JP4788578B2 - Method for producing xylooligosaccharide - Google Patents

Description

  The present invention relates to a method for producing a xylooligosaccharide that provides a useful action such as intestinal regulation to humans and animals. In particular, the present invention relates to a method for producing a xylo-oligosaccharide by enzymatic treatment of a xylan-containing cellulose material.

Oligosaccharides have a function to keep the stomach in good condition through the selective growth promoting effect of useful bacteria in the intestines, and are used for lactic acid bacteria beverages certified as food for specified health use, and also for confectionery such as chocolate It is a useful sugar. In addition to human food use, it is also used as livestock feed. Furthermore, in the fields of pharmaceuticals and sanitary products, they have applications as emulsifiers and skin moisturizing ingredients.
In general, most of the oligosaccharides used in foods for specified health use are intestinal-regulating, that is, reducing the number of bacteria of the genus Clostridium and Eubacterium, which are E. coli, which is an enteric bad bacteria, It has the effect of increasing the number of bifidobacteria, which are said to be relatively good intestinal bacteria. Among various oligosaccharides, for example, xylooligosaccharides derived from wheat bran and corn cob are famous. As for the action of xylo-oligosaccharides, it is said to promote the selective growth of Bifidobacterium, a good enteric fungus, as well as other oligosaccharides, while relatively reducing the number of E. coli that are enteric bad bacteria. . It is known that E. coli and intestinal rot-fermenting bacteria produce carcinogenic substances while growing in the intestine, so reducing the number of E. coli and intestinal rot-fermenting bacteria in the intestine is a long-term health. Is important (see Non-Patent Document 1).

In the case of ingesting oligosaccharides orally in anticipation of intestinal regulation, a major problem is a decrease in the degree of polymerization of oligosaccharides due to acid hydrolysis of gastric acid and digestive enzymes. It is known that oligosaccharides are gradually reduced in molecular weight by hydrolysis with acids and enzymes, and finally decomposed into monosaccharides that can be assimilated by spoilage anaerobes belonging to the genus Escherichia coli and Clostridium. It has been. However, xylooligosaccharide compositions mainly composed of dimers and trimers have a relatively high resistance to gastric acid among oligosaccharides compared to other oligosaccharides (see Patent Document 1) and are not degraded so much. Likely to be delivered to the intestines.
At present, xylo-oligosaccharides having an average degree of polymerization of about a pentamer having a molecular weight much higher than that of a dimer or trimer can be produced (see Patent Document 2). In addition, the present inventors have also proposed a long-chain xylo-oligosaccharide having an average degree of polymerization of about 12-mer (see Patent Document 3). Xylooligosaccharides having a long chain length are difficult to be converted into xylose, which is a monosaccharide even in the intestine, and more effective intestinal regulation is expected. Therefore, development of xylooligosaccharides having a high degree of polymerization is desired.
Furthermore, the present inventors have also proposed an acidic xylo-oligosaccharide composition and a production method thereof (see Patent Document 4).

A typical method for producing xylooligosaccharides is a method of extracting xylan from a plant and treating it with an enzyme.
In Patent Document 1, xylooligosaccharides are obtained by extracting xylan from corn cob, cottonseed husk, malt straw, etc. with a KOH solution and then enzymatically treating with xylanase derived from Trichoderma.
Non-Patent Document 2 describes a method for extracting xylan from broad-leaved trees or conifers by delignining wood flour, obtaining xylan by alkaline extraction, and obtaining xylooligosaccharides by enzyme treatment.

These methods once extract xylan, and there is a problem that xylan extraction residues must be treated. Both methods are inexpensive and mass production methods including the use of xylan extraction residues. Not mentioned.
Japanese Patent No. 2549638 Japanese Patent Laid-Open No. 2001-226409 JP 2003-48901 A JP 2003-183303 A Kanazawa et al .: Colonic bacterial flora -especially about bile acid metabolism and colon carcinogenesis- (general clinical practice, vol.26, 1042-1050 (1977)) Ishihara: Production of xylooligosaccharides from woody biomass (Bioindustry vol.18, No.12, P35-44, 2001)

  The currently marketed xylooligosaccharides are manufactured using herbaceous agricultural waste such as wheat bran and corn cob as raw materials, but the remaining fiber content after the xylooligosaccharide extraction has not been effectively used, and waste treatment There is a problem. In addition, when oligosaccharides are produced by enzymatic treatment, there is a problem that the concentration of oligosaccharides is low and energy is required for concentration. An object of the present invention is to obtain a high concentration oligosaccharide solution. It is another object of the present invention to provide a method for producing xylooligosaccharides that can be produced in large quantities at a low cost with a small amount of waste.

