsequent step (4).

The method for bringing the crushed biomass obtained in the step (1) into contact with the alkaline aqueous medium is not particularly limited as long as it is an alkaline treatment method for cellulose-containing biomass well known to those skilled in the art, but WO2017 / 170552 is preferable. The alkaline treatment method described is adopted. This method is a method of passing an alkaline aqueous medium through a cellulose-containing biomass to obtain a pretreated biomass and an alkaline treated solution rich in coumaric acid or ferulic acid. In the present invention, the alkaline aqueous medium is passed through the pulverized biomass. You just have to make it liquid.

As a method for passing an alkaline aqueous medium through the crushed biomass, the crushed biomass and the alkaline aqueous medium are supplied to a filter according to the method described in WO2017 / 170552, and the crushed biomass and the alkaline medium are supplied using the filter. A method of passing a liquid can be mentioned. The crushed biomass and the alkaline aqueous medium may be mixed in advance and supplied to the filter, or both may be supplied to the filter separately, but the alkaline aqueous medium is placed on the crushed biomass previously supplied into the filter. It is preferable to add it.

The pH of the alkaline filtrate may be in the same range as that of the alkaline aqueous medium, and the preferable pH range is, for example, 7 or more and 12 or less, 8 or more and 12 or less, and the more preferable pH range is 9 or more and 12 or less. A more preferable pH range is 10 or more and 12 or less. The pH of the alkaline filtrate tends to decrease as the reaction progresses. This is because the soluble lignin component acts as a neutralizing agent as the alkaline reaction progresses, and the progress of the reaction can be measured by the degree of this decrease. In particular, the pH range of the pulverized biomass after contacting the pulverized biomass with an alkaline aqueous medium (after the reaction) can be appropriately adjusted depending on the initial alkali concentration and the like, but is preferably 7 or more and 12.5 or less. , 8 or more and 12.5 or less, a more preferable pH range of 8 or more and 12 or less, and a more preferable pH range of 8 or more and 11 or less. Measuring whether the pH of the alkaline filtrate is in the above range is an effective means for assessing whether the reaction has proceeded to a level sufficient to carry out the subsequent hydrolysis step.

Further, it is preferable that the alkaline aqueous medium in contact with the crushed biomass substantially maintains the temperature. If the filter is provided with a filter section that allows the ground biomass to pass an alkaline aqueous medium, it is preferable that the alkaline filtrate filtered from the filter section also substantially retains the temperature. Maintaining the temperature of the alkaline aqueous medium and the alkaline filtrate can be carried out by installing a known heat insulating device or heating device in the filter.

The filtrate that comes out of the filtration section after being brought into contact with the alkaline aqueous medium may be circulated and brought into contact with the pulverized biomass again, and the number of repetitions is not particularly limited, but the suitable number of times is, for example, at least two times or more. 2 times or more and 20000 or less, 2 times or more and 10000 or less, 2 times or more and 1000 or less, 3 times or more and 10000 or less, 3 times or more and 1000 or less, or 3 times or more and 100 or less.

Examples of the alkaline aqueous medium include an alkaline aqueous solution such as an aqueous medium containing ammonia, aqueous ammonia, and a hydroxide, preferably an aqueous medium containing sodium hydroxide and / or potassium hydroxide, and more preferably sodium hydroxide. It is an aqueous medium containing, and more preferably an aqueous solution of sodium hydroxide and / or potassium hydroxide.

The alkali concentration of the alkaline aqueous medium can be calculated from the content of alkaline substances (alkaline solids such as hydroxides) in the alkali-containing medium. The upper limit of the alkali concentration of the alkaline aqueous medium is not particularly limited, but is preferably 3, 2, 1.5, 1, 0.7, 0.6, 0.5, 0.4, 0.3 or 0. It is about 2% by weight, and the lower limit is preferably about 0.05, 0.1, 0.2, 0.3, 0.4 or 0.5% by weight. The preferred range of alkali concentration is, for example, about 0.05% by weight or more and about 0.3% by weight or less, about 0.1% by weight or more and about 3% by weight or less, and about 0.1% by weight or more and about 2% by weight. Hereinafter, the more preferable range is about 0.1% by weight or more and about 2% by weight, about 0.25% by weight or more and about 1.5% by weight or less, about 0.25% by weight or more and about 1.5% by weight or less, further preferable. The range is about 0.25% by weight or more and about 1.0% by weight or less.

