CN115109102A - Method for producing cellooligosaccharide-containing composition and cellooligosaccharide-containing composition - Google Patents

Abstract

The present invention addresses the problem of providing a method for producing a cellooligosaccharide-containing composition having excellent storage stability. The method for producing a cellooligosaccharide-containing composition comprises 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 mass% of xylan relative to 100 mass% of the total content of cellulose and xylan.

Description

Method for producing cellooligosaccharide-containing composition and cellooligosaccharide-containing composition

Technical Field

The present invention relates to a method for producing a cellooligosaccharide-containing composition and a cellooligosaccharide-containing composition.

Background

Cellooligosaccharide is an oligosaccharide in which glucose is bound together by β -1, 4 linkage, and in recent years, it has been found that it has functions such as moisture retention, stickiness inhibition, cooling sensation imparting, starch aging reduction, protein denaturation inhibition, and the like, and is expected to be applied to the fields of medicines, cosmetics, foods, feeds, and the like.

Particularly, cellooligosaccharides having a degree of polymerization of glucose of 3 or more are expected to have increased functionality and new functionalities.

Cellooligosaccharides that are industrially used at present are produced by an enzymatic reaction, and glucose and cellobiose as a dimer are main components (patent document 1).

As techniques for producing cellooligosaccharides other than the enzymatic method, a hydrothermal treatment method (patent documents 2 to 4) and a hydrothermal treatment method using oxidized water containing hypochlorous acid (patent document 5) are known. In either patent document, cellooligosaccharides are considered as an intermediate product in the process of breaking down cellulose into glucose.

Further, a method of mixing and pulverizing a carbon catalyst and cellulose and then hydrolyzing the mixture by a hydrothermal synthesis method is known, and a method of producing cellooligosaccharide which contains glucose and has a polymerization degree of up to 6 has been disclosed (patent document 6).

A method of partially hydrolyzing cellulose by a Semi-Dry Conversion method (Semi-Dry Conversion) using a phosphoric acid catalyst is known (non-patent document 1). The method has relatively high selectivity, and can obtain cellooligosaccharide with polymerization degree of 7 or above.

However, the methods described in patent documents 1 to 5 have a low efficiency as a method for obtaining cellooligosaccharide, because the hydrolysis reaction proceeds excessively to glucose. The method described in patent document 6 is inefficient as a method for obtaining cellooligosaccharide having a relatively high degree of polymerization, because the hydrolysis reaction proceeds to glucose if the conversion of cellulose is to be increased, and temperature control or the like is required to be very precise in order to increase the yield of cellooligosaccharide.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open No. 2009-189293

[ patent document 2] Japanese patent application laid-open No. 2011-

[ patent document 3] International publication No. 2011/036955

[ patent document 4] International publication No. 2012/128055

[ patent document 5] Japanese patent application laid-open No. 2006 and 320261

[ patent document 6] International publication No. 2017/104687

[ non-patent literature ]

[ non-patent document 1] Bull. chem. Soc. Jpn.2020, 93, 273-278

Disclosure of Invention

[ problem to be solved by the invention ]

On the other hand, as a method for obtaining cellooligosaccharide having a relatively high degree of polymerization (for example, the method described in non-patent document 1), the obtained cellooligosaccharide has a disadvantage of insufficient solubility in water, easy precipitation during long-term storage, and poor storage stability.

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

[ means for solving the problems ] to solve the problems

The present inventors have conducted extensive studies to solve the above problems, and as a result, have conceived that hydrolysis is carried out in the presence of an acid catalyst using cellulose containing xylan in a predetermined ratio as a raw material.

As a result, they have found a method for producing a cellooligosaccharide-containing composition, which can solve the above problems by hydrolyzing a mixture containing cellulose and xylan, wherein the xylan content is 5 to 50 mass% relative to 100 mass% of the total content of the cellulose and xylan, in the presence of an acid catalyst.

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

[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, the raw material mixture containing 5 to 50 mass% of the xylan relative to 100 mass% of the total content of the cellulose and the xylan.

[2] The method for producing a cellooligosaccharide-containing composition according to [1], wherein the raw material mixture contains 7 to 40 mass% of the xylan relative to 100 mass% of the total content of the cellulose and the xylan.

[3] The method for producing a cellooligosaccharide-containing composition according to [1] or [2], wherein the acid catalyst is at least one acid selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, perchloric acid, nitric acid, nitrous acid and phosphoric acid, or a partially neutralized salt thereof.

[4] The method for producing a cellooligosaccharide-containing composition according to [3], wherein the acid catalyst is phosphoric acid or a partially neutralized salt thereof.

[5] The method for producing a cellooligosaccharide-containing composition according to [4], wherein the acid catalyst is phosphoric acid.

[6] The process for producing a cellooligosaccharide-containing composition according to any one of [1] to [5], which comprises a step of subjecting the raw material mixture to pulverization treatment in the presence of the acid catalyst to hydrolyze the raw material mixture.

[7] The process for producing a cellooligosaccharide-containing composition according to [6], wherein the pulverization treatment is carried out by using a planetary ball mill or a vibration mill.

