JP2016189747A - Method for producing sugar solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a sugar solution where, in a method for producing a sugar solution derived from cellulose-containing biomass, the reduction of the yield of sugar upon cleaning a precise filtration film and the recovery ratio of enzyme is suppressed, and, while long-stably maintaining productivity, a sugar solution is produced.SOLUTION: Provided is a method for producing a sugar solution of producing a sugar solution using a cellulose-containing biomass as raw material, comprising: a stage (1) where a cellulose-containing biomass is hydrolyzed to produce a sugar aqueous solution; a stage (2) where the biomass residue in the sugar aqueous solution is removed; and a stage (3) where the following steps are included, and the sugar aqueous solution is subjected to precision filtering and is recovered from the permeation side: a filtration step (3-a) where the sugar aqueous solution is passed through a precision filtering membrane so as to be recovered from the filtration side; and a membrane cleaning step (3-b) where the precision filtering membrane used in the above step is cleaned, where the sugar aqueous solution remaining in the raw water side of the precision filtering membrane upon the end of the step (3-a) and/or the membrane cleaning water produced in the step (3-b) is made to flow back to the stage on the upstream than the stage (3).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a sugar solution from cellulose-containing biomass.

  In recent years, environmentally conscious processes, including technologies for efficiently producing sugar aqueous solutions from non-edible biomass such as cellulose-containing biomass, or technologies for efficiently converting the resulting sugar aqueous solutions into fermentation raw materials Construction is required.

  As a method for producing an aqueous sugar solution from cellulose-containing biomass, there is a method for producing an aqueous sugar solution using sulfuric acid, and a method for producing an aqueous sugar solution by acid hydrolysis of cellulose and hemicellulose using concentrated sulfuric acid (Patent Document 1). And 2) are disclosed.

  Moreover, as a method without using an acid, a method of hydrolyzing cellulose-containing biomass using subcritical water at about 250 ° C. to 500 ° C. to produce an aqueous sugar solution (Patent Document 3), A method for producing an aqueous sugar solution by further enzymatic treatment after water treatment (Patent Document 4), and further hydrolyzing the cellulose-containing biomass with pressurized hot water at 240 ° C to 280 ° C, followed by further enzymatic treatment Discloses a method for producing an aqueous sugar solution (Patent Document 5). Non-Patent Document 1 discloses a method for producing an aqueous sugar solution by hydrolyzing cellulose-containing biomass with dilute sulfuric acid and further treating with an enzyme such as cellulase.

  However, since the sugar aqueous solution obtained by these techniques contains a large amount of biomass residue and the sugar concentration is low, an appropriate solid-liquid solution is required to supply the sugar aqueous solution to the fermenter and use it as a fermentation raw material. It is necessary to remove the biomass residue by the separation treatment and then concentrate the aqueous sugar solution to increase the sugar concentration. For example, in Patent Document 6, after treatment with a microfiltration membrane and / or ultrafiltration membrane to remove biomass residue, treatment with a nanofiltration membrane and / or reverse osmosis membrane to concentrate an aqueous saccharide solution and concentration of sugar A method of recovering an enzyme used at the time of hydrolysis from the non-permeation side by filtering through an ultrafiltration membrane while increasing the pH is disclosed.

Japanese National Patent Publication No. 11-506934 JP 2005-229821 A Japanese Patent Laid-Open No. 2003-212888 JP 2001-95597 A Japanese Patent No. 3041380 Japanese Patent No. 4770987

A. Aden et al., “Lignocellulosic Biomass to Ethanol Process Design and Economics Optimized Co-Current Dilute Acid Prehydrology and Enzymatic Recycler NR

However, in the technique disclosed in Patent Document 6, when the operation is performed for a long period of time, cakes are deposited on the membrane of the microfiltration membrane or the pores of the membrane are clogged to cause clogging. For example, even a substance having such a size as to permeate through the microfiltration membrane is supplemented by the cake or clogging material, resulting in a problem that the permeability of the enzyme is deteriorated. In order to solve this problem, it is necessary to periodically clean the microfiltration membrane. In each cleaning operation, the aqueous sugar solution and the sugar and / or enzyme accumulated on the membrane surface are lost along with the cleaning waste water. End up.
The present invention provides a technique for producing a sugar solution stably for a long period of time by suppressing the above-described problems, that is, the decrease in sugar yield and enzyme recovery rate during microfiltration membrane washing.

  In order to solve the above problems, the method for producing a sugar liquid of the present invention comprises any one of the following [1] to [8].

[1] A method for producing a sugar solution comprising cellulose-containing biomass as a raw material and comprising the following steps (1) to (3):
(1) A step of hydrolyzing cellulose-containing biomass to produce a sugar aqueous solution containing monosaccharides and / or oligosaccharides,
(2) A step of removing biomass residues in the aqueous sugar solution obtained in the step (1),
(3) including the following steps, and filtering the aqueous sugar solution obtained in the step (2) through a microfiltration membrane to recover the aqueous sugar solution from the permeation side. A filtration step of filtering through a filtration membrane to recover the aqueous sugar solution from the permeate side; and (3-b) a membrane washing step of washing the microfiltration membrane used in step (3-a) above (3) At the end of -a), the aqueous sugar solution remaining on the non-permeating side of the microfiltration membrane and / or the membrane washing wastewater generated in the step (3-b) is returned to the process upstream of the process (3). A method for producing a sugar solution.

  [2] The method for producing a sugar liquid according to [1], wherein the step upstream of the step (3) is the reaction tank of the step (1).

  [3] The method for producing a sugar solution according to [1], wherein the step upstream from the step (3) is the raw water tank of the step (2).

  [4] The method for producing a sugar liquid according to [1], wherein the sugar aqueous solution in the raw water tank in the step (3) is refluxed to a step upstream of the step (3).

  [5] In the step (3), a buffer tank is provided between the microfiltration membrane and the raw water tank, and the aqueous sugar solution in the buffer tank is returned to the process upstream of the step (3). The method for producing a sugar liquid according to [1].

  [6] In any one of [1] to [5], in the step (3-b), the membrane cleaning waste water having a turbidity of 10 NTU or more is returned to a process upstream of the process (3). A method for producing the sugar solution according to claim 1.

  [7] The method for producing a sugar liquid according to any one of [1] to [6], wherein in step (3-b), an acid is added to the membrane cleaning wastewater when the membrane cleaning wastewater is refluxed. .

  [8] In the step (3-b), the residual sugar aqueous solution in the module is discharged first when the membrane washing wastewater is refluxed, and the residual sugar aqueous solution is refluxed upstream of the step (3). The method for producing a sugar liquid according to any one of [1] to [7].

  [9] The method for producing a sugar liquid according to [8], wherein in the step (3-b), only the residual sugar aqueous solution is refluxed.

[10] A device for producing a sugar solution using cellulose-containing biomass as a raw material,
The manufacturing apparatus includes:
(1) Hydrolysis means for obtaining an aqueous sugar solution containing monosaccharides and / or oligosaccharides by hydrolyzing cellulose-containing biomass,
(2) Solid-liquid separation means for removing biomass residue from the hydrolysis means (1),
(3) A microfiltration means for filtering the liquid obtained from the solid-liquid separation means (2) through a microfiltration membrane,
Means for recovering an aqueous sugar solution from the membrane permeation side of the microfiltration membrane,
Means for discharging aqueous solution such as turbidity remaining on the non-permeate side of the membrane,
A refluxing means for sending the aqueous solution containing turbidity recovered from the discharging means to a process upstream of the microfiltration membrane;
And a means for cleaning the microfiltration membrane,
Sugar liquid production equipment.

