Method for manufacturing water-soluble polysaccharide from chitin

Abstract

To provide a method with which it is possible to manufacture water-soluble polysaccharide from chitin in a high yield.SOLUTION: Water-soluble polysaccharide is manufactured from chitin by carrying out a heating pulverization step of pulverizing chitin under heating, and a solid-liquid separation step of extracting and separating a water-soluble component contained in a pulverized product obtained by the heating pulverization step by using water.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a water-soluble polysaccharide from chitin. [Background technology]

[0002] For example, as described in Patent Document 1, in recent years, active research has been conducted into converting recyclable biomass resources produced by plants and the like into useful substances for use. For example, there is a demand for the production of biofuels using cellulosic biomass, which is a non-food product such as wood, grass, and rice straw, as a raw material.

[0003] Patent Document 2 discloses a method for extracting water-soluble components from cellulose, which includes a heating and crushing step of crushing a cellulose-containing biomass raw material under heating without adding a catalyst, and an extraction step of extracting water-soluble components contained in the crushed product obtained by the heating and crushing step with water. This method is said to be capable of achieving a high solubilization rate of about 90%.

[0004] On the other hand, chitin is a linear nitrogen-containing polysaccharide polymer formed by β-1,4-glycosidic bonds of N-acetylglucosamine (hereinafter sometimes abbreviated as "NAG"), and is a biomass that is abundant in nature, for example, found in crustaceans such as shrimp and crabs, insects, and fungi such as mushrooms.

[0005] Some of the hydrolysis products of chitin can be used as various functional materials with diverse effects and efficacies. For example, NAG, a monomer, i.e., a monosaccharide, has been expected to be used as a functional food, a pharmaceutical raw material, and a cosmetic raw material in recent years. Chitin oligosaccharides are polysaccharides formed by polymerizing about 2 to 7 NAGs, and are useful as a precursor for obtaining NAG, and have also attracted attention as pharmaceutical materials, functional foods, and agricultural materials. The term "polysaccharide" used in this specification is used in a broad sense to include not only a substance formed by polymerizing a large number (e.g., 10 or more molecules) of monosaccharides through glycosidic bonds, but also disaccharides, trisaccharides, and so-called "oligosaccharides" (also called "oligosaccharides") formed by bonding a small number (e.g., 2 to 10 molecules) of multiple monosaccharides.

[0006] In the technical field, various methods for producing water-soluble polysaccharides from chitin have been conventionally known. For example, Patent Document 3 discloses a method for producing a chitin oligosaccharide-containing composition, which includes a step of crushing a mixture of chitin and a carbon catalyst to obtain a crushed product, and a step of adding water to the crushed product to separate the water-soluble component and the solid component. However, this method requires a carbon catalyst during the crushing treatment, so that the carbon catalyst must be removed afterwards, and the yield of water-soluble polysaccharides is only 34% at maximum, which is not sufficient. In other words, in the technical field, a method capable of producing water-soluble polysaccharides from chitin with a high yield has not yet been established. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2014 / 007295 [Patent Document 2] Patent No. 5938879 [Patent Document 3] International Publication No. 2021 / 140789 Summary of the Invention [Problem to be solved by the invention]

[0008] As discussed above, there is a need in the art for a process capable of producing water-soluble polysaccharides from chitin in high yields. [Means for solving the problem]

[0009] In view of the above problems, the present inventor conducted intensive research and discovered that the above problems can be solved by extracting and separating the water-soluble components contained in the ground product obtained by grinding chitin under heating using water.

[0010] That is, the method for producing a water-soluble polysaccharide from chitin according to the present invention (hereinafter, sometimes referred to as the "method of the present invention") includes the heating and grinding step and the solid-liquid separation step described below. The heat-grinding step is a step of grinding chitin under heating. The solid-liquid separation step is a step in which water-soluble components contained in the pulverized product obtained in the heating and pulverizing step are extracted with water and separated. Effect of the Invention

[0011] As described above, in the method of the present invention, the water-soluble components contained in the ground product obtained by grinding chitin under heating are extracted with water and separated. As a result, the method of the present invention makes it possible to produce water-soluble polysaccharides from chitin in high yields without the need for a catalyst.