The lower limit of the pH of the alkaline aqueous medium is not particularly limited as long as it is alkaline, but is 7 or more, preferably pH 8 or more, more preferably pH 9 or more, and further preferably pH 10 or more. The upper limit of pH is not particularly limited as long as it is less than pH 14, but can be set to pH 13.5 or less from the viewpoint of reducing the amount of alkali used. The preferred pH range is, for example, 7 or more and 13.5 or less, 8 or more and 13.5 or less, the more preferable pH range is 9 or more and 13.5 or less, and the more preferable pH range is 10 or more and 13.5 or less. The range.

The upper limit of the temperature of the alkaline aqueous medium is not particularly limited, but is preferably about 110, 100, 95, 90, 80, 75, 70 ° C., and the lower limit is preferably 35, 40, 50, 60, 65. It is about ° C. The temperature range of the alkaline aqueous medium is, for example, about 35 ° C. or higher and 100 ° C. or lower, 40 ° C. or higher and 100 ° C. or lower, 50 ° C. or higher and 100 ° C. or lower, 60 ° C. or higher and 100 ° C. or lower. 65 ° C. or higher and 100 ° C. or lower, 80 ° C. or higher and 100 ° C. or lower, and more preferable temperature ranges are 60 ° C. or higher and 100 ° C. or lower, 65 ° C. or higher and 100 ° C. or lower, 80 ° C. or higher and 100 ° C. The temperature range is 65 ° C. or higher and 100 ° C. or lower, or 80 ° C. or higher and 100 ° C. or lower.

The weight ratio between the alkaline aqueous medium and the ground biomass (dry weight) is not particularly limited, but the preferred ranges are, for example, 100: 1 to 2: 1, 90: 1 to 3: 1, 50: 1 to 5 :. 1, 30: 1 to 5: 1, 25: 1 to 7: 1, 25: 1 to 5: 1, 20: 1 to 5: 1.

The ratio of the alkali-containing aqueous medium to the crushed biomass (dry weight) can also be set using the amount of alkali used (also referred to as the amount of alkali reaction) calculated by the method for calculating the amount of alkali reaction described in Examples as an index. .. The preferred range of alkali usage is, for example, about 20 mg / g or more and about 300 mg / g or less, about 30 mg / g or more and about 200 mg / g or less, about 40 mg / g or more and about 200 mg / g or less, and about 45 mg / g or more and 180 mg / g. It is about g or less, about 45 mg / g or more and about 150 mg / g or less, about 50 mg / g or more and about 120 mg / g or less, about 60 mg / g or more and about 120 mg / g or less, and the more preferable range of alkali usage is 45 mg / g. About 150 mg / g or less, about 50 mg / g or more and about 120 mg / g or less, about 60 mg / g or more and about 120 mg / g or less.

The time for contacting the pulverized biomass with the alkaline aqueous medium is not particularly limited, but the contact time is, for example, about 20 minutes or more and about 72 hours or less, about 20 minutes or more and about 48 hours or less, about 20 minutes or more and about 24 hours or less. About 30 minutes or more and about 48 hours or less, about 30 minutes or more and about 24 hours or less, about 30 minutes or more and about 12 hours or less, about 30 minutes or more and about 6 hours or less, or about 30 minutes or more and about 3 hours or less.

For the pretreated biomass obtained by contacting the crushed biomass with an alkaline aqueous medium, it is preferable that the pretreated biomass is separated and recovered by a method well known to those skilled in the art and supplied to the subsequent step (3). When a filter is used to bring the crushed biomass into contact with an alkaline aqueous medium, the solid content remaining in the filter can be recovered as pretreated biomass.

The water content of the pretreated biomass supplied to the step (3) is not particularly limited, but the preferred ranges are, for example, about 50% by weight or more and about 99% by weight or less, about 60% by weight or more and about 99% by weight or less, and 70% by weight. About 99% by weight or less, about 80% by weight or more and about 99% by weight or less, or about 80% by weight or more and about 95% by weight or less, more preferably about 80% by weight or more and about 99% by weight or less, still more preferable. Is about 80% by weight or more and about 95% by weight or less. The water content of the pretreated biomass is measured by the method detailed in the Examples.

