Method for producing sugar solution

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

[Technical field]

[0001] The present invention relates to a method for producing a sugar liquid that can be used as a fermentation raw material, etc., from cellulose-containing biomass. [Background technology]

[0002] Fermentation production processes for chemicals using carbohydrates as raw materials are used in the production of various industrial raw materials. Currently, carbohydrates derived from edible raw materials such as sugar cane, starch, and sugar beet are used industrially as fermentation raw materials. However, due to the future increase in the world population and the ethical aspect of competing with food, renewable non-edible resources, such as cellulose-containing biomass, are being considered. from The challenge for the future is to develop a process for more efficient sugar liquid production, or a process for efficiently converting the obtained sugar liquid into industrial raw materials using it as fermentation feedstock.

[0003] The carbohydrates in cellulose-containing biomass feedstocks are embedded in complex cell walls, and therefore, to allow efficient enzyme action, it is preferable to subject the biomass feedstocks to an alkaline treatment prior to enzymatic hydrolysis.

[0004] for example, cellulose It has been disclosed that in order to improve the rate of enzymatic hydrolysis, a specific pretreatment is applied to cellulose-containing biomass, in which a cellulose-containing material is brought into contact with an alkaline aqueous solution and the alkaline filtrate is repeatedly used, thereby producing a sugar liquid containing sugars at high purity (Patent Document 1).

[0005] It has also been disclosed that a plant biomass raw material containing cellulose is treated with a treating agent containing ammonia, and then immersed in water at 40 to 100°C to elute polysaccharides into the water, thereby obtaining a raw material for enzymatic saccharification to be subjected to an enzymatic saccharification step. According to the present invention, enzymatic saccharification can be carried out efficiently, and therefore the method is used in a sugar production method with improved sugar production efficiency (Patent Document 2).

[0006] However, there is a quality issue in that fermentation inhibitors such as organic acids and aromatic compounds produced during the alkali treatment are contaminated into the sugar liquid, and there is still a demand for a method for producing a cellulose sugar liquid with reduced fermentation inhibitors. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2017 / 170552 [Patent Document 2] WO2012 / 096236 issue Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for reducing fermentation inhibitors, such as organic acids and aromatic compounds, that are generated by alkali treatment of cellulose-containing biomass when producing a sugar liquid from cellulose-containing biomass. [Means for solving the problem]

[0009] The present inventors have now discovered that a sugar liquid with reduced fermentation inhibitors can be efficiently obtained by crushing cellulose-containing biomass to a specific degree of crushing, contacting it with an alkaline aqueous medium, adding water, subjecting the pretreated biomass to which water has been added to solid-liquid separation, and hydrolyzing the pretreated biomass.

[0010] The present invention is based on this finding and comprises the following items [1] to

[10] . [1] A method for producing a sugar liquid using cellulose-containing biomass as a raw material, comprising: (1) crushing the cellulose-containing biomass so that the weight ratio of the cellulose-containing biomass that does not pass through a sieve having an opening of 1 mm is 50% or less by dry weight; Step (2): contacting the pulverized biomass obtained in step (1) with an alkaline aqueous medium to obtain a pretreated biomass; Step (3): adding water to the pretreated biomass obtained in step (2) to perform solid-liquid separation to obtain a cellulose-containing solid fraction; and Step (4): Hydrolyzing the cellulose-containing solid content obtained in step (3) to obtain a sugar liquid; A method comprising: [2] The method for producing a sugar liquid according to [1], wherein the step (2) is a step of passing an alkaline medium through the pulverized biomass obtained in the step (1) to obtain a pretreated biomass. [3] The method for producing a sugar solution according to [1] or [2], wherein the step (2) is a step of supplying the pulverized biomass obtained in the step (1) and an alkaline medium to a filter and passing the pulverized biomass and the alkaline medium through the filter. [4] The method for producing a sugar liquid according to any one of [1] to [3], wherein the alkaline aqueous medium in the step (2) is an aqueous medium containing sodium hydroxide and / or potassium hydroxide. [5] The method for producing a sugar liquid 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 liquid according to any one of [1] to [5], wherein the cellulose-containing biomass is bagasse. [7] Step (5): filtering the sugar solution obtained in step (4) through a nanofiltration membrane or a reverse osmosis membrane, recovering the sugar solution as a non-permeated liquid, and reusing the permeated liquid as water to be added to the pretreated biomass in step (3); The method for producing a sugar liquid according to any one of [1] to [6], further comprising: [8] A cellulose-containing solid fraction comprising pulverized cellulose-containing biomass and an alkaline aqueous medium, the weight percentage of which not passing through a 1 mm mesh sieve being 50% or less by dry weight, and having a moisture content of 50% or more but less than 70% by weight. [9] The cellulose-containing solid content according to [8], wherein the cellulose-containing biomass is bagasse.

