Method for producing a composition containing xylooligosaccharide and composition containing xylooligosaccharide

Abstract

The object of the present invention is to provide a method for producing a composition containing xylooligosaccharide with excellent storage stability. The method for producing a composition containing xylooligosaccharide that solves the above object includes a step of hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, and the raw material mixture contains 5 to 50% by mass of xylan based on 100% by mass of the total content of cellulose and xylan.

Description

Technical Field

[0001] The present invention relates to a method for producing a composition containing xylooligosaccharide and a composition containing xylooligosaccharide. Background Art

[0002] Xylooligosaccharide is an oligosaccharide in which glucose is bonded together through β-1,4 bonds. In recent years, it has been found to have functions such as moisture retention, suppression of stickiness, imparting a refreshing feeling, reducing starch retrogradation, and suppressing protein denaturation, and is expected to be applied in the fields of medicine, cosmetics, food, feed, etc.

[0003] In particular, xylooligosaccharides with a degree of polymerization of glucose of 3 or more are expected to have greater increases in the above functions and the imparting of new functions.

[0004] The xylooligosaccharide currently used industrially is produced by an enzymatic reaction, and its main components are glucose and cellobiose as a dimer (Patent Document 1).

[0005] As a technology for producing xylooligosaccharide other than the enzymatic method, a hydrothermal treatment method (Patent Documents 2 to 4) and a hydrothermal treatment method using oxidative water containing hypochlorous acid (Patent Document 5) are known. In any of the patent documents, xylooligosaccharide is regarded as an intermediate product in the process of decomposing cellulose into glucose.

[0006] In addition, a method of mixing and pulverizing a carbon catalyst and cellulose and then performing hydrolysis by a hydrothermal synthesis method is known, and a method for producing xylooligosaccharide that obtains an oligosaccharide with a degree of polymerization of glucose up to 6 has been disclosed (Patent Document 6).

[0007] A method of partially hydrolyzing cellulose by a semi-dry conversion method using a phosphoric acid catalyst is known (Non-Patent Document 1). This method has a relatively high selectivity and can obtain xylooligosaccharides with a degree of polymerization of 7 or more.

[0008] However, in the methods described in Patent Documents 1 to 5, the hydrolysis reaction proceeds excessively to glucose, and the method for obtaining xylooligosaccharide is inefficient. In the method described in Patent Document 6, if the conversion rate of cellulose is to be increased, the hydrolysis reaction proceeds to glucose, and in order to increase the yield of xylooligosaccharide, very precise temperature control, etc. are required, and the method for obtaining xylooligosaccharides with a relatively high degree of polymerization is not efficient.

[0009]

Prior Art Documents

[0010]

Patent Documents

[0011]

Patent Document 1

[0012]

Patent Document 2

[0013]

Patent Document 3

[0014]

Patent Document 4

[0015]

Patent Document 5

[0016]

Patent Document 6

[0017]

Non-Patent Document

[0018]

Non-Patent Document 1

[0019]

Problems to be Solved by the Invention

[0020] On the other hand, as a method for obtaining cellooligosaccharides with a relatively high degree of polymerization (for example, the method described in Non-Patent Document 1), the obtained cellooligosaccharides have insufficient solubility in water and have the disadvantages of being easily precipitated during long-term storage and having poor storage stability.

[0021] The present invention has been completed in view of the above circumstances, and its object is to provide a method for producing a cellooligosaccharide-containing composition having excellent storage stability even when the degree of polymerization is relatively high.

[0022]

Means for Solving the Problems

[0023] The inventors of the present invention repeatedly conducted in-depth studies to solve the above problems, and as a result, they conceived of hydrolyzing cellulose containing a specified proportion of xylan in the presence of an acid catalyst.

[0024] As a result, a method for producing a cellooligosaccharide-containing composition was found. By hydrolyzing a mixture containing cellulose and xylan, and having a xylan content of 5 to 50% by mass based on the total content of the cellulose and the xylan, in the presence of an acid catalyst, the above problems can be solved.

[0025] That is, the present invention includes the following aspects [1] to [8].

[0026] [1]. A method for producing a cellooligosaccharide-containing composition, comprising a step of hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, wherein the raw material mixture contains 5 to 50% by mass of the xylan based on 100% by mass of the total content of the cellulose and the xylan.

[0027] [2]. The manufacturing method of the composition containing xylo-oligosaccharides as described in [1], wherein the raw material mixture contains 7 to 40% by mass of the xylan based on 100% by mass of the total content of the cellulose and the xylan.

[0028] [3]. The manufacturing method of the composition containing xylo-oligosaccharides as described in [1] or [2], wherein the acid catalyst is at least one acid selected from sulfuric acid, sulfurous acid, hydrochloric acid, perchloric acid, nitric acid, nitrous acid, and phosphoric acid or its partially neutralized salt.

[0029] [4]. The manufacturing method of the composition containing xylo-oligosaccharides as described in [3], wherein the acid catalyst is phosphoric acid or its partially neutralized salt.

[0030] [5]. The manufacturing method of the composition containing xylo-oligosaccharides as described in [4], wherein the acid catalyst is phosphoric acid.

[0031] [6]. The manufacturing method of the composition containing xylo-oligosaccharides as described in any one of [1] to [5], comprising a step of hydrolyzing the raw material mixture by performing a pulverization treatment in the presence of the acid catalyst.

[0032] [7]. The manufacturing method of the composition containing xylo-oligosaccharides as described in [6], wherein the pulverization treatment is performed by using a planetary ball mill or a vibration mill.