In step (3), the obtained pretreated biomass is solid-liquid separated by adding water for the purpose of separating fermentation inhibitors from the pretreated biomass. By this step, it is possible to reduce the fermentation inhibitor which is considered to be derived from lignin in the cellulose-containing biomass, which is generated by the alkaline treatment of the cellulose-containing biomass contained in the pretreated biomass. Specific examples of fermentation inhibitors include organic acids such as formic acid, acetic acid, citric acid, and lactic acid, and aromatic compounds such as ferulic acid, kumalic acid, vanillin, vanillic acid, acetovanillin, 4-hydroxybenzoic acid, silingaic acid, and gallic acid. , HMF, furfural and other furan compounds.

The amount of water added to the pretreated biomass is not particularly limited by the weight ratio of the pretreated biomass (dry weight) and the water to be added, but the preferable range is, for example, 1: 1 to 1: 100, 1: 1. ~ 1: 50, 1: 1 to 1:30, 1: 1 to 1:20, 1: 1 to 1: 10, 1: 1 to 1: 5, 1: 1 to 1: 3.

The pH of the water added to the pretreated biomass is not particularly limited, but the preferred range is, for example, 3 to 9, 3 to 8, 3 to 7, 4 to 9, 4 to 8, 4 to 7, 5 to 9. 5 to 8, 5 to 7.

The temperature of the water added to the pretreated biomass is not particularly limited, but the preferred range is, for example, 10 to 60 ° C., 10 to 50 ° C., 10 to 40 ° C., 20 to 60 ° C., 20 to 50 ° C., 20 to 20 to. 40 ° C., 30-60 ° C., 30-50 ° C., 30-40 ° C.

As a method of adding water to the pretreated biomass, the pretreated biomass and the water to be added may be mixed in the reaction tank, or the reaction tank may have a stirrer. The shape of the reaction vessel does not matter as long as the pretreated biomass and the water to be added can come into contact with each other. In addition, the pretreated biomass can be transported to the reaction tank by a conveyor or free fall. Further, if the pretreated biomass and water can come into contact with each other, water can be added during transportation such as a conveyor even if it is not in a reaction tank.

As the device used for solid-liquid separation, centrifugation, squeezing, etc. can be applied, and squeezing is preferable. Examples of the pressing include a screw press, a belt press, a filter press and the like, but a screw press is preferable.

The water content of the cellulose-containing solid content after solid-liquid separation is preferably about 50% by weight or more and about 85% by weight or less, more preferably 50% by weight, from the viewpoint of reducing fermentation inhibitors derived from the pretreated biomass. It is more than about 70% by weight and less than about 70% by weight. The water content of the cellulose-containing solid content is measured by the method for measuring the water content described in Examples.

The content of the alkaline aqueous medium in the cellulose-containing solid content is preferably about 5 mg / g-biomass or more and 40 mg / g-biomass or less, and more preferably about 7 mg / g-biomass or more and 35 mg / g-biomass or less. It is more preferably about 10 mg / g-biomass or more and about 30 mg / g-biomass or less. By reducing the content of the alkaline aqueous medium in the cellulose-containing solid content to the above range, it is possible to reduce the fermentation inhibitor derived from the pretreated biomass brought in during the subsequent hydrolysis.

In step (4), the cellulose-containing solid content is hydrolyzed to obtain a sugar solution. In the hydrolysis step, known hydrolysis methods such as acid hydrolysis, alkaline hydrolysis, and enzyme hydrolysis can be applied, but it is preferable to hydrolyze the cell roll-containing solid content in an aqueous medium with an enzyme. The sugar solution obtained by such an enzymatic hydrolysis step can be obtained as an aqueous solution containing oligosaccharides and / or monosaccharides such as glucose, xylose, arabinose, galactose, xylobiose and cellobiose.