[10] Crushed cellulose-containing biomass in which the weight percentage that does not pass through a 1 mm mesh sieve is 40-50% by dry weight. Effect of the Invention

[0011] According to the present invention, a high-purity sugar liquid can be obtained in which the amount of fermentation inhibitors derived from the alkali treatment of cellulose-containing biomass has been reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a process flow diagram showing an example of a method for producing a sugar liquid of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention is a method for producing a sugar liquid using cellulose-containing biomass as a raw material, and is characterized by comprising: step (1): pulverizing the cellulose-containing biomass so that the proportion of the material that does not pass through a sieve with 1 mm mesh size is 50% or less by dry weight; step (2): contacting the pulverized biomass with an alkaline aqueous medium to obtain a pretreated biomass; step (3): adding water to the pretreated biomass for solid-liquid separation to separate the cellulose-containing solid content; and step (4): hydrolyzing the cellulose-containing solid content. An example of a process flow diagram of the present invention is shown in Figure 1, but the flow of the present invention is not limited thereto.

[0014] In the treatment of wastewater in which powder has turned into a slurry, it is known that the higher the degree of grinding of the powder, the more difficult it is to dehydrate it (see Table 2 in J. Soc. Powder Technol., Japan, 38, 177-183 (2001)). However, in the present invention, when the pretreated biomass obtained by alkali treatment of cellulose-containing biomass pulverized to a certain degree is hydrated and subjected to solid-liquid separation, the moisture content after solid-liquid separation is unexpectedly reduced compared to the case where such grinding is not performed, and this reduces the amount of fermentation inhibitors derived from the pretreated biomass that are carried over during the subsequent hydrolysis stage, thereby making it possible to obtain a high-purity sugar liquid.

[0015] The present invention will be described step by step below.

[0016] Cellulose-containing biomass refers to biological resources that contain at least cellulose. Suitable examples of cellulose-containing biomass include herbaceous biomass such as bagasse, switchgrass, napier grass, erianthus, corn stover, straw (rice straw, wheat straw), and empty fruit bunches of oil palm, woody biomass such as trees, wood chips, and waste building materials, biomass derived from aquatic environments such as algae and seaweed, and grain husk biomass such as corn husks, wheat husks, soybean husks, rice husks, and residues (cassava meal) after starch extraction from cassava. Herbaceous biomass such as bagasse, rice straw, and empty fruit bunches of oil palm are preferred.

[0017] The moisture content of the cellulose-containing biomass is not particularly limited, but preferred ranges are, for example, about 3% or more, about 3% to about 60%, about 5% or more, about 5% to about 60%, about 5% to about 55%, and about 5% to about 50%. The moisture content of the cellulose-containing biomass is measured by a method described in detail in the Examples.

[0018] In step (1), the cellulose-containing biomass is pulverized to a specific degree of pulverization to obtain pulverized biomass. The pulverization method is not particularly limited, and can be carried out 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 Willey mill, or a jet mill. This mechanical pulverization may be either dry or wet, but is preferably dry.

[0019] The degree of pulverization of the pulverized biomass obtained in step (1) is such that the weight ratio (dry weight %) that does not pass through a sieve with an opening of 1 mm is about 50% or less by dry weight, preferably about 40% to about 50%, more preferably 40% to about 50%. %degree Over 45 %degreeBy grinding to a moisture content of 20% or less or to 45% to 50% or less, the moisture content after solid-liquid separation is unexpectedly reduced compared to when such grinding is not performed, and this reduces the fermentation inhibitors derived from the pretreated biomass that are carried over during the subsequent hydrolysis step. The degree of grinding is evaluated by drying the ground biomass, reducing the moisture content to 20% or less, and then sieving the ground biomass through a sieve with 1 mm openings. In this specification, the degree of grinding may be expressed as high if the weight ratio (dry weight %) of the ground biomass that does not pass through a sieve with 1 mm openings is low. The sieving method and conditions are in accordance with ISO 2591-1.

[0020] In step (2), the pulverized biomass obtained in step (1) is contacted with an alkaline aqueous medium to obtain a pretreated biomass. The pretreated biomass referred to here refers to a biomass containing a solid fraction of cellulose-containing biomass that has been subjected to an alkaline treatment so that the cellulose-containing biomass is efficiently hydrolyzed in the subsequent step (4).

[0021] The method for contacting the pulverized biomass obtained in step (1) with an 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 preferably, the alkaline treatment method described in WO2017 / 170552 is used. This method is a method in which an alkaline aqueous medium is passed through a cellulose-containing biomass to obtain a pretreated biomass and an alkaline treatment liquid rich in coumaric acid and ferulic acid, and in the present invention, it is sufficient to pass an alkaline aqueous medium through the pulverized biomass.

[0022] An example of a method for passing an alkaline aqueous medium through pulverized biomass is a method in which pulverized biomass and an alkaline aqueous medium are supplied to a filter and the pulverized biomass and the alkaline medium are passed through the filter in accordance with the method described in WO2017 / 170552. The pulverized biomass and the alkaline aqueous medium may be mixed in advance and supplied to the filter, or the two may be supplied separately to the filter. However, it is preferable to add the alkaline aqueous medium onto the pulverized biomass that has been supplied in advance to the filter.