[0033] [8]. A composition containing xylo-oligosaccharides, which is manufactured by hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, wherein the content of the xylan in the raw material mixture is 5 to 50% by mass based on 100% by mass of the total content of the cellulose and the xylan.

[0034]

Invention Effect

[0035] According to the manufacturing method of the composition containing xylo-oligosaccharides of the present invention, a composition containing xylo-oligosaccharides with excellent storage stability can be manufactured even when the degree of polymerization is relatively high (the degree of polymerization is 3 to 6). Description of the Drawings

[0036] Figure 1 is the 1 H-NMR spectrum of the hydrolyzate produced in Example 1.

[0037] Figure 2 is the 1 H-NMR spectrum of the hydrolyzate produced in Example 2.

[0038] Figure 3 is the 1 H-NMR spectrum of the hydrolyzate produced in Comparative Example 1.

[0039] Figure 4 is the 1 H-NMR spectrum of the hydrolyzate produced in Comparative Example 2. Detailed implementation mode

[0040] The following describes the implementation modes of the present invention. In addition, the implementation modes described below are only representative examples of the present invention and are not limited thereto.

[0041] A method for producing a composition containing fiber oligosaccharides according to one implementation mode includes a step of hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, and the raw material mixture contains 5 to 50% by mass of the xylan relative to the total content of 100% by mass of the cellulose and the xylan.

[0042] <Raw material mixture>

[0043] In a method for producing a composition containing fiber oligosaccharides according to one implementation mode, a raw material mixture containing cellulose and xylan (hereinafter sometimes referred to as "cellulose·xylan mixture") is used as the raw material.

[0044] Cellulose and xylan are called biomass, which are not fossil resources but plant-derived organic resources.

[0045] Examples of cellulosic biomass include woody biomass such as cotton, wood pulp, kenaf, hemp, small-diameter wood, thinned wood, sawdust, wood chips, waste paper, newspapers, wrapping paper, paper towels, toilet paper, corrugated paper, etc.; and herbaceous biomass such as bagasse, switchgrass, elephant grass, corn cobs, rice straw, wheat straw, etc. These can be used alone or in combination of two or more. For example, chemical pulp (holocellulose) can be produced by bleaching these biomass through chlorine treatment, and the insoluble cellulose obtained by subjecting the chemical pulp to alkali treatment to remove hemicellulose can be used.

[0046] Cellulose usually shows crystallinity by two or more cellulose molecules being bound together by hydrogen bonds. In one implementation mode, cellulose having such crystallinity can be used as the raw material. In this implementation mode, in order to improve the hydrolysis rate, it is preferable to perform a treatment for reducing crystallinity such as pre-crushing to reduce the crystallinity before use. The cellulose with reduced crystallinity can be partially reduced in crystallinity or have substantially or completely disappeared crystallinity. There is no particular limitation on the method for reducing crystallinity, but a treatment for reducing crystallinity that can cut the above-mentioned hydrogen bonds and at least partially generate cellulose molecules with a single chain is preferred. By using cellulose containing at least partially cellulose molecules with a single chain as the raw material, the hydrolysis efficiency can be significantly improved.

[0047] As a treatment for reducing the crystallinity of cellulose as a raw material, the following can be cited: a method of physically cutting the hydrogen bonds between cellulose molecules to obtain single-chain cellulose molecules, such as ball milling as a pre-crushing method (refer to Zhao et al, Energy&Fuels, 20, 807 (2006)), and a method of chemically cutting the hydrogen bonds between cellulose molecules without applying compressive shear stress, such as treatment with phosphoric acid, to obtain single-chain cellulose (refer to Zhang et al, Biomacromolecules, 7, 644 (2006)). The treatment for reducing the crystallinity of cellulose may not be a treatment until the crystallinity of cellulose completely disappears, or it may be a treatment that partially reduces the crystallinity of the cellulose before treatment. By using cellulose that has undergone these treatments as a raw material, the hydrolysis efficiency can be significantly improved.

[0048] In addition, as a treatment for reducing the crystallinity of cellulose as a raw material, for example, hydrothermal treatment under pressure can be cited (refer to Hayashi et al, J.Jpn.Inst.Energy, 83, 805 (2004), Sasaki et al, Ind.Eng.Chem.Res., 39, 2883 (2000), etc.).

[0049] Xylan refers to a polysaccharide in which D-xylose residues are bound by β-1,4 bonds or β-1,3 bonds. Among the sugars that make up xylan, in addition to xylose, arabinose, glucuronic acid, 4-O-methylglucuronic acid, glucose, galactose, etc. may also be contained.

[0050] Xylan is preferably pre-crushed by applying compressive shear stress before hydrolysis. In order to apply compressive shear stress to xylan to break it up, a compression-shear type crusher can be used. A compression-shear type crusher is a machine that can apply both compressive stress and shear stress, and examples include a vibrating rod mill, a vibrating ball mill, etc. Among them, from the viewpoint of production efficiency, a vibrating rod mill is preferred. The rod is not particularly limited, but preferably has an outer diameter of 0.1 to 100 mm, more preferably 0.5 to 50 mm. The filling rate of the rod (the apparent volume of the rod relative to the volume of the stirring part of the vibrating mill) varies depending on the model, but is preferably 10 to 97%, more preferably 15 to 95%.

[0051] The crushing conditions such as the crushing time and the rotation speed of the crusher can be appropriately set in order to form the desired crushed material. From the viewpoint of obtaining a high hydrolysis rate, it is preferred that the crystallinity in the xylan crushed material is low.

[0052] Xylan can be roughly pulverized in advance before pre-disrupting by compressive shear stress. The method of rough pulverization is not particularly limited. For example, as a pulverizer, a cutter-type pulverizer such as a grinder-roll cutter, an impact pulverizer such as a hammer mill, a pulverizing pulverizer such as a colloid mill, etc. can be used.