  The present inventors paid attention to xylo-oligosaccharides produced by xylanase treatment of xylan-containing cellulose materials, and as a result of intensive research, by returning a part of the xylo-oligosaccharide eluate to the reaction step, a high degree of polymerization and a high concentration of xylo-oligosaccharides were obtained. By recovering the raw material containing sugar and simultaneously reusing the cellulose material separated and recovered, a method for producing a high degree of polymerization of xylooligosaccharides in large quantities and at low cost has been developed.

In order to solve the above problems, the present invention employs the following configurations (1) to (6).
(1) In a method for producing xylo-oligosaccharides by treating xylan-containing cellulose material in an aqueous slurry and separating xylan-oligosaccharides from xylan-containing cellulose material by xylanase, separation for separating cellulose material and xylo-oligosaccharide eluate A method for producing a xylooligosaccharide comprising a step, wherein a part of the separated xylooligosaccharide eluate is returned to the reaction step and the remainder is concentrated to obtain a xylooligosaccharide.
(2) As the xylan-containing cellulose material, a raw material or an intermediate product in the manufacturing process of the cellulose-based industrial product is taken out and used, and the cellulose material separated in the separation process is used by returning to the manufacturing process of the cellulose-based industrial product. The method for producing a xylo-oligosaccharide according to (1), wherein
(3) The method for producing a xylooligosaccharide according to (1) or (2), wherein the xylan-containing cellulose material is a chemical pulp.
(4) The method for producing xylooligosaccharide according to (3), wherein the chemical pulp is hardwood kraft pulp.
(5) The method for producing xylooligosaccharide according to (3) or (4), wherein the chemical pulp is collected from a bleaching step in a pulp manufacturing plant, and the pulp separated in the separation step is returned to the bleaching step. .
(6) A xylooligosaccharide mixed composition containing a dimer to 15mer of xylose by heating the concentrated solution obtained by concentrating the xylooligosaccharide eluate at a pH of 2 to 4 and a temperature of 100 to 170 ° C. for 1 to 120 minutes. The method for producing a xylooligosaccharide according to any one of (1) to (5), wherein

According to the present invention, it is possible to increase the oligosaccharide concentration in the reaction filtrate while maintaining the characteristic that the degree of polymerization is high, and as a result, the oligosaccharide production efficiency can be increased. In addition, energy consumed for manufacturing can be reduced.
In addition, if a xylan-containing cellulose material is taken out from the pulp manufacturing process and used, waste represented by residual fibers will not be generated unlike the production of xylooligosaccharides made from herbaceous agricultural waste. , Environmental impact is small and waste disposal cost is hardly generated.

The raw material from which the xylo-oligosaccharide composition can be obtained by the method of the present invention is a woody plant, a non-woody plant, or a fibrous material or a granular material made from them, and contains cellulose and xylan. Is. Hereinafter, in this invention, it is called a xylan-containing cellulose material. The woody plant may be either a conifer or a hardwood. Non-woody plants may be any of kenaf, hemp, cotton, bamboo, bagasse, rice and the like.
Examples of the fibrous substance or the granular substance include pulp for papermaking, fine wood powder / fine fiber for filler, yarn, and the like, and may be a paper-like sheet formed therefrom.

The xylan-containing cellulose material used in the present invention is preferably a raw material for industrial products or an intermediate product containing cellulose as a main component. The reason for this is that the cellulose material after the xylo-oligosaccharide is dissolved by xylanase treatment is used as an industrial product material as it is, so that there is an advantage that no waste is generated. When the above raw materials and intermediate products are treated with xylanase, all of them may be treated, or some may be taken out and used.
Applicable to such conditions are, for example, a pulp manufacturing process in papermaking, a waste paper processing process, etc., and also a thread manufacturing process, a fine powdered cellulose manufacturing process, a container from a non-woody plant fiber, a net, Examples include a manufacturing process such as candy and a manufacturing process of cellulose fiber food. In particular, a pulp manufacturing process in papermaking is most suitable. Hereinafter, a case where a pulp is partially or entirely treated with a xylanase from the pulp manufacturing process, and the treated pulp is continuously used in the papermaking process will be described as an example.