[0012] Other objects, features and attendant advantages of the present invention will become readily apparent from the following description of the embodiments of the present invention which are given with reference to the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1] 1 is a flow chart showing an example of the process flow in an embodiment embodying the method of producing a water-soluble polysaccharide from chitin according to the present invention (the method of the present invention). [Diagram 2]FIG. 2 is a schematic diagram showing the production of water-soluble polysaccharides from chitin using mechanochemicals in the heating and grinding step included in the method of the present invention. [Diagram 3] FIG. 1 is a schematic diagram showing the configuration of a planetary ball mill used in an embodiment of the method of the present invention. [Figure 4] 1 is a graph showing the change over time in the solubilization rate of chitin at various heating temperatures obtained in an example of the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the method for producing a water-soluble polysaccharide from chitin according to the present invention (the method of the present invention) will be described with reference to the drawings. FIG. 1 is a flow chart showing an example of the process flow in an embodiment of the method of the present invention.

[0015] As mentioned above, chitin is a biomass contained in the shells or skins of crustaceans such as shrimp and crabs, arthropods, insects, squid, shellfish, and okinawa shrimp, and in the cell walls of fungi such as mushrooms. The chitin to be subjected to the heating and crushing process may be a purified product or an unrefined product, but a purified product is preferable. For example, when trying to obtain purified chitin from crab shells, purified chitin can be obtained by carrying out pretreatments such as dissolving protein with an alkali and dissolving calcium with an acid, followed by posttreatments such as neutralization, solid-liquid separation, and washing with water. It is easy to obtain purified chitin that has been industrially prepared. On the other hand, unrefined products can be used as long as substances that hinder the decomposition of chitin by the method of the present invention have been removed.

[0016] Chitin may be dry or wet, crystalline or non-crystalline. For example, when unrefined chitin is used, the chitin may have a shape and size that are inappropriate for subjecting it to the heating and grinding step as is. In such a case, it is preferable to coarsely grind the chitin prior to the heating and grinding step.

[0017] In other words, step S01 in the flowchart shown in Figure 1, in which the coarse grinding process is carried out, is not an essential component of the method of the present invention, but is a step that is adopted when coarsely grinding chitin prior to the heating and grinding process as described above.

[0018] In order to coarsely crush chitin in the coarse crushing step, for example, a coarse crusher such as a shredder, jaw crusher, gyratory crusher, cone crusher, hammer crusher, roll crusher, and roll mill, or a medium crusher such as a stamp mill, edge runner, cutting and shear mill, rod mill, autogenous crusher, and roller mill can be used. The period during which chitin is subjected to the coarse crushing step is not particularly limited as long as the chitin after the treatment is uniformly pulverized to a shape and size suitable for the heat-crushing step. The shape and size of chitin suitable for the heat-crushing step can be, for example, a powder with a particle size of 20 to 1000 μm.

[0019] Next, the heating and grinding step performed in step S02 is a step of grinding chitin under heating. That is, in the heating and grinding step, chitin is subjected to a grinding treatment at a predetermined temperature for a predetermined period of time.

[0020] Examples of the grinding equipment used for the grinding treatment in the heat-grinding step include tumbling ball mills such as pot mills, tube mills, and conical mills; jet grinders such as swirling flow jet mills, collision type jet mills, fluidized bed jet mills, and wet type jet mills; shear mills such as crushers and ong mills; colloid mills such as mortars and stone mills; impact grinders such as hammer mills, cage mills, pin mills, disintegrators, screen mills, turbo mills, and centrifugal classifier mills; vibration mills that grind by vibrating a drum to move the internal medium; and planetary ball mills, which are grinders that utilize the motion of rotation and revolution.

[0021] From the viewpoint of applying a strong compressive force to chitin to apply a tensile stress in the longitudinal direction of the main chain, the grinding device used in the heat-grinding step is preferably a ball mill or a vibration mill. More preferably, the grinding device is a planetary ball mill, a rolling ball mill, or a vibration mill. In addition, it is preferable to use a planetary ball mill in the heat-grinding step at the laboratory level, and it is preferable to use a vibration mill industrially. In the vibration mill, instead of rotating a drum (grinding cylinder) into which the grinding medium is inserted as in the drum rotary ball mill, the drum is vibrated to move the medium inside. As a result, the vibration mill makes it possible to complete grinding in about 1 / 10 to 1 / 20 of the time required when using a drum rotary ball mill.