[0053] In the cellulose-xylan mixture, the content of xylan is 5 to 50% by mass relative to the total content of cellulose and xylan of 100% by mass. By containing 5% by mass or more of xylan, the solubility of the hydrolyzate in water can be improved, and a composition containing fiber oligosaccharides with excellent storage stability can be produced. If the content of xylan is less than 50% by mass, a composition containing fiber oligosaccharides as the target can be obtained in sufficient yield. In the cellulose-xylan mixture, the content of xylan is preferably 7 to 40% by mass, more preferably 10 to 30% by mass, and still more preferably 15 to 25% by mass relative to the total content of cellulose and xylan of 100% by mass.

[0054] In the cellulose-xylan mixture, the content of xylan is determined by the method described in the following examples. Specifically, the mixture used as a raw material is hydrolyzed to the monosaccharide unit with an aqueous sulfuric acid solution, etc., and the glucose content and xylose content in the product are analyzed, whereby the amount of xylan in the mixture used as a raw material relative to the total content of cellulose and xylan of 100% by mass is determined. However, here it is assumed that xylan is composed only of xylose.

[0055] In addition to cellulose and xylan, the cellulose-xylan mixture may contain other components (such as other polysaccharides, etc.). Relative to 100% by mass of the mixture, the amount of the other components is preferably 10% by mass or less, more preferably 5% by mass or less.

[0056] The cellulose and xylan contained in the cellulose-xylan mixture can be mixed before being introduced into the reactor for the hydrolysis reaction, or can be mixed in the reactor for the hydrolysis reaction. As the cellulose-xylan mixture, a commercial product containing cellulose and xylan can be purchased and used. For example, cellulose produced from a cellulose-based biomass in which a xylose skeleton is mixed in addition to the glucose skeleton sometimes contains xylan that has not been completely removed and is mixed in the cellulose. As long as the content of xylan is 5 to 50% by mass relative to the total content of cellulose and xylan of 100% by mass, such commercially available cellulose can be used as the cellulose-xylan mixture.

[0057] <Hydrolysis reaction>

[0058] In a method for manufacturing a composition containing xylooligosaccharides according to an embodiment, xylooligosaccharides are produced by hydrolyzing a cellulose-xylan mixture in the presence of an acid catalyst.

[0059] As the acid catalyst, a known acid can be used. Specifically, at least one acid selected from sulfuric acid, sulfurous acid, hydrochloric acid, perchloric acid, nitric acid, nitrous acid, and phosphoric acid, or a partially neutralized salt thereof can be used. Examples of the partially neutralized salt of the acid include monopotassium dihydrogen phosphate, monoammonium dihydrogen phosphate, potassium bisulfate, etc. The acid catalyst is preferably phosphoric acid or a partially neutralized salt thereof, and more preferably phosphoric acid.

[0060] The amount of the acid catalyst used is preferably such that the mass ratio of the cellulose-xylan mixture to the acid catalyst is: (cellulose-xylan mixture) / (acid catalyst) = 2 to 100, more preferably: (cellulose-xylan mixture) / (acid catalyst) = 4 to 20, and even more preferably: (cellulose-xylan mixture) / (acid catalyst) = 5 to 12. When the mass ratio of the cellulose-xylan mixture to the acid catalyst is 100 or less, the hydrolysis proceeds at a rate that is not problematic in practical applications. If the mass ratio of the cellulose-xylan mixture to the acid catalyst is 2 or more, side reactions such as dehydration reactions and cleavage of carbon-carbon bonds can be suppressed during hydrolysis.

[0061] In the present disclosure, the mass of the cellulose-xylan mixture is the net mass (dry mass) after removing the moisture contained in the raw material. Usually, since cellulose and xylan contain physically adsorbed moisture, the amount of this adsorbed moisture is analyzed, and based on the mass of the cellulose-xylan mixture after removing the moisture, the mass ratio of the cellulose-xylan mixture to the acid catalyst is determined. As a method for analyzing the amount of adsorbed moisture, a quantification method can be cited in which the cellulose-xylan mixture used as the raw material is placed in a constant temperature dryer at 100°C to 150°C and dried until there is no further mass reduction. To prevent the influence of side reactions such as dehydration reactions during drying, it is preferable to dry and quantify using a vacuum dryer at a lower temperature. The mass of the acid catalyst is also the true mass of the acid catalyst (dry mass).

[0062] As described above, the physically adsorbed moisture in the cellulose-xylan mixture before hydrolysis is about 1 to 12% by mass. In addition, acid catalysts such as hydrochloric acid and phosphoric acid mostly contain moisture in their usual commercially available forms. Therefore, even without adding water, hydrolysis can be carried out using the moisture physically adsorbed in the cellulose-xylan mixture and the moisture contained in the acid catalyst. Usually, even without adding water, the amount of moisture is mostly sufficient, but for a cellulose-xylan mixture with a high degree of dryness, water can also be added for hydrolysis.

[0063] Whether in the case of not adding water or adding water, the cellulose-xylan mixture contains about 1 to 12% by mass of physically adsorbed water. Therefore, the amount of water in the hydrolysis reaction is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 8 parts by mass, based on 100 parts by mass of the net mass (dry mass) of the cellulose-xylan mixture, with respect to the physically adsorbed water in the cellulose-xylan mixture and the water contained in the acid catalyst (including this amount of water in the case of further adding water). If it is below 15 parts by mass, not only can a sufficient hydrolysis rate be obtained, but also the operation can be prevented from being impossible due to fixed adhesion to the device. In addition, if it is 0.1 part by mass or more, side reactions such as dehydration reactions can be suppressed.