[0023] The pH of the alkaline filtrate may be within the same range as that of the alkaline aqueous medium, and the preferred pH range is, for example, 7 to 12, 8 to 12, more preferably 9 to 12, and even more preferably 10 to 12. The pH of the alkaline filtrate tends to decrease as the reaction proceeds. This is because the soluble lignin component acts as a neutralizer as the alkaline reaction proceeds, and the progress of the reaction can be measured by the degree of decrease. In particular, the pH range of the pulverized biomass after contacting the pulverized biomass with the alkaline aqueous medium (after the reaction) can be appropriately adjusted by the initial alkali concentration, etc., and is preferably, for example, 7 to 12.5, 8 to 12.5, more preferably 8 to 12, and even more preferably 8 to 11. Measuring whether the pH of the alkaline filtrate is within the above range is an effective means for evaluating whether the reaction has progressed to a level sufficient for performing the subsequent hydrolysis step.

[0024] In addition, it is preferable that the temperature of the alkaline aqueous medium in contact with the pulverized biomass is substantially maintained. When the filter is equipped with a filtration section that passes the alkaline aqueous medium through the pulverized biomass, it is preferable that the temperature of the alkaline filtrate filtered through the filtration section is also substantially maintained. The temperatures of the alkaline aqueous medium and the alkaline filtrate can be maintained by providing a known heat retaining device or heating device in the filter.

[0025] The filtrate coming out of the filtration section after contacting with the alkaline aqueous medium may be circulated and contacted again with the pulverized biomass. The number of times this is repeated is not particularly limited, but suitable numbers are, for example, at least 2 times, 2 to 20,000 times, 2 to 10,000 times, 2 to 1,000 times, 3 to 10,000 times, 3 to 1,000 times, or 3 to 100 times.

[0026] Examples of the alkaline aqueous medium include alkaline aqueous solutions such as aqueous media containing ammonia, ammonia water, and hydroxides, and are preferably aqueous media containing sodium hydroxide and / or potassium hydroxide, more preferably aqueous media containing sodium hydroxide, and even more preferably aqueous solutions of sodium hydroxide and / or potassium hydroxide.

[0027] The alkali concentration of the alkaline aqueous medium can be calculated from the content of the alkaline substance (alkali 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 about 3, 2, 1.5, 1, 0.7, 0.6, 0.5, 0.4, 0.3 or 0.2% 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 the alkali concentration is, for example, about 0.05% by weight to about 0.3% by weight, about 0.1% by weight to about 3% by weight, about 0.1% by weight to about 2% by weight, and a more preferred range is about 0.1% by weight to about 2% by weight. below , 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, and a more preferable range is about 0.25% by weight or more and about 1.0% by weight or less.

[0028] 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 8 or more, more preferably 9 or more, and even more preferably 10 or more. The upper limit of the 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, more preferably 9 or more and 13.5 or less, and even more preferably 10 or more and 13.5 or less.

[0029] 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, or 70° C., and the lower limit is preferably about 35, 40, 50, 60, or 65° C. The preferred temperature range of the alkaline aqueous medium is, for example, about 35° C. to about 100° C., about 40° C. to about 100° C., about 50° C. to about 100° C., about 60° C. to about 100° C., about 65° C. to about 100° C., or about 80° C. to about 100° C., more preferred temperature ranges are about 60° C. to about 100° C., about 65° C. to about 100° C., and about 80° C. to about 100° C., and even more preferred temperature ranges are about 65° C. to about 100° C. or about 80° C. to about 100° C.

[0030] The weight ratio of the alkaline aqueous medium to the pulverized biomass (dry weight) is not particularly limited, but 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, and 20:1 to 5:1.

[0031] The ratio of the alkali-containing aqueous medium to the pulverized biomass (dry weight) can be set using the amount of alkali used (also called the amount of alkali reaction) calculated by the calculation method of the amount of alkali reaction described in the Examples as an index. The range of the amount of alkali used is, for example, about 20 mg / g to about 300 mg / g, about 30 mg / g to about 200 mg / g, about 40 mg / g to about 200 mg / g, about 45 mg / g to about 180 mg / g, about 45 mg / g to about 150 mg / g, about 50 mg / g to about 120 mg / g, about 60 mg / g to about 120 mg / g, and more preferably, the range of the amount of alkali used is about 45 mg / g to about 150 mg / g, about 50 mg / g to about 120 mg / g, and about 60 mg / g to about 120 mg / g.

[0032] The time for which the pulverized biomass is contacted with the alkaline aqueous medium is not particularly limited, but the contact time is, for example, from about 20 minutes to about 72 hours, from about 20 minutes to about 48 hours, from about 20 minutes to about 24 hours, from about 30 minutes to about 48 hours, from about 30 minutes to about 24 hours, from about 30 minutes to about 12 hours, from about 30 minutes to about 6 hours, or from about 30 minutes to about 3 hours.