[8] A cellooligosaccharide-containing composition produced by hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, the xylan content in the raw material mixture being 5 to 50 mass% relative to 100 mass% of the total content of the cellulose and xylan.

[ Effect of the invention ]

According to the method for producing a cellooligosaccharide-containing composition of the present invention, a cellooligosaccharide-containing composition having excellent storage stability can be produced even when the degree of polymerization is relatively high (the degree of polymerization is 3 to 6).

Drawings

FIG. 1 shows a hydrolysate produced in example 1 ¹ H-NMR chart.

FIG. 2 shows a hydrolysate produced in example 2 ¹ H-NMR chart.

FIG. 3 shows a hydrolysate produced in comparative example 1 ¹ H-NMR chart.

FIG. 4 shows a hydrolysate produced in comparative example 2 ¹ H-NMR chart.

Detailed Description

Embodiments of the present invention will be described below. The embodiments described below are merely representative examples of the present invention and are not intended to limit the present invention.

A method for producing a cellooligosaccharide-containing composition according to one embodiment includes a step of hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, the raw material mixture containing the xylan in an amount of 5 to 50% by mass relative to 100% by mass of the total content of the cellulose and the xylan.

< mixture of raw materials >

In one embodiment, a method for producing a cellooligosaccharide-containing composition uses a raw material mixture containing cellulose and xylan (hereinafter, sometimes referred to as a "cellulose-xylan mixture") as a raw material.

Cellulose and xylan are referred to as biomass, not fossil resources, but organic resources of plant origin.

Examples of the cellulosic biomass include woody biomass such as cotton, woody pulp, kenaf, hemp, small-diameter wood, intermediate cut wood, sawdust, wood chips, waste paper, newspaper, wrapping paper, paper towel, toilet paper, and corrugated paper; and herbaceous biomass such as bagasse, switchgrass, elephant grass, corn cob, straw, wheat straw, etc., which may be used alone or in combination of two or more. For example, water-insoluble cellulose obtained by bleaching these biomasses with chlorine to produce chemical pulp (holocellulose) and subjecting the chemical pulp to alkali treatment to remove hemicellulose can be used.

Cellulose generally exhibits crystallinity by two or more cellulose molecules bonded together through hydrogen bonds. In one embodiment, cellulose having such crystallinity may be used as a raw material. In this embodiment, in order to increase the hydrolysis ratio, it is preferable to perform treatment for reducing crystallinity such as preliminary crushing to reduce crystallinity and then reuse the product. The cellulose having reduced crystallinity may have its crystallinity partially reduced or substantially or completely disappeared. The method of the crystallinity-reducing treatment is not particularly limited, but the crystallinity-reducing treatment is preferably a treatment capable of cleaving the above-mentioned hydrogen bond to produce cellulose molecules having at least one chain partially. By using cellulose containing at least a part of cellulose molecules having one chain as a raw material, the hydrolysis efficiency can be greatly improved.

Examples of the crystallinity-reducing treatment of the raw material cellulose include: as a method of physically cleaving hydrogen bonds between cellulose molecules to obtain a single-stranded cellulose molecule (see Zhao et al, Energy & Fuels, 20, 807(2006)) such as a ball milling method for preliminary disintegration, and a method of chemically cleaving hydrogen bonds between cellulose molecules by a phosphoric acid treatment or the like without applying a compressive shear stress to obtain a single-stranded cellulose (see Zhang et al, Biomacromolecules, 7, 644 (2006)). The treatment for reducing the crystallinity of the cellulose may be performed not until the crystallinity of the cellulose completely disappears, or may be performed by partially reducing the crystallinity of the cellulose before the treatment. By using cellulose subjected to these treatments as a raw material, the hydrolysis efficiency can be greatly improved.

Examples of the crystallinity-reducing treatment of the raw material cellulose include hot water treatment under pressure (see Hayashi et al, j.jpn.inst.energy, 83, 805(2004), Sasaki et al, ind.eng.chem.res, 39, 2883(2000), and the like).

Xylan refers to a polysaccharide in which D-xylose residues are bound to beta-1, 4 or beta-1, 3. The sugar constituting xylan may contain arabinose, glucuronic acid, 4-0-methylglucuronic acid, glucose, galactose, and the like, in addition to xylose.

The xylan is preferably subjected to compressive shear stress prior to hydrolysis to be preliminarily subjected to preliminary disintegration. In order to apply a compressive shear stress to the xylan to be disintegrated, a compressive shear type disintegrator may be used. The compression-shear type disintegrator is a device capable of applying both compressive stress and shear stress, and examples thereof include a vibration rod mill (rodmill), a vibration ball mill, and the like. Among them, from the viewpoint of production efficiency, a vibration rod mill is preferable. The rod is not particularly limited, but is preferably 0.1 to 100mm in outer diameter, 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 section of the vibration mill) varies depending on the type of the machine, but is preferably 10 to 97%, more preferably 15 to 95%.

The crushing conditions such as the crushing time and the number of rotations of the crusher can be set as appropriate to form a desired crushed product. From the viewpoint of obtaining a high hydrolysis rate, it is preferable that the crystallinity in the xylan crumble is low.