  The pulp used in the present invention may be any chemical pulp, mechanical pulp, deinked pulp, etc., but hardwood chemical pulp is preferred. As the cooking method for obtaining chemical pulp, known cooking methods such as kraft cooking, polysulfide cooking, soda cooking, alkali sulfite cooking, etc. can be used, but considering the pulp quality, energy efficiency, etc., the kraft cooking method is used. Preferably used. Furthermore, pulp obtained by oxygen bleaching hardwood kraft pulp after cooking is more preferably used. Oxygen-bleached pulp has free lignin removed, and xylanase treatment produces xylo-oligosaccharides. At the same time, the lignin and xylan complex adsorbed on the pulp elutes, and further xylo-oligosaccharides are obtained from this. This is because the sugar yield is improved. In particular, when hardwood kraft pulp is used, there is a feature that almost no constituent sugars such as glucose and arabinose are present, and xylose is almost 100%.

  Any xylanase can be used as the xylanase used in the reaction step of the present invention as long as the enzyme has xylanase activity. For example, the brand names Cartazyme (Clariant), Pulpzyme (Novo Nordisk), Eco Pulp (Rohm Enzyme), Sumiteam (New Nippon Chemical Industries), Multifect Xylanase (Genencor), Xylanase Conk ( Advanced Biochemicals) and other commercially available enzyme preparations, Trichoderma genus, Thermomyces genus, Aureobasidium genus, Streptomyces genus, Aspergillus genus, Clostridium genus, Bacillus genus, Thermotoga genus, Telmotus genus, Xylanases produced by microorganisms such as Thermomospora can be used.

In the present invention, the pulp in the pulp manufacturing process is used as the xylan-containing cellulose, but it is preferable to take out and treat a part of the pulp rather than treating all the pulp in the process with xylanase.
That is, since a minimum amount of pulp is processed for the purpose of producing xylooligosaccharides in a route different from the main stream of pulp production, it is possible to wash away various impurities generated in the cooking and oxygen exposure processes in advance. As a result, the amount of impurities remaining in the reaction solution after the xylanase treatment is reduced, and the purification load can be reduced. Moreover, since there is no restriction | limiting by the reaction conditions of a pulp manufacturing process, a xylanase process can be implemented on conditions optimal for elution of a xylooligosaccharide, such as a pulp density | concentration, enzyme addition amount, reaction pH, reaction temperature, and reaction time. For this reason, it becomes possible to arbitrarily change the xylanase treatment conditions of the pulp.

  In addition, excessive xylanase treatment for pulp reduces the hemicellulose content in the pulp and lowers the yield of the pulp. Therefore, when producing xylo-oligosaccharides from the xylanase treatment liquid in the pulp production process as the starting material, There was a problem that the sugar concentration could not be increased. In the present invention, since the minimum necessary amount of pulp according to the oligosaccharide production amount can be taken out from the pulp manufacturing process and used as a raw material, the xylooligosaccharide can be more efficiently produced while minimizing the decrease in the yield of the pulp. Can be manufactured.

  As a means for extracting pulp used for the production of xylo-oligosaccharides from the pulp production process, it is possible to transfer the line by a pump if it is a low concentration pulp, and use a transfer means such as a belt conveyor if it is a high concentration pulp. However, the means is not particularly limited as long as the amount of pulp required for oligosaccharide production can be extracted and transferred.

  The pulp is washed for the purpose of reducing the load when refining xylo-oligosaccharides, and as a means of removing soluble impurities such as fine suspended impurities, lignin and organic acids, the pulp is diluted and washed using, for example, a drum filter. Any device can be used, as long as the pulp can be washed. In addition, the reaction conditions for carrying out the xylanase treatment of pulp are adjusted in advance by carrying out displacement washing with washing water that matches the optimum reaction conditions for xylanase, such as addition of a pH adjuster and temperature adjustment of the washing water. You can also keep it.

