KR20000036774A - Preparing Methode for Aqueous Chitosan - Google Patents

Abstract

PURPOSE: A process for producing chitosan for food is provided which can prepare high-purity aqueous chitosan in a simple manner. CONSTITUTION: A process comprises dissolving chitosan in an organic acid selected from the group consisting of purified water, acetic acid and lactic acid, enzymolysis of the chitosan solution by adding 0.5 to 1.5 units chitosanase to the chitosan solution, terminating the chitosanase reaction by heating at 85°C for 30 min when the solution does not become cloudy at pH 6 to 7.5, purifying by an ion exchange resin, and freeze drying. By this process, beta-1,4-poly-glucosamine having a molecular weight of 20,000 to 100,000 is prepared.

Description

Preparation Method of Aqueous Chitosan {Preparing Methode for Aqueous Chitosan}

The present invention relates to a method for producing a water-soluble chitosan to accept the chitosan having an effect of enhancing the immune system of the human body. More specifically, the present invention relates to a method for producing food chitosan (β-1,4-poly-glucosamime, molecular weight 20,000 to 100,000) by adjusting the molecular weight of chitosan.

The conventional chitosan production method is roughly divided into three as follows.

1) Preparation of water-soluble chitosan (oligosaccharide) by a chemical method (conventional method)

Chitosan is an excellent material for food and medicine because its molecular structure is almost the same as that of human tissues and its affinity does not cause an immune reaction (rejection reaction). However, such polymer chitosan is insoluble in water, and dissolved in organic acids (acetic acid, lactic acid, etc.) and inorganic acids (HCl).

To make chitosan water-soluble, it must be dissolved near acidity (pH) 7.However, the conventional method for preparing water-soluble chitosan (oligosaccharide) by hydrochloric acid (HCl) hydrolysis uses a large amount of hydrochloric acid (HCl) relative to chitosan. It requires a long time. The order is as follows.

Hydrochloric acid hydrolysis → filtration → concentration → ethanol fraction → ion exchange chromatography → fractionation → drying

As an example, 250 ml of concentrated hydrochloric acid is added to 25 g of chitosan and hydrolyzed at 80 ° C. for 2 hours. Insoluble matter of this decomposition solution is removed by centrifugation, activated carbon is added to the supernatant, decolorized, and concentrated under reduced pressure. 200 ml of ethanol was added to the decomposed product, the mixture was stirred at room temperature for 2 hours, insolubles were removed by suction filtration, and the filtrate was concentrated under reduced pressure.

Dissolution separation of ethanol yields 14.5 g of chitosan digest.

3.0 g of this partial decomposition product was dissolved in water and adsorbed onto a 200 ml ion exchange resin column (Dowex × 50w OH ^- form), and the hydrochloric acid concentration was sequentially 1.15 N (150 ml), 1.81 N (300 ml), 2.54 N (400 ml). Elevated step by step to elute. Water-soluble chitosan (oligosaccharide) detection is carried out by measuring the absorbance at 510 nm by ninhydrin coloration and fractionating a series of water-soluble chitosan (oligosaccharide). This result

0.25 g of D-glucosamine hydrochloride (GlcN-HCl) (yield from 3 g of 8.3% chitooligosaccharide mixture),

Chitobis hydrochloride (GlcN ₂ HCl) 0.82 (27.3%),

Chitotrios hydrochloride (GlcN ₃ HCl) 0.62 (20.7%),

Chitotetraose hydrochloride (GlcN ₄ HCl) 0.14 (4.7%),

Chitopentaose hydrochloride (GlcN ₅ HCl) 0.10 (3.3%),

As a method of obtaining 0.05 (1.7%) of chitohexaosphate hydrochloride (GlcN ₆ · HCl), the process is not only complicated but has a disadvantage of producing 400 to 2,000 low molecular weight (MW) water-soluble chitosan.

2) Preparation of Water Soluble Chitosan (Oligo Sugar) by Enzymatic Method (Conventional Method)

Thus far, conventional methods for preparing and purifying water-soluble chitosan are as follows.

