KR19990084226A - Method for producing chitosan oligosaccharides - Google Patents

Abstract

Provided is a method of hydrolyzing chitosan having low absorption rate in human body into chitosan oligosaccharides using edible organic acid useful for human body.

Description

Method for producing chitosan oligosaccharides

The present invention relates to a method for producing chitosan oligosaccharides, which are used as food additives or pharmaceuticals, by hydrolysis from polymer chitosan having low absorption in the human body using edible organic acids necessary for metabolism of the human body. The present invention also relates to a method of increasing the hydrolysis reaction rate using microwave during this process.

The chemical names of chitin and chitosan are poly-β (1,4) -N-acetyl-D-glucosamine [poly-β (1,4) -N-acetyl-D-glucosamine] and poly-β-D-, respectively. As glucose- [poly-β-D-glucosamine], chitin refers to a chemical substance in which one OH group in a polysaccharide is substituted with -NHCOCH ₃ and chitosan is deacetylated and substituted with -NH ₂ in this chitin. In general, chitin is contained in the epidermis of crustaceans, but some are known to be present in some fungal plants such as mushrooms and the stems of ordinary plants. Among them, the shell of red crab with high content and high quality is most commonly used as a raw material of chitin. Chitin extracted from the shell of the red crab is deacetylated to produce chitosan in a high concentration solution of a strong base such as NaOH, etc. The chitosan thus prepared is a polymer material and its molecular weight reaches hundreds of thousands.

Until now, polymer chitosan has been widely used only as a heavy metal adsorbent for treating wastewater contaminated with heavy metals. Recently, advanced countries such as Japan have developed fiberization process technology to increase demand for antibacterial clothing and deodorant fiber materials. In addition, after the results of clinical trials showing that chitosan had anti-cancer effects in Japanese medicine in September 1991, chitosan has gained great attention as a food and medicine.In the United States, chitosan has become a dietary treatment for weight control. Also well known. In accordance with this trend, many small and medium-sized enterprises in Korea have participated in the manufacture and sale of chitosan. However, polymer chitosan by itself is very low in the body, so in order to increase the body absorption rate of water-soluble oligosaccharides must be converted to.

In general, two methods are commonly used to hydrolyze such chitosan polymers and convert them into oligosaccharides. One is a chemical method of dissolving chitosan in concentrated hydrochloric acid solution (about 33-37%) for a long time to hydrolyze it. The other is a biological method of hydrolyzing chitosan polymers using enzymes in aqueous or low acid solutions. Although acetic acid was used as an acid solution in this biological method, in this case, acetic acid only allows a hydrolysis reaction by enzymes by maintaining a constant pH, and no hydrolysis reaction by acetic acid alone is known.

It is known that the above two methods are used as a hydrolysis method used in Korea, but it is difficult to grasp the exact technical contents because each company does not disclose their technology. However, since the wastewater from such a manufacturing method may cause environmental pollution, such a domestic chitosan manufacturing industry is likely to be the object of criticism as an environmental hazardous industry. That is, since the problem of the discharge of wastewater by treatment in various strong acid and strong alkaline solutions becomes very serious, there is an urgent need for a hydrolysis method of chitosan that can prevent environmental pollution.

In addition, when concentrated hydrochloric acid is used, the possibility of residual chlorine substituents and the like may be a problem, and in the case of a method using an enzyme, the cost increases and economical disadvantages occur.

Accordingly, in the production of chitosan oligosaccharides, organic acids useful for humans are used instead of the strong acids that are harmful to the human body, thereby cleaning the chitosan production process and preventing environmental pollution, and the production of chitosan oligosaccharides as food or pharmaceutical products. It is an object of the present invention to improve safety.

1 is a diagram showing the FT-IR spectrum after the hydrolysis reaction of chitosan using lactic acid, ascorbic acid, acetic acid and hydrochloric acid.

2 shows FT-IR spectra of chitin and chitosan.

The present invention consists of hydrolyzing chitosan by dissolving high molecular weight chitosan in an aqueous solution of organic acid useful for the human body to prepare a chitosan-organic acid solution, increasing the solubility of the high molecular chitosan in the aqueous organic acid solution and increasing the reaction rate of the hydrolysis reaction. It can also be performed while heating.

In addition, the hydrolysis reaction of the present invention includes a method of greatly improving the reactivity of the hydrolysis and increasing the reaction rate by maintaining the pressurized state at atmospheric pressure or higher after dissolving the polymer chitosan in the organic acid aqueous solution. The pressure required under these pressurization conditions depends on the amount of reactants and the reaction temperature, but the optimum pressure appeared to be about 2-12 atmospheres. The reaction time depends on the amount of the reactants, the reaction temperature and the pressure, but the hydrolysis reaction proceeds sufficiently within about 1-2 hours.