  As for the reaction apparatus for carrying out xylanase treatment of pulp, any apparatus can be used in both shape and form. For medium and high-concentration pulp, use a medium- and high-concentration pulp pump or screw feeder to push into a cylindrical reaction tank and give it an optimal residence time for xylanase treatment, followed by a reaction containing oligosaccharides. What is necessary is just to extrude and collect the liquid and the xylanase-treated pulp. For low-concentration pulp, xylanase treatment is performed while stirring in a reaction vessel equipped with a stirrer, and the reaction is performed with an average residence time optimal for elution of xylo-oligosaccharides, and the reaction solution containing oligosaccharides and xylanase treatment are completed. The pulp can also be extracted continuously. When medium and high concentration pulp is treated with xylanase, the pulp and xylanase are preferably mixed uniformly before being transferred to the reaction vessel using a mixer such as a screw mixer. On the other hand, when low-concentration pulp is treated with xylanase, xylanase can be added to the reaction tank, and the pulp and xylanase can be uniformly mixed in the reaction tank. These reaction tanks are preferably equipped with a temperature-adjusting jacket and a heat insulating material casing in order to maintain the optimum reaction temperature of xylanase.

In the step of eluting xylo-oligosaccharide by xylanase treatment of pulp, it is possible to change the concentration of xylo-oligosaccharide to be eluted and the polymerization degree of xylo-oligosaccharide by changing the amount of xylanase added to the pulp and the reaction time. Generally, the greater the amount of xylanase added and the longer the reaction time, the higher the xylo-oligosaccharide concentration and the lower the degree of polymerization of the xylo-oligosaccharide. By simply increasing the amount of xylanase added or lengthening the reaction time, a filtrate containing a high concentration of xylo-oligosaccharide can be obtained, but a high-polymerization degree xylo-oligosaccharide cannot be obtained. This is because the high-polymerization xylo-oligosaccharides that have been decomposed and eluted by xylanase are further decomposed and excessively decomposed into oligosaccharides having a short chain length such as xylose, xylobiose, and xylotriose.
In order to stably obtain a high concentration and high degree of polymerization of xylooligosaccharide, it is preferable to circulate a part of the filtrate containing the xylooligosaccharide to the reaction system. By returning a part of the reaction filtrate containing xylo-oligosaccharides to the reaction tank inlet, the sugar concentration can be increased over time while maintaining the degree of polymerization of xylo-oligosaccharides at a high level. Presumably, xylanase preferentially acts on the unreacted pulp, so that the high polymerization degree xylo-oligosaccharide contained in the reaction filtrate returned to the reaction tank is not decomposed and xylo-oligo newly eluted from the unreacted pulp. Combined with sugar, the concentration is thought to increase.

  The pulp concentration in the reaction tank, the reaction time, and the amount of xylanase added can be arbitrarily set, but the pulp concentration is preferably 2% to 20%, more preferably 7% to 15%. If the pulp concentration is too low, it is difficult to increase the xylooligosaccharide concentration and the amount of liquid increases, resulting in a problem that the equipment is enlarged. On the other hand, when the pulp concentration is too high, not only uniform mixing of xylanase and pulp and transfer of the pulp become difficult, but also the amount of recovered sugar solution decreases. The reaction time and the amount of xylanase added vary depending on the type of enzyme used. For example, in the case of xylanase concentrate, the reaction time is 10 minutes to 240 minutes, more preferably 30 minutes to 90 minutes, and the amount of enzyme added is 2 [unit / g-dry pulp] to 200 [unit / g-dry pulp], more preferably 10 [unit / g-dry pulp] to 100 [unit / g-dry pulp]. If the reaction time is too short or the amount of enzyme added is too small, the sugar concentration cannot be increased. If the reaction time is too long or the amount of enzyme added is too large, the degree of polymerization will be small.

According to the present invention, the composition ratio of xylo-oligosaccharides produced in the reaction filtrate obtained by treating pulp with xylanase varies depending on the type of enzyme used and the reaction conditions. For example, when xylanase concentrate is used, the pulp concentration is 10%, If the reaction time is 45 minutes, the reaction temperature is 50 ° C., the reaction pH is 6.0, and the enzyme addition amount is 50 [unit / g-dried pulp],
A xylo-oligosaccharide having a dimer to 15-mer oligosaccharide distribution and an average degree of polymerization of around 5 mer can be produced.

