JP2016007160A - Manufacturing method of sugar solution, and manufacturing method of polysaccharide-based biomass-derived compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing sugar solution which is capable of realizing increase in yield of a fermentation product when the solution is used as a fermentation raw material.SOLUTION: There is provided a method for manufacturing sugar solution by using polysaccharide-based biomass as a raw material. The method includes: (I) a step of preparing first solution containing at least oligosaccharide which is obtained by decomposing the polysaccharide-based biomass; (II) a step of allowing the first solution to pass through a first separation membrane and recovering second solution from a non-passing side; (III) a step of performing saccharification treatment in which oligosaccharide is decomposed into monosaccharide to the second solution to obtain third solution; and (IV) a step of allowing the third solution to pass through the second separation membrane, and recovering fourth solution from a passing side to obtain sugar solution. The first separation membrane has an NaCl-rejection rate of 5% or more when NaCl aqueous solution of 2000 ppm is evaluated at solution temperature of 25°C, 1.0 MPa, and pH 6.5, and the second separation membrane has a rejection rate lower than the NaCl-rejection rate of the first separation membrane.

Description

  The present invention relates to a method for producing a sugar solution from polysaccharide-based biomass such as cellulose-containing biomass, and a method for producing a polysaccharide-based biomass-derived compound using the sugar solution obtained by the method.

  In the production of bioethanol, it is desired to use cellulose-containing biomass that is abundant in non-edible parts of agricultural products. For example, rice straw, which is an agricultural residue of gramineous cereals, is one of the candidates for cellulose-containing biomass because of its high yield.

  Cellulose-containing biomass such as rice straw is mainly composed of cellulose, hemicellulose, and lignin. When producing bioethanol using cellulose-containing biomass as a raw material, the raw material is usually pretreated to produce a sugar solution, and the resulting sugar solution is subjected to a fermentation treatment.

  In the pretreatment, for example, cellulose and hemicellulose are separated from lignin and hydrolyzed to decompose into monosaccharides and / or oligosaccharides. This may be further subjected to saccharification treatment. Examples of the hydrolysis method include acid treatment, alkali treatment, and hydrothermal treatment. In this pretreatment, decomposition of sugar (overdecomposition of sugar) also proceeds, so that furan compounds such as furfural and 5-hydroxymethylfurfural (5-HMF), and organic acids such as acetic acid and formic acid are also generated. These compounds inhibit fermentation by microorganisms in the subsequent fermentation process, and cause a reduction in the yield of the fermentation product. Therefore, these compounds are called fermentation inhibitors, and have been a major issue when sugar solutions prepared from cellulose-containing biomass are used as fermentation raw materials.

  Conventionally, various methods have been proposed for removing the above-mentioned fermentation-inhibiting substances in the production process of sugar solution. Among them, a separation membrane is used as a method for easily obtaining a high removal effect. And the method of removing a fermentation inhibitor from a sugar liquid is proposed (patent documents 1 and 2).

  In Patent Document 1, a saccharide solution containing monosaccharides and / or oligosaccharides is prepared by saccharifying a product obtained by hydrolyzing a polysaccharide-based biomass, and from this saccharide solution, a specific parameter is set. The method of removing a fermentation inhibitor using the separation membrane which satisfy | fills is described. The parameters to be satisfied by the separation membrane used in this method are that the glucose removal rate under a specific condition is 80% or more, and the difference between the glucose removal rate and the isopropyl alcohol removal rate is 20% or more. It is.

  In Patent Document 2, in a method for producing a sugar solution using cellulose-containing biomass as a raw material, an aqueous sugar solution obtained by hydrolyzing cellulose-containing biomass is filtered through a nanofiltration membrane, and a purified sugar solution on the non-permeate side is obtained. It is described to recover and remove the permeation-side fermentation inhibitor. In addition, Patent Document 2 discloses a nanofiltration membrane before permeation through the nanofiltration membrane in order to remove fine particles and water-soluble polymers that cause fouling in the treatment using the nanofiltration membrane from the aqueous sugar solution. It is also described that a sugar solution is permeated through a microfiltration membrane and / or an ultrafiltration membrane having pores having a larger pore diameter.

International Publication No. 2009/110374 International Publication No. 2010/067785

  According to the methods described in Patent Documents 1 and 2, a sugar solution in which fermentation inhibitors such as furfural, 5-HMF, acetic acid and formic acid are reduced can be obtained. Therefore, by using such a sugar solution for fermentation treatment, inhibition of fermentation is reduced, and the yield of the fermentation product can be increased.

  However, the yield of fermented products is complicated not only by the presence of the above-mentioned fermentation inhibitor that should be removed in the sugar solution of the fermentation raw material, but also by various other factors such as the concentration and purity of monosaccharides. It seems to be related. Therefore, as described in Patent Documents 1 and 2, the method of removing a fermentation inhibitor using a separation membrane to produce a sugar solution is further improved in order to further increase the yield of the fermentation product. There was room for. Moreover, the conversion efficiency from polysaccharide-based biomass, which is a raw material, to fermentation products (polysaccharide-based biomass-derived compounds) is increased, that is, the saccharides are efficiently extracted from the polysaccharide-based biomass, and the saccharides are efficiently fermented to produce fermentation products. From the viewpoint of increasing productivity, it is considered that there is room for further improvement in the conventional method.