The xylan can be coarsely comminuted beforehand before being comminuted beforehand by compressive shear stress. The method of rough pulverization is not particularly limited, and for example, a cutter type pulverizer such as a grinding and roll cutter (グラインダー and ロールカッター), an impact type pulverizer such as a hammer mill (ハンマーミル), a pulverization type pulverizer such as a colloid mill (コロイドミル), or the like can be used as the pulverizer.

In the cellulose-xylan mixture, the content of xylan is 5 to 50 mass% relative to 100 mass% of the total content of cellulose and xylan. By containing xylan in an amount of 5 mass% or more, the solubility of the hydrolysate in water can be improved, and a cellooligosaccharide-containing composition having excellent storage stability can be produced. If the content of xylan is less than 50 mass%, a cellooligosaccharide-containing composition as a target can be obtained in a sufficient yield. In the mixture of cellulose and xylan, the content of xylan is preferably 7 to 40% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass, with respect to 100% by mass of the total content of cellulose and xylan.

The content of xylan in the cellulose-xylan mixture is determined by the method described in the examples described later. Specifically, the mixture used as the raw material is hydrolyzed to monosaccharide units by an aqueous sulfuric acid solution or the like, and the glucose content and xylose content in the product are analyzed, whereby the amount of xylan content relative to the total content of cellulose and xylan of 100 mass% in the mixture used as the raw material is determined. However, it is assumed here that xylan consists only of xylose.

The cellulose-xylan mixture may contain other components (e.g., other polysaccharides) in addition to cellulose and xylan. The amount of the other component is preferably 10% by mass or less, more preferably 5% by mass or less, based on 100% by mass of the mixture.

The cellulose and xylan contained in the cellulose-xylan mixture may be mixed before being charged into the hydrolysis reactor, or may be mixed in the hydrolysis reactor. As the cellulose-xylan mixture, a commercial product containing cellulose and xylan can be purchased and used. For example, cellulose produced from a cellulosic biomass containing, as a raw material, a xylose skeleton in addition to a glucose skeleton may not be completely removed and xylan may be mixed in the cellulose. As long as the xylan content relative to cellulose and xylan content of 100 mass% is 5 ~ 50 mass%, can use this kind of commercially available cellulose as cellulose xylan mixture.

< hydrolysis reaction >

In one embodiment, a method for producing a cellooligosaccharide-containing composition includes hydrolyzing a cellulose-xylan mixture in the presence of an acid catalyst to produce cellooligosaccharides.

Known acids known in the past can be used as the acid catalyst. 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 may be used. Examples of the partially neutralized salt of the acid include monopotassium phosphate, monoammonium phosphate, and potassium hydrogen sulfate. The acid catalyst is preferably phosphoric acid or a partially neutralized salt thereof, more preferably phosphoric acid.

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) in an amount of 2 to 100, more preferably: (cellulose-xylan mixture)/(acid catalyst) in an amount of 4 to 20, and more preferably: (cellulose-xylan mixture)/(acid catalyst) in an amount of 5 to 12. When the mass ratio of the cellulose-xylan mixture to the acid catalyst is 100 or less, hydrolysis proceeds at a rate that causes no problem in practical use. When the mass ratio of the cellulose/xylan mixture to the acid catalyst is 2 or more, side reactions such as dehydration and carbon-carbon bond cleavage can be suppressed during hydrolysis.

The mass of the cellulose-xylan mixture in the present disclosure is a net mass (dry mass) obtained by removing water contained in the raw material. In general, cellulose and xylan contain physically adsorbed water, and therefore the amount of water adhering to these components is analyzed, and the mass ratio of the cellulose-xylan mixture to the acid catalyst is determined from the mass of the cellulose-xylan mixture after removal of the water. The method of analyzing the amount of adhering moisture includes a quantitative method in which a cellulose/xylan mixture used as a raw material is dried in a constant temperature dryer at 100 to 150 ℃ until no mass reduction occurs. In order to prevent the influence of side reactions such as dehydration reaction during drying, it is preferable to dry and quantify the product at a relatively low temperature using a vacuum dryer. The mass of the acid catalyst is also the mass of the real acid catalyst (dry mass).

As described above, the cellulose-xylan mixture before hydrolysis has a physically adsorbed water content of about 1 to 12 mass%. In addition, acid catalysts such as hydrochloric acid and phosphoric acid generally contain moisture in a commercially available form. Therefore, even if water is not added, hydrolysis can be performed by utilizing moisture physically adsorbed in the cellulose-xylan mixture and moisture contained in the acid catalyst. In general, although the amount of water is often sufficient even if water is not added, water may be added to a cellulose/xylan mixture having high dryness for hydrolysis.

The cellulose-xylan mixture contains physically adsorbed water in an amount of about 1 to 12 mass% in both cases where no water is added and where water is added. 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, based on the amount of water physically adsorbed in the cellulose-xylan mixture and the amount of water contained in the acid catalyst (including the amount of water in the case of further adding water). If the amount is 15 parts by mass or less, not only a sufficient hydrolysis rate can be obtained, but also the trouble of handling due to fixation to the apparatus or the like can be prevented. In addition, if the amount is more than 0.1 parts by mass, side reactions such as dehydration reaction can be suppressed.