The process of separating the xylo-oligosaccharide eluate containing xylo-oligosaccharide from the xylanase-treated pulp will be described.
Separation means in the step is not particularly limited, for example, the pulp may be squeezed using a device such as a screw press, or the pulp is replaced and washed using a device such as a drum filter, and a filtrate containing xylooligosaccharides. May be recovered. A part of the filtrate containing xylo-oligosaccharide thus obtained is returned to the reaction vessel, and a part is recovered as a xylo-oligosaccharide raw material.
In this case, the amount to be returned is 20 to 80% by mass, preferably 40 to 60% by mass, based on the total filtrate. The returning ratio varies depending on the desired xylo-oligosaccharide concentration, degree of polymerization, etc., but if it exceeds 80% by mass, the production efficiency is poor, and if it is less than 20%, the oligosaccharide concentration is difficult to increase. For the same reason, considering the overall balance, 40 to 60% by mass is preferable.

  The xylo-oligosaccharide complex contained in the pulp xylanase reaction-treated filtrate is concentrated by physical and chemical treatments such as evaporation, solvent extraction, and membrane concentration. When concentrating the sugar solution obtained according to the present invention, a part of xylo-oligosaccharide having a small degree of polymerization such as xylobiose and xylotriose permeates and the xylo-oligosaccharide complex remains in the membrane and is concentrated by the membrane. This method is industrially advantageous. One of the reasons is that membrane concentration without phase change is low in operating cost and does not require the use of special chemicals such as solvents, and is also included in the enzyme reaction treatment solution at the same time as xylooligosaccharides. And some of the low-molecular organic substances derived from monosaccharides or oligosaccharides such as glucose, xylose and arabinose, organic acids and lignin are discharged together with the permeated water during membrane concentration and separated. This is because it can be removed.

  In general, when membrane elements such as reverse osmosis membranes, NF membranes, and ultrafiltration membranes are operated, colloidal substances and fine suspended substances existing in the raw water adhere to, accumulate and concentrate on the membrane surface. The filtration specific resistance increases with the passage of time, and the permeation flux decreases. Furthermore, the operating pressure rises, causing an increase in operating costs. Since it is practically important to minimize the performance degradation of such membrane elements and operate stably over a long period of time, turbidity treatment by coagulation sedimentation, clarification filtration, etc. is performed as a pretreatment. . In the pulp xylanase treatment reaction filtrate, fine insoluble components such as pulp and suspended solids are suspended, which may cause a decrease in permeation flux during membrane concentration, and membrane damage due to an increase in membrane differential pressure. It may cause.

  As the pretreatment before the membrane concentration, a bag filter, a filter press, a precoat filter, a ceramic filter microfiltration treatment, a coagulation sedimentation treatment, or a combination thereof may be used. A filter with submicron order filtration accuracy is more preferable when performing microfiltration. When performing coagulation and precipitation treatment, inorganic flocculants such as sulfuric acid bands and polyaluminum chloride, and polyacrylamide and polyamidine A natural polymer flocculant such as a molecular flocculant or chitosan can be used, but the method is not particularly limited as long as fine insoluble components such as pulp and suspended substances can be removed.

Xylooligosaccharide is a dimer or higher oligomer. In addition, the molecular weight of xylose is 150, the dimer is 282, the trimer is 414, and the molecular weight is increased by 132 each time one xylose residue is added, and the 10-mer is 1338. The concentrated xylo-oligosaccharide complex forms a complex with the xylanase reaction-treated filtrate of the pulp with the high-molecular substance produced during the cooking process, such as lignin or lignocellulosic substances, or furan derivatives derived from hemicellulose. It is thought that.
The total sugar contained in the membrane concentrate consists almost exclusively of xylose, and the xylooligosaccharide can be liberated by adding an acid to the membrane concentrate to adjust the pH below 5 and heating at high temperature. The acid in this case is not particularly limited, and any acid can be used. Examples thereof include mineral acids such as sulfuric acid and hydrochloric acid, and organic acids such as oxalic acid and acetic acid. The pH during acid treatment of the concentrate is preferably 2 to 4, more preferably in the range of 3 to 3.5. When the pH is 1.5 or less, hydrolysis to xylose is promoted, and the recovery rate of xylooligosaccharide is lowered. When the pH is 5 or more, the release of xylo-oligosaccharides is not promoted at temperatures up to about 150 ° C.
The heating temperature necessary for releasing the xylooligosaccharide is not particularly limited as long as the xylooligosaccharide is liberated. However, the temperature is preferably from 100 to 200 ° C, particularly preferably from 105 to 170 ° C, and more preferably 110 ° C to 125 ° C. At a processing temperature of less than 100 ° C., xylo-oligosaccharide is not released from the xylo-oligosaccharide complex. Moreover, when it exceeds 170 degreeC, the decomposition reaction to the xylose which is monosaccharide will be accelerated | stimulated, and the yield of xylooligosaccharide will fall.