The enzyme used is not particularly limited as long as it is cellulose or hemicellulose hydrolase, but for example, a relatively inexpensive commercially available one may be used, and the cellulase enzyme agent is "acremonium cellulase", which is an enzyme derived from the genus Acremonium. (Meiji Seika Pharma Co., Ltd.), "Axel Race Duet" (Danisco Japan Co., Ltd.), an enzyme derived from the genus Trichoderma, "Cellulose" 1.5L (Novozyme Co., Ltd.) and the like can be used. As the hemicellulase enzyme agent, "Optimash BG" (Genencore Co., Ltd.) or the like can be used. The origin of the enzyme is not particularly limited, but more preferably the enzyme is derived from filamentous fungi. Enzymes derived from filamentous fungi are rich in polysaccharide-degrading enzymes derived from cellulose-containing biomass such as cellulase, hemicellulase, and β-glucosidase, and are advantageous for hydrolyzing biomass after alkali treatment. Is.

The enzyme used can be used alone or in combination in consideration of the properties of the enzyme preparation, the composition of the desired product, and the like. The amount of suitable enzyme is also not particularly limited and can be appropriately determined. The amount of such an enzyme can be, for example, 0.01 g or more and 1 g or less per 1 g of the raw material substrate, preferably 0.001 g or more and 0.1 g or less. The temperature, pH and time of enzyme hydrolysis can be appropriately set depending on the properties and combinations of enzymes. As a preferable range, for example, the temperature is 30 or more and 60 ° C. or less, more preferably 35 ° C. or more and 50 ° C. or less. The pH is, for example, pH 3 or more and 8 or less, preferably pH 4 or more and 7 or less. The reaction time is, for example, 1 hour or more and 48 hours or less, preferably 6 hours or more and 24 hours or less.

The concentration of glucose, xylose or xylobiose in the sugar solution obtained in step (4) is not particularly limited and can be appropriately set by adjusting the reaction conditions of each step. Suitable glucose concentrations include, for example, about 5 g / L or more and 1000 g / L or less, 5 g / L or more and 700 g / L or less, 5 g / L or more and 550 g / L or less, or 10 g / L or more and 550 g / L. It is below the degree. The suitable xylose concentration is, for example, about 1 g / L or more and 100 g / L, 1 g / L or more and 50 g / L or less, or 1 g / L or more and about 10 g / L or less. As a suitable xylobiose concentration, for example, about 1 g / L or more and 100 g / L, 1 g / L or more and 50 g / L or less, 1 g / L or more and 20 g / L or less, or 1 g / L or more and 15 g / L or more. It is below the degree.

The sugar solution produced in step (4) can be used as it is for various industrial applications, but may be post-treated if desired, and specifically, it is subjected to treatments such as membrane treatment, centrifugation, concentration, and drying. You may.

Preferable membrane treatment of the sugar solution produced in step (4) includes nanofiltration membrane treatment or reverse osmosis membrane treatment.

The nanofiltration membrane is also called a nanofilter (nanofiltration membrane, NF membrane), and is a membrane generally defined as "a membrane that allows monovalent ions to permeate and blocks divalent ions". .. It is a membrane that is considered to have microvoids of several nanometers, and is mainly used to block fine particles, molecules, ions, salts, etc. in water.

A reverse osmosis membrane is also called an RO membrane, and is a membrane generally defined as "a membrane having a desalination function including monovalent ions", and is an ultra-small membrane of several angstroms to several nanometers. A membrane that is thought to have voids and is mainly used for removing ionic components such as desalination of seawater and production of ultrapure water.

The nanofiltration membrane or reverse osmosis membrane treatment refers to the sugar solution produced in step (4) being filtered through the nanofiltration membrane or reverse osmosis membrane treatment, and dissolved sugars, particularly monosaccharides such as glucose and xylose. , Xylobiose, cellobiose, and other oligosaccharides are blocked or filtered to the non-permeable side of the membrane, and the fermentation inhibitor remaining in the sugar solution is permeated as a permeate, and is carried out by the method described in WO2010 / 067785. can.

The sugar solution recovered from the non-permeable side of the nanofiltration membrane or reverse osmosis membrane has a further reduction in fermentation inhibitors compared to before the membrane treatment, and the fermentation performance should be improved compared to before the main membrane treatment. Further, the permeated water recovered from the permeation side of the nanofiltration membrane or the reverse osmosis membrane can be used as water to be added to the pretreated biomass in the step (3) (step (5)). By this step, the amount of water used in all the steps can be reduced, and the unexpected effect that the aromatic compound which is a fermentation inhibitor can be further removed by the solid-liquid separation in the step (3) can be obtained.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, the units and measurement methods described in this specification are in accordance with the Japanese Industrial Standards (JIS).