In the method for producing a cellooligosaccharide-containing composition according to one embodiment, a method (mechanochemical method) of hydrolyzing a cellulose-xylan mixture by applying a mechanical external force by pulverization treatment is preferably used.

Examples of the pulverizing device used for the pulverization treatment include a rotary ball mill such as a pot mill, a tube mill, and a cone mill, a vortex jet mill, an impact jet mill, a fluidized bed jet mill, and a wet jet mill, a shear mill such as a mill mixer and an angle mill, a colloid mill such as a mortar and a mortar, an impact mill such as a hammer mill, a cage mill, a pin mill, a pulverizer, a screen mill, a turbine mill, and a centrifugal separator mill, and a vibration mill in which a drum is vibrated to move a medium inside and pulverize the medium; a stirring mill for placing the medium and the raw materials into a tank body with stirring blades and crushing the medium and the raw materials by rotating the medium and the raw materials; and a planetary ball mill using rotation and revolution motions.

The pulverizing device is preferably a ball mill, a vibration mill or a stirring mill, and is capable of applying a compressive force to the cellulose-xylan mixture and a tensile stress in both directions of the main chain. The pulverizing 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.

At the laboratory level, preference is given to using a planetary ball mill. The vibration mill is good for industrial use. The vibration mill is capable of pulverizing in a time period of about 1/10 to 1/20 compared to a roller rotary ball mill by vibrating a drum (pulverizing drum) into which a pulverizing medium is inserted, instead of rotating the drum. The stirring mill can pulverize the medium in a time period of about 1/10 to 1/20 compared to a roller rotary ball mill by moving the medium by rotating the stirring blade, not by rotating the drum.

The pulverization treatment may be performed continuously or intermittently. In order to suppress the temperature rise of the object to be treated accompanying the pulverization treatment, the pulverization treatment is preferably performed intermittently. In the case of the intermittent pulverization treatment, the optimum value varies greatly depending on the pulverization apparatus, and for example, in the case of a planetary ball mill, the pulverization treatment is repeated by repeating such a cycle with a rest time of 5 to 15 minutes interposed therebetween every 5 to 15 minutes. When the pulverization treatment is continuously performed, it is preferable to perform the pulverization treatment while maintaining an appropriate temperature by cooling the pulverization apparatus by providing a jacket or the like.

When the cellulose/xylan mixture is hydrolyzed using a pulverizing apparatus such as a ball mill, the cellulose or xylan may be hydrolyzed while reducing its crystallinity by pulverization treatment, or the cellulose or xylan may be subjected to treatment for reducing its crystallinity in advance as described above and then hydrolyzed by adding an acid catalyst. When cellulose or xylan is preliminarily disintegrated by a henschel mixer and then subjected to pulverization treatment by a ball mill or the like, the acid catalyst may be mixed from the preliminary disintegration stage.

In the method for producing a cellooligosaccharide-containing composition according to one embodiment, hydrolysis is performed without pulverization, and examples of the method without pulverization include a method in which kneading is performed using a pressure kneader, and a method in which reaction is performed using an extruder after kneading using a kneader.

The hydrolysis temperature is preferably from room temperature to 110 ℃, more preferably from 50 ℃ to 100 ℃. If the temperature is not lower than the normal temperature, the decomposition does not progress slowly, and the time required for decomposition does not excessively extend. The hydrolysis may also be carried out at high temperature in order to accelerate the decomposition rate. If the hydrolysis temperature is 110 ℃ or lower, side reactions such as dehydration reaction can be suppressed. Since shear heat generation may be large depending on the reaction apparatus, it is preferable to control the hydrolysis temperature by repeating the cycle with a rest time therebetween or by introducing cooling water into the jacket of the reaction apparatus as described above.

The time for hydrolysis depends on the reaction apparatus used, but is usually preferably 2 to 150 hours, more preferably 5 to 80 hours, still more preferably 10 to 60 hours, and particularly preferably 15 to 40 hours. When the hydrolysis time is 2 hours or more, the decomposition of the cellulose-xylan mixture can be promoted. If the hydrolysis time is 150 hours or less, the hydrolysate can be obtained more efficiently. In the present disclosure, when the pulverization treatment is performed intermittently in the case of hydrolysis by the pulverization treatment, the time of hydrolysis means a net pulverization treatment time after a rest time is removed.

The progress of hydrolysis of the cellulose-xylan mixture can be confirmed by collecting a small amount of the treatment object over time and measuring the amount of the water-soluble component contained in the collected object.

< other step >

The method for producing a cellooligosaccharide-containing composition according to one embodiment may include the following steps, if necessary, in addition to the step of performing the hydrolysis reaction described above.