  Then, this invention relates to manufacture of the sugar liquid which uses polysaccharide biomass as a raw material, and it aims at providing the method of manufacturing the sugar liquid which can implement | achieve the yield increase of a fermentation product, when used as a fermentation raw material. . Furthermore, this invention also aims at providing the method of obtaining a polysaccharide biomass origin compound by high productivity by performing a fermentation process using the sugar liquid manufactured by such a method as a fermentation raw material. .

  The inventors of the present invention have conducted intensive research on sugar solutions that can increase the yield of fermentation products when used as fermentation raw materials. As a result, the present inventors have found that sugar solutions produced using polysaccharide-based biomass as raw materials include low-molecular compounds such as furfural, 5-HMF, acetic acid, and formic acid that have been conventionally recognized as fermentation inhibitors (hereinafter referred to as “fermentation substances”). In addition to low-molecular-weight fermentation inhibitors, it has been found that there is a polymer compound with a higher molecular weight (hereinafter sometimes referred to as a high-molecular fermentation inhibitor) that can be a factor that inhibits fermentation. It was. Based on such knowledge, the present inventors have developed a sugar solution in which the content of a polymer compound newly recognized as a fermentation inhibitor is reduced without reducing the yield of saccharides from polysaccharide biomass. As a novel method for obtaining, the following sugar solution production method of the present invention has been reached.

The present invention is a method for producing a sugar solution using polysaccharide-based biomass as a raw material,
(I) preparing a first solution containing at least an oligosaccharide obtained by decomposing the polysaccharide-based biomass;
(II) allowing the first solution to permeate the first separation membrane and recovering the second solution from the non-permeating side;
(III) subjecting the second solution to a saccharification treatment for decomposing oligosaccharides into monosaccharides to obtain a third solution;
(IV) allowing the third solution to permeate the second separation membrane and recovering the fourth solution from the permeation side to obtain a sugar solution;
Including
The first separation membrane is a separation membrane having a NaCl rejection of 5% or more when evaluated with a 2000 ppm NaCl aqueous solution at a liquid temperature of 25 ° C., 1.0 MPa, and pH 6.5.
The second separation membrane has a rejection rate lower than the NaCl rejection rate of the first separation membrane;
A method for producing a sugar solution is provided.

The present invention also provides:
(I) a step of preparing a sugar solution using the method for producing a sugar solution of the present invention;
(Ii) using the sugar solution as a fermentation raw material, and fermenting the sugar solution;
The manufacturing method of the polysaccharide biomass origin compound containing this is also provided.

  In the sugar liquid production method of the present invention, the first solution obtained by decomposing polysaccharide biomass is first treated with the first separation membrane. Since this first separation membrane is a separation membrane having a NaCl rejection rate of 5% or more, the low molecular weight fermentation inhibitor that has been conventionally recognized as a fermentation inhibitor passes through the first separation membrane, while the first separation membrane On the non-permeating side, the second solution in which the saccharide in the first solution is purified and concentrated remains. Next, the oligosaccharide contained in the second solution is decomposed into monosaccharides to obtain a third solution. Therefore, the saccharide contained in the third solution is almost a monosaccharide. This third solution is permeated through the second separation membrane, and the fourth solution is recovered from the permeation side. Since the second separation membrane is a separation membrane having a rejection rate lower than the NaCl rejection rate of the first separation membrane, the saccharide (monosaccharide) contained in the third solution permeates the second separation membrane, and the third solution The high-molecular-weight fermentation inhibiting substance contained in is blocked by the second separation membrane and remains on the non-permeable side. The fourth solution obtained from the permeation side of the second separation membrane through this step is a purified monosaccharide concentrate in which the high-molecular fermentation inhibitor is reduced in addition to the low-molecular fermentation inhibitor. Furthermore, in the production method of the present invention, in order to remove fermentation inhibitors having a wide molecular weight from low molecules to high molecules, the treatment in the first separation membrane → the saccharification treatment → the treatment in the second separation membrane Since each process is carried out, saccharides can be efficiently recovered from the polysaccharide biomass as a raw material without wasting as much as possible. Therefore, according to the method for producing saccharides of the present invention, the yield, concentration and purity of monosaccharides used as fermentation raw materials are improved, and fermentation inhibitors having a wide molecular weight ranging from low molecules to high molecules can be sufficiently reduced. Therefore, when this sugar solution is used as a fermentation raw material, an increase in the yield of the fermentation product can be realized.

  Since the manufacturing method of the polysaccharide biomass origin compound of this invention performs fermentation processing using the sugar liquid which has said effect as a fermentation raw material, it can improve the productivity of a polysaccharide biomass origin compound.