[0033] The pretreated biomass obtained by contacting the pulverized biomass with an alkaline aqueous medium is preferably 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 contact the pulverized biomass with the alkaline aqueous medium, the solid content remaining in the filter can be recovered as the pretreated biomass.

[0034] The moisture content of the pretreated biomass supplied to step (3) is not particularly limited, but preferred ranges are, for example, from about 50% by weight to about 99% by weight, from about 60% by weight to about 99% by weight, from about 70% by weight to about 99% by weight, from about 80% by weight to about 99% by weight, or from about 80% by weight to about 95% by weight, more preferably from about 80% by weight to about 99% by weight, and even more preferably from about 80% by weight to about 95% by weight. The moisture content of the pretreated biomass is measured by a method described in detail in the Examples.

[0035] In step (3), water is added to the obtained pretreated biomass for the purpose of separating fermentation inhibitors from the pretreated biomass, and solid-liquid separation is performed. This step can reduce fermentation inhibitors that are generated by the alkali treatment of the cellulose-containing biomass contained in the pretreated biomass and are thought to be derived from lignin in the cellulose-containing biomass. Specific examples of fermentation inhibitors include organic acids such as formic acid, acetic acid, citric acid, and lactic acid, aromatic compounds such as ferulic acid, coumaric acid, vanillin, vanillic acid, acetovanillin, 4-hydroxybenzoic acid, syringic acid, and gallic acid, and furan compounds such as HMF and furfural.

[0036] The amount of water added to the pretreated biomass is expressed as the weight ratio of the pretreated biomass (dry weight) to the water added, and is not particularly limited; preferred ranges are, for example, 1:1 to 1:100, 1:1 to 1:50, 1:1 to 1:30, 1:1 to 1:20, 1:1 to 1:10, 1:1 to 1:5, and 1:1 to 1:3.

[0037] The pH of the water added to the pretreated biomass is not particularly limited, but preferred ranges are, for example, 3-9, 3-8, 3-7, 4-9, 4-8, 4-7, 5-9, 5-8, and 5-7.

[0038] The temperature of the water added to the pretreated biomass is not particularly limited, but preferred ranges are, for example, 10 to 60°C, 10 to 50°C, 10 to 40°C, 20 to 60°C, 20 to 50°C, 20 to 40°C, 30 to 60°C, 30 to 50°C, and 30 to 40°C.

[0039] As a method for adding water to the pretreated biomass, the pretreated biomass and the water to be added may be mixed in a reaction tank, or the reaction tank may have an agitator. The reaction tank may be of any shape as long as the pretreated biomass and the water to be added can come into contact with each other. The pretreated biomass can be transported to the reaction tank by a conveyor or by natural fall. As long as the pretreated biomass and the water can come into contact with each other, water can be added during transport by a conveyor or the like, even if it is not a reaction tank.

[0040] The apparatus used for solid-liquid separation may be a centrifugal separator, a squeezer, or the like, with the squeezer being preferred. As the squeezer, there are a screw press, a belt press, a filter press, and the like, with the screw press being preferred.

[0041] The moisture 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 about 50% by weight or more and less than about 70% by weight, from the viewpoint of reducing fermentation inhibitors derived from the pretreated biomass. The moisture content of the cellulose-containing solid content is measured by the moisture content measurement method described in the Examples.

[0042] The content of the alkaline aqueous medium in the cellulose-containing solids is preferably from about 5 mg / g biomass to about 40 mg / g biomass, more preferably from about 7 mg / g biomass to about 35 mg / g biomass, and even more preferably from about 10 mg / g biomass to about 30 mg / g biomass. By reducing the content of the alkaline aqueous medium in the cellulose-containing solids to the above range, it is possible to reduce the amount of fermentation inhibitors derived from the pretreated biomass that are carried over during the subsequent hydrolysis.

[0043] In step (4), cellulose The solid content is hydrolyzed to obtain a sugar liquid. In the hydrolysis step, known hydrolysis methods such as acid hydrolysis, alkali hydrolysis, and enzymatic hydrolysis can be applied. cellulose The solid content is preferably hydrolyzed with an enzyme in an aqueous medium. 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.

[0044] The enzyme to be used is not particularly limited as long as it is a cellulose or hemicellulose hydrolase, but may be, for example, a relatively inexpensive commercially available one. As the cellulase enzyme preparation, "Acremonium Cellulase" (Meiji Seika Pharma Co., Ltd.), which is an enzyme derived from the genus Acremonium, "Accelrace Duet" (Danisco Japan Co., Ltd.), "Celluclast" 1.5L (Novozymes), etc., which are enzymes derived from the genus Trichoderma, can be used. As the hemicellulase enzyme preparation, "Optimash BG" (Genencor Co., Ltd.), etc. can be used. The origin of the enzyme is not particularly limited, but more preferably, it is an enzyme derived from a filamentous fungus. Enzymes derived from filamentous fungi are rich in decomposing enzymes for polysaccharides derived from cellulose-containing biomass, such as cellulase, hemicellulase, and β-glucosidase, and are advantageous in carrying out a hydrolysis reaction on biomass after alkali treatment.