  According to the present invention, sugars such as glucose and xylose can be produced with high purity and high yield from an aqueous sugar solution derived from cellulose-containing biomass.

It is an apparatus flow figure showing one embodiment of the present invention. It is a schematic flowchart which shows one Embodiment of this invention. It is a schematic flowchart which shows one Embodiment which concerns on the process (3) of this invention.

  Hereinafter, the present invention will be described in more detail with specific configurations.

I. Manufacturing process of aqueous sugar solution: Step (1)
The method for producing a sugar liquid of the present invention comprises a step of hydrolyzing cellulose-containing biomass to produce an aqueous sugar solution.

[Cellulose-containing biomass]
Cellulose-containing biomass contains a polysaccharide such as cellulose or hemicellulose, which is a polysaccharide obtained by dehydrating and condensing sugar. Examples of the cellulose-containing biomass include herbaceous biomass such as bagasse, switchgrass, corn stover, corn cob, rice straw, and straw; and woody biomass such as trees and waste building materials. Moreover, as long as it contains cellulose, corn hull, corn starch, sugar cane, sugar beet, potato starch and the like can be mentioned as examples. By hydrolyzing a polysaccharide such as cellulose or hemicellulose as described later, an aqueous sugar solution that can be used as a fermentation raw material can be produced.

[Sugar aqueous solution]
An aqueous sugar solution obtained by hydrolysis of cellulose-containing biomass will be described below.

  In general, sugars are classified according to the degree of polymerization of monosaccharides, such as monosaccharides such as glucose and xylose, oligosaccharides obtained by dehydration condensation of 2 to 9 monosaccharides, and polysaccharides obtained by dehydration condensation of 10 or more monosaccharides. Classified as a saccharide.

  The aqueous sugar solution obtained in the step (1) can contain a monosaccharide as a main component, and specifically can contain glucose or xylose as a main component. Moreover, although it is a small amount, oligosaccharides such as cellobiose and monosaccharides such as arabinose and mannose may also be included. Here, “comprising a monosaccharide as a main component” means that 80% by weight or more of the total weight of monosaccharides, oligosaccharides and polysaccharides dissolved in water is a monosaccharide.

  Specifically, monosaccharides, oligosaccharides and polysaccharides dissolved in water can be quantified by high performance liquid chromatography (HPLC) by comparison with a standard product. The specific HPLC conditions were as follows: no reaction solution was used, LunaNH2 (Phenomenex) was used for the column, the mobile phase was ultrapure water: acetonitrile = 25: 75, the flow rate was 0.6 mL / min, and the measurement time was 45 min, detection method is RI (differential refractive index), and temperature is 30 ° C.

  In the sugar aqueous solution obtained in the step (1), not only sugar but also biomass residue containing colloidal components, turbid components, fine particles and the like may exist. Examples of components of such biomass residue include lignin, tannin, silica, calcium, and undecomposed cellulose, but are not particularly limited thereto.

[Hydrolysis]
Next, a method for producing an aqueous sugar solution by hydrolyzing cellulose-containing biomass in the step (1) will be described. Step (1) involves a reaction vessel, and hydrolysis is carried out in this reaction vessel.

  When the cellulose-containing biomass is subjected to hydrolysis, the cellulose-containing biomass may be used as it is, but it is possible to perform known treatments such as steaming, pulverization, and explosion, and the efficiency of hydrolysis can be improved by such treatment. It is possible to improve.

  Although there is no restriction | limiting in particular about the hydrolysis process of cellulose containing biomass, Specifically, the processing method A: The method of using only an acid, The processing method B: The method of performing the process using an enzyme after an acid treatment, A processing method C: Method using only hydrothermal treatment, Treatment method D: Method of performing treatment using an enzyme after hydrothermal treatment, Treatment method E: Method of using an enzyme after alkali treatment, Treatment method F: After treatment with ammonia There are mainly six methods using an enzyme. Since ammonia is a kind of alkali, the ammonia treatment can be regarded as one of the alkali treatments. Treatment methods A and C can prevent the loss of sugar during membrane cleaning by the effect of the present invention, and can produce a sugar solution with high purity and high yield. Treatment method B and treatment methods D to F can prevent the loss of sugar and enzyme during microfiltration membrane washing by the effect of the present invention, and can produce a sugar solution with high purity and high yield.

(Treatment method A)
In the processing method A, an acid is used for hydrolysis of cellulose-containing biomass. Although sulfuric acid, nitric acid, hydrochloric acid, etc. are mentioned regarding the acid to be used, it is preferable to use a sulfuric acid.

  Although it does not specifically limit regarding the density | concentration of an acid, 0.1-99weight% of an acid can be used.

  When the acid concentration is 0.1 to 15% by weight or 0.5 to 5% by weight, the reaction temperature is preferably set in the range of 100 to 300 ° C, more preferably 120 to 250 ° C, and the reaction time is preferably Is set in the range of 1 sec to 60 min. When the acid concentration is 15 to 95% by weight or 60 to 90% by weight, the reaction temperature is preferably set in the range of 10 to 100 ° C., and the reaction time is preferably set in the range of 1 sec to 60 min. .

  The number of acid treatments is not particularly limited, and may be one time or two or more times. In particular, when the processing is performed twice or more, the first processing and the subsequent processing may be performed under different conditions.

  Since the hydrolyzate obtained by the acid treatment contains an acid such as sulfuric acid, in order to use this hydrolyzate as a fermentation raw material, it is preferable to further carry out a neutralization treatment after the hydrolysis. Although the kind of alkali reagent used for neutralization is not particularly limited, when an acid having a valence of 2 or more is used for hydrolysis, a monovalent alkali reagent is preferably used. This is because a salt formed by an acid having a valence of 2 or more and an alkali having a valence of 2 or more is precipitated in the liquid during the process of concentration of the liquid and becomes a fouling factor of the film. It is.

  In the case of using a monovalent alkali, ammonia, sodium hydroxide, potassium hydroxide and the like can be mentioned, but are not particularly limited.

  In the case of using a divalent or higher valent alkali reagent, the above-mentioned fouling problem can be avoided by providing a mechanism for suppressing the precipitation of salt by reducing the amount of acid and alkali used or by eliminating the precipitate. .

  In hydrolysis using an acid, a hemicellulose component having low crystallinity is generally hydrolyzed, and then a cellulose component having high crystallinity is decomposed. Therefore, it is possible to obtain a liquid containing a large amount of xylose derived from hemicellulose using an acid.

  Moreover, you may perform the acid treatment of 2 times or more from which a pressure and temperature differ. For example, after the first acid treatment, the second acid treatment may be performed at a higher pressure and a higher temperature than the first acid treatment. Since the cellulose component having high crystallinity can be further decomposed in the second acid treatment, a liquid containing a large amount of glucose derived from cellulose can be obtained.

  As described above, when hydrolysis is performed in a plurality of stages, hydrolysis conditions suitable for the degradation of hemicellulose and cellulose can be set in each stage. Therefore, decomposition efficiency and sugar yield can be improved.

  Further, by separating the aqueous sugar solution obtained by the first hydrolysis and the aqueous sugar solution obtained by the second hydrolysis, two types of aqueous sugar solutions having different monosaccharide component ratios can be produced. That is, after performing the first hydrolysis under the condition that a sugar aqueous solution containing xylose as a main component is obtained, the obtained first sugar aqueous solution is separated, and then a sugar aqueous solution containing glucose as a main component is obtained. A second hydrolysis is performed under conditions. Thus, two types of aqueous sugar solutions having different compositions can be obtained.