It is a flowchart which shows the outline of the manufacturing method of the sugar liquid of this invention, and the manufacturing method of the polysaccharide biomass origin compound of this invention. It is the schematic which shows the apparatus used for the membrane separation implemented in the Example and the comparative example. It is a graph which shows the change with respect to the fermentation time of the density | concentration of glucose, xylose, fructose, ethanol, glycerol, and xylitol in the ethanol fermentation liquid of Example 1. It is a graph which shows the change with respect to the fermentation time of the density | concentration of glucose, xylose, fructose, ethanol, glycerol, and a xylitol in the ethanol fermentation liquid of the comparative example 1. It is a graph which shows the change with respect to fermentation time of the density | concentration of glucose in the ethanol fermentation liquid of Example 2, xylose, fructose, ethanol, glycerol, and a xylitol. It is a graph which shows the change with respect to fermentation time of the density | concentration of glucose in the ethanol fermentation liquid of the comparative example 2, xylose, fructose, ethanol, glycerol, and xylitol. It is a graph which shows the change with respect to the fermentation time of the density | concentration of glucose, xylose, fructose, ethanol, glycerol, and a xylitol in the ethanol fermentation liquid of the comparative example 3.

  Hereinafter, embodiments of the present invention will be described. The following description does not limit the present invention.

The method for producing a sugar solution of the present embodiment is a method for producing a sugar solution using polysaccharide-based biomass as a raw material,
(I) preparing a first solution containing at least an oligosaccharide obtained by decomposing the polysaccharide-based biomass;
(II) allowing the first solution to permeate the first separation membrane and recovering the second solution from the non-permeating side;
(III) subjecting the second solution to a saccharification treatment for decomposing oligosaccharides into monosaccharides to obtain a third solution;
(IV) allowing the third solution to permeate the second separation membrane and recovering the fourth solution from the permeation side to obtain a sugar solution;
including.

  Here, the polysaccharide-based biomass in the present invention mainly contains cellulose, hemicellulose, and lignin. Agricultural and forestry product resources such as chips, wood fiber, chemical pulp, waste paper and plywood, agricultural and forestry product waste, and processed agricultural and forestry products. In addition, as long as it contains or purifies a fermentation inhibitor represented by a sugar hyperdegradation product such as sucrose-containing resources, starch-containing resources such as corn and sweet potatoes, the production method of the present invention may be used. . These polysaccharide biomasses may be used alone or as a mixture.

  In addition, the monosaccharide in the present invention is a so-called pentose having 5 carbons as structural units such as xylose and arabinose, and 6 carbons as examples of glucose, fructose and mannose. Includes what is called hexose. Oligosaccharide means a sugar in which two or more monosaccharides are linked, and specific examples include dimers, trimers, and multimers of each monosaccharide. Sucrose to which fructose is bound is also classified as an oligosaccharide. In addition, both the same monosaccharide linked and the different monosaccharide linked are defined as oligosaccharide.

  Hereinafter, each process will be described in detail with reference to the flowchart of FIG.

  First, an example of the step (I) will be described.

  In step (I), a first solution obtained by decomposing polysaccharide-based biomass is prepared.

  As described above, the polysaccharide biomass contains lignin in addition to cellulose and hemicellulose. In the degradation treatment of the polysaccharide biomass, cellulose and hemicellulose are separated from lignin and decomposed into sugars. A known pretreatment technique can be appropriately selected for the degradation treatment of polysaccharide biomass. In general, polysaccharide biomass is hydrolyzed by acid treatment, alkali treatment or hydrothermal treatment. Prior to this hydrolysis treatment, treatments such as grinding, grinding and explosion may be performed. In the present embodiment, the first solution preferably contains more oligosaccharides than monosaccharides, and more preferably the sugar contained in the first solution contains oligosaccharides as the main component. Here, the saccharide contained in the first solution is mainly composed of oligosaccharide. The oligosaccharide is 60% by mass or more, more preferably 70% or more, based on the total amount of saccharide dissolved in the first solution. The most desirable content is 80% or more. Since the first solution contains more oligosaccharides than monosaccharides, when the first solution is subjected to membrane separation using the first separation membrane in the subsequent step (II), all the monosaccharides are added to the oligosaccharides. Therefore, it is not necessary to select a separation membrane that can prevent the separation of the first separation membrane. Furthermore, since the membrane separation in the step (II) is performed to separate the sugar and the low-molecular-weight fermentation inhibitor from the first solution from each other, there is a difference in molecular size between the sugar and the low-molecular-weight fermentation inhibitor. The larger one is desirable because the separation performance becomes higher. Therefore, a solution containing more oligosaccharides as monosaccharides than sugars is more efficient than a solution containing more monosaccharides than oligosaccharides (sugars are almost composed of monosaccharides). Fermentation-inhibiting substances can be removed.