[0045] The enzymes used can be used alone or in combination, taking into consideration the properties of the enzyme preparation, the composition of the desired product, and the like. The amount of suitable enzymes is also not particularly limited and can be appropriately determined. The amount of such enzymes can be, for example, 0.01 g to 1 g per 1 g of raw material substrate, and preferably 0.001 g to 0.1 g. The temperature, pH, and time of enzymatic hydrolysis can be appropriately set depending on the properties and combination of enzymes. As a suitable range, for example, the temperature is 30 to 60°C, more preferably 35 to 50°C. The pH is, for example, 3 to 8, preferably 4 to 7. The reaction time is, for example, 1 hour to 48 hours, preferably 6 to 24 hours.

[0046] 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 are, for example, from about 5 g / L to about 1000 g / L, from about 5 g / L to about 700 g / L, from about 5 g / L to about 550 g / L, or from about 10 g / L to about 550 g / L. Suitable xylose concentrations are, for example, from about 1 g / L to about 100 g / L. below the level , about 1 g / L to about 50 g / L or about 1 g / L to about 10 g / L. below the level , from about 1 g / L to about 50 g / L, from about 1 g / L to about 20 g / L, or from about 1 g / L to about 15 g / L.

[0047] The sugar liquid produced in step (4) can be used as is for various industrial applications, but may be subjected to post-treatment, if desired. Specifically, it may be subjected to treatments such as membrane treatment, centrifugation, concentration, drying, etc.

[0048] Preferred membrane treatment of the sugar liquid produced in step (4) includes nanofiltration membrane or reverse osmosis membrane treatment.

[0049] Nanofiltration membranes, also known as nanofilters (nanofiltration membranes, NF membranes), are generally defined as membranes that allow monovalent ions to pass through and block divalent ions. These membranes are thought to have tiny pores of about a few nanometers in size, and are primarily used to block microparticles, molecules, ions, salts, etc. in water.

[0050] Reverse osmosis membranes, also known as RO membranes, are generally defined as "membranes with desalination capabilities, including for monovalent ions," and are thought to have ultra-micropores of a few angstroms to a few nanometers. They are primarily used to remove ionic components in seawater desalination and ultrapure water production.

[0051] The nanofiltration or reverse osmosis membrane treatment is a process in which the sugar solution produced in step (4) is filtered through a nanofiltration membrane or reverse osmosis membrane. To the membrane This treatment involves filtering the sugar solution through a membrane, blocking or filtering out dissolved sugars, particularly monosaccharides such as glucose and xylose, and oligosaccharides such as xylobiose and cellobiose, on the non-permeating side of the membrane, and allowing fermentation inhibitors remaining in the sugar solution to permeate as the permeate, and can be carried out by the method described in WO2010 / 067785.

[0052] The sugar liquid recovered from the non-permeated side of the nanofiltration membrane or reverse osmosis membrane has further reduced fermentation inhibitors compared to before membrane treatment, and the fermentation performance can be improved compared to before this membrane treatment, and further, the permeate recovered from the permeated side of the nanofiltration membrane or reverse osmosis membrane can be used as water to be added to the pretreated biomass in the above step (3) (step (5)). This step can reduce the amount of water used in all steps, and can have the unexpected effect of further removing aromatic compounds, which are fermentation inhibitors, by the solid-liquid separation in step (3). EXAMPLES

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Furthermore, unless otherwise specified, the units and measurement methods described in this specification are in accordance with the Japanese Industrial Standards (JIS).

[0054] The various analytical methods used in this example are as follows.

[0055] [Method of measuring sugar concentration] The sugar concentration in the saccharified solution obtained in each of the Examples and Comparative Examples was quantified by comparison with a standard sample under the high performance liquid chromatography (HPLC) conditions shown below. Column: Luna NH2 (Phenomenex) Mobile phase: ultrapure water; acetonitrile = 25:75 Flow rate: 0.6mL / min Reaction solution: None Detection method: RI (differential refractive index) Temperature: 30℃.

[0056] [Method for measuring the concentration of furan and aromatic compounds] The concentrations of furan compounds (HMF, furfural) and phenolic compounds (vanillin, etc.) contained in the sugar solution were analyzed by HPLC under the conditions shown below and quantified by comparison with standards. Column: Synergi HidroRP 4.6mm x 250mm (Phenomenex) Mobile phase: acetonitrile-0.1% H3PO4 (flow rate 1.0 mL / min) Detection method: UV (283 nm) Temperature: 40℃.

[0057] [Method for measuring 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 standards. Column: Shim-Pack SPR-H and Shim-Pack SCR101H (Shimadzu Corporation) in series Mobile phase: 5 mM p-toluenesulfonic acid (flow rate 0.8 mL / min) Reaction solution: 5 mM p-toluenesulfonic acid, 20 mM BisTris, 0.1 mM EDTA·2Na (flow rate 0.8 mL / min) Detection method: Electrical conductivity Temperature: 45℃.