The various analysis methods in this example are as follows.

[Measurement method of sugar concentration]
The sugar concentration contained in the saccharified solution obtained in each Example and Comparative Example was quantified by comparison with the standard under the conditions of high performance liquid chromatography (HPLC) shown below.
Column: Luna NH ₂ (manufactured by Phenomenex)
Mobile phase: Ultrapure water; Acetonitrile = 25: 75
Flow velocity: 0.6 mL / min
Reaction solution: None Detection method: RI (differential refractive index)
Temperature: 30 ° C.

[Method for measuring the concentration of furan / aromatic compounds]
The concentrations of furan compounds (HMF, furfural) and phenol compounds (vanillin, etc.) contained in the sugar solution were analyzed by HPLC under the conditions shown below and quantified by comparison with the standard.
Column: Synergy HydroRP 4.6 mm x 250 mm (manufactured by Phenomenex)
Mobile phase: Acetonitrile-0.1% H ₃ PO ₄ (flow velocity 1.0 mL / min) Detection method: UV (283 nm)
Temperature: 40 ° C.

[Measurement method of organic acid concentration]
The organic acids (acetic acid, formic acid) contained in the sugar solution were analyzed by HPLC under the conditions shown below and quantified by comparison with the standard.
Column: Series mobile phase of Sim-Pack SPR-H and Sim-Pack SCR101H (manufactured by Shimadzu Corporation): 5 mM p-toluenesulfonic acid (flow velocity 0.8 mL / min)
Reaction solution: 5 mM p-toluenesulfonic acid, 20 mM bis tris, 0.1 mM EDTA · 2Na (flow rate 0.8 mL / min)
Detection method: Electrical conductivity Temperature: 45 ° C.

[Measurement method of water content]
The water content of cellulose-containing biomass, pretreated biomass, and cellulose-containing solids used in the following experiments was measured. The water content (% by weight; hereinafter simply indicated by%) is determined by holding the sample at a temperature of 120 ° C. using an infrared moisture meter (“FD-720”, manufactured by Kett Scientific Research Institute) and after evaporation. The water content, which is a value obtained from the difference between the stable value and the initial value, was measured.

For reference, Table 1 shows the water content of various cellulose-containing biomass measured by this method. Bagasse, rice straw, and oil palm empty fruit bunches are classified as herbaceous biomass.

[Calculation method of alkali reaction amount]
Regarding the calculation method of the alkali reaction amount, for example, when a reaction is carried out by adding y (%) sodium hydroxide aqueous solution b (g) to cellulose-containing biomass raw material a (g) having a water content of x (%). The reaction amount of alkali (unit: mg / g-dry biomass) was calculated by the following formula 1.

Alkaline reaction amount = y × b × 1000 / {(100-x) × a} ... (Equation 1).

Comparative Reference Example 1: Relationship between the degree of bagasse crushing during hydrothermal treatment and the moisture content of cellulose-containing solids As step (1), use a cutter mill (Varionics BRX-400, manufactured by Nara Kikai Seisakusho Co., Ltd.) for bagasse with a moisture content of 50%. Used and crushed bagasse. As the crushing conditions, the screen hole diameter of the cutter mill was set to 30 mm, and crushing was performed while supplying at a rotation speed of 600 rpm and a supply speed of 1000 kg / hr. The crushed biomass was dried to a moisture content of 20% for measuring the dry weight ratio, sieved with a 1 mm opening under the conditions of ISO 2591-1, and the weight ratio that did not pass was measured and found to be 45%.

As step (2), bagasse after crushing (moisture content 50%) was hydrothermally treated at 180 ° C. at high pressure for 10 minutes at a solid content of 5%. The obtained pretreated bagasse was filtered through a stainless steel colander (opening ratio: 30%) having an opening of 3 mm, and the solid content (pretreated biomass) remaining on the upper surface of the colander was manually pressed against the colander surface and squeezed. The water content of the obtained pretreated biomass was 90%.

As step (3), water is added to the pretreated biomass in an amount 1.6 times the solid content (dry weight), and the pretreated biomass to which water is added is applied to a small screw press for a laboratory (HX100 manufactured by Toguni Kogyo Co., Ltd., frequency 10 Hz). ) Was separated into solid and liquid. When the water content of the cellulose-containing solid content after solid-liquid separation was measured, the water content was 75%. The results are shown in Table 2.

