JP2006265285A - Method for producing xylo-oligosaccharide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing xylo-oligosaccharide in which a step for refining a crude solution containing xylo-oligosaccharide can be simplified and sugar solution having high refining degree can be obtained, particularly to provide a method for producing xylo-oligosaccharide in which nonionic impurity in which effective removal by treatment using an ion exchange resin is difficult is simply and efficiently removed. <P>SOLUTION: An ester compound contained as the impurity in the crude solution containing xylo-oligosaccharide is decomposed to an acid and an alcohol which can readily be removed by irradiating the crude solution containing the xylo-oligosaccharide with ultraviolet light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing xylooligosaccharides.

  Due to the recent health boom, consumers are becoming more aware of health. Along with this, the demand and sales of health foods have increased dramatically year by year, and the number of companies that obtain approval for “food for specified health use” has also increased. Oligosaccharides occupy the largest number of foods for specified health use, and the types of oligosaccharides currently on the market include fructooligosaccharides, soybean oligosaccharides, galactooligosaccharides, maltooligosaccharides, and xylooligosaccharides. By ingesting these oligosaccharides, the effect of reducing the number of Clostridium bacteria, which are bad bacteria that inhabit the intestines, and relatively increasing the number of Bifidobacterium, which are good bacteria, can be obtained. Among these oligosaccharides, for example, the minimum effective amount of xylo-oligosaccharides obtained from hemicellulose in plants such as wood chips, corn shin, and straw is 0.2 to 0.7 g / day (published by Confectionery Technical Center, “ Oligosaccharide handbook ”), which provides an intestinal effect in an amount that is an order of magnitude less than other oligosaccharides. Xylooligosaccharides are oligosaccharides obtained by hydrolyzing xylan, which is a polysaccharide present in various plant bodies. Specifically, raw materials such as corn shin, wood, straw, etc. are subjected to chemical treatment using acids and alkalis, physical treatment such as blasting, or treatment with high-temperature high-pressure water. It can be obtained as a crude liquid containing oligosaccharides by performing enzyme treatment as necessary. Since the crude liquid containing the oligosaccharide thus obtained contains various colored and colorless impurities, decolorization and purification treatment is indispensable in order to obtain products such as food additives.

  Conventionally, as a means for purifying a crude liquid containing sugar, it is known that treatment with an ion exchange resin is effective, and the treatment can be easily incorporated into a production line by using a column as an apparatus. Also excellent in terms. However, it is necessary to use different types of ion exchange resins and pass through at least 2 to 3 columns, and irreversible adsorption of the dye to the ion exchange resin occurs, and the resin is frequently exchanged. Since it is necessary, the amount of ion-exchange resin used becomes enormous, and the manufacturing cost becomes extremely high. Furthermore, it is difficult to efficiently remove nonionic impurities by treatment with an ion exchange resin.

  Moreover, after processing using the column filled with granular activated carbon, the purification method processed with ion exchange resin is also performed widely. However, in general treatment using granular activated carbon, decolorization can be performed relatively effectively. However, for example, the effect of removing colorless impurities that cause bitterness is low, and thus the purification load of the ion exchange resin is large.

  Furthermore, since oligosaccharides are more easily adsorbed on granular activated carbon than monosaccharides, when trying to purify crude liquid containing oligosaccharides by activated carbon treatment, not only impurities but also the target oligosaccharide is adsorbed on activated carbon, yielding. Decrease.

  In addition, chromatographic separation is carried out by passing a xylobiose-containing hemicellulose solution through a strongly acidic cation exchange resin packed bed and then passing through an eluent, and an elution section mainly containing impurities and a sugar as the main ingredient. A method for fractionation into elution sections is disclosed (see Patent Document 1). However, in this method, several steps are required, and the degree of purification is not sufficient, so that treatment with an ion exchange resin is required later. As a result, the resulting oligosaccharide solution becomes very dilute, increasing the labor and cost required for concentration. Further, since the chromatographic separation apparatus used for this treatment is expensive, there is no cost when the production amount is less than a certain amount.

Japanese Patent Laid-Open No. 1-254692

  In view of the above problems, an object of the present invention is to provide a method for producing a xylo-oligosaccharide that simplifies the process of purifying a crude liquid containing oligosaccharide and that provides an oligosaccharide liquid having a high degree of purification. In particular, the object is to provide a method for producing xylooligosaccharides that easily and efficiently removes nonionic impurities that are difficult to remove effectively by treatment with an ion exchange resin, and further reduces oligosaccharide loss by purification treatment. To do.