[0058] [Method of measuring moisture content] The moisture content of the cellulose-containing biomass, pretreated biomass, and cellulose-containing solid used in the following experiments was measured. The moisture content (wt%; hereinafter, simply indicated as %) was measured using an infrared moisture meter ("FD-720", Kett Electric Laboratory) by holding the sample at 120°C and measuring the moisture content, which is the value obtained by subtracting the initial value from the stable value after evaporation.

[0059] For reference, the moisture contents of various cellulose-containing biomass measured by this method are shown in Table 1. Bagasse, rice straw, and oil palm empty fruit bunches are classified as herbaceous biomass.

[0060] [Table 1]

[0061] [How to calculate the amount of alkali reaction] Regarding the method for calculating the amount of alkali reaction, for example, when a (g) of cellulose-containing biomass material with a moisture content of x (%) is reacted with an aqueous sodium hydroxide solution b (g) of y (%), the amount of alkali reaction (unit: mg / g-dry biomass) was calculated using the following formula 1.

[0062] Amount of alkali reaction = y × b × 1000 / {(100 - x) × a} (Equation 1).

[0063] Comparative Reference Example 1: Relationship between bagasse crushing degree during hydrothermal treatment and moisture content of cellulose-containing solids In step (1), bagasse with a moisture content of 50% was pulverized using a cutter mill (Nara Machinery Manufacturing Co., Ltd., Varionyx BRX-400). The pulverization conditions were set to a cutter mill screen hole size of 30 mm, and pulverization was performed while feeding at a rotation speed of 600 rpm and a feed rate of 1000 kg / hr. The pulverized biomass was dried to a moisture content of 20% in order to measure the dry weight ratio, and passed through a sieve with 1 mm openings under the conditions of ISO 2591-1. The weight ratio that did not pass through was measured and found to be 45%.

[0064] In step (2), the crushed bagasse (moisture content: 50%) was subjected to hydrothermal treatment at high pressure at 180°C for 10 minutes with a solid content of 5%. The obtained pretreated bagasse was filtered through a stainless steel sieve with 3 mm openings (opening rate: 30%), and the solids remaining on the top of the sieve (pretreated biomass) were pressed against the surface of the sieve by hand and squeezed. The moisture content of the obtained pretreated biomass was 90%.

[0065] In step (3), water was added to the pretreated biomass in an amount 1.6 times the amount of solids (dry weight), and the pretreated biomass to which water had been added was subjected to solid-liquid separation using a small laboratory screw press (HX100, manufactured by Fukoku Kogyo Co., Ltd., frequency 10 Hz). The moisture content of the cellulose-containing solids after solid-liquid separation was measured and found to be 75%. The results are shown in Table 2.

[0066] Comparative Reference Example 2: Relationship between bagasse crushing degree during hydrothermal treatment and moisture content of cellulose-containing solids The grinding conditions were the same as for comparison, except that the screen hole diameter of the cutter mill was 40 mm. reference The experiment was carried out under the same conditions as in Example 1. The pulverized biomass was dried to a moisture content of 20% to measure the dry weight ratio, and sieved through a 1 mm sieve under the conditions of ISO 2591-1. The weight ratio of the material that did not pass through was measured and found to be 50%. The moisture content of the cellulose-containing solid matter after solid-liquid separation was 73%. The results are shown in Table 2.

[0067] Comparative Reference Example 3: Relationship between bagasse crushing degree during hydrothermal treatment and moisture content of cellulose-containing solids The grinding conditions were the same as for comparison, except that the screen hole diameter of the cutter mill was 50 mm. reference The experiment was carried out under the same conditions as in Example 1. The pulverized biomass was dried to a moisture content of 20% to measure the dry weight ratio, and sieved through a 1 mm sieve under the conditions of ISO 2591-1. The weight ratio of the material that did not pass through was measured and found to be 55%. The moisture content of the cellulose-containing solid matter after solid-liquid separation was 70%. The results are shown in Table 2.

[0068] Comparative Reference Example 4: Relationship between bagasse crushing degree and moisture content of cellulose-containing solids during alkali treatment In step (1), pulverization was performed under the same pulverization conditions as in Comparative Example 3, except that the screen hole diameter of the cutter mill was 50 mm. The pulverized biomass was dried to a moisture content of 20% to measure the dry weight ratio, and sieved through a sieve with 1 mm openings under the conditions of ISO 2591-1. The weight ratio of the material that did not pass through was measured and found to be 55%.