[0064] In a method for producing a fiber oligosaccharide-containing composition according to one embodiment, it is preferable to use a method (mechanochemical method) in which the cellulose-xylan mixture is hydrolyzed by applying mechanical external force through a pulverization process.

[0065] Examples of the pulverization device for the pulverization process include rotary ball mills such as pot mills, tube mills, and conical mills, jet pulverizers such as vortex jet mills, impact jet mills, fluidized bed jet mills, and wet jet mills, shear mills such as attrition stirrers and angle mills, colloid mills such as mortars and stone mortars, impact pulverizers such as hammer mills, cage mills, needle mills, crushers, screen mills, turbo mills, and centrifugal separation mills, vibration mills that pulverize by vibrating the drum to move the medium inside, stirring mills that place the medium and raw material in a tank with stirring blades and rotate them to pulverize, and planetary ball mills of the type that use rotation and revolution motions.

[0066] The pulverization device is preferably a ball mill, a vibration mill, or a stirring mill, which can apply a compressive force to the cellulose-xylan mixture and apply tensile stress in two directions of the main chain. The pulverization device is more preferably a planetary ball mill, a rotary ball mill, a vibration mill, or a stirring mill, and even more preferably a planetary ball mill or a vibration mill.

[0067] At the laboratory level, it is preferable to use a planetary ball mill. It is better to use a vibration mill industrially. The vibration mill does not rotate the drum (pulverization cylinder) inserted with the pulverization medium, but vibrates the drum to move the medium inside, so that pulverization can be achieved in about 1 / 10 to 1 / 20 of the time compared to a rotary drum ball mill. The stirring mill does not rotate the drum, but rotates the stirring blades to move the medium, so that pulverization can be achieved in about 1 / 10 to 1 / 20 of the time compared to a rotary drum ball mill.

[0068] The comminution treatment can be carried out continuously or intermittently. In order to suppress the temperature rise of the object to be treated accompanying the comminution treatment, it is preferable to carry out the comminution treatment intermittently. In the case of carrying out the comminution treatment intermittently, depending on the comminution device, the optimum value varies greatly. For example, in the case of a planetary ball mill, the comminution treatment is carried out for 5 to 15 minutes each time, followed by a rest period of 5 to 15 minutes, and this cycle is repeated. When carrying out the comminution treatment continuously, it is preferable to cool by providing a jacket or the like on the comminution device and carry out the comminution treatment while maintaining an appropriate temperature.

[0069] When hydrolyzing a cellulose / xylan mixture using a comminution device such as a ball mill, etc., the crystallinity of cellulose or xylan can be reduced while hydrolyzing by comminution treatment, or the treatment for reducing the crystallinity of cellulose or xylan can be carried out in advance as described above, and then an acid catalyst is added for hydrolysis. When cellulose or xylan is pre-crushed by a Henschel mixer and then comminution treatment is carried out by a ball mill or the like, an acid catalyst can be mixed from the pre-crushing stage.

[0070] In a method for manufacturing a composition containing fiber oligosaccharide in one embodiment, in the case of carrying out hydrolysis without accompanying comminution treatment, as a method without comminution, for example, a method of carrying out kneading treatment using a pressure kneader, and a method of carrying out a reaction using an extrusion molding machine after kneading in a kneader can be cited.

[0071] The temperature of hydrolysis is preferably from normal temperature to 110 °C, more preferably from 50 °C to 100 °C. If it is above normal temperature, the progress of decomposition will not slow down and the time required for decomposition will not be overly extended. In order to accelerate the decomposition rate, hydrolysis can also be carried out at a high temperature. If the temperature of hydrolysis is below 110 °C, side reactions such as dehydration reactions can be suppressed. Since depending on the reaction device, sometimes the shear heat generation is large, as described above, it is preferable to repeat the cycle with a rest period in between, or to pass cooling water through the jacket of the reaction device to control the hydrolysis temperature.

[0072] The time of hydrolysis depends on the reaction device used, but is usually preferably from 2 hours to 150 hours, more preferably from 5 hours to 80 hours, further more preferably from 10 hours to 60 hours, and particularly preferably from 15 hours to 40 hours. When the time of hydrolysis is 2 hours or more, the decomposition of the cellulose / xylan mixture can be promoted. If the time of hydrolysis is 150 hours or less, the hydrolyzate can be obtained more effectively. In the present disclosure, in the case of carrying out hydrolysis by comminution treatment and carrying out the comminution treatment intermittently, the time of hydrolysis refers to the net comminution treatment time after removing the rest time.

[0073] The progress of the hydrolysis of the cellulose·xylan mixture can be confirmed by collecting a small amount of the object to be treated over time and measuring the amount of water-soluble components contained in the collected sample.

[0074] <Other steps>

[0075] The method for producing a composition containing a fiber oligosaccharide according to one embodiment may include the following steps as needed in addition to the above hydrolysis reaction step.

[0076] [Extraction step]

[0077] The method for producing a composition containing a fiber oligosaccharide according to one embodiment may have a step of adding water to the reaction product to extract water-soluble components after the above hydrolysis reaction. When the amount of water used during hydrolysis is small, the reaction product will be in a solid state, so the extraction step is preferably carried out.

[0078] The mass ratio of the amount of water added to the reaction product is preferably: (amount of water added) / (reaction product)=0.5-100, more preferably 1-20, and even more preferably 2-10. If the mass ratio is 0.5 or more, the soluble components in the reaction product can be effectively dissolved. If the mass ratio is 100 or less, the container for dissolution will not be too large, so the efficiency is good.