  The xylo-oligosaccharide composition after acid treatment still contains insoluble matters such as lignin and colored substances. Insoluble matter can be removed by processes such as centrifugation, filter filtration, and filtration with a filter cloth. The method for removing impurities such as dissolved coloring substances is not particularly limited, and a method using activated carbon known so far, a strong basic anion exchange resin such as amberlite, a weak basic anion, etc. A method using an exchange resin, a strong acid cation exchange resin, a weak acid cation exchange resin, and a membrane filtration method may be repeated or a combination thereof.

  EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, all percentages shown below mean mass%, and the addition ratio of pulp is the ratio of mass to the absolute dry mass of pulp. In addition, each measuring method is as follows.

<Outline of measurement method>
(1) Quantification of total sugar amount The total sugar amount was prepared using a calibration curve using D-xylose (manufactured by Wako Pure Chemical Industries, Ltd.) and quantified by the phenol-sulfuric acid method (quantitative method for reducing sugar; Academic Publishing Center).
(2) Quantification of reducing sugar amount The reducing sugar amount was prepared by using D-xylose (manufactured by Wako Pure Chemical Industries, Ltd.) as a calibration curve, and quantified by the Sommoji-Nelson method (reducing sugar quantification method; Academic Publishing Center).
(3) Determination method of average degree of polymerization The sample sugar solution is kept at 50 ° C. and centrifuged at 15000 rpm for 15 minutes to remove insoluble matter, and the total amount of sugar in the supernatant is divided by the amount of reducing sugar (both converted to xylose). The average degree of polymerization was determined.
(4) Definition of enzyme titer Birchwood xylan (manufactured by Sigma) was used for measuring the activity of xylanase used as an enzyme. Enzyme titer is defined by measuring the reducing power of reducing sugar obtained by decomposing xylan by xylanase using the DNS method (quantitative method for reducing sugar; Academic Publishing Center) to 1 micromole of xylose per minute. The amount of enzyme that generates the corresponding reducing power was defined as 1 unit.

<Example 1>
As a raw material, pulp obtained by kraft cooking and oxygen delignification of mixed hardwood chips made of 20% domestic hardwood chips and 80% eucalyptus wood was used. This pulp was washed, diluted sulfuric acid was added to adjust the pH to 5, and then the pulp concentration was adjusted to 20%. Dilute to 50 g of 20% pulp using 50 ml of 50 ° C. warm water to which xylanase conk (manufactured by Advanced Biochemicals) was added so as to be 50 [unit / g] of pulp. 10%. After treating at 50 ° C. for 45 minutes, the mixture was filtered through a 100-mesh filter cloth to obtain a pulp xylanase reaction filtrate. Subsequently, the xylanase reaction filtrate, which had been added so that xylanase was 50 [units / g], was added to 50 g of 20% pulp and diluted to a final pulp concentration of 10% at 45C. After treating for a minute, a xylanase reaction filtrate of pulp was obtained in the same manner. The same procedure as described above was further repeated once to obtain a pulp enzyme treatment solution which had been reacted three times in total. The xylo-oligosaccharide contained in the thus obtained xylanase reaction filtrate had a total sugar concentration of 0.98% and an average degree of polymerization of 4.8.