  A plurality of types of sugar aqueous solutions having different monosaccharide components thus obtained can be used for fermentation under different conditions. That is, fermentation using xylose in an aqueous sugar solution as a fermentation raw material and fermentation using glucose as a fermentation raw material can be performed separately. By separating the monosaccharide components in this way, it becomes possible to select and use the optimum microbial species used for each fermentation.

  In addition, you may obtain the saccharide | sugar derived from both components in one step, without isolate | separating a hemicellulose component and a cellulose component by performing the high pressure high temperature process with an acid for a long time.

(Treatment method B)
In the treatment method B, the cellulose-containing biomass is further hydrolyzed by further treating the treatment liquid obtained by the treatment method A (that is, hydrolysis with an acid) with an enzyme.

  In the treatment method B, the conditions for hydrolysis with an acid are as described for the treatment method A. Specifically, the concentration of the acid used is preferably 0.1 to 15% by weight, more preferably 0.5 to 5% by weight. The reaction temperature for hydrolysis with an acid is set in the range of 100 to 300 ° C, preferably 120 to 250 ° C. The reaction time for hydrolysis with acid can be set in the range of 1 sec to 60 min. The frequency | count of the hydrolysis process by an acid is not specifically limited, Any of 1 time or 2 times or more may be sufficient. In particular, when the above process is performed twice or more, the first process and the second and subsequent processes may be performed under different conditions.

  The hydrolyzate obtained by the acid treatment contains an acid such as sulfuric acid, and further needs to be neutralized in order to perform an enzymatic hydrolysis reaction or use as a fermentation raw material. The neutralization is as described in the explanation of the processing method A.

  The enzyme used for hydrolysis may be any enzyme having cellulolytic activity, and a general cellulase can be used. In particular, the enzyme is preferably an exo-type cellulase having a decomposition activity of crystalline cellulose or a cellulase containing an endo-type cellulase. As such a cellulase, a cellulase produced by Trichoderma is preferable. The genus Trichoderma is a microorganism classified as a filamentous fungus, and is a microorganism that secretes a large amount of various cellulases extracellularly. A cellulase derived from Trichoderma reesei is particularly preferably used.

  Moreover, in order to improve the production | generation efficiency of glucose as an enzyme used for a hydrolysis, you may add (beta) glucosidase which is a cellobiose decomposing enzyme, and may use it for a hydrolysis together with the above-mentioned cellulase. The β-glucosidase is not particularly limited, but is preferably derived from Aspergillus.

  The hydrolysis reaction using such an enzyme is preferably performed in the vicinity of pH 3 to 7, more preferably in the vicinity of pH 5. The reaction temperature is preferably 40 to 70 ° C.

  When hydrolyzing cellulose-containing biomass using an enzyme after acid treatment, the hemicellulose having low crystallinity is hydrolyzed by acid treatment in the first hydrolysis, and then the enzyme is used as the second hydrolysis. It is preferable to hydrolyze cellulose with high crystallinity. By using an enzyme in the second hydrolysis, the hydrolysis process of the cellulose-containing biomass can be advanced more efficiently.

  Specifically, in the first hydrolysis with acid, among the components contained in the cellulose-containing biomass, hydrolysis of the hemicellulose component and partial decomposition of lignin mainly occur. After separating the hydrolyzate into an acid solution and a solid content containing cellulose, the solid content component containing cellulose is hydrolyzed by adding an enzyme.

  The acid solution obtained by the first hydrolysis contains xylose, which is pentose, as a main component. Therefore, an aqueous sugar solution can be obtained by neutralizing the acid solution thus obtained. Moreover, the monosaccharide component which has glucose as a main component can be obtained by further hydrolyzing the solid content containing a cellulose. In addition, the sugar aqueous solution obtained by neutralizing an acid solution may be mixed with solid content, and it may hydrolyze by adding an enzyme to this mixture.

(Treatment method C)
In the treatment method C, no special acid is added, and water is added so that the cellulose-containing biomass is 0.1 to 50% by weight, and then heat treatment is performed at a temperature of 100 to 400 ° C. for 1 sec to 60 minutes.

  By treating at such temperature conditions, hydrolysis of cellulose and hemicellulose occurs. Such hydrolysis by heat treatment is called hydrothermal treatment. In the hydrolysis using hydrothermal treatment, generally, the hemicellulose component having low crystallinity is hydrolyzed, and then the cellulose component having high crystallinity is decomposed. Therefore, it is possible to obtain a liquid containing a large amount of xylose derived from hemicellulose by hydrothermal treatment.

  The number of hydrothermal treatments is not particularly limited, and may be one time or two or more times. When hydrothermal treatment is performed twice or more, the first treatment and the subsequent treatment may be performed under different conditions.

  Further, in the hydrothermal treatment, after the first treatment, as a second treatment, the biomass solids are treated at a higher pressure and a higher temperature than the first treatment, thereby further decomposing the highly crystalline cellulose component. Can do. By performing such a two-stage process, a liquid containing more cellulose-derived glucose can be obtained.

  Thus, when hydrothermal treatment is performed in a plurality of stages, hydrolysis conditions suitable for the decomposition of hemicellulose and cellulose can be set in each stage. Therefore, it becomes possible to improve decomposition efficiency and sugar yield.

  Also, by separating the aqueous sugar solution obtained by the first treatment and the aqueous sugar solution obtained by the second treatment, two types of aqueous sugar solutions having different monosaccharide component ratios can be produced. In other words, after the first treatment is performed under the condition that a sugar aqueous solution containing xylose as a main component is obtained, the first sugar aqueous solution obtained is separated and then a sugar aqueous solution containing glucose as a main component is obtained. Then, the second process is performed. Thus, two types of aqueous sugar solutions having different compositions can be obtained.

  A plurality of types of sugar aqueous solutions having different monosaccharide components thus obtained can be used for fermentation under different conditions. That is, fermentation using xylose in an aqueous sugar solution as a fermentation raw material and fermentation using glucose as a fermentation raw material can be performed separately. By separating the monosaccharide components in this way, it becomes possible to select and use the optimum microbial species used for each fermentation.

(Treatment method D)
In the treatment method D, the cellulose-containing biomass is further hydrolyzed by further treating the treatment liquid obtained by the treatment method C (that is, hydrothermal treatment) with an enzyme.

  The enzyme is as described in the processing method. Moreover, the same conditions as the processing method B can be employ | adopted also about enzyme processing conditions.

  In the processing method D, after hydrothermal treatment, the cellulose-containing biomass is hydrolyzed using an enzyme. First, hydrolytic heat treatment hydrolyzes low crystalline hemicellulose, and then hydrolyzes high crystalline cellulose using the enzyme. Can do. Thus, the hydrolysis process of cellulose-containing biomass can be efficiently advanced by using an enzyme.

  Specifically, the hemicellulose component mainly contained in the cellulose-containing biomass is hydrolyzed and the lignin is partially decomposed by hydrothermal treatment. Next, the hydrolyzate is separated into a solid content containing an aqueous solution and cellulose. About the obtained solid content, it hydrolyzes by adding an enzyme. Here, the aqueous solution obtained by hydrothermal treatment contains xylose, which is pentose, as a main component. Moreover, the monosaccharide component which has glucose as a main component can be obtained by the hydrolysis by the subsequent enzyme. Note that an aqueous solution obtained by hydrothermal treatment may be mixed with a solid content, and an enzyme may be added to the mixture to perform hydrolysis.

(Treatment method E)
In the processing method E, the alkali used is preferably sodium hydroxide or calcium hydroxide. It is preferable that the density | concentration with respect to the cellulose containing biomass of these alkalis is the range of 0.1-60 weight%. After adding an alkali, it can hydrolyze by processing in the temperature range of 100-200 degreeC, Preferably it is 110 to 180 degreeC. The number of treatments is not particularly limited, and may be one time or two or more times. When the hydrolysis treatment with alkali is performed twice or more, the first treatment and the subsequent treatment may be performed under different conditions.