[0079] The water added to the reaction product is not particularly limited, but usually distilled water is used. In addition to distilled water, a solution containing salt, a buffer solution, etc. can also be used. An organic solvent miscible with water can also be added within the range that does not affect the dissolution of the soluble components in the reaction product.

[0080] The separation of the water-soluble components and the solid components can be carried out by a generally used method for removing solid components from a suspension. Filtration can be carried out using, for example, filter paper, filter cloth, membrane filters, pressure filters, centrifugal filters, cross-flow filters, etc., or natural sedimentation or centrifugal sedimentation can also be carried out.

[0081] In order to obtain a fiber oligosaccharide with high purity, the following purification operations can be carried out: after removing the solid components from the reaction product, adding ethanol, etc. to the aqueous solution containing the water-soluble components to reprecipitate the fiber oligosaccharide, dissolving the obtained precipitate in water again, and repeating ethanol reprecipitation, etc.

[0082] [Neutralization step]

[0083] The method for producing a composition containing a fiber oligosaccharide according to one embodiment may have a step of adding a basic compound to neutralize the reaction product after the above hydrolysis reaction. Since the acid catalyst used in the hydrolysis remains in the reaction product obtained by the above hydrolysis reaction, the acid catalyst can be neutralized by adding a basic compound.

[0084] In the case where the above extraction step is carried out after the hydrolysis reaction, the neutralization step can be carried out after the extraction step and can be carried out simultaneously with the extraction step.

[0085] The basic compound is preferably at least one selected from potassium salts, phosphates, ammonium salts, and ammonia.

[0086] In the case of using a potassium salt as the basic compound, for example, potassium hydroxide, potassium carbonate, potassium formate, potassium acetate, potassium ethoxide, monopotassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium amide, etc. can be used. Among them, potassium hydroxide, potassium carbonate, dipotassium hydrogen phosphate, and tripotassium phosphate are preferred.

[0087] When using a phosphate as the basic compound, monopotassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, diammonium hydrogen phosphate, triammonium phosphate, etc. can be used. Thus, the phosphate can be both a potassium salt or an ammonium salt at the same time.

[0088] When using an ammonium salt as the basic compound, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, triammonium phosphate, ammonium nitrate, ammonium sulfate, etc. can be used. Among them, diammonium hydrogen phosphate and ammonium sulfate are preferred.

[0089] When using ammonia as the basic compound, aqueous ammonia is preferably used.

[0090] The temperature of the neutralization reaction, in order to prevent the products of the hydrolysis reaction from reacting excessively, is preferably 0°C to 50°C, more preferably 5°C to 40°C, and still more preferably 20°C to 30°C. The neutralization reaction itself is relatively fast, but in the presence of insoluble substances derived from the raw materials, sufficient diffusion of the acid is required, so the time of the neutralization reaction is preferably 0.1 hour to 10 hours, more preferably 0.5 hour to 5 hours, and still more preferably 1 hour to 3 hours. As the device for the neutralization reaction, no special one is required, and a general stirring tank can be used. In the case of using hydrochloric acid or sulfuric acid as the acid catalyst, a stirring tank with a corrosion-resistant lining such as glass is preferably used.

[0091] In the case of carrying out the neutralization step, since precipitation sometimes occurs by changing the pH to the neutral side, it is preferable to separate the solid part by filtration after the neutralization reaction. In the case of carrying out filtration after the neutralization reaction, after extracting the water-soluble components in the above extraction step, the operation of separating the water-soluble components and the solid components (filtration) can also be omitted.

[0092] The separation of the solid part after the neutralization reaction can be carried out by a generally used method for removing the solid part from the suspension. For example, filtration can be carried out using filter paper, filter cloth, membrane filters, pressure filters, centrifugal filters, cross-flow filters, etc., and natural sedimentation or centrifugal sedimentation can also be carried out.

[0093] <Product of hydrolysis reaction>

[0094] As a method for producing a composition containing cellooligosaccharides by hydrolyzing cellulose, a carbon catalyst method and an acid catalyst method are known.

[0095] The carbon catalyst method is a method of hydrolyzing cellulose in the presence of a carbon catalyst such as activated carbon and water. In this method, as shown in the following formula (1), only linear cellooligosaccharides are produced.

[0096]

[0097] (In formula (1), m and n represent the degree of polymerization.)

[0098] The acid catalyst method is a method of hydrolyzing cellulose in the presence of an acid catalyst. In this method, in addition to the reaction shown in the above formula (1), a reaction for producing branched cellooligosaccharides also occurs as shown in the following formula (2). That is, by reacting the hydroxyl group at the 6-position with cellulose, cellooligosaccharides having a branched skeleton can be produced. Compared with the linear form, this branched form has higher solubility in water.

[0099]

[0100] (In formula (2), m, n, x, and y represent the degree of polymerization.)

[0101] In a method for producing a composition containing cellooligosaccharides according to one embodiment, in the acid catalyst method, a cellulose-xylan mixture containing a predetermined proportion of xylan is used as a raw material for the reaction. Although not bound by any theory, in this reaction, as shown in the following formula (3), the hydroxyl group at the 6-position also reacts with xylan (or the hydrolysis product xylose of xylan, not shown in formula (3)), generating branched cellooligosaccharides in which xylan residues (or xylose residues) are bound to the cellulose skeleton. As described above, it can be presumed that the branched cellooligosaccharides bound with xylan residues or xylose residues have further higher solubility in water.

[0102]

[0103] (In formula (3), m, n, x, and y represent the degree of polymerization.)