In addition, a method of greatly increasing the rate of hydrolysis by using microwaves is also included in the present invention. At this time, microwaves of 2.45 GHz, which are used in the home or food industry, can be used, and the use of the microwave has a merit that the reaction time is greatly reduced to 10 minutes or less. The size and power of the microwave oven can be determined by the amount of reactants and the degree of hydrolysis required.

Since the organic acid used in the hydrolysis reaction of the present invention can proceed the reaction without using a high concentration, the cost can be greatly reduced, and the material of the food or pharmaceutical product as it is without additional organic acid removal step after the completion of the hydrolysis reaction Since it can be used as, the manufacturing process has the advantage that can be simplified. Of course, in some cases, it can also be used after removing residual organic acid by a simple method.

Organic acids that can be used in the present invention include all organic acids useful for the human body, which are included in various natural foods and can be absorbed by the human body, or are produced in the process of using the absorbed foods for metabolism of the human body; For example, tartaric acid, pyruvic acid, ascorbic acid, citric acid, citric acid, lactic acid, propionic acid, acetic acid, and combinations thereof.

Such an organic acid may be used in an aqueous solution state in the hydrolysis process of the present invention. At this time, the concentration of the organic acid is not particularly limited, preferably 3-8% by weight, the organic acid concentration is less than 3% by weight at room temperature, When the solubility of chitosan under normal pressure decreases and the concentration of the organic acid exceeds 8% by weight, the efficiency of the hydrolysis reaction does not increase significantly compared to the increase of the concentration. However, even if the organic acid concentration is less than 3% by weight, since the chitosan can be dissolved by heating or the like, the concentration of the organic acid is not necessarily limited to this range. Overall, although the cost increases as the concentration of organic acid increases, the side effects of organic acids useful for the human body can be expected.

According to the present invention, after hydrolysis of chitosan by adding microwaves with ascorbic acid, lactic acid and acetic acid as an example of organic acid, the resulting chitosan oligosaccharides are mixed with KBr to make a pallet to obtain infrared spectral spectra using FT-IR. (a), (b) and (c) are shown in FIG. 1, and in the same manner, after hydrolysis of chitosan with concentrated hydrochloric acid, an FT-IR spectrum was obtained by the same method and shown in FIG. 1 as (d). . In addition, the FT-IR spectrum of the polymer chitosan (Aldrich) before the hydrolysis reaction as another control is shown in Figure 1 as (e). This spectrum can be used to compare the degree of acetylation of each hydrolysis reaction.

In FIG. 2, FT-IR spectra of chitin and chitosan are shown as (A) and (B), respectively, for reference. This spectrum shows that the chitin and chitosan groups are NH and C = O groups. It can be seen from the comparison of the difference in intensity. In other words, the chitosan has a smaller C = O group than the N-H group compared to the chitin, and as a result, the smaller the strength of the C = O group than the N-H group, the greater the deacetylation.

Therefore, in Fig. 1, the chitosan powder of (e) still has a lot of C═O groups, and the strength of this C═O group is further reduced in (c) than in (d), and in (a) and (b), It can be seen that the reduction is more significant. This shows that the degree of deacetylation is higher in the hydrolysis reaction with acetic acid, lactic acid and ascorbic acid than in the hydrolysis reaction with concentrated hydrochloric acid. These results indicate that the chitosan hydrolyzed by the present invention can be more effectively absorbed and acted in the body due to the large progress of deacetylation. In addition, the edible organic acid of the present invention suggests the possibility that the chito-oxidation reaction and the oligosaccharide reaction by the deacetylation reaction from the chitin polymer may simultaneously occur, that is, the hydrolysis reaction of the chitosan oligosaccharide through the present invention. That means you can simplify the manufacturing process.

The present invention will be described in more detail with reference to the following examples. However, these examples are merely a part of the scope of the present invention, and are intended to illustrate the present invention, and are not intended to limit the present invention.

Example 1

2 g of polymer chitosan (purchased from Aldrich, USA; molecular weight = 310,000-375,000) were dissolved in 100 mL of a 3% by weight aqueous solution of lactic acid. 50 mL of a sufficiently dissolved chitosan-lactic acid aqueous solution was taken in an autoclave made of Teflon ^R having a diameter of 6 cm and a height of 10 cm, and sufficiently sealed using a lid made of Teflon prepared in advance. . The reactor set thus assembled was then placed in a microwave oven and heated for 8 minutes in a discontinuous mode. After heating, the mixture was removed from the oven, cooled for about 3 hours, and the lid was opened to store a hydrolyzed chitosan-lactic acid aqueous solution in a glass bottle.