  Since the treated product obtained by the alkali treatment contains an alkali such as sodium hydroxide, it needs to be neutralized in order to perform an enzymatic hydrolysis reaction. The acid reagent used for neutralization is not particularly limited, but when an alkali having a valence of 2 or more is used for hydrolysis, a monovalent acid reagent is preferably used. This is because a salt formed by an acid having a valence of 2 or more and an alkali having a valence of 2 or more is precipitated in the liquid during the process of concentration of the liquid and becomes a fouling factor of the film. It is.

  When a monovalent acid is used, nitric acid, hydrochloric acid and the like can be mentioned but are not particularly limited.

  When a divalent or higher acid reagent is used, the above-mentioned fouling problem can be avoided by providing a mechanism that suppresses salt precipitation by reducing the amount of acid and alkali used or excludes precipitates. . As the divalent or higher acid, sulfuric acid and phosphoric acid are preferable.

  As the enzyme in treatment method E, the same enzyme as in treatment method B is used. Moreover, the same conditions as the processing method B can be employ | adopted also about enzyme processing conditions.

  In the processing method E, first, the lignin component existing around the hemicellulose component and the cellulose component is removed by mixing with an aqueous solution containing an alkali and heating. Thereby, the hemicellulose component and the cellulose component can be easily reacted. Thereafter, hemicellulose having low crystallinity and cellulose having high crystallinity that have not been decomposed by the alkali treatment can be hydrolyzed by an enzyme.

  Specifically, the process can proceed as follows. First, among the components contained in the cellulose-containing biomass, mainly hemicellulose components are hydrolyzed and lignin is partially decomposed by alkali treatment. Next, the hydrolyzate is separated into an alkaline solution and a solid containing cellulose. About the obtained solid content component, pH is adjusted and it hydrolyzes by adding an enzyme further. Further, when the concentration of the solid content in the alkaline solution is dilute, it may be hydrolyzed by adding an enzyme after neutralization without separation of the solid content.

  By hydrolyzing the solid content containing cellulose with an enzyme, a monosaccharide component mainly composed of glucose and xylose can be obtained. Moreover, the alkali solution separated from the solid content after the alkali treatment contains xylose, which is pentose, as a main component in addition to lignin. Therefore, an aqueous sugar solution can also be obtained by neutralizing this alkaline solution. Alternatively, the aqueous sugar solution obtained by neutralization may be mixed with the solid content, and the mixture may be hydrolyzed by adding an enzyme.

(Treatment method F)
The ammonia treatment conditions for treatment method F are in accordance with the treatment conditions described in JP 2008-161125 A and JP 2008-535664 A.

  For example, the preferable range of the ammonia concentration with respect to the cellulose-containing biomass is 0.1 to 15% by weight. Ammonia to be added may be in a liquid state or a gaseous state. Further, the form of addition may be pure ammonia or an aqueous ammonia solution. After the ammonia is added, the hydrolysis proceeds by setting the temperature to 4 ° C to 200 ° C, preferably 90 ° C to 150 ° C. The number of treatments is not particularly limited, and may be one time or two or more times. In particular, when the process is performed twice or more, the first process and the subsequent process may be performed under different conditions.

  In order to further hydrolyze the treated product obtained by the ammonia treatment with an enzyme, it is preferable to neutralize ammonia or remove ammonia.

  The kind of acid reagent used for neutralization is not particularly limited. Examples of the acid reagent include hydrochloric acid, nitric acid, sulfuric acid and the like. In particular, sulfuric acid is preferable because it hardly corrodes the process piping and does not inhibit fermentation.

  The removal of ammonia may be performed by volatilizing ammonia into a gaseous state by keeping the ammonia-treated product in a reduced pressure state. The removed ammonia may be recovered and reused.

  The hydrolysis using an enzyme after the ammonia treatment will be described.

  It is generally known that when ammonia treatment is performed, cellulose crystals change to a structure that is susceptible to enzymatic reaction. Therefore, it can hydrolyze efficiently by making an enzyme act on the solid content after such ammonia treatment.

  As the enzyme, an enzyme similar to the treatment method B is used. Moreover, the same conditions as in the treatment method B can be adopted for the enzyme treatment conditions.

  In addition, when an aqueous ammonia solution is used in the ammonia treatment, the same effect as that of the treatment method C (that is, hydrothermal treatment) may be obtained depending on the water component in addition to the action of ammonia during the ammonia treatment. As described above, hydrothermal treatment causes hydrolysis of hemicellulose and decomposition of lignin.

  That is, when the cellulose-containing biomass is hydrolyzed using an enzyme after treatment with an aqueous ammonia solution, the specific treatment process is as follows.

  By mixing and heating the aqueous solution containing ammonia and biomass, the lignin component present around the hemicellulose component and the cellulose component is removed. Thereby, the hemicellulose component and the cellulose component can be easily reacted. As described above, hydrothermal treatment also proceeds during the ammonia treatment. Thereafter, hemicellulose having low crystallinity and cellulose having high crystallinity that were not decomposed by ammonia treatment and hydrothermal treatment can be hydrolyzed by an enzyme.

  More specifically, the process proceeds as follows. By the treatment with the aqueous ammonia solution, among the components contained in the cellulose-containing biomass, some hemicellulose components are mainly hydrolyzed and lignin is partially decomposed. Next, the hydrolyzate is separated into an aqueous ammonia solution and a solid content containing cellulose. About the obtained solid content component, pH is adjusted and it hydrolyzes by adding an enzyme further. If the ammonia concentration is high (for example, close to 100%), after removing a large amount of ammonia by deaeration, neutralize it without separating the solids, and then add the enzyme and hydrolyze it. Good.

  A monosaccharide component mainly composed of glucose and xylose can be obtained from the hydrolysis product of the solid content. Further, since the aqueous ammonia solution separated from the solid content after the ammonia treatment contains xylose, which is pentose, as a main component in addition to lignin, it is also possible to neutralize the alkaline solution to obtain an aqueous sugar solution. Moreover, the sugar aqueous solution obtained by neutralization may be mixed with solid content, and an enzyme may be added to this mixture to perform hydrolysis.

II. Solid-liquid separation step: Step (2)
[Solid-liquid separation]
The method for producing a sugar liquid of the present invention includes a solid-liquid separation step of removing solid content (biomass residue) that has not been decomposed from the aqueous sugar solution obtained in step (1).

  In the step (2), when the hydrolysis is performed a plurality of times, the solid-liquid separation may be performed after each hydrolysis. Various methods such as filtration / squeezing, sedimentation separation, and centrifugation are applied to the step (2). That is, a filter press, a belt press, a centrifuge, a sedimentation tank, or the like is used as the solid-liquid separator. The aqueous sugar solution is recovered as a liquid component from the apparatus and sent to the downstream process. In order to efficiently recover the liquid component, it is desirable to use a pressure filtration type device or a centrifuge as the solid-liquid separation device. When using a centrifuge, it is preferable to separate by applying a centrifugal force of 5000 G or more.

[Sugar aqueous solution]
In step (2), the aqueous sugar solution recovered as a liquid component of the solid-liquid separation device is the same as the aqueous sugar solution in step (1) except that various components were removed by the separation device used in step (2). Has a similar composition.

III. Microfiltration process: Process (3)
The method for producing a sugar liquid of the present invention includes a step (3) of filtering the aqueous sugar solution obtained in the step (2) by passing it through a microfiltration membrane. By this step, an aqueous sugar solution is recovered from the permeate side, and inorganic components such as silica having a particle size of several tens of nanometers or more adhering to undecomposed cellulose and biomass are blocked to the raw water side.

