JP4468665B2 - Production method of plant chitosan - Google Patents

Description

  The present invention relates to a method for producing vegetable chitosan.

  There are two main types of organisms that contain chitin in nature. One is crustaceans such as shrimp and crab or insects, and the other is basidiomycetes represented by mushrooms, enoki and shiitake mushrooms. And most of the conventional chitosan was obtained from crustaceans such as crabs. Plant-derived chitosan has not been industrialized to date even though it was discovered by French botanist Braconeau. The basidiomycete chitin contains a large amount of high-molecular polysaccharides such as cellulose and glucan, so the viscosity is high, and the viscosity increases with high-concentration alkali treatment, and the structure becomes brittle. It is considered that it was difficult to obtain a high purity and that the material was more expensive than a crab shell.

  Currently, chitosan, which is used industrially, is made from cuticles of crustaceans such as crabs and shrimps. The distribution of chitin was also known in the fungal and plant kingdoms, but these were not industrially used as chitosan. This is because the content of chitin in the cuticle layer such as shrimp and crab is high and the alkali removal treatment such as washing with water is very easy after high concentration alkali treatment of chitin. On the other hand, in the case of plant-derived chitin, the structure of basidiomycetes becomes extremely weak after high-concentration alkali heat treatment, which requires high-capacity high-speed centrifugation in the removal and cleaning of residual alkali. Since the polysaccharide is contained, the viscosity is high, and a simple manufacturing process such as filtration treatment cannot be employed in washing with water. In this respect, the difficulty of manufacturing crab chitosan differs greatly.

  In this way, the production of plant chitosan uses high-speed centrifugation, which is dangerous in the treatment of high-concentration alkali, and the production process is complicated. Therefore, it has been difficult to industrially mass-produce plant chitosan.

  Furthermore, since the freeze-drying method is employed in the drying process, it takes too much time and money. Thus, a method for industrially producing plant chitosan has not been established. We have earnestly researched a method for producing plant chitosan industrially at a high yield and at a low cost, and finally completed the present invention.

  “Plant chitosan” obtained by this production method contains 50% or more of high molecular weight polysaccharides in addition to the chitosan component. Furthermore, this is dissolved in an organic acid such as acetic acid, citric acid, malic acid, etc., and the resulting insoluble components are removed by centrifugation. When NaOH is added to the transparent supernatant to a pH of 11 or more, chitosan precipitates. . When this precipitate is collected by centrifugation and further washed with water by a centrifugal separation method, “high-purity plant chitosan” is obtained. In the following section, this is called “vegetable chitosan” and is distinguished from “vegetable chitosan” in this production method.

  In order to produce vegetable chitosan, a high concentration of alkali treatment is required. The alkali must be removed by some method. Plants that have been treated with alkali are weak in their higher-order structure, so when washed with water to remove alkali, glucan and fine fibers dissolve, viscosity increases, and fine particles are generated. Simple processes such as separate processing cannot be used. However, plant chitosan can be recovered in the precipitate by high-speed centrifugation. Therefore, if such viscosity and generation of fine particles can be suppressed before the water washing treatment, the alkali and its neutralized salt can be easily removed by filtration.

  The basidiomycete is finally immersed in a 40% to 60% alkaline solution by adding a concentrated alkaline solution to the basidiomycete or by adding solid alkali and water so that the liquid temperature becomes 60 to 120 degrees. Heat for 1 to 24 hours. The heating container is preferably made of stainless steel that can withstand high temperature and high concentration alkali. As the basidiomycetes used as raw materials, most edible basidiomycetes such as enoki, shiitake mushrooms, shimeji mushrooms, mushrooms, agaricus brazei, maitake, eringi, and sea cucumber can be used. These basidiomycetes can be used as either dried products or fresh products. After the high-concentration alkali heat treatment is completed, the alkali solution is lightly removed by scooping it into a coarse stainless steel net, and the alkali is removed as much as possible by applying pressure from the top. The weight of basidiomycetes treated with alkali is measured, and the contained alkali concentration is calculated. A 10 to 80% organic acid solution or weak acid solution or solid is added to this so as to be equivalent to the calculated alkali, and neutralized so as to be in the range of pH 9 to pH 6.5. For example, when citric acid is used, 1/3 molar equivalent is added because citric acid is a trivalent acid. Since acetic acid is a monovalent acid, it is added in an equimolar amount with alkali.