[ extraction procedure ]

The method for producing a cellooligosaccharide-containing composition according to one embodiment may include a step of extracting a water-soluble component by adding water to the reaction product after the hydrolysis reaction. When the amount of water used in the hydrolysis is small, the reaction product is in a solid state, and therefore, it is preferable to perform the extraction step.

The mass ratio of the added amount of water to the reactant is preferably: the ratio of (amount of water added)/(reactant) is 0.5 to 100, preferably 1 to 20, and more preferably 2 to 10. If the mass ratio is 0.5 or more, the soluble component in the reactant can be dissolved efficiently, and if the mass ratio is 100 or less, the vessel for dissolution is not excessively large, and therefore the efficiency is good.

The water to be added to the reactant is not particularly limited, but distilled water is usually used. In addition to distilled water, a salt-containing solution, a buffer, or the like may be used. An organic solvent miscible with water may also be added within a range not affecting the dissolution of soluble components in the reactants.

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

In order to obtain high purity cellooligosaccharide, the following purification operations may be performed: after removing solid components from the reaction product, cellooligosaccharide is reprecipitated by adding ethanol or the like to an aqueous solution containing water-soluble components, the obtained precipitate is dissolved in water again, and ethanol reprecipitation or the like is repeated.

[ neutralization step ]

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

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

The basic compound is preferably at least one selected from potassium salts, phosphate salts, ammonium salts, and ammonia.

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, or the like can be used. Among them, potassium hydroxide, potassium carbonate, monopotassium phosphate and tripotassium phosphate are preferable.

When a phosphate is used as the basic compound, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, diammonium phosphate, triammonium phosphate, and the like can be used. Thus, the phosphate may be both potassium or ammonium.

When an ammonium salt is used as the alkaline compound, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium carbonate, diammonium hydrogen phosphate, triammonium phosphate, ammonium nitrate, ammonium sulfate, or the like can be used. Among them, diammonium hydrogen phosphate and ammonium sulfate are preferable.

When ammonia is used as the basic compound, aqueous ammonia is preferably used.

The temperature of the neutralization reaction is preferably 0 to 50 ℃, more preferably 5 to 40 ℃, and still more preferably 20 to 30 ℃ in order to prevent the product of the hydrolysis reaction from excessively proceeding. The rate of the neutralization reaction itself is high, but the acid must be sufficiently diffused when insoluble substances derived from the raw material are present, and therefore the time of the neutralization reaction is preferably 0.1 to 10 hours, more preferably 0.5 to 5 hours, and still more preferably 1 to 3 hours. The neutralization reaction apparatus does not need to be special, and a general agitation tank can be used. When hydrochloric acid or sulfuric acid is used as the acid catalyst, a stirring tank lined with corrosion resistance such as glass is preferably used.

In the case where the neutralization step is carried out, since the precipitation may be caused by changing the pH to the neutral side, it is preferable to separate the solid portion by filtration after the neutralization reaction. In the case of performing filtration after the neutralization reaction, after the water-soluble component is extracted in the above-mentioned extraction step, the operation of separating (filtering off) the water-soluble component and the solid component may be omitted.

The separation of the solid fraction after the neutralization reaction can be carried out by a commonly used method of removing the solid fraction from the suspension. Filtration may be carried out using, for example, a filter paper, a filter cloth, a membrane filter, a pressure filter, a centrifugal filter, a cross-flow filter, or the like, and natural sedimentation or centrifugal sedimentation may also be carried out.

< product of hydrolysis reaction >

As a method for producing a cellooligosaccharide-containing composition by hydrolysis of cellulose, a carbon catalyst method and an acid catalyst method are known.

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, only linear cellooligosaccharides are produced as shown in the following formula (1).

(in the formula (1), m and n represent the degree of polymerization.)

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 represented by the above formula (1), a reaction to produce a branched cellooligosaccharide is also caused as represented by the following formula (2). That is, cellooligosaccharide having a branched skeleton can be produced by reacting the hydroxyl group at the 6-position with cellulose. Such a branched species has a higher solubility for water than the linear species.

(in the formula (2), m, n, x and y represent the degree of polymerization.)

In one embodiment, in the method for producing a cellooligosaccharide-containing composition, a reaction is carried out using a cellulose-xylan mixture containing xylan in a predetermined ratio as a raw material in an acid catalyst method. 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 hydrolysate xylose of xylan, not shown in formula (3)) to produce a branched cellooligosaccharide having xylan residues (or xylose residues) incorporated in the cellulose backbone. As described above, it is presumed that the branched cellooligosaccharide having xylan residues or xylose residues bonded thereto has further increased solubility in water.

(in the formula (3), m, n, x and y represent the degree of polymerization.)

Although the details are not clear, it is presumed that in the method for producing a cellooligosaccharide-containing composition according to one embodiment, since a branched cellooligosaccharide to which a xylan residue or a xylose residue is bonded is partially produced as described above, the solubility in water is improved, the occurrence of turbidity in an aqueous cellooligosaccharide solution can be suppressed, and the storage stability is improved.