Comparative Reference Example 2: Relationship between the degree of bagasse pulverization during hydrothermal treatment and the moisture content of cellulose-containing solids The pulverization was carried out under the same conditions as in Comparative Example 1 except that the screen hole diameter of the cutter mill was 40 mm. Further, the crushed biomass was dried to a moisture content of 20% for measuring the dry weight ratio, sieved with a mesh opening of 1 mm under the condition of ISO 2591-1, and the weight ratio of not passing was measured and found to be 50%. The water content of the cellulose-containing solid content after solid-liquid separation was 73%. The results are shown in Table 2.

Comparative Reference Example 3: Relationship between the degree of bagasse pulverization during hydrothermal treatment and the moisture content of cellulose-containing solids The pulverization conditions were the same as those of Comparative Example 1 except that the screen hole diameter of the cutter mill was 50 mm. Further, the crushed biomass was dried to a moisture content of 20% for measuring the dry weight ratio, sieved with an opening of 1 mm under the condition of ISO 2591-1, and the weight ratio of not passing was measured and found to be 55%. The water content of the cellulose-containing solid content after solid-liquid separation was 70%. The results are shown in Table 2.

Comparative Reference Example 4: Relationship between the degree of bagasse pulverization during alkaline treatment and the moisture content of cellulose-containing solids As step (1), pulverization was performed under the same pulverization conditions as in Comparative Example 3 except that the screen pore diameter of the cutter mill was 50 mm. Was done. The crushed biomass was dried to a moisture content of 20% for measuring the dry weight ratio, sieved with a 1 mm opening under the conditions of ISO 2591-1, and the weight ratio that did not pass was measured and found to be 55%.

As step (2), 5.0 kg of the obtained crushed bagus (water content 50%) was put into a multifunctional extractor (manufactured by Izumi Food Machinery Co., Ltd.), and a predetermined concentration was obtained from a spray ball at the top of the tank of the multifunctional extractor. Add 45 kg of the sodium hydroxide aqueous solution (initial temperature: 90 ° C., pH is about 13), and refill the liquid (alkaline filtrate) obtained by self-weight filtration from the filtration net provided in the tank from the spray ball. Was repeated. The reaction was carried out for a predetermined time while monitoring the temperature by providing a mechanism for heating between the filtration net and the upper spray ball. During the reaction, the alkaline filtrate was adjusted so as not to drop from 90 ° C. Further, the stirring blade attached to the multifunctional extractor was not used, the bagasse and the cellulose-containing solids were placed on the filtration net, and the shape was adjusted by the stirring blade or the like, or the operation of making a slurry was not performed. The alkaline filtrate was continuously circulated for a predetermined reaction time. The obtained sample was further filtered through a stainless steel colander with a mesh opening of 3 mm (opening ratio: 30%), and the solid content (pretreated biomass) remaining on the upper surface of the colander was manually pressed against the colander surface and squeezed. The water content of the obtained pretreated biomass was 90%.

As step (3), water was added to the pretreated biomass in an amount 1.6 times the solid content (dry weight), and the pretreated biomass was solid-liquid separated by a small laboratory screw press. When the water content of the cellulose-containing solid content after solid-liquid separation was measured, the water content was 75%. The results are shown in Table 2.

Reference Example 1: Relationship between the degree of bagasse pulverization during alkaline treatment and the water content of cellulose-containing solids The pulverization conditions were the same as those of Comparative Reference Example 4 except that the screen hole diameter of the cutter mill was 40 mm. Further, the crushed biomass was dried to a moisture content of 20% for measuring the dry weight ratio, sieved with a mesh opening of 1 mm under the condition of ISO 2591-1, and the weight ratio of not passing was measured and found to be 50%. The water content of the cellulose-containing solid content after solid-liquid separation was 64%. The results are shown in Table 2.