[0104] Although the details are not clear, it can be presumed that in a method for producing a composition containing cellooligosaccharides according to one embodiment, as described above, since partially branched cellooligosaccharides bound with xylan residues or xylose residues are generated, the solubility in water is improved, turbidity generation in the cellooligosaccharide aqueous solution can be suppressed, and the storage stability is improved.

[0105] The number-average molecular weight of the xylo-oligosaccharide produced by the production method of the xylo-oligosaccharide-containing composition according to one embodiment is preferably from 340 to 1640, more preferably from 420 to 1320, still more preferably from 500 to 990. The number-average molecular weight of the xylo-oligosaccharide is determined by the method described in the examples below. In addition, when the xylo-oligosaccharide contains a xylose unit, the number-average molecular weight of the xylo-oligosaccharide is the molecular weight including the xylose unit as well.

[0106] With respect to the total polymerization bonds of the xylo-oligosaccharide produced by the production method of the xylo-oligosaccharide-containing composition according to one embodiment, the proportion of the α-1,6-glycosidic bond (hereinafter, sometimes referred to as the "degree of branching" of the xylo-oligosaccharide) is preferably from 1 to 50%, more preferably from 3 to 40%, still more preferably from 5 to 30%, and particularly preferably from 5 to 20%. The "polymerization bond" in the xylo-oligosaccharide refers to the bond that links monosaccharides to form an oligosaccharide, and is typically a glycosidic bond. The degree of branching is determined based on the area ratio of the NMR spectrum by the method described in the examples below. Note that the degree of branching is a value including the proportion of the α-1,6-glycosidic bond that binds to a xylan residue or a xylose residue as shown in the above formula (3).

[0107]

Examples

[0108] Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0109] <1. Raw material analysis>

[0110] The polysaccharide used as a raw material was hydrolyzed to the monosaccharide unit by the following method, and the composition of the raw material was analyzed.

[0111] 100 mg of the polysaccharide and 1 mL of a 72 mass% sulfuric acid aqueous solution were mixed and stirred at 30°C for 1 hour. Then, 28 mL of water was added to the mixture, and after stirring at 120°C for 1 hour, it was cooled and filtered. By analyzing the obtained filtrate by HPLC, the glucose content and the xylose content in the filtrate were obtained.

[0112] [HPLC analysis conditions]

[0113] Column: 3 columns of Shodex (registered trademark) GF-210 (manufactured by Showa Denko K.K.)

[0114] Eluent: 0.2 M acetic acid aqueous solution

[0115] Column temperature: 40°C

[0116] Eluent flow rate: 0.6 mL / min

[0117] Detector: Differential refractive index detector

[0118] Based on the glucose content and xylose content obtained by HPLC analysis, the composition of the polysaccharide used as a raw material was determined. In addition, it was assumed that xylan was composed only of xylose. The results are as follows.

[0119] · Cellulose Arbocel B600 (produced by Rettenmaier & Söhne): 80% by mass of cellulose, 20% by mass of xylan

[0120] · Avicel (crystalline microfine cellulose produced by Merck): 99% by mass of cellulose, 1% by mass of xylan

[0121] · Xylan (produced by Sigma-Aldrich, xylan from the epidermis layer material (oak wood)): 100% by mass of xylan

[0122] <2. Production of Oligosaccharides>

[0123] [Example 1] Production of a composition containing cellooligosaccharides using cellulose (Arbocel) as a raw material by an acid catalyst method

[0124] Cellulose Arbocel B600 (produced by Rettenmaier & Söhne) was used as the raw material mixture.

[0125] 3.79 kg of the above raw material mixture (water content 3.4% by mass, dry mass 3.66 kg, xylan content: 20%) was mixed with 0.53 kg of an 85% aqueous phosphoric acid solution (special grade reagent produced by Fujifilm Wako Pure Chemical Corporation) using a Henschel mixer (equipment name: FM 20C / I, produced by Nippon Coke & Engineering Co., Ltd.). The mass ratio of the cellulose·xylan mixture to the acid catalyst was: (cellulose·xylan mixture) / (acid catalyst) = 8.1. The mixing conditions were a rotation speed of 1400 rpm and aeration of 0.4 m 3 / hour.

[0126] 350 g of this mixture was transferred to a vibration mill (equipment name: MB-1 type, produced by Chuo Kakoki Co., Ltd.) and pulverized at 75°C for 72 hours while undergoing hydrolysis. The pulverization conditions were a total amplitude of 8 mm, a rotation speed of 1000 rpm, and carbon steel balls of φ3 / 4 inches were used.

[0127] The pulverized material was taken out of the vibration mill and separated from the balls, and 300 g of the pulverized material was transferred to a dissolving device (5 L container). 2817 g of ion-exchanged water was added, and it was stirred at 25°C for 1 hour using a Three One Motor (registered trademark) stirrer. Thereby, the water-soluble components were dissolved to obtain an extract of the hydrolyzate.

[0128] 61 g of a 48% aqueous potassium hydroxide solution was added to the extract, and the mixture was stirred at 25 °C for 1 hour using a Three One Motor blender. 122 g of perlite #31 (manufactured by Showa Chemical Industry Co., Ltd.) was added as a filter aid, and the mixture was filtered using a pressure filter (KST-293-20, manufactured by Advantech Toyo Co., Ltd.) to obtain 2533 g of a filtrate.

[0129] The pH of the filtrate was 6.8. Sulfuric acid hydrolysis was carried out in the same manner as the raw material analysis, and the resulting monomers were analyzed by HPLC. As a result, 167 g of cellulose hydrolyzate and 42 g of xylan hydrolyzate were contained.

[0130] The obtained filtrate was diluted with water so that the sugar concentration (total concentration of cellulose hydrolyzate and xylan hydrolyzate) was 5% by mass, and used as a sample solution in the turbidity measurement described later.