The number average molecular weight of the cellooligosaccharide produced by the method for producing a cellooligosaccharide-containing composition according to one embodiment is preferably 340 to 1640, more preferably 420 to 1320, and even more preferably 500 to 990. The number average molecular weight of cellooligosaccharide is determined by the method described in the examples described later. In addition, when a xylose unit is contained in cellooligosaccharide, the number average molecular weight of cellooligosaccharide is a molecular weight also containing a xylose unit.

The proportion of α -1, 6-glycosidic linkages (hereinafter, sometimes referred to as "degree of branching" of cellooligosaccharide) to the total polymeric linkages of cellooligosaccharide produced by the method for producing a cellooligosaccharide-containing composition according to one embodiment is preferably 1 to 50%, more preferably 3 to 40%, even more preferably 5 to 30%, and particularly preferably 5 to 20%. The "polymeric bond" in cellooligosaccharide means a bond that links monosaccharides to form oligosaccharide, and typically means a glycosidic bond. The degree of branching is determined from the area ratio of NMR spectra by the method described in examples described later. Note that the degree of branching is a value containing the proportion of α -1, 6-glycosidic bonds bound to xylan residues or xylose residues as shown in the above formula (3).

[ examples ] A method for producing a compound

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

<1. analysis of raw materials >

The polysaccharides used as the raw materials were hydrolyzed to monosaccharide units by the following method, and the composition of the raw materials was analyzed.

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

[ conditions for HPLC analysis ]

Column: shodex (registered trademark) GF-210 (manufactured by Showa Denko K.K.) 3

Eluent: 0.2M aqueous acetic acid

Column temperature: 40 deg.C

Eluent flow rate: 0.6mL/min

A detector: differential refractive index detector

The composition of the polysaccharide used as the raw material was determined from the glucose content and the xylose content obtained by HPLC analysis. In addition, it is assumed that xylan is composed of xylose only. The results are shown below.

セルロースアーボセル B600(レッテンマイヤー corporation): cellulose 80% by mass and xylan 20% by mass

アビセル (crystalline microfine cellulose manufactured by Merck Co.): 99% by mass of cellulose and 1% by mass of xylan

Xylan (produced by シグマアルドリッチ, xylan from a skin layer material (カバ material)): xylan 100% by mass

<2 > production of oligosaccharide

Example 1 production of a composition containing cellooligosaccharide by an acid catalyst method Using cellulose (アーボセル) as a raw Material

セルロースアーボセル B600 (manufactured by レッテンマイヤー) was used as a raw material mixture.

3.79kg (water content 3.4 mass%, dry mass 3.66kg, xylan content: 20 mass%) of the above raw material mixture was mixed with 0.53kg of 85% phosphoric acid aqueous solution (Fuji フイルム and a specialty reagent produced by photoresin Kagaku K.K.) using a Henschel mixer (device name: FM 20C/I, Japan コークス K. K.K.). The mass ratio of the cellulose-xylan mixture to the acid catalyst is as follows: (cellulose-xylan mixture)/(acid catalyst) ═ 8.1. The mixing conditions were 1400rpm in rotation number and 0.4m in aeration ³ In terms of hours.

350g of the mixture was transferred to a vibration mill (equipment name: MB-1, manufactured by CENTRAL CHEMICAL Co., Ltd.), and the mixture was pulverized at 75 ℃ for 72 hours and hydrolyzed. The crushing conditions were 8mm in total amplitude, 1000rpm in rotation speed, and a carbon steel ball having a diameter of 3/4 inches was used.

The pulverized material was taken out from the vibration mill and separated from the balls, and 300g of the pulverized material was transferred to a dissolving apparatus (5L container). 2817g of ion-exchanged water was added thereto, and the mixture was stirred with a stirrer スリーワンモータ (registered trademark) at 25 ℃ for 1 hour. Thereby dissolving the water-soluble component to obtain the extract of hydrolysate.

61g of a 48% aqueous solution of potassium hydroxide was added to the extract, and the mixture was stirred at 25 ℃ for 1 hour using a stirrer スリーワンモータ. 122g of perlite パーライト #31 (available from Showa chemical industries, Ltd.) was added as a filter aid, and the mixture was filtered by a filter press (available from KST-293-20, アドバンテック, imperial corporation) to obtain 2533g of a filtrate.

The filtrate had a pH of 6.8, and was subjected to sulfuric acid hydrolysis in the same manner as in the analysis of the starting material, and the obtained monomer was subjected to HPLC analysis, whereby 167g of a cellulose hydrolysate and 42g of a xylan hydrolysate were contained.

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

The number average molecular weight and the branching degree of the hydrolysate in the filtrate were determined by the following methods. In addition, the measurement was performed without separating the xylan hydrolysate contained in the filtrate.

[ method of analyzing number average molecular weight ]

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

The respective standard samples prepared under the conditions shown in table 1 were irradiated with ultrasonic waves for 5 minutes, and the dispersed and dissolved standard samples were left overnight and then filtered through a 0.45 μm PTFE membrane filter (model No. 25HP045AN, アドバンテック manufactured by ocean corporation) to prepare standard samples. "Standard 1" and "Standard 2" were used in the analysis of cellooligosaccharides. In Table 1, "Mp" represents the peak molecular weight.