[0022] As described above, in the heating and grinding process, chitin is subjected to a grinding process at a predetermined temperature for a predetermined period of time. Therefore, in the heating and grinding process, in addition to the grinding device, a heating device is used that includes a temperature sensor that detects the temperature of the ground chitin, a heater that heats the chitin, and a control unit that controls the heater so that the temperature detected by the temperature sensor coincides with a preset temperature. Examples of the temperature sensor include thermometers that use a resistance thermometer, thermometers that use a thermocouple, or radiation thermometers, which are well known to those skilled in the art. Examples of the heater include heaters that are well known to those skilled in the art, such as electric heaters or infrared heaters. Furthermore, the control unit is, for example, an electronic control device that includes a microcomputer as a main part, and includes a CPU (processor), a ROM, a RAM, a non-volatile memory, and an interface. The CPU is configured to realize the above-mentioned control by executing instructions (programs, routines) stored in the ROM.

[0023] The temperature (heating temperature) and period (grinding period) at which chitin is heated and ground in the heat-grinding step vary depending on, for example, the amount of chitin and the specifications of the grinding machine (for example, the capacity, the shape and size of the grinding medium, and the amount of the grinding medium relative to the amount of chitin). When attempting to obtain water-soluble polysaccharides in sufficient yields by a grinding period of 1 to 12 hours, the heating temperature is preferably 100 to 200°C, more preferably 150 to 190°C. If the heating temperature is 100°C or lower, it is difficult to sufficiently decompose chitin to obtain water-soluble polysaccharides by a grinding period of 1 to 12 hours. On the other hand, if the heating temperature is 200°C or higher, for example, the amount of water-insoluble or volatile by-products produced increases, and there is a high possibility that problems such as a decrease in the yield of water-soluble polysaccharides will occur. The above-mentioned "by-products" refer to products other than NAG and linear chitin oligosaccharides. Specific examples of by-products include branched oligosaccharides, dehydrates, and / or other unidentified substances.

[0024] As described above, the heating and grinding step included in the method of the present invention is a step in which chitin is ground under heating to cleave the main chain of chitin using mechanochemicals to obtain water-soluble polysaccharides (see FIG. 2). Unlike the method disclosed in the above-mentioned Patent Document 3, the heating and grinding step included in the method of the present invention does not require a catalyst such as a carbon catalyst, so there is no need to remove the catalyst afterwards. Furthermore, the heating and grinding step included in the method of the present invention can hydrolyze chitin to produce water-soluble polysaccharides without the presence of compressed hot water (i.e., liquid water) that remains liquid even at high temperatures of 100°C or higher, as in the conventional method of solubilizing biomass by hydrothermal treatment. Therefore, since no mechanism is required to maintain high pressure and provide compressed hot water, the production cost can be reduced.

[0025] Next, the solid-liquid separation process carried out in step S03 is a process of extracting and separating the water-soluble components contained in the pulverized material obtained by the heating and pulverizing process with water. The polysaccharides contained in the obtained pulverized material are mainly chitin oligosaccharides, which are water-soluble unlike the raw chitin. Therefore, by adding water to the pulverized material and performing operations such as stirring, and then separating the water-soluble components from water-insoluble components such as solid components, a composition containing water-soluble polysaccharides at a high ratio can be obtained. The obtained water-soluble polysaccharide-containing composition may contain water-soluble components such as NAG in addition to chitin oligosaccharides.

[0026] The water to be added to the ground material is usually distilled water, but is not particularly limited thereto. Specific examples other than distilled water include a solution containing a salt and a buffer solution. In addition, an organic solvent miscible with water can be added as long as it does not affect the dissolution of the water-soluble polysaccharide to be obtained.

[0027] The method for separating the water-soluble component from the water-insoluble component may be a method generally used for removing solids from a suspension, and specific examples of such a method include filtration using filter paper, filter cloth, or membrane filter, and sedimentation separation such as natural sedimentation or centrifugal sedimentation.

[0028] The water-soluble polysaccharide-containing composition obtained by the method of the present invention does not contain acid or alkali, and can be used for various purposes as it is without neutralization. Depending on the purpose, the water-soluble polysaccharide may be further purified by, for example, reprecipitation with an alcohol solvent or chromatography such as high performance liquid chromatography (HPLC).

[0029] As described above, in the method of the present invention, the water-soluble components contained in the ground product obtained by grinding chitin under heating are extracted and separated with water. As a result, the method of the present invention can reduce the production of by-products and produce water-soluble polysaccharides from chitin in high yields. Furthermore, in the method of the present invention, the heating and grinding step can be performed in the absence of either a catalyst or liquid water, thereby reducing the production cost of water-soluble polysaccharides. EXAMPLES

[0030] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0031] The raw chitin used was in powder form commercially available from Fujifilm Wako Pure Chemical Industries, Ltd. Therefore, in this example, the above-mentioned coarse grinding step was not carried out, and the method of the present invention was started from the heating and grinding step.