  For the above reasons, it is preferable to select a method in which the first solution to be obtained contains more oligosaccharides than monosaccharides as the degradation treatment of the polysaccharide-based biomass. An example of such a method is hydrothermal treatment. Hydrothermal treatment is a method of separating cellulose and hemicellulose from lignin by hydrolysis using heated hot water of 100 ° C. or higher. Pressurized hot water acts in the same way as an acid. Hemicellulose is hydrolyzed at around 150 ° C. and cellulose is hydrolyzed at around 230 ° C. Hydrothermal treatment also has the advantage of being cheaper than methods that require organic solvents and acid / base catalysts.

  After hydrolyzing the polysaccharide-based biomass, the solid fraction and the liquid fraction are separated from each other, and the obtained liquid fraction can be used as the first solution in the next step (II). In addition, well-known methods, such as a centrifugation method and a membrane separation method, can be used for the separation of the solid fraction and the liquid fraction at this time.

  Next, step (II) is performed. In step (II), the first solution prepared in step (I) is permeated through the first separation membrane, and the second solution is recovered from the non-permeating side. Since the low-molecular-weight fermentation-inhibiting substance in the first solution permeates the first separation membrane, the second solution on the non-permeation side is a solution in which sugar is purified and concentrated.

  Fermentation-inhibiting substances are substances that inhibit fermentation by microorganisms, and when they are included in fermentation raw materials, they are substances that reduce the yield of fermentation products compared to when they are not included. is there. The low-molecular-weight fermentation inhibitors here are furan compounds (furfural and 5-hydroxymethylfurfural (5-HMF), etc.) and organic acids (acetic acid) that have been conventionally recognized as fermentation inhibitors. And formic acid, etc.) and lignin degradation products (vanillin, syringaldehyde, etc.) and the like, and among the fermentation inhibitors, a low molecular weight compound having a molecular weight of 200 or less.

  The first separation membrane is a separation membrane having a NaCl blocking rate of 5% or more when a 2000 ppm NaCl aqueous solution is evaluated at a liquid temperature of 25 ° C., 1.0 MPa, and pH 6.5. Preferably, the NaCl rejection of the first separation membrane is preferably 20% or more, and more preferably 50% or more. As such a separation membrane, for example, a nanofiltration membrane (NF membrane) and a reverse osmosis membrane (RO membrane) can be used. The first separation membrane may be a separation membrane that can block at least oligosaccharides contained in the first solution on the membrane. When the first solution contains a relatively large amount of monosaccharides, the first separation membrane is preferably a separation membrane that can also block monosaccharides contained in the first solution on the membrane with a high blocking rate. In this case, the monosaccharide (glucose) inhibition rate (glucose inhibition rate when a 2000 ppm glucose aqueous solution is evaluated at a liquid temperature of 25 ° C. and 1.0 MPa) in the first separation membrane is 80% or more. desirable. On the other hand, when the first solution contains almost no monosaccharide (when the oligosaccharide is the main component), the first separation membrane contains an oligosaccharide in order to enhance the separation performance between the sugar and the low-molecular-weight fermentation inhibitor. A separation membrane that can be blocked on the membrane with a higher blocking rate and can permeate the low-molecular-weight fermentation-inhibiting substance with a higher transmittance is preferable. In this case, the monosaccharide (glucose) blocking rate in the first separation membrane is desirably less than 80%.

Here, the RO membrane is a membrane that does not permeate ions and salts. For example, when a solute (sodium chloride) 2000 mg / L solution is evaluated at a pressure of 1.0 MPa at a temperature of 25 ° C., the salt rejection is 80. It means a semi-permeable membrane showing% or more. The salt rejection can be calculated by the following equation using a NaCl concentration obtained by preparing a correlation (calibration curve) between the NaCl concentration and the aqueous solution conductivity in advance.
Salt rejection (%) = {1− (NaCl concentration in the permeate [mg / L]) / (NaCl concentration in the feed liquid [mg / L])} × 100

  The NF membrane is generally a semi-permeable membrane that has lower blocking performance than the RO membrane and is superior in performance of removing divalent ions, but is also used for organic matter and decolorization. For example, in the evaluation of the blocking performance of sodium chloride used for specifying the RO membrane, a membrane having a blocking rate of 10% or more falls into the category of NF membranes.

  The material of the first separation membrane is not particularly limited. For example, a cellulose ester polymer such as cellulose acetate, a polymer material such as polyamide, polyester, polyimide, vinyl polymer, polyethersulfone, sulfonated polyethersulfone, and polyamide is used. Can be used. Multiple materials may be used. Among these, polyamide is suitably used for the RO membrane since it has a record of high blocking performance. The NF membrane is appropriately selected depending on the object to be separated, but polyamide, polyethersulfone, polyvinyl alcohol, a mixture thereof and the like are preferably used.

  The shape of the first separation membrane is not particularly limited, and can be selected from a flat membrane shape, a hollow fiber membrane shape, a pleated membrane shape, a tubular membrane shape, and the like. In particular, a so-called spiral element film, which is formed by processing a flat film into an envelope shape and winding the film in a spiral shape together with a support such as a net, is preferable because the film area can be increased.