[filtration]
The microfiltration membrane used in the present invention is a membrane having an average pore diameter of 0.01 μm to 5 mm. The microfiltration membrane is also called a microfiltration membrane and is abbreviated as MF membrane. By passing through a microfiltration membrane, silica having a particle size of several tens of nanometers or more attached to cellulose or biomass that is not decomposed to monosaccharides from the aqueous sugar solution recovered as a liquid component in step (2) It is possible to remove inorganic components and the like. In addition, when cells such as lactic acid bacteria are mixed in the aqueous sugar solution, the product sugar may be consumed by cell metabolism. By passing the aqueous sugar solution through the microfiltration membrane, these sugars and cells are separated into the membrane permeation side and the non-permeation side, suppressing sugar consumption and stable quality with little change in sugar concentration due to storage time. It is possible to produce an aqueous sugar solution. In order to separate the cells reliably and without causing membrane fouling, it is desirable that the average pore diameter is 0.02 μm or more and 1.0 μm or less.
The filtration operation may be multi-stage filtration using a microfiltration membrane twice or more for efficient removal, and the membrane material and membrane type to be used may be different for each stage.
Further, filtration may be performed with a microfiltration membrane, and the filtrate may be further filtered with an ultrafiltration membrane. In this method, colloidal components of several tens of nm or less that cannot be removed with microfiltration membranes, water-soluble polymer components derived from lignin (tannins), saccharides such as oligosaccharides to polysaccharides, and enzymes used for hydrolysis Etc. can be excluded.
The ultrafiltration membrane here is a membrane having a molecular weight cut off of 1,000 to 200,000, which is also referred to as an ultrafiltration membrane, and is abbreviated as a UF membrane. Since the pore diameter on the surface of the ultrafiltration membrane is very small, it is difficult to measure with an electron microscope or the like. Therefore, instead of the average pore size, the molecular weight cut off is used as an index of the size of the pore size.

  The molecular weight cutoff refers to the Membrane Society of Japan, Membrane Experiment Series Volume III, Artificial Membrane Editor / Naofumi Kimura, Shinichi Nakao, Haruhiko Ohya, Tsutomu Nakagawa (1993 Kyoritsu Shuppan) p. No. 92, “The molecular weight of the solute is plotted on the horizontal axis and the blocking rate is plotted on the vertical axis, and the data plotted is called the fractional molecular weight curve. And the molecular weight at which the blocking rate is 90% is called the membrane molecular weight cut-off. Is known as an index representing the membrane performance of the ultrafiltration membrane.

  The enzyme used for hydrolysis has a molecular weight in the range of 10,000 to 100,000. By using an ultrafiltration membrane having a fractional molecular weight capable of preventing permeation of these enzymes, the enzymes can be recovered from the non-permeate side fraction. Preferably, by using an ultrafiltration membrane having a fractional molecular weight of 10,000 to 30,000, the enzyme used for hydrolysis can be efficiently recovered. The form of the ultrafiltration membrane to be used is not particularly limited, and may be either a flat membrane or a hollow fiber membrane. The recovered enzyme can be reused for the hydrolysis in step (1), thereby reducing the amount of enzyme used.

  The materials for the microfiltration membrane and the ultrafiltration membrane are not particularly limited as long as the biomass residue described above can be removed. Specifically, as materials constituting these filtration membranes, cellulose, cellulose ester, polysulfone, polyethersulfone, chlorinated polyethylene, polypropylene, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene Or an organic material such as stainless steel, or an inorganic material such as ceramic. The material of the microfiltration membrane and the ultrafiltration membrane may be appropriately selected in view of the properties of the hydrolyzate or the running cost, but is preferably an organic material in view of ease of handling. In particular, chlorinated polyethylene, polypropylene, polyvinylidene fluoride, polysulfone, and polyethersulfone are preferable as the organic material.

  In addition, as the form of the microfiltration membrane of the present invention, either a hollow fiber membrane or a flat membrane can be adopted, but an external pressure type hollow fiber membrane module is preferably adopted when back pressure washing described later is performed.

Filtration methods include total-volume filtration and cross-flow filtration, both of which can be employed. The total amount filtration is a method of filtering the whole amount without circulating the liquid to be filtered supplied to the membrane surface, and is also referred to as dead end filtration. On the other hand, the cross-flow filtration is a method in which the filtration target liquid is filtered so as to flow parallel to the membrane surface by partially circulating the filtration target liquid to the storage tank of the filtration target liquid. The total filtration method accumulates everything on the membrane surface, whereas the crossflow filtration method can be expected to remove deposits on the separation membrane surface due to the shearing force of the crossflow flow parallel to the separation membrane. It is preferably used for processing a target liquid having a high quality concentration.
On the other hand, the cross-flow filtration method requires more energy for circulating the liquid to be filtered than the full-volume filtration method, so the full-volume filtration method is more advantageous in terms of energy.

[Washing step]
In the step (3), the method for producing a sugar liquid of the present invention includes a step (3-a) of filtering an aqueous sugar solution with a microfiltration membrane used and a step (3-b) of washing the filtration membrane. . The filtration step (3-a) removes inorganic components such as silica that has a particle size of several tens of nanometers or larger and adheres to cellulose that has not been decomposed to monosaccharides or biomass, and uses enzymes or oligos used for hydrolysis. Permeate sugars and monosaccharides to the permeate side of the microfiltration membrane. However, in step (3-a), as time passes, cake accumulates on the non-permeation side membrane surface or the inside of the membrane pores is blocked, and the liquid flow resistance increases. Furthermore, it is a colloidal component of several tens of nanometers or less that normally passes through a microfiltration membrane, tannin, an enzyme used for hydrolysis, and a product due to deposits on the membrane surface and clogged pores. As oligosaccharides and monosaccharides are trapped on the non-permeating side, the liquid flow resistance further increases. In the constant-speed filtration that always obtains a constant filtration amount, the filtration pressure increases as the liquid flow resistance increases. The filtration pressure here is a pressure difference necessary for transporting the liquid from the non-permeation side to the permeation side of the filtration membrane. A cake made of a material removed by a microfiltration membrane as described above is compressed even if the dry weight is equal, and when the filtration pressure becomes high, the liquid is pushed out and the liquid is pushed out, increasing the cake density. Narrower and more difficult to continue filtration due to higher resistance to fluid flow, as well as increased colloidal components below tens of nanometers, tannins, enzymes used for hydrolysis, oligosaccharides and monosaccharides To do. Therefore, the washing step (3-b) is inserted after the filtration step (3-a), and the cake is peeled off and removed from the surface of the membrane, or the clogging of the membrane is eliminated, thereby suppressing the increase in fluid flow resistance. This makes it possible to operate for a long time. In addition, it is possible to suppress an increase in the amount of supplements in the microfiltration membrane of enzymes, oligosaccharides and monosaccharides used for hydrolysis, and to maintain the permeation side enzyme concentration and sugar concentration.

  A known film cleaning method can be applied to this step (3-b). That is, in the cleaning method, on the primary side of the membrane, water is passed in parallel to the membrane surface from one end of the membrane membrane to the other end of the membrane, such as from the lower end of the membrane module to the upper end of the membrane module. There are cleaning methods that apply shear flow near the membrane surface and drain the cake, cleaning methods that pass water from the primary side to the secondary side of the membrane, and cleaning methods that pass water from the secondary side to the primary side of the membrane. . The third cleaning method is called so-called back pressure cleaning. As the washing water, water and various additives such as a pH adjusting agent can be used. The cleaning may further include a plurality of steps, and the conditions such as the composition of the cleaning water and the pressure may be different in each step, or the above-described cleaning methods may be combined.