  As a result of intensive studies to solve the above problems, the present inventor irradiates a crude liquid containing oligosaccharides with ultraviolet rays, thereby eliminating impurities in the crude liquid, particularly ester compounds that are difficult to remove with an ion exchange resin. The inventors have found that ionic impurities can be decomposed into an ionic compound (acid) that can be easily removed by an ion exchange resin and an alcohol having a boiling point lower than that of water, thereby completing the present invention.

  That is, the present invention provides a method for producing a xylooligosaccharide by purifying a crude liquid containing xylooligosaccharide to obtain an xylooligosaccharide, which comprises a step of irradiating the crude liquid with ultraviolet rays.

  The time for irradiating with ultraviolet rays is preferably 10 minutes or longer.

  Purifying a crude liquid containing xylooligosaccharides by the method for producing xylooligosaccharides of the present invention simplifies the complicated purification process, which requires a combination of many conventional processes, and provides a highly purified xylooligosaccharide liquid. Obtainable. In particular, it is possible to effectively remove nonionic impurities that are difficult to remove with an ion exchange resin.

  Furthermore, when the method of the present invention and treatment with an ion exchange resin are performed in combination, the load on the ion exchange resin can be greatly reduced, reducing the labor and cost required for regeneration and replacement of the ion exchange resin. An inexpensive xylo-oligosaccharide can be provided.

  Further, the present invention provides an efficient method for producing xylo-oligosaccharides with little loss of oligosaccharides due to purification treatment.

  According to the method of the present invention, a crude liquid containing xylo-oligosaccharide obtained from xylan-containing biomass as a raw material can be purified to produce xylo-oligosaccharide. Almost all plant bodies can be used as the xylan-containing biomass, and are not particularly limited. However, for example, hardwoods such as corn shin, white birch, beech, and Japanese oak are suitable because they contain a large amount of xylan components. .

A crude liquid containing xylo-oligosaccharide can be obtained by hydrolyzing such xylan-containing biomass. Specifically, for example, a method in which a raw material is subjected to a chemical treatment such as acid or base or a physical treatment such as blasting and then decomposed by an enzyme, or a method of hydrolyzing and extracting by high-temperature high-pressure water treatment is known. Yes. The method using high-temperature and high-pressure water treatment is superior in that no subsequent neutralization treatment is required as in the case of using an acid / base, and a large-scale apparatus is not required as in physical treatment. In the case of producing a crude liquid containing oligosaccharides by high-temperature and high-pressure water treatment, the raw material and water crushed into chips and fibers are placed in a container capable of high-temperature and high-pressure treatment such as an autoclave and heated and pressurized. do it. The amount of water used at this time is not particularly limited as long as the raw material is immersed in water. For example, it is about 10 to 150 times the dry weight of the raw material. The temperature during the high-temperature and high-pressure water treatment is preferably 180 to 200 ° C. The processing time is not particularly limited, but is, for example, about 5 to 30 minutes. After completion of the high-temperature and high-pressure water treatment, the crude liquid containing the oligosaccharide may be quickly cooled with a cooling coil or the like, and impurities insoluble in water may be removed by a treatment such as filtration or centrifugation.

  The crude liquid containing xylo-oligosaccharide thus obtained usually has a brown color due to impurities, and has a bitter taste such as bitterness. As impurities, furfural, which is a secondary decomposition product of xylose, has been confirmed, and various lignin-derived components, ester compounds, and the like are included. Of these, the method of the present invention particularly effectively removes the ester compound.

  The crude liquid containing xylo-oligosaccharide obtained as described above may be irradiated with ultraviolet rays. However, if the crude liquid contains a coloring component, it is not preferable because the ultraviolet rays are not transmitted. Prior to this, it is preferable to remove the coloring component by an appropriate method such as activated carbon treatment. The activated carbon treatment can be performed by a method such as passing through a column filled with granular activated carbon, adding powdered activated carbon to the crude liquid and stirring, and then removing the activated carbon by an operation such as filtration.

  Ultraviolet rays can be irradiated using an appropriate ultraviolet lamp such as a black light lamp, a chemical lamp, a mercury lamp, or a metal halide lamp, and the irradiation method is not particularly limited. As the ultraviolet rays, it is preferable to irradiate ultraviolet rays having a long wavelength of 250 nm or more, particularly 300 nm or more. In view of this, it is possible to use at high output, and maintenance is easy, and therefore, a high-pressure mercury lamp can be preferably used.