  The method of membrane separation using the first separation membrane is not particularly limited, and a known membrane separation method can be used. For example, by diluting the second solution obtained by membrane separation with water, supplying the obtained diluted solution again as the first solution and permeating the first separation membrane, a plurality of steps (II) are continuously performed. May be repeated. That is, it is possible to perform membrane separation by the first separation membrane in multiple stages. The first separation membrane used in this case is not particularly limited as long as it satisfies the NaCl rejection rate (NaCl rejection rate: 5% or more) specified above, and the same type of separation membrane may be used in all stages. Alternatively, different types of separation membranes may be used at each stage. By performing membrane separation with the first separation membrane in multiple stages, a second solution with a reduced concentration of the low-molecular-weight fermentation inhibitor can be obtained, so that the sugar purity of the sugar solution finally obtained can be increased. it can. The flow diagram shown in FIG. 1 shows an example in which membrane separation by the first separation membrane is performed twice. The number of membrane separations is preferably the number of times that the concentration of the low-molecular-weight fermentation inhibitor becomes a level that does not inhibit the fermentation of microorganisms (about the stock solution or less).

  Next, step (III) is performed. In step (III), the second solution collected in step (II) is saccharified to decompose the oligosaccharide into monosaccharides. As the saccharification treatment, it is preferable to use an enzymatic saccharification treatment that does not use chemicals or energy. The saccharifying enzyme used for this enzymatic saccharification treatment is not particularly limited, and a known enzyme can be used. The enzymatic saccharification treatment can be performed by adding a saccharifying enzyme to the second solution.

  Next, step (IV) is performed. In step (IV), the third solution obtained in step (III) is permeated through the second separation membrane. Since the high-molecular fermentation inhibitor in the third solution is blocked by the second separation membrane and remains on the non-permeate side, the fourth solution on the permeate side reduces the high-molecular fermentation inhibitor and further refines and concentrates the sugar. Solution. This fourth solution is recovered as a sugar solution.

  The term “polymer fermentation inhibitor” as used herein refers to a substance that has not been recognized as a factor that inhibits fermentation, and is a polymer compound having a molecular weight of 1000 or more, such as lignin and lignin degradation products. it is conceivable that.

  The second separation membrane is a separation membrane having a rejection rate lower than the NaCl rejection rate of the first separation membrane. It is preferable that the second separation membrane does not exhibit salt separation performance. Therefore, the second separation membrane can permeate the monosaccharide and block the high-molecular fermentation inhibitor on the membrane.

  For example, a microfiltration membrane (MF membrane) and an ultrafiltration membrane (UF membrane) can be used as the second separation membrane. It is preferable to use a UF membrane as the second separation membrane so that the second separation membrane can remove even a relatively low molecular weight component among the high molecular weight inhibitors. The second separation membrane is preferably one that can permeate monosaccharides and can block substances that inhibit ethanol fermentation by microorganisms in the permeate as much as possible. From such a viewpoint, it is also possible to use an NF membrane as the second separation membrane.

  In order to more reliably permeate monosaccharides and block high-molecular fermentation inhibitors on the membrane, as a second separation membrane, glucose inhibition when a 2000 ppm glucose aqueous solution was evaluated at a liquid temperature of 25 ° C. and 1.0 MPa It is preferable to use a separation membrane having a rate of 5% or less.

  The MF membrane is a membrane having an average pore diameter of about 0.01 μm to 10 μm. The UF membrane is a membrane having an average pore diameter of about 0.001 μm to 0.01 μm.

  The material of the second separation membrane is not particularly limited, and for example, a polymer material such as cellulose ester polymer such as cellulose acetate, polyethylene, polypropylene, polysulfone, polyvinylidene fluoride, polyethersulfone, or the like can be used. Polyvinylidene fluoride and polyethersulfone are preferable from the viewpoint of durability and detergency.

  The shape of the second separation membrane is not particularly limited, and can be selected from a flat membrane shape, a hollow fiber membrane shape, a pleated membrane shape, a Tuple membrane shape, and the like. In particular, a so-called spiral element film, which is formed by processing a flat film into an envelope shape and winding the film in a spiral shape together with a support such as a net, is preferable because the film area can be increased.

  The method of membrane separation using the second separation membrane is not particularly limited, and a known membrane separation method can be used.

The sugar solution recovered as the fourth solution is used as a fermentation raw material for obtaining a polysaccharide-based biomass-derived compound by fermentation. That is, the method for producing the polysaccharide-based biomass-derived compound of the present embodiment is as follows:
(I) a step of preparing a sugar solution using the method for producing a sugar solution of the present embodiment;
(Ii) using the sugar solution as a fermentation raw material, and fermenting the sugar solution;
including.

  The polysaccharide biomass-derived compound here refers to a sugar solution produced using polysaccharide biomass as a raw material (a sugar solution produced by the method for producing a sugar solution of this embodiment) as a fermentation raw material, and this is subjected to a fermentation treatment. For example, alcohols such as ethanol and butanol, lactic acid which is a bioplastic raw material, and succinic acid are exemplified.