① dissolving chitosan in dilute acid;

② about 24 hours of hydrolysis by enzyme treatment;

③ freeze drying and packing step; ⇒ Conventionally, the acidic reactant was dried without purifying the low molecular weight water-soluble chitosan (oligosaccharide).

However, the method is present in the product without the acid (hydrochloric acid, acetic acid, lactic acid, etc.) introduced during the dissolution of chitosan, it may adversely affect the human body when ingested.

In addition, since most of the material produced by enzymatic degradation of about 24 hours is oligosaccharide, it should be referred to as chitosan oligosaccharide (MW 400 to 2,000) rather than water-soluble chitosan. The oligosaccharides are known to be less effective in enhancing human immunity than high molecular weight chitosan.

3) Water solubilization method of chitosan with salt

Another manufacturing method of water-soluble chitosan is a method in which a salt is added to chitosan so as to be a polymer and a water-soluble state without lowering the molecular weight of chitosan.

However, the acidity (pH) when dissolved in water is about 3 (based on 1% solution), and is very strong acid, and hydrochloric acid solution with acidity (pH) of 2.0 or less (pH of 1.0 to 1.5) Does not melt There is a problem in the inherent function as a dietary supplement because of the inferior solubility in vivo.

In general, chitosan is a β-1,4 conjugated pyranose unit of glucosamine, and is a natural polymer having a molecular weight of 1 million or more, in which 5,000 or more glucosamine residues are bound. Chitosan, whose chemical name is poly-β-1,4-glucosamine, has a strong structure that is firmly bonded by hydrogen bonds with neighboring molecules, and is insoluble in water. Chitosan is a dilute organic acid (acetic acid, lactic acid, etc.). ) And dissolved in dilute inorganic acids (such as hydrochloric acid), the first product was dissolved in vinegar used in health food. However, when the water-soluble chitosan prepared by conventional chemical treatment, the molecular weight (MW) was extremely reduced during hydrolysis in the concentrated hydrochloric acid, and only the low molecular water-soluble chitosan (oligosaccharide) was produced.

As a result of extensive efforts to develop an efficient method for producing chitosan, the inventors noticed that the pH at which chitosan dissolves differs depending on the size of the molecular weight. A water-soluble chitosan of 20,000 to 100,000 was prepared, and water-soluble chitosan obtained by removing excess salt was obtained by using an ion exchange resin (Dowex quaternary amine type OH ^- form).

Accordingly, it is an object of the present invention to provide a process for the preparation of water soluble chitosan which is water soluble, polymer and purified from organic acid odors and salts.

At this time, these acids were removed using an anion exchange resin. For example, acetic acid (CH ₃ COOH) is dissociated into CH ₃ COO ⁻ and H ⁺ in the reaction solution. The anion exchange resin is filled in the ion exchange column in the form of R-OH, and when the enzyme reaction solution is passed through, the CH ₃ COO ^- groups are bound to the anion exchange resin and the OH ^- groups in the anion exchange resin are exchanged and discharged. . In this way, the acid is removed.

In addition, the following are implemented as a method of improving (or purifying) the purity of the water-soluble chitosan product.

① Strictly use the chitosan (raw material) standard.

② All the water used in the manufacturing process is carbon filtered and deionized using activated carbon to prevent foreign matters from being mixed with water.

③ All acids used for dissolving chitosan should be used only for medicine.

In the last step, the solution is dried. Drying adopts a freeze-drying (F / D) method to minimize the molecular weight decrease of the water-soluble chitosan.

By production by the above production method, a water-soluble chitosan having a yield of 99% or more and a molecular weight of 2 to 100,000 can be obtained.

1) Quality Control of Water-soluble Chitosan Chitosan usually has a molecular weight of 1 million or more (residual number 5,000 or more). ) And an inorganic acid (hydrochloric acid, etc.), followed by the addition of an enzyme (Chitosnase) between 40 and 50 ° C. and the chitosan decomposition step by time to adjust the molecular weight by a test method by pH. The pH test is a method of controlling the decomposition reaction of chitosan by using the principle that chitosan does not precipitate at high pH as the molecular weight is low, but at low pH as the molecular weight is high. By adjusting the polymer to prepare a water-soluble chitosan.