<Comparative Example 1>
Dilute to 50 g of 20% pulp prepared in the same manner as in Example 1 with 50 ml of warm water at 50 ° C. so that the xylanase concentrate is 50 [unit / g] of pulp, and the final concentration of the pulp 10%. After 135 minutes of treatment at 50 ° C., the mixture was filtered through a 100 mesh filter cloth to obtain a xylanase reaction filtrate of pulp. The xylo-oligosaccharide contained in the thus obtained xylanase reaction filtrate had a total sugar concentration of 0.49% and an average degree of polymerization of 3.4.

<Comparative example 2>
Dilute to 50 g of 20% pulp prepared in the same manner as in Example 1 with 50 ml of hot water at 50 ° C. so that the xylanase concentrate was 150 [unit / g] for pulp, and the final concentration of the pulp 10%. After 135 minutes of treatment at 50 ° C., the mixture was filtered through a 100 mesh filter cloth to obtain a xylanase reaction filtrate of pulp. The xylo-oligosaccharide contained in the thus obtained xylanase reaction filtrate had a total sugar concentration of 0.61% and an average polymerization degree of 2.7.

<Comparative Example 3>
Dilute to 50 g of 20% pulp prepared in the same manner as in Example 1 with 50 ml of warm water at 50 ° C. so that the xylanase concentrate is 50 [unit / g] of pulp, and the final concentration of the pulp 10%. After treating at 50 ° C. for 360 minutes, the mixture was filtered through a 100 mesh filter cloth to obtain a pulp xylanase reaction filtrate. The xylo-oligosaccharide contained in the thus obtained xylanase reaction filtrate had a total sugar concentration of 0.68% and an average degree of polymerization of 2.1.
As is clear from the comparison between Example 1 and Comparative Examples 1 to 3, in the xylanase treatment of the pulp, simply increasing the amount of xylanase added or increasing the reaction time increases the degree of polymerization and high concentration of xylo-oligo. A reaction filtrate containing sugar cannot be obtained. A part of the reaction filtrate is returned to the reaction system, and a new xylooligosaccharide is eluted from the pulp as the reaction substrate, whereby a reaction filtrate containing a high degree of polymerization and a high concentration of xylooligosaccharide can be obtained. Obtaining a high-concentration sugar solution is advantageous in that the equipment cost can be reduced and the running cost can be reduced when performing unit operations represented by membrane concentration and evaporation.

<Example 2>
As a raw material, pulp obtained by kraft cooking and oxygen delignification of mixed hardwood chips made of 20% domestic hardwood chips and 80% eucalyptus wood was used. Using 60 ° C. hot water, the pulp concentration was diluted to 1.6% and received in a 10 m ³ tank. Subsequently, concentrated sulfuric acid was added to the tank and stirred to adjust the pH to 5.5, and then the pulp was dehydrated and washed with a drum filter (Shinryo Seisakusho: φ2000 × 600SUF). The pulp concentration after dehydration was about 20%. Warm water at 50 ° C. was added to the 20% pulp to dilute the pulp concentration to 10%, and at the same time, the xylanase conc was continuously added so as to be 50 [unit / g] of pulp, and thoroughly mixed with a tram screw. The mixed pulp is pushed into a cylindrical reaction tank (φ800mm × 4000mmH) with a volume of 2m ³ with a medium concentration pump (Shinryo Seisakusho: 200 x RPK), and continuously treated so that the reaction time is 40 minutes, then the reaction The subsequent pulp was dehydrated to about 40% with a screw press (manufactured by Shinryo Seisakusho: 250 × 1000 SPH-EN) to obtain a xylanase reaction filtrate of the pulp. After 60 minutes from the start of the reaction, 50% by mass of the xylanase reaction filtrate, not 50 ° C warm water, is returned to the trump screw, and 20% pulp dehydrated with a drum filter is diluted to 10% and xylanase treatment is performed continuously. It was. From 150 minutes after the start of the reaction, the total sugar concentration in the xylanase reaction filtrate increased to 0.92%, and the average degree of polymerization of the xylo-oligosaccharide at this time was 4.7. By continuously performing such xylanase treatment on the pulp for 24 hours, the reaction filtrate having a sugar concentration of about 0.9% can be stably removed after 150 minutes from the start of the reaction. 15 m ^{3 of} 9% xylanase reaction filtrate could be obtained. The obtained reaction filtrate was filtered through a back filter (manufactured by ISP Filters) with a micron rate of 1 μm, and subsequently with a ceramic filter (manufactured by Nippon Pole) with a micron rate of 0.2 μm to obtain a clear reaction filtrate. Further, by concentrating 15 times with a reverse osmosis membrane (manufactured by Nitto Denko: NTR-7450), 1 m ³ of a concentrated solution having a total sugar concentration of 11% could be obtained. The pulp dehydrated with a screw press was collected and returned to the pulp manufacturing process.