  In the method for producing a polysaccharide biomass-derived compound using the sugar solution obtained by the method for producing a sugar solution of the present embodiment as a fermentation raw material, a known method can be used as a fermentation method, and it is also known as a microorganism used for fermentation. Yeast or the like can be used. The microorganism to be used may be isolated from the natural environment, or may be partially modified by mutation or genetic recombination. The sugar liquid produced using polysaccharide biomass as a raw material contains pentose sugar such as xylose. Therefore, it is preferable to select a microorganism that can ferment pentose as a microorganism used for fermentation. In addition, since a sugar solution used as a fermentation raw material may contain an acid such as acetic acid which is a low molecular fermentation inhibitor, a microorganism having acid resistance is preferably used for fermentation.

  The sugar solution used in the method for producing a polysaccharide-based biomass-derived compound of the present embodiment is obtained by reducing fermentation inhibitors having a wide range of molecular weights from low molecules to high molecules and highly refined and concentrated sugar solution. is there. Therefore, according to the fermentation process of the sugar solution in step (ii) of the production method of the present embodiment, a high fermentation yield is obtained and the yield of the fermentation product is increased. Thereby, according to the manufacturing method of this embodiment, a polysaccharide biomass origin compound can be manufactured with high productivity from polysaccharide biomass.

  Next, the manufacturing method of the saccharide | sugar of this invention and the manufacturing method of a polysaccharide biomass origin compound are demonstrated concretely using an Example.

Example 1
<Manufacture of sugar solution>
[Preparation of first solution]
The product obtained by hydrothermally treating rice straw as polysaccharide-based biomass at around 200 ° C. under a pressure of 10 MPa or less was filtered to separate it into a solid fraction and a liquid fraction. The liquid fraction had a pH of 4.4 and was designated as the first solution.

[Membrane separation of the first solution using the first separation membrane]
As the first separation membrane, an NF membrane (“ESNA3”, manufactured by Nitto Denko Corporation) was used. For membrane separation of the first solution, a batch type flat membrane test cell (“Membrane Master C40-B”, manufactured by Nitto Denko Corporation) (diameter: 104 mm, high) 147 mm). The maximum capacity of this test cell was 380 mL. Specifically, as shown in FIG. 2, the test cell 21 is placed on a magnetic stirrer (“IS-10P”, manufactured by Ikeda Science Co., Ltd.) 22, and the first solution 23 in the test cell 21 is stirred. The mixture was stirred at 400 rpm with the child 24. Membrane separation was performed at a room temperature of 25 ° C. by applying a pressure of 2.8 MPa in the test cell 21 with nitrogen gas. By this membrane separation, a concentrated solution in which the sugars in the first solution were concentrated 10.2 times on the non-permeating side of the first separation membrane 25 was obtained (second solution) (first membrane separation). Membrane separation was performed again in the same manner (second membrane separation) using the concentrate diluted 4-fold with Milli-Q water as the first solution. That is, in this example, membrane separation by the first separation membrane was performed twice continuously. The concentration of the concentrated solution (second solution) finally concentrated on the non-permeating side of the first separation membrane was 10.2 times.

[Saccharification treatment]
To the concentrated solution (second solution), 10 g / L hemicellulase (“G-Amano”, manufactured by Amano Enzyme) was added and subjected to enzymatic saccharification treatment at 37 ° C. for 24 hours to obtain a third solution.

[Membrane separation of the third solution using the second separation membrane]
As the second separation membrane, a UF membrane (“RS50”, manufactured by Nitto Denko Corporation) was used. Except for using this UF membrane for membrane separation, membrane separation of the third solution was performed by the same method as membrane separation of the first solution by the first separation membrane. The permeate (fourth solution) was recovered as a sugar solution from the permeation side of the third separation membrane.

<Ethanol fermentation of sugar solution>
The sugar solution obtained by the above method was subjected to ethanol fermentation. First, Saccharomyces cerevisiae MN8140X / TF-TF strain was prepared. What was pre-cultured in YPX medium (10 g / L yeast extract, 20 g / L polypeptone, 20 g / L xylose) at 30 ° C. and 150 rpm for 96 h was collected and used as the MN8140X / TF-TF strain. To the sugar solution (fourth solution), 10 g / L yeast extract, 20 g / L polypeptone, 50 wet-g / L (corresponding to 10 g / L in the dry state) yeast MN8140X / TF-TF strain was added (in this case, The sugar solution was diluted 0.8 times.), And ethanol fermentation was performed at 30 ° C. for 48 hours. Fermentation was performed while rotating the fermentation liquor in a 50 mL bottle equipped with an exhaust port for releasing CO ₂ gas.