Analytical samples were prepared by diluting the filtrates in 1g of water in a ratio of 0.10g each.

TABLE 1

The number average molecular weight of all peaks of each analysis sample was obtained by performing measurement under the following analysis conditions using GPC-LS (1260 Infinity, manufactured by Agilent Co.).

(analysis conditions)

Column: shodex (registered trademark) SB-G6B (guard column) + SB802.5H

Q (analytical column). times.3

Column temperature: 40 deg.C

Eluent: 30 v/v% acetonitrile +70 v/v% water 0.2M aqueous acetic acid

Flow rate: 0.5mL/min

Injection amount: 20 μ L

A detector: differential Refractometer (RI)

[ method of analyzing the degree of branching ]

The branching degree was determined by using an NMR (nuclear magnetic resonance) apparatus under the following conditions.

(NMR conditions)

Equipment: bruker AVANCE 500(500MHz)

The measuring method comprises the following steps: ¹ H-NMR、 ¹³ C-NMR、 ¹³ C-DEPT135、HSQC

lock field solvent: d ₂ O

Internal standard: TSP-d ₄ (sodium trimethylsilylpropionate) ═ 0ppm

Temperature: at room temperature

Sample preparation: powder sample (50mg)/D ₂ O(1mL)+TSP-d ₄ (5mg)

The filtrate was dried in vacuum to prepare a powder sample in advance, and a measurement sample was prepared by the following method. The powder sample was accurately weighed at 50mg, and 1mL of D was added to a50 mL sample bottle ₂ O was dissolved, and the mixture was shaken for 5 minutes by an ultrasonic washer, dried and solidified by a vacuum drier (30 ℃ C.), accurately weighed again, and the amount of dehydration was calculated. TSP-d was again added ₄ (5mg) and D ₂ O (1mL), was shaken for 5 minutes by an ultrasonic washer, then filtered through a 0.45 μm filter ディスポフィルター (model: 25HP045AN, アドバンテック manufactured by ocean corporation, Bay.) and the filtrate was put into a 5mm φ NMR sample tube and immediately subjected to NMR measurement after sampling.

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 to 5.0ppm and the spectrum of" β -1, 4-H1 "detected at 4.4 to 4.6 ppm.

Degree of branching ═ α -1, 6-H1 ÷ [ (α -1, 6-H1) + (β -1, 4-H1) ]. times.100 (%)

The number average molecular weight of the hydrolysate produced in example 1 was 800 (in glucose units)Calculated number average degree of polymerization of 4.8) and degree of branching of 14%. FIG. 1 shows a hydrolysate produced in example 1 ¹ H-NMR spectrum.

EXAMPLE 2 production of a composition containing cellooligosaccharide by an acid catalyst method Using cellulose (アビセル) and xylan as raw materials

Hydrolysis reaction, extraction of hydrolysate, and filtration of extract were carried out in the same manner as in example 1 except that アビセル (crystalline microfine cellulose manufactured by Merck corporation) 3.02kg (water content: 3.1 mass%, dry mass: 2.93kg) and xylan (xylan from a skin layer material manufactured by シグマアルドリッチ corporation) 0.81kg (water content: 9.8 mass%, dry mass: 0.73kg) were used as a raw material mixture (xylan content: 21 mass%). The mass ratio of the cellulose-xylan mixture to the acid catalyst is as follows: (cellulose-xylan mixture)/(acid catalyst) ═ 8.1.

The filtrate had a pH of 6.8, and was subjected to sulfuric acid hydrolysis in the same manner as in the analysis of the starting material, and HPLC analysis of the obtained monomer showed that 166g of cellulose hydrolysate and 42g of xylan hydrolysate were contained.

The filtrate thus obtained was diluted with water to have a sugar concentration (total concentration of the cellulose hydrolysate and the xylan hydrolysate) of 5 mass%, and the resulting solution was used as a sample solution for turbidity measurement described later.

The number average molecular weight and the branching degree of the hydrolysate in the filtrate were determined by the methods described in example 1. As a result, the number average molecular weight was 780 (number average degree of polymerization in terms of glucose units was 4.7) and the degree of branching was 18%. FIG. 2 shows the hydrolyzate produced in example 2 ¹ H-NMR spectrum.

Comparative example 1 production of a composition containing cellooligosaccharide by an acid catalyst method Using cellulose (アビセル) as a raw Material

Hydrolysis reaction, extraction of hydrolysate, and filtration of extract were carried out in the same manner as in example 1 except that アビセル (crystalline fine powder cellulose manufactured by Merck) was used as a raw material in an amount of 3.91kg (water content: 3.1%, dry mass: 3.79kg), and a filtrate was obtained. The mass ratio of the cellulose-xylan mixture to the acid catalyst is as follows: (cellulose-xylan mixture)/(acid catalyst) ═ 8.4.

The filtrate had a pH of 6.8, and was subjected to sulfuric acid hydrolysis in the same manner as in the analysis of the starting material, and the monomer thus obtained was subjected to HPLC analysis, whereby 207g of a cellulose hydrolysate was contained. The obtained filtrate was diluted with water so that the sugar concentration (concentration of cellulose hydrolysate) became 5 mass%, and the sample solution was used for turbidity measurement described later.