  Irradiation with ultraviolet rays is not particularly limited as long as the crude liquid to be treated is placed in an appropriate container that does not impede transmission of ultraviolet rays. The shape of the container is not particularly limited as long as it can irradiate the entire crude liquid with ultraviolet rays. In addition, when irradiated with ultraviolet rays, the crude liquid generates heat and the water temperature rises (usually about 60 to 70 ° C.). As a result, evaporation of water in the crude liquid is promoted and a concentration effect is also obtained. Therefore, it is better not to close the container during ultraviolet irradiation and to increase the area where the air and the crude liquid come into contact. In addition, it is preferable to increase the surface area of the crude liquid because the irradiation of ultraviolet rays can be performed efficiently and evenly. Irradiation with ultraviolet rays may be performed from one direction or from multiple directions. For example, it is a case where the crude liquid is poured and irradiated from two directions, from above and from below.

  Irradiation with ultraviolet rays may be performed in a state where the crude liquid is allowed to stand, or may be performed while stirring or circulating. Irradiation with ultraviolet rays may be performed in a batch system, and for example, it may be performed in a continuous system using an apparatus such as a belt conveyor.

  The irradiation time of ultraviolet rays is not particularly limited, but is preferably about 10 to 150 minutes, more preferably 20 minutes or more, and particularly preferably 30 minutes or more. When the irradiation time of ultraviolet rays is less than 10 minutes, the effect of the present invention cannot be sufficiently obtained, and even if irradiation is performed for 150 minutes or more, the effect is hardly changed.

  By going through the above-described ultraviolet irradiation step, impurities having absorption at a wavelength of 280 nm can be significantly reduced. As will be described later in detail in Examples, this impurity is considered to be an ester compound, and is decomposed into a corresponding acid and alcohol by irradiation with ultraviolet rays. Ester compounds are difficult to remove by treatment with an ion exchange resin, but the acid produced by UV irradiation can be easily removed by treatment with an ion exchange resin, and alcohol has a lower boiling point than water, so it is heated and evaporated. Can be easily removed.

  The step of irradiating with ultraviolet rays may be provided immediately after a decoloring step such as activated carbon treatment, or after the decoloring step, a step of removing ionic impurities with an ion exchange resin may be provided and then provided. Furthermore, it is not particularly limited to be performed in combination with other known purification treatments.

  According to the present invention, it is difficult to remove by simple treatment, and colorless impurities, particularly nonionic impurities, which have been removed by complicated treatment such as treatment with several types of ion exchange resins in the past can be easily obtained. It can be removed by treatment and the degree of purification is high. Even when it is intended to further increase the degree of purification by combining the method of the present invention with other treatments, it can be carried out easily because less labor and time are required for the method of the present invention. Further, in many conventional processing methods, the sugar solution is diluted in the processing process, and a large amount of labor is required for the subsequent concentration step. However, in the method of the present invention, the crude solution containing the oligosaccharide is diluted. It is not expected to be concentrated. The high-purity xylo-oligosaccharide solution thus obtained may be concentrated by, for example, an evaporator, and may be used as a saccharide solution containing xylo-oligosaccharide at a high concentration, or the xylo-oligosaccharide may be isolated by an appropriate method. Good.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Production of crude liquid containing xylooligosaccharide]
10 g of xylan-containing biomass and 100 g of pure water chipped with a pulverizer were placed in an autoclave and heated to 190 ° C. with a band heater. This temperature was maintained for 10 minutes after the temperature in the autoclave reached 190 ° C., and high-temperature high-pressure water treatment was performed. It cooled to room temperature immediately after completion | finish of a high temperature / high pressure water treatment. The obtained extract was centrifuged and then filtered through a 0.2 μm filter to remove insoluble components. Furthermore, in order to convert the undegraded xylan component into xylo-oligosaccharides, enzymatic hydrolysis was performed using xylanase derived from Aspergillus niger. To this hydrolysis treatment liquid, 25% by weight of powdered activated carbon was added to the sugar component in the liquid and stirred for 1 hour. The activated carbon was removed by filtration. Further, the solution was passed through a column (inner diameter: 1 mc, height: 20 cm) packed with 15 ml of an anion exchange resin (manufactured by Organo: trade name “Amberlite IRA96SB”) (liquid passage conditions / flow rate: 1 ml / min, temperature: room temperature, Eluent: water), a crude liquid containing xylooligosaccharide was obtained. The obtained crude liquid containing xylo-oligosaccharide is colorless and transparent, but contains impurities, and the impurities absorb at 280 nm in ultraviolet absorption analysis.