[0069] In step (2), 5.0 kg of the obtained crushed bagasse (water content 50%) was put into a multifunctional extractor (manufactured by Izumi Food Machinery Co., Ltd.), 45 kg of a sodium hydroxide solution of a predetermined concentration (initial temperature: 90°C, pH about 13) was added from the spray ball at the top of the tank of the multifunctional extractor, and the liquid obtained by gravity filtration from a filter net attached in the tank (alkaline filtrate) was added again from the spray ball. The reaction was carried out for a predetermined time while monitoring the temperature by providing a heating mechanism between the filter net and the upper spray ball. During the reaction, the alkaline filtrate was adjusted so that it did not drop below 90°C. In addition, the stirring blade attached to the multifunctional extractor was not used, and the bagasse and cellulose-containing solids were placed on the filter net, and no operation of adjusting the shape or making a slurry with a stirring blade or the like was performed. The alkaline filtrate was kept circulating for a predetermined reaction time. The obtained sample was further filtered through a stainless steel sieve with 3 mm openings (opening rate: 30%), and the solid matter remaining on the top of the sieve (pretreated biomass) was pressed against the surface of the sieve by hand and squeezed. The moisture content of the obtained pretreated biomass was 90%.

[0070] In 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 subjected to solid-liquid separation using a small laboratory screw press. The moisture content of the cellulose-containing solid content after solid-liquid separation was measured and found to be 75%. The results are shown in Table 2.

[0071] Reference Example 1: Relationship between bagasse crushing degree and moisture content of cellulose-containing solids during alkali treatment The grinding conditions were the same as those of Comparative Reference Example 4, except that the screen hole diameter of the cutter mill was 40 mm. In addition, the ground biomass was dried to a moisture content of 20% to measure the dry weight ratio, and sieved through a sieve with 1 mm openings under the conditions of ISO 2591-1. The weight ratio of the material that did not pass through was measured and found to be 50%. The moisture content of the cellulose-containing solid matter after solid-liquid separation was 64%. The results are shown in Table 2.

[0072] Reference Example 2: Relationship between bagasse crushing degree and moisture content of cellulose-containing solids during alkali treatment The grinding conditions were the same as those of Comparative Reference Example 4, except that the screen hole diameter of the cutter mill was 30 mm. The ground biomass was dried to a moisture content of 20% to measure the dry weight ratio, and sieved through a 1 mm sieve under the conditions of ISO 2591-1 to measure the weight ratio, which was 45%. The moisture content of the cellulose-containing solid after solid-liquid separation was 60%. The results are shown in Table 2.

[0073] [Table 2]

[0074] table 2 As can be seen from the results, when the pretreatment is hydrothermal treatment, the proportion of the pulverized biomass that does not pass through a 1 mm sieve (dry weight %) decreases (the degree of pulverization increases), and the moisture content (%) of the cellulose-containing solids after solid-liquid separation increases, which is consistent with the information known to those skilled in the art that the higher the degree of pulverization of the powder, the more difficult it is to dehydrate it in the treatment of wastewater in which the powder has been turned into a slurry (see Table 2 in J. Soc. Powder Technol., Japan, 38, 177-183 (2001)). On the other hand, when the pretreatment is alkali treatment, the proportion of the pulverized biomass that does not pass through a 1 mm sieve (dry weight %) decreases (the degree of pulverization increases), which is contrary to the information known to those skilled in the art, and it has been found that by increasing the degree of pulverization of the pulverized biomass, it is possible to reduce the fermentation inhibitors derived from the pretreatment that are mixed in when producing a sugar solution by hydrolysis in the subsequent stage.

[0075] Comparative Example 1: Example of production of sugar liquid from bagasse (steps (1) and (3) not performed) The same grinding and pretreatment conditions as those of Comparative Reference Example 4 were carried out to obtain a pretreated biomass. The obtained pretreated biomass was not subjected to the addition of water and solid-liquid separation in step (3), but instead, in step (4), pure water and 35% hydrochloric acid were added to the pretreated biomass so that the dry solid concentration was 5% and the pH was 5.0 to prepare a slurry containing a cellulose-containing solid. 5 mL of the enzyme "Accel Race Duet" manufactured by Danisco Japan Co., Ltd. was added to 500 mL of the obtained slurry, and the reaction was carried out for 8 hours while maintaining the slurry temperature at 50°C and constantly stirring. The sugar, acetic acid, and aromatic compound concentrations of the obtained reaction solution were measured, and the weights of acetic acid and coumaric acid per 100 g of the obtained glucose were calculated. The results are shown in Table 3.

[0076] Comparative Example 2: Example of production of sugar liquid from bagasse (step (1) not performed) The same pulverization conditions, pretreatment conditions, water addition and solid-liquid separation conditions were carried out as in Comparative Reference Example 4. Using the cellulose-containing solid fraction after solid-liquid separation, the same hydrolysis operation as in Comparative Example 1 was carried out as step (4). The concentrations of sugar, acetic acid and aromatic compounds in the resulting reaction liquid were measured, and the weights of acetic acid and coumaric acid per 100 g of the resulting glucose were calculated. The results are shown in Table 3.