To precipitate pure chitosan oligosaccharide (hydrolyzed chitosan), 20 mL of hydrolyzed chitosan-lactic acid aqueous solution was taken, mixed with 80 mL of acetone, and stirred. At this time, a chitosan oligosaccharide having low solubility in acetone was precipitated as a pale solid component. The resulting solids, ie chitosan oligosaccharides, were filtered off and dried. This process was repeated several times to increase the purity of chitosan oligosaccharides. After the sufficiently dried chitosan oligosaccharide was ground to a fine powder form, the following various analyzes were performed.

First, by producing an aqueous solution of 2% by weight with the chitosan oligosaccharide powder thus prepared, it was observed that the chitosan oligosaccharide obtained by the production method of the present invention is very soluble in water. In order to grasp the degree of oligoglycosylation of the chitosan oligosaccharide, the viscosity of the aqueous chitosan oligosaccharide solution was measured, and when measured using a Brookfield viscometer at 20 ° C., 2.5 cP or less appeared. This is a value similar to the viscosity measured by the aqueous solution of the same concentration using a commercially available chitosan oligosaccharide product.

Chitosan oligosaccharide powder prepared as described above was mixed with KBr to make a pallet to obtain an infrared spectral spectrum using FT-IR. The results are shown in FIG.

Example 2

Chitosan was hydrolyzed and purified in the same manner as in Example 1 except that tartaric acid was used instead of lactic acid. The obtained chitosan oligosaccharide powder was made into a 2 wt% aqueous solution, and the viscosity was measured to be 2 cP or less.

In addition, the FT-IR spectrum was obtained from the hydrolyzed chitosan powder as described above, and as in Example 1, it showed a very high degree of deacetylation compared to the hydrolyzed chitosan using acetic acid or hydrochloric acid.

Example 3

Chitosan-lactic acid aqueous solution was prepared in the same manner as in Example 1, and 50 mL was taken in an autoclave made of stainless steel having a height of 18 cm and an inner diameter of 13 cm. Sufficiently sealed using a lid made of stainless steel prepared in advance, and the reactor set thus assembled was heated while stirring. At this time, the reaction temperature was 100-150 ° C., and the reaction pressure was 2-12 atmospheres at this reaction temperature.

Viscosity change of the resulting aqueous solution was observed as the reaction time increased. After treating the chitosan-lactic acid aqueous solution obtained for each condition by the method used in Example 1 to obtain pure hydrolyzed chitosan powder, the viscosity was measured. To 2% aqueous solution. As a result of the measurement, the viscosity of the aqueous chitosan solution began to decrease significantly after the first 15 minutes of reaction, and the viscosity after 2 hours of reaction decreased to 2 cP or less.

In addition, the FT-IR spectrum was obtained from the hydrolyzed chitosan powder obtained as described above in the same manner as in Example 1, and as a result, the degree of deacetylation was much higher than that of chitosan hydrolyzed using acetic acid or hydrochloric acid. It was.

Example 4

Chitosan was hydrolyzed and purified in the same manner as in Example 1 except that citric acid was used instead of lactic acid. The obtained chitosan oligosaccharide powder was made into a 2 wt% aqueous solution, and the viscosity was measured to give 20-80 cP. It can be seen that citric acid also has a great effect on the hydrolysis reaction of the chitosan polymer.

However, as a result of obtaining the FT-IR spectrum of the pure chitosan powder obtained through hydrolysis and purification as described above, no increase in the degree of deacetylation reaction shown in Examples 1 and 2 was observed.

Example 5

Chitosan-citric acid aqueous solution was prepared in the same manner as in Example 4, and the hydrolysis reaction was performed under the same autoclave and reaction conditions described in Example 3. In the reaction at 120 and 150 ° C., after about 1 hour of reaction, the viscosity of the solution decreased to 2 cP or less, indicating that the solution was hydrolyzed to very small oligosaccharides.

However, as described above, the chitosan purified through recrystallization after hydrolysis was measured by FT-IR, and as in Example 4, the degree of deacetylation did not increase.

Example 6

Chitosan was hydrolyzed and purified in the same manner as in Example 1 except that propionic acid was used instead of citric acid. The obtained chitosan oligosaccharide powder was made into a 2% by weight aqueous solution, and the viscosity was measured, resulting in 20-65 cP. Therefore, it can be seen that propionic acid also has a great effect on the hydrolysis reaction of the chitosan polymer.