<Analysis and evaluation method>
[Measurement of each component concentration in ethanol fermentation broth]
The concentrations of glucose, xylose, fructose, ethanol, glycerol and xylitol in the ethanol fermentation broth were analyzed by high performance liquid chromatography (“Prominence”, manufactured by Shimadzu Corporation). In addition, each component density | concentration in ethanol fermentation liquid was implemented when the elapsed time from fermentation start was 0, 3, 6, 9, 24, 48 hours. The results are shown in FIG. In Table 1, the ethanol yield is the ethanol concentration in the fermented liquid 48 hours after the start of fermentation, and the ethanol yield was determined by ethanol yield (g) / consumed sugar amount (g). Value.

(Comparative Example 1)
A sugar solution was prepared in the same manner as in Example 1 except that the membrane separation step using the second separation membrane (UF membrane) was not performed. Moreover, by the same method as Example 1, each component density | concentration measurement in ethanol fermentation of fermentation liquid and fermentation liquid was performed. The results are shown in FIG.

  As can be seen from FIGS. 3 and 4, the sugar solution of Example 1 and the sugar solution of Comparative Example 1 had substantially the same sugar concentration. However, as shown in Table 1, the ethanol yield was higher in Example 1 than in Comparative Example 1. This is considered to be because the high-molecular-weight fermentation inhibitor was reduced in the sugar solution of Example 1 by performing membrane separation using a UF membrane. That is, it is considered that the sugar solution of Example 1 contained less high-molecular fermentation inhibitor and the purity of monosaccharides was higher than that of Comparative Example 1. Therefore, ethanol fermentation using the sugar solution of Example 1 has a higher xylose utilization rate than that of Comparative Example 1, and in Example 1, 0.64 ± 0.04 g / L / hour (from 6 to 48 hours). In Comparative Example 1, it was 0.42 ± 0.01 g / L / hour (9 to 48 hours). As a result, it is considered that the ethanol yield in Example 1 also increased. It is considered that there is no difference in the ethanol yield.

(Example 2)
The product obtained by hydrothermally treating rice straw as polysaccharide-based biomass at around 200 ° C. under a pressure of 10 MPa or less was filtered to separate it into a solid fraction and a liquid fraction. The liquid fraction had a pH of 4.4 and was designated as the first solution. The first solution prepared in Example 2 had a higher saccharide concentration than the first solution in Example 1. The membrane separation of the first solution using the first separation membrane was performed at a room temperature of 25 ° C. by applying a pressure of 2.8 MPa in the test cell 21 with nitrogen gas using the apparatus shown in FIG. By this membrane separation, a concentrated solution in which the saccharide in the first solution was concentrated 5.1 times was obtained on the non-permeating side of the first separation membrane 25 (second solution) (first membrane separation). This concentrated solution was diluted 5-fold with Milli-Q water as a first solution, and membrane separation was performed again by the same method (second membrane separation). Membrane separation was performed again by the same method using the concentrate obtained by the second membrane separation diluted 5 times with Milli-Q water as the first solution (third membrane separation). That is, in this example, membrane separation by the first separation membrane was performed three times continuously. The concentration of the concentrated solution (second solution) finally concentrated on the non-permeating side of the first separation membrane was 5.3 times. Thereafter, saccharification and membrane separation of the third solution using the second separation membrane were performed in the same manner as in Example 1. Furthermore, by the same method as in Example 1, ethanol fermentation of the sugar solution and the concentration of each component in the fermentation solution were measured. The results are shown in FIG.

(Comparative Example 2)
Same as Example 2 except that the membrane separation of the first solution using the first separation membrane was performed only once and the membrane separation step using the second separation membrane (UF membrane) was not performed. A sugar solution was prepared by the method. Moreover, by the same method as Example 1, each component density | concentration measurement in ethanol fermentation of fermentation liquid and fermentation liquid was performed. The results are shown in FIG.

(Comparative Example 3)
The same solution as the first solution of Example 2 was used as the first solution. The first solution was passed through a UF membrane (“RS50”, manufactured by Nitto Denko Corporation), and the permeate was collected. The specific method was the same as the membrane separation of the third solution by the second separation membrane performed in Example 2, but the pressure in the test cell was 0.4 MPa. Thereafter, as in Comparative Example 2, membrane separation using the first separation membrane and enzyme saccharification treatment were performed to produce a sugar solution, and further, the concentration of each component in the ethanol fermentation and fermentation broth using the sugar solution Measurements were made. The results are shown in FIG.