[0077] Comparative Example 3: Example of production of sugar liquid from bagasse (step (3) not performed) The same operation as in Comparative Example 4 was carried out, except that the milling conditions were a cutter mill screen hole diameter of 40 mm, and solid-liquid separation was carried out without adding water to the pretreated biomass. Using the cellulose-containing solid fraction obtained after solid-liquid separation, a hydrolysis operation similar to that in Comparative Example 1 was carried out as step (4). The sugar, acetic acid, and aromatic compound concentrations of the obtained reaction liquid were measured, and the weights of acetic acid and coumaric acid per 100 g of the obtained glucose were calculated. The results are shown in Table 3.

[0078] Example 1: Example of production of sugar liquid from bagasse (steps (1) to (4) carried out) Using the cellulose-containing solid fraction after solid-liquid separation obtained in Reference Example 1, a hydrolysis operation was carried out as step (4) in the same manner as in Comparative Example 1. The concentrations of sugar, acetic acid, and aromatic compounds in the resulting reaction liquid were measured, and the weights of acetic acid and coumaric acid per 100 g of the resulting glucose were calculated. The results are shown in Table 3.

[0079] Example 2: Example of production of sugar liquid from bagasse (steps (1) to (4) carried out) Using the cellulose-containing solid fraction after solid-liquid separation obtained in Reference Example 2, a hydrolysis operation was carried out as step (4) in the same manner as in Comparative Example 1. The concentrations of sugar, acetic acid, and aromatic compounds in the resulting reaction liquid were measured, and the weights of acetic acid and coumaric acid per 100 g of the resulting glucose were calculated. The results are shown in Table 3.

[0080] Example 3: Example of production of sugar liquid from bagasse (steps (1) to (5) carried out) The sugar solution obtained after hydrolysis in step (4) in Example 1 was subjected to solid-liquid separation by centrifugation (Saito Centrifuge Co., Ltd., 2,000 rpm), filtered using a microfiltration membrane (Millipore, PVDF membrane with a pore size of 0.05 μm), and then passed through a reverse osmosis membrane (Toray Industries, Inc., cross-linked fully aromatic polyamide reverse osmosis membrane UTC80) to recover the sugar solution as a concentrate, and the raw water was Volume Water was collected as the permeate, so as to be concentrated to one-fourth the volume.

[0081] Steps (1) to (4) were carried out again under the same conditions as in Example 1, and the water added in step (3) was the water recovered as the permeate of the reverse osmosis membrane (step (5)). The sugar, acetic acid, and aromatic compound concentrations in the sugar solution obtained in step (4) were measured, and the weights of acetic acid and coumaric acid per 100 g of the obtained glucose were calculated. The results are shown in Table 3.

[0082] [Table 3]

[0083] 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 compared to Comparative Examples 1 to 3 in which none of steps (1) to (4) were performed. In particular, the comparison results of Comparative Example 2 and Examples 1 and 2 revealed that when the weight ratio (dry weight %) of powdered biomass that does not pass through a 1 mm mesh sieve exceeds 50%, the concentration of fermentation inhibitors in the sugar solution increases. In addition, the results of Examples 1 and 3 revealed that the concentration of coumaric acid in the sugar solution was further reduced by performing step (5).

Claims

1. A method for producing a sugar liquid using cellulose-containing biomass as a raw material, comprising the steps of: Step (1): A step of crushing a cellulose-containing biomass so that the weight ratio that does not pass through a sieve having an opening of 1 mm is 50% or less by dry weight; Step (2): contacting the pulverized biomass obtained in step (1) with an alkaline aqueous medium to obtain a pretreated biomass; Step (3): adding water to the pretreated biomass obtained in step (2) and subjecting it to solid-liquid separation to obtain a cellulose-containing solid fraction having a moisture content of 50% by weight or more and less than 70% by weight; and Step (4): Hydrolyzing the cellulose-containing solid content obtained in step (3) to obtain a sugar liquid; A method comprising:

2. The method for producing a sugar liquid according to claim 1, wherein the step (2) is a step of passing an alkaline medium through the pulverized biomass obtained in the step (1) to obtain a pretreated biomass.

3. 3. The method for producing a sugar liquid according to claim 1 or 2, wherein the step (2) is a step of supplying the pulverized biomass obtained in the step (1) and the alkaline medium to a filter and passing the pulverized biomass and the alkaline medium through the filter.

4. The method for producing a sugar liquid according to any one of claims 1 to 3, wherein the alkaline aqueous medium in the step (2) is an aqueous medium containing sodium hydroxide and / or potassium hydroxide.

5. The method for producing a sugar liquid according to any one of claims 1 to 4, wherein the solid-liquid separation in the step (3) is pressing.

6. The method for producing a sugar liquid according to any one of claims 1 to 5, wherein the cellulose-containing biomass is bagasse.

7. Step (5): filtering the sugar liquid obtained in step (4) through a nanofiltration membrane or a reverse osmosis membrane to recover the sugar liquid as a non-permeated liquid, and reusing the permeated liquid as water to be added to the pretreated biomass in step (3); The method for producing a sugar liquid according to any one of claims 1 to 6, further comprising:

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