  As the acid used for neutralization, an organic acid such as acetic acid, lactic acid, citric acid, malic acid, ascorbic acid, or a weak acid such as carbon dioxide is used. The high-concentration alkaline heat-treated basidiomycetes thus neutralized contain the desired plant chitosan, but possess an appropriate structural strength and have extremely low viscosity. The washing process becomes very easy.

  Basidiomycetes containing plant chitosan are collected by filtration and washed several times with pure water. The obtained plant chitosan is easily dried with warm air to obtain the final product plant chitosan powder. As described above, this production method is characterized in that the plant chitosan can be easily dealkalized and recovered with high reproducibility and high yield. In addition, plant chitosan can be produced at low cost because it does not use a high-speed and large-capacity centrifuge or an expensive organic solvent such as alcohol.

  As the alkali for deacetylation, NaOH (caustic soda), KOH (caustic potash) or the like is used. The alkalis may be solid or solution, but those that enable 50% of the final concentration are preferred. The alkali heating reaction is preferably 80 ° C. or more and 4 hours or more. Under these conditions, since deacetylation proceeds smoothly, plant chitosan can be produced with high reproducibility and high yield. The degree of deacetylation of the chitin can be freely adjusted by changing the alkali concentration, the heat treatment time, and the heat treatment temperature.

  As the solvent for washing, a hydrophilic organic solvent such as ethanol, acetone, isopropanol, propanol, butanol, etc. can be used in addition to distilled water, ion exchange water, and pure water. It is possible to use tap water or groundwater for the first water washing after neutralization, but use water with a purity of at least ion-exchanged water, considering that chitosan is likely to adsorb metal ions. It is preferable.

  Drying with warm air of 80 to 105 degrees is sufficient for drying, but it can be dried under reduced pressure or freeze drying at about 50 degrees. In order to obtain fine particles as much as possible by pulverization, lyophilization is preferred. In addition, you may use ethanol, acetone, ether, etc. for a drying process like a normal saccharide polymer compound. Drying at a high temperature makes it difficult to pulverize, so drying at a low temperature is preferable. Or a drying process can be abbreviate | omitted and a water-containing vegetable chitosan can also be grind | pulverized as it is. For example, immediately after washing with water, the mixture may be pulverized with a mixer and, if necessary, a vegetable chitosan solution mixed with a carrier such as dextrin or β-glucan may be spray-dried. As other pulverization methods, a pulverizer such as a jet mill and a polishing apparatus such as a stone mill can be used.

  By using the method of the present invention, it is easy to filter and remove alkali from an alkali-treated basidiomycete and wash it with water, and it is easy to recover high-purity plant chitosan. Can be produced industrially. That is, in plants, it is known that chitin binds to soluble β-glucan to produce an insoluble chitin / glucan compound. Therefore, when basidiomycetes are heat-treated with a high concentration of alkali in the same way as crab chitosan, vegetable chitosan is obtained, but this plant chitosan has a high viscosity because it contains a large amount of glucan at a high concentration. The usual alkali removal and water washing steps used in production are difficult.

  Although an Example is described below, this does not specifically limit a manufacturing method or material.

  10 kg of solid NaOH was added to 1 kg of dried enoki, and 8 kg of water was added thereto and stirred well. Since the NaOH treatment solution generates heat and rises to about 100 ° C., the high temperature can be maintained only by light heating thereafter. The enoki heated at 95 ° C. for 4 hours was transferred to a stainless steel frame and excess NaOH was removed by filtration. The high-concentration alkali after use can be recovered and reused. The enoki containing high-concentration NaOH thus obtained has a relatively solid structure and is easy to handle. Furthermore, in order to remove NaOH completely, it applied and pressed from the top. When about 13.5 L of 20% acetic acid equivalent to the calculated amount of NaOH is gradually added to about 4.4 kg of NaOH-treated enoki, the pH drops to around 7. When neutralization is performed with an equivalent amount of organic acid in this way, the structure of enoki is hard and the viscosity is low, and the following filtration and water washing steps can be easily performed using a stainless steel net. If neutralization is insufficient at this time, the viscosity increases, and filtration and washing with water become extremely difficult. The neutralized enoki was thoroughly washed with running tap water, finally washed once with distilled water, drained again and lightly squeezed and dried in warm air at 80 degrees. Thus, 236 g of plant chitosan derived from enoki was obtained. The recovery rate is 24%.

  A 48% NaOH solution was added to 1 kg of dried shiitake mushrooms, and NaOH was added to a final concentration of 50% or more, and heated to 95 ° C. for 5 hours. NaOH was squeezed and removed on a stainless steel net, and the remaining NaOH was neutralized with a calculated amount of 20% citric acid, washed with water, and dried with warm air to obtain 300 g of shiitake-derived vegetable chitosan. The recovery rate is 30%.