The number average molecular weight and the branching degree of the hydrolysate in the filtrate were determined by the methods 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%. FIG. 3 shows a hydrolysate produced in comparative example 1 ¹ H-NMR spectrum.

Comparative example 2 production of a cellooligosaccharide-containing composition by a carbon catalyst method Using cellulose (アビセル) as a raw Material

アビセル (crystalline microfine cellulose manufactured by Merck Co., Ltd.) and 1.5g of activated charcoal BA50 (manufactured by Meizisu ファインテクノ Co., Ltd.) were put into a ceramic pot mill having a capacity of 3600mL together with 2000g of alumina balls having a diameter of 1.5cm, and the resultant mixture was set on a rotary table type pot mill (manufactured by Nidoku K.K., Takara Shuzo (Tokyo ポットミル), model ANZ-51S), and treated at 60rpm for 48 hours to obtain a reaction material. The temperature starts at room temperature, and the temperature is naturally increased by shear heat generation.

Then, 0.374g of the reaction raw material and 40mL of water were placed in a high-pressure reactor (100 mL in internal volume, an autoclave manufactured by オーエムラボテック K., manufactured by Hastelloy ハステロイ C22), the reaction temperature was heated to 230 ℃ at 10 to 30 ℃/min (average rate of temperature rise 11.3 ℃/min) while stirring at 600rpm, the heating was immediately stopped, and the reactor was air-cooled at 10 to 30 ℃/min (average rate of temperature fall 16.7 ℃/min) to prepare a reaction solution.

Subsequently, the supernatant recovered from the reaction solution by the centrifugal separator was freeze-dried to obtain cellooligosaccharide powder. The obtained powder was dissolved in water so that the sugar concentration (concentration of cellulose hydrolysate) was 5% by mass, and the solution was used as a sample solution for turbidity measurement described later.

The number average molecular weight and the degree of branching of the hydrolysate 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%. FIG. 4 shows a hydrolysate produced in comparative example 2 ¹ H-NMR spectrum.

<3. Observation of the Presence of cloudiness and measurement of turbidity >

Each of the sample solutions obtained in examples 1 to 2 and comparative examples 1 to 2 was subjected to observation of turbidity and measurement of turbidity at the time of preparation and after 7 days of storage. The results are shown in Table 2.

The sample solution was stored by filling 40mL of the sample solution into a50 mL glass screw-top bottle container and allowing the sample solution to stand in a constant temperature bath set at 30 ℃.

The following methods were used for the measurement of turbidity. A well-dispersed sample solution (sample 1) and a sample solution (sample 2) obtained by filtering the sample 1 through a 0.45 μm membrane were prepared, and each sample was placed in a 1 cm-square cell and the absorbance at a wavelength of 660nm was measured. From the measured absorbance, the turbidity was calculated by the following calculation formula.

Turbidity (absorbance of sample 1) - (absorbance of sample 2)

TABLE 2

As can be seen from the results in table 2, in examples 1 and 2 in which a cellulose-xylan mixture containing xylan at a predetermined ratio was used as a raw material, the sample solution was not 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 a raw material developed turbidity after 7 days of storage, and comparative example 2 developed turbidity just after production.

Industrial applicability

The method for producing a cellooligosaccharide-containing composition of the present invention can produce a cellooligosaccharide-containing composition having excellent storage stability even when the polymerization degree is relatively high.

Claims (8)

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, the raw material mixture containing 5 to 50 mass% of the xylan relative to 100 mass% of the total content of the cellulose and the xylan.

2. The method for producing a cellooligosaccharide-containing composition according to claim 1, wherein the raw material mixture contains 7 to 40 mass% of the xylan relative to 100 mass% of the total content of the cellulose and the xylan.

3. The method for producing a cellooligosaccharide-containing composition according to claim 1 or 2, wherein the acid catalyst is at least one acid selected from the group consisting of sulfuric acid, sulfurous acid, hydrochloric acid, perchloric acid, nitric acid, nitrous acid and phosphoric acid, or a partially neutralized salt thereof.

4. The method for producing a cellooligosaccharide-containing composition according to claim 3, wherein the acid catalyst is phosphoric acid or a partially neutralized salt thereof.

5. The method for producing a cellooligosaccharide-containing composition according to claim 4, wherein the acid catalyst is phosphoric acid.

6. The method for producing a cellooligosaccharide-containing composition according to claim 1 or 5, comprising a step of subjecting the raw material mixture to pulverization treatment in the presence of the acid catalyst for hydrolysis.

7. The method for producing a cellooligosaccharide-containing composition according to claim 6, wherein the pulverization treatment is carried out by using a planetary ball mill or a vibration mill.

8. A cellooligosaccharide-containing composition produced by hydrolyzing a raw material mixture containing cellulose and xylan in the presence of an acid catalyst, the xylan content in the raw material mixture being 5 to 50 mass% relative to 100 mass% of the total content of the cellulose and xylan.

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