  The washing step (3-b) is performed after the filtration step (3-a) is completed. Immediately after the end of step (3-a), an aqueous sugar solution to be filtered remains on the non-permeate side of the membrane module.

  In the washing step (3-b), the washing water flows into the membrane module, and the remaining aqueous sugar solution is pushed out of the membrane module with the washing water. Alternatively, only the remaining aqueous sugar solution may be discharged first before the washing water flows into the membrane module.

  The remaining sugar solution contains sugar and enzyme having a concentration equal to or higher than that of the aqueous sugar solution obtained in the step (2), and a part of the substance blocked and accumulated by the microfiltration membrane.

  Sugar and enzymes, substances blocked by microfiltration membranes, and cake deposited on the membrane surface are also loosened and suspended in the washing wastewater, and the concentration varies depending on the amount of washing water used. By draining these materials without circulating them to the raw water tank in step (3), the concentration of the microfiltration membrane blocking component in the raw water is reduced, and clogging of the membrane and cake accumulation are suppressed to achieve long-term stable operation. Is possible.

  In addition, when several membrane modules are provided, a buffer tank may be provided between the raw water tank and the membrane module in the step (3). During the washing step (3-b), the aqueous sugar solution remaining in the membrane module Together, they may be refluxed to the upstream process. When the cross flow filtration method is adopted as the filtration method, a part of the sugar aqueous solution is circulated in the raw water tank and the buffer tank in the filtration step (3-a), so that it is removed from the separation membrane surface by the shear force of the cross flow flow. Sediment accumulates and concentrates in raw water tank and buffer tank. Therefore, in the washing step (3-b), the concentration of the microfiltration membrane blocking component in the raw water is reduced by refluxing to the upstream process together with the aqueous sugar solution remaining in the membrane module, thereby clogging the membrane and depositing cake. It is possible to suppress long-term stable operation. The sugar aqueous solution in the raw water tank or the buffer tank does not need to be refluxed at the same frequency as the residual sugar aqueous solution in the membrane module, and may be once every several hours to several tens of hours. Depends on tank size, filtration flux, cross flow rate, etc. In addition, even when the total filtration method is adopted as the filtration method, it can be returned to the upstream process when draining the aqueous sugar solution in the raw water tank and / or the buffer tank before entering maintenance such as periodic chemical cleaning. .

[Washing waste water]
In the above-described washing step (3-b), together with the aqueous sugar solution remaining at the end of the filtration step (3-a), the washing water that has passed through the membrane module is discharged out of the membrane module as washing waste water. In the washing waste water, substances adhering to the membrane such as saccharides, tannins, colloidal particles and enzymes are suspended and / or dissolved, and these are discharged out of the membrane module together with the washing water.

  The remaining sugar solution and washing wastewater are returned to the raw water in step (1) and / or step (2) to prevent loss of sugar and enzymes and suppress the decrease in sugar concentration of the product sugar solution. By doing so, it is possible to improve the quality and to perform periodic cleaning while improving the recovery rate of the enzyme, thereby realizing a long-term stable operation with high productivity. By returning to the raw water of step (1) and / or step (2), sugar and enzyme can be recovered from the drained liquid without requiring a special separation device. After returning to step (1), the recovered enzyme can be used again for hydrolysis, and the recovered sugar flows to the downstream process together with the newly hydrolyzed sugar in step (1), and the product It is made sugar solution. When refluxed to the step (2), the recovered enzyme flows again to the step (3) and flows to the permeate side of the microfiltration membrane. When ultrafiltration is performed at the subsequent stage of the microfiltration membrane and the enzyme is recovered on the non-permeating side, it is recovered in the non-permeating liquid of the ultrafiltration membrane and can be reused. In addition, the sugar in the liquid refluxed in the step (2) is sequentially processed together with the newly hydrolyzed sugar aqueous solution to finally become the sugar liquid of the product. FIG. 1 shows an example of a recirculation destination of the residual sugar aqueous solution and the washing waste water in the present invention. As shown in the figure, the steps to be refluxed do not have to be the same step, and some of them may be refluxed to step (1) and the rest to step (2). Further, as described above, the sugar aqueous solution in the raw water tank can be refluxed together with the residual sugar aqueous solution in the microfiltration membrane module.

In addition, as described above, the washing wastewater contains a lot of organic substances and has a high TOC (total organic carbon concentration) and TN (total nitrogen), and the load on wastewater treatment is large. The load can be reduced.
In the washing step (3-b), only the aqueous sugar solution previously left in the membrane module may be drained and returned to the raw water in step (1) and / or step (2). A liquid having a high enzyme concentration or high sugar concentration can be efficiently recovered. At this time, as shown in FIG. 2, the remaining sugar aqueous solution drained first may be returned to the raw water in step (2), and the washing waste water is returned to step (1). In the case of FIG. 2, not only sugar and enzymes but also wash water can be reused as water for suspending the biomass in step (1).
Moreover, only the residual sugar aqueous solution drained first may be refluxed, and the washing waste water may be discarded as it is. Furthermore, the cleaning waste water may be returned to the upstream process in some cases, and waste water may be discharged in some cases. For example, as shown in FIG. 3, in the washing step twice in three times, only the residual sugar aqueous solution is refluxed and the washing wastewater is drained. In the remaining one washing step, the residual sugar aqueous solution and the washing wastewater are refluxed and refluxed. Therefore, it is possible to prevent the amount of water to be excessively increased and the process processing time from being significantly extended. Moreover, you may recirculate to a process in every washing | cleaning step (3-b), and you may recirculate | restore residual sugar aqueous solution and / or washing waste_water | drain in one washing | cleaning step (3-b) among several times. .
It is not necessary to recirculate all the washing wastewater, and it is sufficient that at least a part of it is recirculated. For example, the cleaning step (3-b) may be started, and the cleaning waste water immediately after the start to the step end time may be returned to the step (1) and / or the step (2), or the step (3-b) The washing waste water from the start to the intermediate elapsed time may be returned to step (1) and / or step (2), and the rest may be drained. Thereby, only the solution with high sugar concentration and enzyme concentration in the washing waste water can be refluxed.
Whether or not the cleaning wastewater is returned may be determined by measuring the turbidity of the cleaning wastewater. For example, by returning to step (1) when the turbidity is high, it becomes possible to selectively recirculate the washing wastewater when the solid content concentration is high. When measuring turbidity, it is preferable to recirculate washing wastewater when the turbidity is 10 NTU or more. Furthermore, it is preferable to reflux in the case of 50 NTU or more.
In addition, when the washing wastewater is refluxed to the process, the acid may be added before refluxing before refluxing. Enzymes used for the hydrolysis have different enzyme activities depending on the pH. By adjusting the pH by adding an acid, the enzyme can be efficiently reused. The pH of the washing waste water to which the acid is added is preferably in the vicinity of 3 to 7, more preferably in the vicinity of pH 5.
The process to be refluxed does not need to be the same process every time. For example, the washing step twice in 3 times returns to the process (2), and sugars and enzymes are collected on the permeate side of the microfiltration membrane, The remaining operation may be performed such as refluxing to step (1).

[Sugar aqueous solution]
The aqueous sugar solution recovered from the permeate side in step (3) is the same as the aqueous sugar solution in step (1) except that various components are removed by the filtration membrane used in step (2) and step (3). Having a composition of
IV. Reuse of cleaning wastewater:
The manufacturing method of the sugar liquid of this invention includes recirculating the washing waste_water | drain produced in step (3-b) of process (3) to the process before process (3). The washing waste water does not have to be reused at all, and at least a part of the washing waste water may be reused.