[0131] The number average molecular weight and degree of branching of the hydrolyzate in the filtrate were determined by the following method. In addition, the measurement was carried out without separating the xylan hydrolyzate contained in the filtrate.

[0132] [Analysis method for number average molecular weight]

[0133] The number average molecular weight was obtained by GPC (gel permeation chromatography) analysis using an HPLC (high performance liquid chromatography) apparatus.

[0134] Each standard sample prepared under the conditions shown in Table 1 was irradiated with ultrasonic waves for 5 minutes. After the dispersed and dissolved standard sample was left overnight, it was filtered using a 0.45 μm PTFE membrane filter (model 25HP045AN, manufactured by Advantech Toyo Co., Ltd.) to prepare a standard sample. "Standard 1" and "Standard 2" were used in the analysis of cellooligosaccharides. In Table 1, "Mp" represents the peak molecular weight.

[0135] The analysis sample was prepared by diluting the filtrate at a ratio of 0.10 g in 1 g of water.

[0136] Table 1

[0137]

[0138] As an analysis device, GPC-LS (manufactured by Agilent, 1260 Infinity) was used, and the measurement was carried out under the following analysis conditions to obtain the number average molecular weight of all peaks of each analysis sample.

[0139] (Analysis conditions)

[0140] Column: Shodex (registered trademark) SB-G 6B (guard column) + SB802.5H

[0141] Q (Analysis column) × 3 pieces

[0142] Column temperature: 40 °C

[0143] Eluent: 30 v / v% acetonitrile + 70 v / v% water 0.2 M acetic acid aqueous solution

[0144] Flow rate: 0.5 mL / min

[0145] Injection volume: 20 μL

[0146] Detector: Differential refractometer (RI)

[0147] [Analysis method of degree of branching]

[0148] The degree of branching is determined using an NMR (nuclear magnetic resonance) apparatus under the conditions shown below.

[0149] (NMR conditions)

[0150] Equipment: Bruker AVANCE 500 (500 MHz)

[0151] Measurement method: 1 1H-NMR, 13 13C-NMR, 13 13C-DEPT135, HSQC

[0152] Locking solvent: D2O

[0153] Internal standard: TSP-d4 (sodium trimethylsilylpropionate) = 0 ppm

[0154] Temperature: Room temperature

[0155] Sample preparation: Powder sample (50 mg) / D2O (1 mL) + TSP-d4 (5 mg)

[0156] The filtrate is pre-dried to a powder sample under vacuum, and the measurement sample is prepared by the following method. Weigh 50 mg of the powder sample accurately, add 1 mL of D2O to a 50 mL sample bottle to dissolve it, vibrate it with an ultrasonic cleaner for 5 minutes, dry it with a vacuum dryer (30 °C), weigh it accurately again, and calculate the water loss. Add TSP-d4 (5 mg) and D2O (1 mL) again, vibrate it with an ultrasonic cleaner for 5 minutes, filter it with a 0.45 μm filter (model: 25HP045AN, manufactured by Advantec Toyo Co., Ltd.), put the filtrate into a 5 mmφ NMR sample tube, and perform NMR measurement immediately after sampling.

[0157] The degree of branching is calculated by the following formula based on the area ratio of the spectrum of α-1,6-H1" detected at 4.9 - 5.0 ppm and the spectrum of "β-1,4-H1" detected at 4.4 - 4.6 ppm.

[0158] Degree of branching = (α-1,6-H1) ÷ [(α-1,6-H1) + (β-1,4-H1)] × 100 (%)

[0159] The number average molecular weight of the hydrolyzate produced in Example 1 was 800 (the number average degree of polymerization in terms of glucose units was 4.8), and the degree of branching was 14%. Figure 1 The 1 H-NMR spectrum of the hydrolyzate produced in Example 1 is shown.

[0160] [Example 2] Production of a cellooligosaccharide-containing composition from cellulose (Avicel) and xylan by an acid catalyst method

[0161] Except for using 3.02 kg of Avicel (crystalline fine powder cellulose produced by Merck & Co., Inc., moisture content 3.1% by mass, dry mass 2.93 kg) and 0.81 kg of xylan (xylan produced by Sigma-Aldrich, from the epidermal layer material, moisture content 9.8% by mass, dry mass 0.73 kg) as the raw material mixture (xylan content: 21% by mass), the hydrolysis reaction, extraction of the hydrolyzate, and filtration of the extract were carried out in the same manner as in Example 1 to obtain a filtrate. The mass ratio of the cellulose·xylan mixture to the acid catalyst was: (cellulose·xylan mixture) / (acid catalyst) = 8.1.

[0162] The pH of the filtrate was 6.8. Sulfuric acid hydrolysis was carried out in the same manner as for the raw material analysis, and the resulting monomers were analyzed by HPLC. As a result, 166 g of cellulose hydrolyzate and 42 g of xylan hydrolyzate were contained.

[0163] The obtained filtrate was diluted with water to make the sugar concentration (total concentration of cellulose hydrolyzate and xylan hydrolyzate) 5% by mass, and used as the sample solution in the turbidity measurement described below.

[0164] The number average molecular weight and degree of branching of the hydrolyzate in the filtrate were determined by the method described in Example 1. As a result, the number average molecular weight was 780 (the number average degree of polymerization in terms of glucose units was 4.7), and the degree of branching was 18%. Figure 2 The 1 H-NMR spectrum of the hydrolyzate produced in Example 2 is shown.