  To 1 kg of dry Agaricus blazei, 10 kg of granular NaOH and 10 kg of water were added and stirred, and heated to 95 ° C. for 4 hours. After squeezing out NaOH, it was neutralized by adding 20% acetic acid equimolar to NaOH in the calculated amount. This was taken up in a stainless steel net, the neutralized solution was filtered off, and washed with pure water. The same operation was performed twice with pure water to remove the sodium acetate contained therein. The resulting precipitate was dried with warm air at 80 degrees. In this way, 189 g of plant chitosan derived from Agaricus blazei was obtained. The yield is 19%.

  120 kg of fresh mushrooms and 120 kg of fresh enoki are added to about 80 kg of solid content obtained by extracting 12 kg of dried Agaricus blazei and 12 kg of dried shiitake mushrooms with 200 L of hot water, and 600 kg of granular NaOH and 180 L of pure water are added to it. In addition, mix well. Heat is generated at 90 ° C. or higher, but heating is continued for 4 hours so that the temperature does not drop below 95 ° C. The NaOH is filtered off and lightly squeezed to remove excess NaOH. About 300 kg of alkali-treated basidiomycetes are obtained. To this, 1200 L of 20% acetic acid is added to neutralize the pH to 7. Let stand for about 1 hour and then filter using a cloth or a slightly finer stainless steel filter. Subsequently, it was washed thoroughly with tap water and dried with warm air to obtain 5.6 kg of mixed basidiomycete chitosan. Using a portion of this 2.8 kg, the content of plant pure chitosan was examined. That is, 10% acetic acid was added to 2.8 kg of plant chitosan, dissolved, filtered through a stainless steel net, and neutralized to pH 10 with 50% NaOH. The precipitate was washed with water and lyophilized. The weight of the pure vegetable chitosan after drying was 1.4 kg. The recovery rate of plant pure chitosan from plant chitosan was about 50%.

アルカリ加熱処理の温度が高くなると植物性キトサンの回収率は低下する。加熱温度は９５度がより好ましい。Table 1 shows the results of examining the relationship between the temperature of the alkali heat treatment and the recovery rate of plant chitosan.

When the temperature of the alkali heat treatment increases, the recovery rate of plant chitosan decreases. The heating temperature is more preferably 95 degrees.

  The plant chitosan of the present invention, unlike animal chitosan made from crabs, is characterized by almost no unpleasant taste or bitterness, and can be expected to be widely applied to foods. Furthermore, plant chitosan is expected to have unique physical properties and bioactivity different from crab-derived chitin / chitosan by binding to glucan. That is, in addition to the respective physiological activities inherent to glucan and chitosan, it possesses a physiological activity as a mixture or heteropolymer of chitosan and glucan.

Claims (7)

A method for producing vegetable chitosan comprising the following steps:
(A) a step of immersing basidiomycetes in an aqueous alkali solution having a concentration of 40 to 60%, heat-treating at 60 to 120 ° C., and deacetylating the plant chitin contained in the basidiomycetes to convert to plant chitosan;
(B) filtering the reaction mixture obtained in step (A),
(C) the step of neutralizing the solid fraction obtained by filtration in step (B) with an acid so as to be in the range of pH 9 to pH 6.5, and (D) the solid fraction neutralized in step (C). The process of washing with water.   The method according to claim 1, wherein the basidiomycete is at least one selected from the group consisting of shiitake mushroom, enoki mushroom, maitake, agaricus blazei, nameko, eringgi, shimeji fruiting body and mycelium.   The acids used for neutralization are formic acid, acetic acid, lactic acid, propionic acid, butyric acid, citric acid, malic acid, succinic acid, fumaric acid, ascorbic acid, adipic acid, aspartic acid, glutamic acid, carbon dioxide, liquefied carbon dioxide, dry carbon The method according to claim 1 or 2, which is at least one selected from the group consisting of ice and carbonated water.   The method according to any one of claims 1 to 3, further comprising (E) a drying step after the water washing step.   The vegetable chitosan produced by the method according to any one of claims 1 to 4 is dissolved in an organic acid aqueous solution, and the pH of the supernatant obtained by removing the insoluble fraction is adjusted to 10 or more to produce plant matter. A method for producing pure plant chitosan, comprising reprecipitation of chitosan and solid-liquid separation.   The method according to claim 5, further comprising the step of washing the solid fraction with water after the solid-liquid separation.   The method according to claim 6, further comprising the step of drying the washed solid fraction.