V. Concentration process:
The method for producing a sugar liquid of the present invention comprises a step of filtering the aqueous sugar solution obtained in step (3) through a nanofiltration membrane and recovering the permeated water from the permeate side and the sugar liquid from the non-permeate side. May be.

  By this step, the aqueous sugar solution is “filtered through a nanofiltration membrane” to prevent or filter sugars dissolved in the aqueous sugar solution, particularly monosaccharides such as glucose and xylose, on the non-permeate side. The fermentation inhibitor can be permeated to the permeate side to remove the fermentation inhibitor or reduce the concentration of the fermentation inhibitor.

[Fermentation inhibitor]
Here, the fermentation inhibitory substance is a compound produced by hydrolysis of cellulose-containing biomass, and a substance that acts inhibitory as described above in the fermentation process using the purified sugar aqueous solution obtained by the production method of the present invention as a raw material. Refers to that. Typical fermentation inhibitors include organic acids, furan compounds, and phenol compounds that are produced particularly in the acid treatment step of cellulose-containing biomass.

  Specific examples of the organic acid include acetic acid, formic acid, levulinic acid and the like. Examples of furan compounds include furfural and hydroxymethylfurfural (HMF). Such an organic acid or furan compound is a product of decomposition of monosaccharides such as glucose or xylose.

  In addition, examples of phenolic compounds include vanillin, acetovanillin, vanillic acid, syringic acid, gallic acid, coniferyl aldehyde, dihydroconiphenyl alcohol, hydroquinone, catechol, acetogicon, homovanillic acid, 4-hydroxybenzoic acid, 4-hydroxybenzoic acid Specific examples include hydroxy-3-methoxyphenyl derivatives (Hibbert's ketones). These compounds are derived from lignin or lignin precursors.

  In addition, when using waste building materials or plywood as cellulose-containing biomass, components such as adhesives and paints used in the lumbering process may be included as fermentation inhibitors. Examples of the adhesive include urea resin, melamine resin, phenol resin, and urea melamine copolymer resin. Examples of fermentation inhibitors derived from such adhesives include acetic acid, formic acid, formaldehyde and the like.

[Sugar solution]
In the sugar solution, the concentration of the substance that permeates the nanofiltration membrane (for example, the fermentation inhibiting substance) is lower than that of the aqueous sugar solution obtained in step (3).

  The sugar component contained in the sugar solution obtained from the non-permeating side of the nanofiltration membrane is a sugar derived from cellulose-containing biomass, but depending on the removal performance of the nanofiltration membrane, the sugar component obtained by hydrolysis in step (1) The ratio of sugar components may differ.

  The monosaccharide contained in the sugar liquid of the present invention is composed mainly of glucose and / or xylose, but the ratio of glucose and xylose depends on the hydrolysis step of step (1) and the removal performance of the nanofiltration membrane. It fluctuates and is not limited to specific numerical values. For example, when hemicellulose is mainly hydrolyzed, xylose is the main monosaccharide component in the resulting sugar solution. After hemicellulose decomposition, only the cellulose component is decomposed and hydrolyzed to obtain the sugar The main monosaccharide component in the liquid is glucose. In addition, when the cellulose component is not particularly separated after the decomposition of hemicellulose, the main monosaccharide components in the obtained sugar liquid are glucose and xylose.

VI. Filtration Step Using Reverse Osmosis Membrane The method for producing a sugar solution of the present invention may further comprise a step of filtering the sugar solution obtained in the concentration step through a reverse osmosis membrane.

  The sugar component contained in the sugar solution obtained from the non-permeating side of the reverse osmosis membrane is a sugar derived from cellulose-containing biomass, and is essentially different from the sugar component obtained by hydrolysis in the step (1). Absent. That is, the monosaccharide contained in the sugar liquid of the present invention is composed mainly of glucose and / or xylose. The ratio of glucose and xylose varies depending on the hydrolysis step of step (1). That is, when hemicellulose is mainly hydrolyzed, xylose becomes the main monosaccharide component, and after hemicellulose decomposition, only the cellulose component is separated and hydrolyzed, and glucose becomes the main monosaccharide component. . In addition, after the decomposition of hemicellulose, glucose and xylose are included as main monosaccharide components unless the cellulose component is specifically separated.

  Before passing through the reverse osmosis membrane, it may be concentrated using a concentrating device represented by an evaporator, and the sugar solution may be further filtered through a separation membrane to increase the concentration. From the viewpoint of reducing energy consumption, a step of further increasing the concentration of sugar solution by filtration through a separation membrane can be preferably employed.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Reference Example 1) Method for Analyzing Monosaccharide Concentration The concentration of monosaccharide (glucose and xylose) contained in the obtained aqueous sugar solution was quantified by comparison with a standard under the following HPLC conditions.

Column: Luna NH2 (Phenomenex)
Mobile phase: Ultrapure water: Acetonitrile = 25: 75 (flow rate 0.6 mL / min)
Reaction solution: None
Detection method: RI (differential refractive index)
Temperature: 30 ° C
(Reference Example 2) Method for Measuring Turbidity The turbidity of an aqueous sugar solution was measured using an indoor advanced turbidimeter (2100N) manufactured by HACH. After stirring, 100 mL was taken, and the turbidity of the aqueous sugar solution in the liquid temperature range of 45 to 50 ° C. was measured three times. The average value was defined as turbidity. For calibration of the turbidimeter, a formazine standard solution was used, and the turbidimetric turbidity was detected from 90 ° scattered light, transmitted light, and forward scattered light.

Reference Example 3 Method for Measuring pH The pH value of the cellulose-derived sugar aqueous solution was measured with a handy pH meter “D-50” manufactured by Horiba. After stirring, 500 mL was taken into a beaker and measured three times. The average value was defined as the pH value.
(Reference Example 4) Step of hydrolyzing cellulose-containing biomass with dilute sulfuric acid treatment and enzyme With respect to the step of hydrolyzing cellulose-containing biomass in step (1), cellulose using 0.1 to 15% by weight of dilute sulfuric acid and enzyme An example is given and demonstrated about the hydrolysis method of contained biomass.

  Rice straw was used as the cellulose-containing biomass. The cellulose-containing biomass was immersed in a 1% sulfuric acid aqueous solution and autoclaved (manufactured by Nitto Koatsu) at 150 ° C. for 30 minutes. After the treatment, solid-liquid separation was performed to separate into a sulfuric acid aqueous solution (hereinafter, dilute sulfuric acid treatment liquid) and sulfuric acid-treated cellulose. Next, after mixing with sulfuric acid-treated cellulose and dilute sulfuric acid treatment solution so that the solid content concentration becomes 10% by weight, pH was adjusted to around 5 with sodium hydroxide. To this mixed solution, Trichoderma cellulase (Sigma Aldrich Japan) and Novozyme 188 (Aspergillus niger-derived β-glucosidase preparation, Sigma Aldrich Japan) were added as cellulases, and the hydrolysis reaction was performed while stirring and mixing at 50 ° C. for 3 days. To obtain a reaction solution.

  Thereafter, as a step of removing biomass residues in the aqueous sugar solution in step (2), the reaction solution in step (1) is subjected to solid-liquid separation using a pressure filter (KST-90-UH, manufactured by Advantech). Then, undegraded cellulose or lignin was separated and removed to obtain a sugar-containing aqueous solution (aqueous sugar solution). The turbidity of the aqueous sugar solution was 70 NTU. Furthermore, the composition of the monosaccharides in the aqueous saccharide solution was as shown in Table 1.

(Comparative Example 1)
A sugar solution was produced through the following three steps.