However, the FT-IR spectrum of the pure chitosan powder obtained through the hydrolysis and purification process as described above was measured. As in Example 4, no increase in the degree of deacetylation of chitosan was observed.

Example 7

An aqueous chitosan-propionic acid solution was prepared in the same manner as in Example 6, and the hydrolysis reaction was performed under the same autoclave and reaction conditions described in Example 3. After 2 hours at 120 ° C, the viscosity of the solution decreased to about 2 cP. After 150 minutes of reaction at 150 ° C, the viscosity of the solution decreased to 1.3 cP. It can be seen that the hydrolysis.

As described above, the chitosan purified through recrystallization after hydrolysis was measured by FT-IR, and as in the case of Example 4, the degree of deacetylation did not increase.

Example 8

Chitosan was hydrolyzed and purified in the same manner as in Example 1 except that pyruvic acid was used instead of propionic acid. The obtained chitosan oligosaccharide powder was made into a 2% by weight aqueous solution, and the viscosity was measured to come out as 15-70 cP. Therefore, it can be seen that pyruvic acid also has a great effect on the hydrolysis reaction of the chitosan polymer.

In addition, FT-IR spectrum of the pure chitosan powder obtained through the hydrolysis and purification process as described above was obtained. As in Example 6, no increase in the degree of deacetylation of chitosan was observed.

Example 9

Chitosan-pyruvic acid aqueous solution was prepared in the same manner as in Example 8, and the hydrolysis reaction was performed under the same autoclave and reaction conditions described in Example 3. In the reaction at 120 ° C., after 1 hour, the viscosity of the solution decreased to 1.9 cP, indicating that the chitosan polymer was hydrolyzed to very small oligosaccharides by propionic acid.

In addition, as described above, the chitosan purified through recrystallization after hydrolysis was measured by FT-IR, and as in Example 4, the degree of deacetylation did not increase.

Example 10

Except for using ascorbic acid instead of lactic acid, the chitosan was hydrolyzed using microwave in the same manner as in Example 1, and the viscosity of the solution was measured. As a result, the viscosity of the solution is reduced to about 11-20 cP after 7 minutes of microwave reaction at 20,000 cP or more, it can be seen that ascorbic acid also has a great effect on the hydrolysis reaction of chitosan polymer.

As described above, the chitosan purified after recrystallization after hydrolysis was measured by FT-IR, and ascorbic acid was observed to be effective in increasing the degree of deacetylation of chitosan similarly to the lactic acid of Example 1. The results are shown in FIG.

However, in this embodiment, ascorbic acid itself is also observed to change from a transparent color to yellow by a reaction, and ascorbic acid is not suitable for the hydrolysis reaction at a high temperature of about 100 ° C. However, if the reaction does not proceed at high temperatures, it may be used sufficiently as a hydrolyzate.

Example 11

Chitosan was hydrolyzed and purified in the same manner as in Example 1 except that acetic acid was used instead of lactic acid. The obtained chitosan oligosaccharide powder was made into a 2% by weight aqueous solution and the viscosity was measured to be 5.5 cP or less. Thus, it can be seen that the present invention has a great effect on the hydrolysis of nitric acid chitosan.

In addition, FT-IR spectra were obtained with the hydrolyzed chitosan powder as described above, and the results are shown in FIG. 1.

As described above, the production method of the present invention for producing chitosan oligosaccharides by hydrolyzing chitosan by using organic acids useful for the human body, can use the resulting chitosan oligosaccharides directly as a material for food or pharmaceutical products, Useful effects on the human body have the advantage of using side effects, and since this treatment process is harmless to the environment, its industrial applicability is very high.

In other words, on the premise that human life is healthy in a pollution-free and pleasant environment, the pollution-free production technology of chitosan by the manufacturing method of the present invention based on environmentally friendly technology is very desirable. do.

Claims (5)

A method for producing a chitosan oligosaccharide, comprising dissolving high molecular weight chitosan in an edible organic acid aqueous solution to hydrolyze it. The method of claim 1, wherein the edible organic acid is selected from the group consisting of tartaric acid, pyruvic acid, ascorbic acid, citric acid, lactic acid, propionic acid, acetic acid and combinations thereof. The method of claim 1, wherein the concentration of the aqueous organic acid solution is 3-8% by weight. The method of claim 1 wherein said hydrolysis reaction is carried out in an autoclave. The method according to any one of the preceding claims, wherein the hydrolysis reaction is carried out by adding microwaves.