<Example 3>
The concentrated sugar solution 1m ³ obtained in Example 2 was adjusted to pH 3.5 with concentrated sulfuric acid and then acid-treated at 121 ° C. for 45 minutes. After cooling to 50 ° C., the insoluble residue produced after the acid treatment was removed with a ceramic filter (manufactured by Nippon Pole) with a micron rate of 0.2 μm, decolorized with a UF membrane (manufactured by Kuraray: MU-6025), and further activated carbon ( 10 kg of Mikura Kasei Co., Ltd. (PM-SX) was added and treated at 50 ° C. for 2 hours to obtain a decolorized sugar solution. The obtained sugar solution was subjected to SV1.5 with a strong cation resin (Mitsubishi Chemical: PK-218, 300 L) → weak anion resin (Mitsubishi Chemical: WA30, 300 L) → strong cation resin (Mitsubishi Chemical: PK-218). , 300L) → Purified xylooligosaccharide solution (sugar concentration: 4.3%) by ion-exchange treatment and desalting / decolorization using a 4-bed, 4-tower system consisting of weak anion resin (Mitsubishi Chemical: WA30, 300L) 1100 L). The obtained xylo-oligosaccharide solution was treated with a spray dryer (Okawara Kakoki: ODA-25 type) to obtain 45 kg of xylo-oligosaccharide powder. The average degree of polymerization of the obtained xylo-oligosaccharide was 5.1.

<Example 4>
In Example 3, after obtaining a purified xylo-oligosaccharide solution, a 75 mM sodium chloride aqueous solution was allowed to flow through the weak anion resin of the second and fourth towers at SV1.5 to obtain an acidic xylo-oligosaccharide solution (sugar concentration of 2. 8%, 600 L) was recovered. The collected acidic xylo-oligosaccharide solution is adjusted to pH 5 with a strong cation resin, concentrated to a sugar concentration of 20%, treated with a spray dryer (Okawara Kakoki: ODA-25 type), and 15 kg of acidic xylo-oligosaccharide powder is obtained. Obtained. The average degree of polymerization of the obtained acidic xylo-oligosaccharide was 10.8.

  INDUSTRIAL APPLICABILITY According to the present invention, there is provided a technology capable of producing a large amount and a low cost of xylooligosaccharides and acidic xylooligosaccharides having an excellent function as a functional food material or a skin external preparation.

Claims (6)

In the method of producing xylo-oligosaccharides by treating xylan-containing cellulose material in an aqueous slurry, xylanase has a reaction step of eluting xylo-oligosaccharide from xylan-containing cellulose material and a separation step of separating the cellulose material and the xylooligosaccharide eluate. Then, a part of the separated xylooligosaccharide eluate is returned to the reaction step, and the remainder is concentrated to obtain a xylooligosaccharide. As the xylan-containing cellulose material, the raw material or intermediate product in the manufacturing process of the cellulose-based industrial product is taken out and used, and the cellulose material separated in the separation process is used by returning to the manufacturing process of the cellulose-based industrial product. The method for producing xylo-oligosaccharide according to claim 1. The method for producing xylooligosaccharide according to claim 1 or 2, wherein the xylan-containing cellulose material is a chemical pulp. The method for producing xylooligosaccharide according to claim 3, wherein the chemical pulp is hardwood kraft pulp. The method for producing xylooligosaccharide according to claim 3 or 4, wherein the chemical pulp is collected from a bleaching step in a pulp manufacturing plant, and the pulp separated in the separation step is returned to the bleaching step. A xylooligosaccharide mixture composition containing a dimer to 15mer of xylose is obtained by heating the concentrated solution obtained by concentrating the xylooligosaccharide eluate at a pH of 2 to 4 and a temperature of 100 to 170 ° C. for 1 to 120 minutes. A method for producing a xylo-oligosaccharide according to any one of claims 1 to 5, characterized in that it is characterized in that