As step (1), according to the method described in Reference Example 4, the cellulose-containing biomass is hydrolyzed,
As step (2), according to the method described in Reference Example 4, the biomass residue was removed from the aqueous sugar solution obtained in step (1).
As step (3), the aqueous sugar solution obtained in step (2) was filtered through a microfiltration membrane.
As a microfiltration membrane, a hollow fiber membrane made of polyvinylidene fluoride having a nominal pore diameter of 0.05 μm used in Toray Industries' microfiltration membrane module “Trefil” (registered trademark) HFS is cut out and molded from a polycarbonate resin. A hollow fiber membrane module housed in a case was used.

  In the step (3), the following two steps were alternately repeated 25 times to obtain an aqueous sugar solution.

As the step (3-a), the aqueous sugar solution obtained in the step (2) is supplied from the raw water tank of the step (3) to the hollow fiber membrane module, and the flow rate of the filtration flux is 1 m ³ / m ² / day. Filtration for minutes was performed. The liquid that permeated through the microfiltration membrane was recovered as an aqueous sugar solution.

As a step (3-b), distilled water was passed for 2 minutes at a flow rate of 4 m ³ / m ² / day from the membrane permeation side into the hollow fiber membrane module, the membrane was washed, and during the washing period and washing After the completion, the turbid-containing sugar aqueous solution and washing waste water remaining in the non-membrane permeation channel of the hollow fiber membrane module were drained.

  As a result of analyzing the amount of glucose in the aqueous sugar solution, the amount of glucose contained in the aqueous sugar solution was 23 g / L.

Example 1
As the step (3-b), first, after collecting the turbid-containing sugar aqueous solution remaining in the non-membrane permeation channel of the hollow fiber membrane module, the membrane is washed, and during the washing period and after completion of the washing, the hollow fiber membrane module The sugar solution was produced by employing the method described in Comparative Example 1 except that the washing waste water remaining in the non-membrane permeation channel was drained.

Thereafter, as a step of hydrolyzing the cellulose-containing biomass in the step (1), the turbidity-containing sugar aqueous solution recovered above is added to a mixed solution of sulfuric acid-treated cellulose, dilute sulfuric acid treatment liquid, sodium hydroxide and cellulase, A sugar solution was produced in the same manner as in the method of Comparative Example 1 except that the hydrolysis reaction was carried out while stirring and mixing at 50 ° C. for 3 days, and the sugar aqueous solution obtained from the supply of step (3) and from step (3) The amounts of glucose contained therein were 26.4 g / L and 24.3 g / L, respectively. Compared to the comparative example, the glucose yield could be improved.
(Example 2)
As the step (3-b), first, after collecting the turbid-containing sugar aqueous solution remaining in the non-membrane permeation channel of the hollow fiber membrane module, the membrane is washed, and during the washing period and after completion of the washing, the hollow fiber membrane module The sugar solution was produced by employing the method described in Comparative Example 1 except that the washing waste water remaining in the non-membrane permeation channel was drained.

Thereafter, a sugar solution was produced in the same manner as in Comparative Example 1 except that the suspended saccharide-containing sugar aqueous solution recovered above was added as a step of removing the biomass residue in the sugar aqueous solution in step (2). The amounts of glucose contained in the aqueous sugar solution obtained at the time of feeding and from step (3) were 26.4 g / L and 24.3 g / L, respectively. Compared to the comparative example, the glucose yield could be improved.
Example 3
After adopting the method described in Comparative Example 1 and producing a sugar solution, the aqueous sugar solution remaining in the raw water tank in step (3) is recovered, and the cellulose-containing biomass in step (1) is hydrolyzed. The addition of the turbidity-containing sugar aqueous solution collected above to a mixed solution of sulfuric acid-treated cellulose, dilute sulfuric acid-treated solution, sodium hydroxide and cellulase, and performing a hydrolysis reaction while stirring and mixing at 50 ° C. for 3 days When a sugar solution was produced in the same manner as in the method of Comparative Example 1, the amounts of glucose contained in the aqueous sugar solution obtained from the supply of step (3) and from the step (3) were 26.5 g / L and 24. It was 4 g / L. Compared to the comparative example, the glucose yield could be improved.

  The present invention produces a sugar solution stably for a long period of time by suppressing a decrease in the yield of the sugar and the recovery rate of the enzyme at the time of washing the microfiltration membrane in the filtration operation in which the sugar aqueous solution to be the cellulose-containing biomass is passed through the microfiltration membrane. It is possible to provide a high quality sugar aqueous solution at low cost.

Claims (10)

A method for producing a sugar solution comprising cellulose-containing biomass as a raw material and comprising the following steps (1) to (3):
(1) A step of hydrolyzing cellulose-containing biomass to produce a sugar aqueous solution containing monosaccharides and / or oligosaccharides,
(2) A step of removing biomass residues in the aqueous sugar solution obtained in the step (1),
(3) including the following steps, and filtering the aqueous sugar solution obtained in the step (2) through a microfiltration membrane to recover the aqueous sugar solution from the permeation side. A filtration step of filtering through a filtration membrane to recover the aqueous sugar solution from the permeate side; and (3-b) a membrane washing step of washing the microfiltration membrane used in step (3-a) above (3) At the end of -a), the aqueous sugar solution remaining on the non-permeating side of the microfiltration membrane and / or the membrane washing wastewater generated in the step (3-b) is returned to the process upstream of the process (3). A method for producing a sugar solution.   The method for producing a sugar liquid according to claim 1, wherein the step upstream of the step (3) is the reaction tank of the step (1).   The method for producing a sugar liquid according to claim 1, wherein the step upstream of the step (3) is the raw water tank of the step (2).   The method for producing a sugar liquid according to claim 1, wherein the aqueous sugar solution in the raw water tank of the step (3) is refluxed to a step upstream of the step (3).   In the step (3), a buffer tank is provided between the microfiltration membrane and the raw water tank, and the aqueous sugar solution in the buffer tank is refluxed to a process upstream of the step (3). 2. A method for producing a sugar liquid according to 1.   The saccharide according to any one of claims 1 to 5, wherein in the step (3-b), the membrane washing wastewater having a turbidity of 10 NTU or more is returned to a process upstream of the process (3). Liquid manufacturing method.   The method for producing a sugar solution according to any one of claims 1 to 6, wherein, in the step (3-b), an acid is added to the membrane cleaning wastewater when the membrane cleaning wastewater is refluxed.   In the step (3-b), the aqueous sugar solution remaining in the module at the time of reflux of the membrane cleaning wastewater is discharged first, and the residual aqueous sugar solution is refluxed upstream of the step (3). The manufacturing method of the sugar liquid in any one of Claims 1-7.   The method for producing a sugar liquid according to claim 8, wherein in the step (3-b), only the residual sugar aqueous solution is refluxed. An apparatus for producing a sugar solution using cellulose-containing biomass as a raw material,
The manufacturing apparatus includes:
(1) Hydrolysis means for obtaining an aqueous sugar solution containing monosaccharides and / or oligosaccharides by hydrolyzing cellulose-containing biomass,
(2) Solid-liquid separation means for removing biomass residue from the hydrolysis means (1),
(3) A microfiltration means for filtering the liquid obtained from the solid-liquid separation means (2) through a microfiltration membrane,
Means for recovering an aqueous sugar solution from the membrane permeation side of the microfiltration membrane,
Means for discharging the aqueous sugar solution remaining on the raw water side of the membrane,
A refluxing means for sending the aqueous solution containing turbidity recovered from the discharging means to a process upstream of the microfiltration membrane;
And a means for cleaning the microfiltration membrane,
Sugar liquid production equipment.

Images