Example 1
The crude liquid containing xylo-oligosaccharide obtained as described above was irradiated with ultraviolet rays for 60 minutes using a mercury lamp to obtain a xylo-oligosaccharide liquid.

(Example 2)
A xylooligosaccharide solution was obtained in the same manner as in Example 1 except that the ultraviolet irradiation time was changed to 30 minutes.

(Example 3)
A xylooligosaccharide solution was obtained in the same manner as in Example 1 except that the ultraviolet irradiation time was 120 minutes.

Example 4
A xylooligosaccharide solution was obtained in the same manner as in Example 1 except that the ultraviolet irradiation time was changed to 10 minutes.

(Comparative Example 1)
The crude liquid obtained in [Production of crude liquid containing xylooligosaccharide] was placed in an oven heated to 70 ° C. and heat-treated for 60 minutes to obtain a xylooligosaccharide liquid.

(Comparative Example 2)
In [Production of crude liquid containing xylooligosaccharide], the treatment up to activated carbon was performed, and the crude liquid was produced without performing the treatment of passing through a column filled with an anion exchange resin. This crude liquid was treated with a strong anion exchange resin (manufactured by Organo: trade name “Amberlite IRA410J CL”), then a strong cation exchange resin (manufactured by Organo: trade name “Amberlite IR120B Na”), Treatment with a weak anion exchange resin (manufactured by Organo Corporation: trade name “Amberlite IRA96SB”) was performed to obtain a xylooligosaccharide solution. In the treatment with each ion exchange resin, 15 ml of ion exchange resin was packed in a column (inner diameter 1 cm, height 20 cm), and a crude liquid was passed through this column. The flow conditions are flow rate: 1 ml / min, temperature: room temperature, eluent: water. In addition, according to examination of this inventor, the process by these three types of ion exchange resins is a method which can achieve the highest purity degree among the refinement | purification processes by an ion exchange resin.

(Test evaluation)
By measuring the absorbance at 280 nm of the crude liquid containing xylo-oligosaccharide obtained in [Production of crude liquid containing xylo-oligosaccharide] and the xylo-oligosaccharide liquid obtained in Examples and Comparative Examples, The relative concentration of impurities contained was measured. The measurement results are shown in Table 1.

The crude liquid not subjected to the ultraviolet irradiation treatment obtained in [Production of crude liquid containing xylooligosaccharide] and the xylooligosaccharide liquid obtained in Example 1 and Comparative Example 1 were subjected to HPLC measurement. A chart showing the measurement results is shown in FIG.
HPLC measurement conditions / column: TOSO TSKgelSCX (× 2)
・ Eluent: Water ・ Detector: RI

  As performed in the examples, the liquid temperature rises to 60 to 70 ° C. by irradiating with ultraviolet rays for about 10 to 120 minutes. Comparative Example 1 was conducted to examine the possibility that the decrease in impurities was due to heat. As shown in Table 1, since there is almost no decrease in impurities in Comparative Example 1, it can be seen that the decrease in impurities is not due to heat but due to ultraviolet rays.

  Next, studies were conducted to identify impurities that were reduced by UV irradiation.

<Acid / alkali resistance>
When wood is steamed, acetic acid is generated, but impurities having an absorption at 280 nm remain undecomposed by this acetic acid, indicating that it is stable against weak acids. When sodium hydroxide was added to the crude liquid containing xylooligosaccharide so as to have a concentration of 0.5 N and allowed to stand for 1 hour 30 minutes, impurities having absorption at 280 nm decreased. From these facts, the impurities are expected to be ester compounds.
<GC / MS measurement>
The crude liquid which was not irradiated with ultraviolet rays obtained in [Production of crude liquid containing xylooligosaccharide] was separated and collected by HPLC, and GC / MS measurement was performed on the fraction having absorption at 280 nm. The compound mainly present in this fraction was found to be acetate. From the MS cleavage pattern, the closest compound was isopropyl acetate, and the relatively similar compound was allyl acetate, but was not fully identified. When ethyl acetate was added to water and irradiated with ultraviolet rays for 30 minutes in the same manner as in Example 2, ethyl acetate was not detected from the solution after ultraviolet irradiation.

It is a chart which shows the HPLC measurement result of the xylooligosaccharide liquid before ultraviolet irradiation, after ultraviolet irradiation, and after heat processing.

Claims (2)

  A method for producing a xylo-oligosaccharide by purifying a crude liquid containing xylo-oligosaccharide, comprising irradiating the crude liquid with ultraviolet rays.   The method for producing a xylo-oligosaccharide according to claim 1, wherein the time for irradiation with ultraviolet rays is 10 minutes or longer.

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