Reference Example 2: Relationship between the degree of bagasse pulverization during alkaline treatment and the water content of cellulose-containing solids The pulverization conditions were the same as those of Comparative Reference Example 4 except that the screen hole diameter of the cutter mill was 30 mm. Further, the crushed biomass was dried to a moisture content of 20% for measuring the dry weight ratio, sieved with an opening of 1 mm under the condition of ISO 2591-1, and the weight ratio was measured and found to be 45%. The water content of the cellulose-containing solid content after solid-liquid separation was 60%. The results are shown in Table 2.

As can be seen from Table 1, when the pretreatment is hydrothermal treatment, the content of cellulose after solid-liquid separation decreases as the proportion of crushed biomass that does not pass through a sieve with a mesh size of 1 mm (dry weight%) decreases (the degree of crushing increases). Information well known to those skilled in the art that the higher the degree of crushing of the powder, the more difficult it is to dehydrate in the treatment of wastewater in which the solid content moisture content (%) is increased and the powder is made into a slurry (J. Soc Power Technology, Japan, Japan, The results were in agreement with Table 2 of 38,177-183 (2001). On the other hand, when the pretreatment is an alkaline treatment, as the proportion of the crushed biomass that does not pass through the sieve with a mesh size of 1 mm (dry weight%) decreases (the degree of crushing increases), it is hardened contrary to the information well known to those skilled in the art. The moisture content (%) of the cellulose-containing solid content after liquid separation is reduced, and the degree of crushing of the crushed biomass is increased to reduce the fermentation inhibitor derived from the pretreatment that is mixed in when the sugar solution is produced by the subsequent hydrolysis. The possibility of being able to do it was found.

Comparative Example 1: Production example of sugar solution from bagasse (steps (1) and (3) not performed)
The same pulverization conditions and pretreatment conditions as in Comparative Reference Example 4 were carried out to obtain pretreated biomass. The obtained pretreated biomass was not subjected to the addition of water and solid-liquid separation in step (3), and was pure so that the solid content concentration of the dry base was 5% and the pH was 5.0 in step (4). Water and 35% hydrochloric acid were added to prepare a slurry liquid containing a cellulose-containing solid content. To 500 mL of the obtained slurry liquid, 5 mL of "Axel Race Duet", an enzyme manufactured by Danisco Japan Co., Ltd., was added, and the slurry temperature was maintained at 50 ° C., and the mixture was constantly stirred and reacted for 8 hours. Table 3 shows the results of measuring the sugar, acetic acid, and aromatic compound concentrations of the obtained reaction solution and determining the weights of acetic acid and coumaric acid with respect to 100 g of the obtained glucose.

Comparative Example 2: Production Example of Sugar Solution from Bagasse (Step (1) Not Implemented)
The same pulverization conditions, pretreatment conditions, and water addition / solid-liquid separation conditions as in Comparative Reference Example 4 were carried out. Using the cellulose-containing solid content after solid-liquid separation, the same hydrolysis operation as in Comparative Example 1 was carried out as step (4). Table 3 shows the results of measuring the sugar, acetic acid, and aromatic compound concentrations of the obtained reaction solution and determining the weights of acetic acid and coumaric acid with respect to 100 g of the obtained glucose.

Comparative Example 3: Production Example of Sugar Solution from Bagasse (Step (3) Not Implemented)
The crushing conditions were such that the screen hole diameter of the cutter mill was 40 mm, and the same operation as in Comparative Reference Example 4 was carried out except that solid-liquid separation was performed without adding water to the pretreated biomass. Using the obtained cellulose-containing solid content after solid-liquid separation, the same hydrolysis operation as in Comparative Example 1 was carried out as step (4). Table 3 shows the results of measuring the sugar, acetic acid, and aromatic compound concentrations of the obtained reaction solution and determining the weights of acetic acid and coumaric acid with respect to 100 g of the obtained glucose.

Example 1: Production example of sugar solution from bagasse (implementation of steps (1) to (4))
Using the cellulose-containing solid content after solid-liquid separation obtained in Reference Example 1, the same hydrolysis operation as in Comparative Example 1 was carried out as step (4). Table 3 shows the results of measuring the sugar, acetic acid, and aromatic compound concentrations of the obtained reaction solution and determining the weights of acetic acid and coumaric acid with respect to 100 g of the obtained glucose.