[0165] [Comparative Example 1] Production of a cellooligosaccharide-containing composition from cellulose (Avicel) by an acid catalyst method

[0166] In addition to using 3.91 kg of Avicel (crystalline microfine cellulose produced by Merck & Co., Inc., water content 3.1%, dry mass 3.79 kg) as the raw material, the hydrolysis reaction, extraction of the hydrolyzate, and filtration of the extract were carried out in the same manner as in Example 1 to obtain a filtrate. The mass ratio of the cellulose·xylan mixture to the acid catalyst was: (cellulose·xylan mixture) / (acid catalyst) = 8.4.

[0167] The pH of the filtrate was 6.8. Sulfuric acid hydrolysis was carried out by the same method as the analysis of the raw material, and the resulting monomers were analyzed by HPLC. As a result, 207 g of cellulose hydrolyzate was contained. The obtained filtrate was diluted with water to make the sugar concentration (concentration of cellulose hydrolyzate) 5% by mass, which was used as the sample solution in the turbidity measurement described below.

[0168] The number-average molecular weight and degree of branching of the hydrolyzate in the filtrate were determined by the method described in Example 1. As a result, the number-average molecular weight was 810 (the number-average degree of polymerization in terms of glucose units was 4.9), and the degree of branching was 12%. Figure 3 The 1 1H-NMR spectrum of the hydrolyzate produced in Comparative Example 1 is shown.

[0169] [Comparative Example 2] Production of a composition containing cellooligosaccharides by a carbon catalyst method using cellulose (Avicel) as a raw material

[0170] 10 g of Avicel (crystalline microfine cellulose produced by Merck & Co., Inc.) and 1.5 g of activated carbon BA50 (produced by Ajinomoto Fine-Techno Co., Inc.) were placed together with 2000 g of alumina balls with a diameter of 1.5 cm in a ceramic jar mill with a capacity of 3600 mL, and set on a bench-top jar mill rotary table (produced by Nippon Tokushu Tougyo Co., Ltd., bench-top pot mill, model ANZ-51S). After treatment at 60 rpm for 48 hours, a reaction raw material was obtained. In addition, the temperature started at room temperature, and the temperature rise caused by shear heating was left as it was.

[0171] Next, 0.374 g of the reaction raw material and 40 mL of water were placed in a high-pressure reactor (internal volume 100 mL, autoclave produced by OMR Labo Tech Co., Ltd., made of Hastelloy C22). While stirring at 600 rpm, the reaction temperature was heated to 230 °C at a rate of 10 - 30 °C / min (average heating rate 11.3 °C / min), and then the heating was immediately stopped. The reactor was air-cooled at a rate of 10 - 30 °C / min (average cooling rate 16.7 °C / min) to prepare a reaction solution.

[0172] Next, the supernatant recovered from the reaction solution by a centrifugal separation device was freeze-dried to obtain a fiber oligosaccharide powder. The obtained powder was dissolved in water to make the sugar concentration (concentration of cellulose hydrolyzate) 5% by mass, which was used as the sample solution in the turbidity measurement described below.

[0173] The number average molecular weight and degree of branching of the hydrolyzate were obtained by the method described in Example 1. As a result, the number average molecular weight was 780 (the number average degree of polymerization in terms of glucose units was 4.7), and the degree of branching was 0%. Figure 4 The hydrolyzate produced in Comparative Example 2 is shown 1 1H-NMR spectrum.

[0174] <3. Observation of turbidity and measurement of turbidity>

[0175] For each sample solution obtained in Examples 1 to 2 and Comparative Examples 1 to 2, the presence or absence of turbidity was observed and the turbidity was measured when it was prepared and after 7 days of storage. The results are shown in Table 2.

[0176] The sample solution was stored by filling 40 mL of the sample solution into a 50 mL glass screw-top bottle container and allowing it to stand in a constant temperature bath set at 30°C.

[0177] The turbidity was measured using the following method. A well-dispersed sample solution (Sample 1) and a sample solution obtained by filtering Sample 1 through a 0.45 μm membrane (Sample 2) were prepared. Each sample was placed in a 1 cm square cell, and the absorbance at a wavelength of 660 nm was measured. Based on the measured absorbance, the turbidity was calculated using the following formula.

[0178] Turbidity = (Absorbance of Sample 1) - (Absorbance of Sample 2)

[0179] Table 2

[0180]

[0181] From the results in Table 2, it can be seen that in Examples 1 and 2 using a cellulose·xylan mixture containing xylan in a specified ratio as the raw material, the sample solution did not become turbid even after 7 days of storage, and the storage stability was excellent. On the other hand, Comparative Example 1 using cellulose containing almost no xylan as the raw material became turbid after 7 days of storage, and Comparative Example 2 was already turbid when it was just prepared.

[0182] Industrial applicability

[0183] By the method for producing a composition containing fiber oligosaccharide of the present invention, a composition containing fiber oligosaccharide having excellent storage stability can be produced even when the degree of polymerization is relatively high.

Claims

1. A method for producing a composition containing xylooligosaccharides, comprising a step of hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, wherein the raw material mixture contains 10 to 30% by mass of the xylan based on 100% by mass of the total content of the cellulose and the xylan, and the acid catalyst is phosphoric acid or a partially neutralized salt thereof.

2. The method for producing a composition containing xylooligosaccharides according to claim 1, wherein the acid catalyst is phosphoric acid.

3. The method for producing a composition containing xylooligosaccharides according to claim 1 or 2, comprising a step of hydrolyzing by subjecting the raw material mixture to a pulverization treatment in the presence of the acid catalyst.

4. The method for producing a composition containing xylooligosaccharides according to claim 3, wherein the pulverization treatment is carried out by using a planetary ball mill or a vibration mill.

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