[0032] In the heating and grinding process, a two-pot planetary ball mill 1 as shown in FIG. 3 was used. Each mill pot (container) 2 was made of zirconia (ZrO2) and had a capacity of 45 ml. The radius r of the stage (rotating table) 3 was S The diameter of the balls was 124.75 mm, and balls 4 made of zirconia (ZrO2) with a diameter of 5 mm were used as the medium. Furthermore, the planetary ball mill 1 was surrounded by a heater provided in a heating device (not shown), and temperature sensors were provided near each mill pot 2, so that each mill pot 2 could be maintained at a desired temperature.

[0033] In the heating and grinding process, 75 g of balls 4 and 0.3 g of chitin were put into each mill pot 2, and the chitin was ground using the planetary ball mill 1 while maintaining the temperature at a predetermined level using a heating device (not shown). M and Stage 3 revolution N SBy performing the above steps in the opposite directions, a strong centrifugal force was applied (see the white arrows in the figure), and the chitin 5 was pulverized inside each mill pot 2. The rotation speed of the planetary ball mill 1 was set to 300 rpm.

[0034] Next, in the solid-liquid separation process, distilled water was added to the ground material obtained by the heating and grinding process and stirred, and then the mixture was filtered through filter paper and the filtrate was collected to obtain a water-soluble polysaccharide-containing composition including chitin oligosaccharides.

[0035] In this example, the heating temperature and grinding time in the heating and grinding step were changed in various ways, and the yield (solubilization rate) of water-soluble polysaccharide was measured based on the total organic carbon (TOC) value of the water-soluble polysaccharide-containing composition obtained as described above and the net amount of chitin charged. The results are shown in Table 1 below and the graph in Figure 4.

[0036] [Table 1]

[0037] As is clear from Table 1 and FIG. 3, when the heating temperature in the heating and grinding process was 100°C, the solubilization rate of chitin remained at 9% even when the grinding period was extended to 6 hours. On the other hand, when the heating temperature was set to a temperature higher than 100°C, a high solubilization rate of more than 60% could be achieved by setting the grinding period according to each heating temperature. In particular, when the heating temperature was set to 150°C to 190°C, a very high solubilization rate of 85% or more could be achieved by setting the grinding period according to each heating temperature. In addition, the grinding period at which the highest solubilization rate was achieved at each heating temperature (shown in bold and underlined in Table 1) tended to become shorter as the heating temperature increased. The reason why the solubilization rate decreased beyond the grinding period at which the highest solubilization rate was achieved at each heating temperature is considered to be due to the increase in the amount of water-insoluble or volatile by-products produced as described above due to excessive decomposition and / or structural changes such as branching of chitin.

[0038] From the above results, it was confirmed that the method for producing water-soluble polysaccharides from chitin according to the present invention (the method of the present invention) can produce water-soluble polysaccharides from chitin in high yield without the need for a catalyst by carrying out a heating and grinding process in which heating and grinding are carried out simultaneously at a predetermined heating temperature for a predetermined grinding period.

[0039] For the purpose of explaining the present invention, several embodiments and examples having specific configurations have been described above, sometimes with reference to the attached drawings. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments and examples, and it goes without saying that appropriate modifications can be made within the scope of the claims and the matters described in the specification. [Explanation of symbols]

[0040] 1…Planetary ball mill 2. Mill pot 3. Stage 4. Ball 5. Chitin

Claims

1. A heating and crushing step of crushing chitin under heating; a solid-liquid separation step of extracting and separating water-soluble components contained in the pulverized product obtained by the heating and pulverizing step with water; The method for producing a water-soluble polysaccharide from chitin comprises:

2. A method for producing water-soluble polysaccharides from chitin according to claim 1, comprising the steps of: The heating and grinding step is carried out in the absence of any catalyst or liquid water. A method for producing water-soluble polysaccharides from chitin.

3. A method for producing a water-soluble polysaccharide from chitin according to claim 1 or 2, comprising the steps of: The heating temperature in the heating and grinding step is 100 to 200 ° C., and the grinding period is 1 to 12 hours. A method for producing water-soluble polysaccharides from chitin.

4. A method for producing a water-soluble polysaccharide from chitin according to claim 3, comprising the steps of: The heating temperature in the heating and grinding step is 150 to 190 ° C., and the grinding period is 1 to 12 hours. A method for producing water-soluble polysaccharides from chitin.

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