  Although Example 2 and Comparative Examples 2 and 3 used the same first solution, ethanol yields higher than Comparative Examples 2 and 3 were obtained in ethanol fermentation using the sugar solution prepared in Example 2. And an ethanol yield was obtained. This is considered to be because in Example 2, membrane separation using an NF membrane was first performed, then enzymatic saccharification treatment was performed, and finally membrane separation using a UF membrane was performed. The first solution pretreated by hydrothermal treatment contains not only monosaccharides but also oligosaccharides in a high ratio as saccharides. Such a first solution is first subjected to membrane separation using an NF membrane, thereby obtaining a second solution in which a low-molecular-weight fermentation inhibitor is permeated and monosaccharides and oligosaccharides are concentrated on the non-permeating side of the NF membrane. It is done. Next, the second solution is subjected to an enzymatic saccharification treatment to obtain a third solution in which the oligosaccharide is decomposed into monosaccharides. That is, it can be said that the saccharide contained in the third solution is substantially composed of monosaccharides. Finally, by carrying out membrane separation using a UF membrane, a substance having a large molecular weight is removed from the third solution, so that the yield, concentration and purity of the monosaccharide as a fermentation raw material are improved, and the polymer It is considered that a sugar solution with sufficiently reduced fermentation inhibiting substances was obtained. In Example 2, since such a sugar solution was used as a fermentation raw material, an increase in ethanol yield could be realized.

  The sugar solution produced by the method of Comparative Example 2 was subjected to membrane separation using an NF membrane, so that the low molecular weight fermentation inhibitor was removed to some extent, but the high molecular fermentation inhibitor was not removed. Furthermore, since the separation with the NF membrane is performed once, the low molecular weight fermentation inhibitor is not completely removed. On the other hand, since Comparative Example 3 includes a membrane separation step using a UF membrane, the loss of oligosaccharide is reduced because the implementation of the step is prior to membrane separation using an NF membrane and enzymatic saccharification treatment. However, ethanol is recovered at a higher yield and yield than Comparative Example 2 by removing the high-molecular fermentation inhibitor. The results of Comparative Example 2 and Comparative Example 3 are results suggesting the presence of a high-molecular fermentation inhibitor. In Table 3 below, when the membrane separation using the UF membrane as in Comparative Example 3 is performed before the membrane separation using the NF membrane, the oligosaccharide in the first solution is not removed. It shows that the amount of sugar in the obtained sugar solution is reduced. Table 3 shows the concentration of monosaccharides in the sugar solutions prepared in Comparative Examples 2 and 3. The sugar solution of Comparative Example 3 has a sugar concentration lower than that of Comparative Example 2. This is probably because, in Comparative Example 3, the first solution was first treated with the UF membrane, so that the oligosaccharide in the first solution was removed, and the amount of sugar finally obtained was reduced.

  According to the present invention, since it is possible to produce a sugar solution that can increase the yield of fermentation products when used as a fermentation raw material, the present invention can be used for a wide range of applications for converting saccharides into chemicals by fermentation. .

21 Test Cell 22 Magnetic Stirrer 23 First Solution 24 Stirrer 25 First Separation Membrane

Claims (10)

A method for producing a sugar solution using polysaccharide biomass as a raw material,
(I) preparing a first solution containing at least an oligosaccharide obtained by decomposing the polysaccharide-based biomass;
(II) allowing the first solution to permeate the first separation membrane and recovering the second solution from the non-permeating side;
(III) subjecting the second solution to a saccharification treatment for decomposing oligosaccharides into monosaccharides to obtain a third solution;
(IV) allowing the third solution to permeate the second separation membrane and recovering the fourth solution from the permeation side to obtain a sugar solution;
Including
The first separation membrane is a separation membrane having a NaCl rejection of 5% or more when evaluated with a 2000 ppm NaCl aqueous solution at a liquid temperature of 25 ° C., 1.0 MPa, and pH 6.5.
The second separation membrane has a rejection rate lower than the NaCl rejection rate of the first separation membrane;
A method for producing a sugar solution. The first separation membrane is a nanofiltration membrane or a reverse osmosis membrane,
The manufacturing method of the sugar liquid of Claim 1. The second separation membrane is a nanofiltration membrane, a microfiltration membrane or an ultrafiltration membrane,
The manufacturing method of the sugar liquid of Claim 1 or 2. The second separation membrane is a separation membrane having a glucose inhibition rate of 5% or less when a 2000 ppm glucose aqueous solution is evaluated at a liquid temperature of 25 ° C. and 1.0 MPa.
The manufacturing method of the sugar liquid of Claim 3. The saccharification treatment in the step (III) is an enzymatic saccharification treatment.
The manufacturing method of the sugar liquid of any one of Claims 1-4. The first solution prepared in the step (I) contains more oligosaccharides than monosaccharides,
The manufacturing method of the sugar liquid of any one of Claims 1-5. The decomposition treatment of the polysaccharide biomass in the step (I) is hydrothermal treatment,
The manufacturing method of the sugar liquid of any one of Claims 1-6. The step (II) is repeated a plurality of times in succession by diluting the second solution with water and supplying the obtained diluted solution again as the first solution.
The manufacturing method of the sugar liquid of any one of Claims 1-7. (I) a step of preparing a sugar solution using the method according to any one of claims 1 to 8;
(Ii) using the sugar solution as a fermentation raw material, and fermenting the sugar solution;
The manufacturing method of the polysaccharide biomass origin compound containing this. The polysaccharide-based biomass-derived compound is ethanol,
The manufacturing method of the polysaccharide biomass origin compound of Claim 9.

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