Example 2: Production example of sugar solution from bagasse (implementation of steps (1) to (4))
Using the cellulose-containing solid content after solid-liquid separation obtained in Reference Example 2, the same hydrolysis operation as in Comparative Example 1 was carried out as step (4). Table 3 shows the results of measuring the sugar, acetic acid, and aromatic compound concentrations of the obtained reaction solution and determining the weights of acetic acid and coumaric acid with respect to 100 g of the obtained glucose.

Example 3: Production example of sugar solution from bagasse (implementation of steps (1) to (5))
The sugar solution after hydrolysis in the step (4) obtained in Example 1 is solid-liquid separated by centrifugation (manufactured by Saito Centrifuge Industry Co., Ltd., 2,000 rpm), and then microfiltered membrane (manufactured by Millipore). After filtration using a pore diameter of 0.05 μm PVDF membrane), the sugar solution is recovered as a concentrated solution through a reverse osmosis membrane (cross-linked total aromatic polyamide reverse osmosis membrane UTC80 manufactured by Toray Co., Ltd.), and raw water is collected. Water was recovered as a permeate so that it was concentrated to a quarter.

Steps (1) to (4) were carried out again under the same conditions as in Example 1, and water recovered in step (3) was added as the permeate of the reverse osmosis membrane (step (step (step)). 5)). Table 3 shows the results of measuring the sugar, acetic acid, and aromatic compound concentrations of the sugar solution obtained in step (4) and determining the weights of acetic acid and coumaric acid with respect to 100 g of the obtained glucose.

As can be seen from Table 3, the weights of acetic acid and coumaric acid relative to glucose were relatively reduced in Examples 1 to 3 as compared with Comparative Examples 1 to 3 in which all of steps (1) to (4) were not performed. .. In particular, from the comparative results of Comparative Example 2 and Examples 1 and 2, when the weight ratio (dry weight%) of the powdery biomass that does not pass through the sieve with an opening of 1 mm exceeds 50%, fermentation in the sugar solution It became clear that the concentration of the inhibitor increased. Further, from the results of Examples 1 and 3, it was clarified that the coumaric acid concentration in the sugar solution was further reduced by carrying out the step (5).

Claims

A method for producing a sugar solution using cellulose-containing biomass as a raw material.
Step (1): A step of crushing cellulose-containing biomass so that the weight ratio that does not pass through a sieve having a mesh size of 1 mm is 50% or less in terms of dry weight.
Step (2): A step of contacting the crushed biomass obtained in the step (1) with an alkaline aqueous medium to obtain a pretreated biomass.
Step (3): Water is added to the pretreated biomass obtained in step (2) and solid-liquid separation is performed to obtain a cellulose-containing solid content, and step (4): cellulose obtained in step (3). The process of hydrolyzing the contained solids to obtain a sugar solution,
Including methods.
The method for producing a sugar solution according to claim 1, wherein the step (2) is a step of passing an alkaline medium through the crushed biomass obtained in the step (1) to obtain pretreated biomass.
The step (2) is a step of supplying the crushed biomass and the alkaline medium obtained in the step (1) to a filter and passing the crushed biomass and the alkaline medium through the filter using the filter. Alternatively, the method for producing a sugar solution according to 2.
The method for producing a sugar solution according to any one of claims 1 to 3, wherein the alkaline aqueous medium of the step (2) is an aqueous medium containing sodium hydroxide and / or potassium hydroxide.
The method for producing a sugar solution according to any one of claims 1 to 4, wherein the solid-liquid separation in the step (3) is pressing.
The method for producing a sugar solution according to any one of claims 1 to 5, wherein the cellulose-containing biomass is bagasse.
Step (5): The sugar solution obtained in step (4) is filtered through a nanofiltration membrane or a reverse osmosis membrane, the sugar solution is recovered as a non-permeable solution, and the permeated solution is pretreated biomass in step (3). The process of reusing water to be added to
The method for producing a sugar solution according to any one of claims 1 to 6, further comprising.
Cellulose-containing solid content containing crushed cellulose-containing biomass and an alkaline aqueous medium having a dry weight of 50% or less that does not pass through a sieve having an opening of 1 mm and having a water content of 50% by weight or more and less than 70% by weight.
The cellulose-containing solid content according to claim 8, wherein the cellulose-containing biomass is bagasse.
Biomass containing crushed cellulose having a dry weight of 40 to 50% that does not pass through a sieve with a 1 mm opening.