2) Purification of Water Soluble Chitosan

The most important step in the purification of water-soluble chitosan is to hydrolyze the chitosan to acid (inorganic acid, organic acid) to form salt, and then use an excessive amount of "acid" added at this time. degree) of chitosan of the pure salt form ^{_{(R-NH 3 + Cl -}} , CH 3 COO -, CH 3 CH (OH) COO -) and the remaining salt _{^{(Cl -, CH 3 COO -}} , CH 3 CH (OH) COO - ) Is present in the presence of residual salts after the reaction (Chitosanase) decomposition (titration temperature, time, concentration), and when reacted with organic acid (CH ₃ COOH), the odor after the reaction (organic acid odor) appears. Use ^- (form Dowex 4 amine type OH) salt remained in the aqueous chitosan solution to solve the problem _{^{(Cl -, CH 3 COO -}} -, CH 3 CH (OH) COO) and an organic acid smell to an anion exchange resin Purified in vacuo.

If the product is purified under normal pressure and not in vacuum, the pH of the aqueous chitosan solution rises to 12 or more (problems due to molecular weight), which causes problems of solidification and alkalizing of the product, so the design process of the ion exchange resin tower is important.

1 is a flow chart of a manufacturing method of the present invention.

2A, 2B and 2C are infrared spectrum graphs of chitosan prepared according to the present invention and conventional chitosan.

The present invention is a method for producing a water-soluble chitosan consisting of the following steps.

A first step as an optional step for preparing deionized water used for dissolving chitosan;

A second step of dissolving chitosan by adding 0.3 times the amount of organic acid (vinegar, lactic acid) to the amount of chitosan in water of 10 to 100 times the weight of chitosan (acetic acid solution, lactic acid solution);

Stirring the chitosan solution at 40 ° C. to 50 ° C. and adding an enzyme (Chitosnase) to hydrolyze chitosan;

A fourth step of stopping the reaction when the solution is not cloudy (white turbidity and precipitation) even at a pH of 6 to 7.5;

A fifth step of removing salt from the solution using an anion exchange resin;

The sixth step is an optional step of lyophilizing the solution.

Hereinafter, with reference to the accompanying drawings (Fig. 2 a, b, c) will be described in more detail.

In the first step, the general pure water was removed and softened by suspended solids (SS) using a carbon filter, and then deionized through a mixed ion exchange resin, and purified water was again prepared using a carbon filter.

In the second step, a predetermined amount of highly purified chitosan for food is mixed, and about 0.3 times the amount of acetic acid of chitosan weight is mixed with 10 to 100 times the amount of chitosan water and stirred to completely dissolve the chitosan. The amount of acetic acid to be added is not limited in the present invention as long as chitosan can be completely dissolved.

In the third step, the solution is fixed to 40 ℃ to 50 ℃ after the enzyme is added. The amount of enzyme (Chitosanase) is put 0.5 to 1.5 units (unit) per gram weight of chitosan to allow the reaction to proceed slowly to facilitate the control of the molecular weight.

In the fourth step, the reaction solution has a pH of 5 to 5.5 and is a pale yellow transparent solution. After the hydrolysis time by the enzyme, take a small amount of the reaction solution, dilute with 2 times water and add 1N-sodium hydroxide (NaOH) little by little while stirring. At this time, even if the pH of the reaction solution is 6 to 7.5, if not turbid, the temperature of the reaction solution is raised to 85 ℃ and heated for 30 minutes to terminate the enzyme (Chitosanase) reaction.

In the fifth step, the reaction solution is removed using an anion exchange resin. The ion exchange resin used at this time is manufactured by Dowex (quaternary amine type 0H ^- form).

Chitosan is an insoluble substance that is insoluble in water and has a property of being soluble in weak acids. Chitosan is dissolved in weak acid (acetic acid, hydrochloric acid) for the enzymatic reaction to produce water-soluble chitosan. After stopping the enzyme reaction, it is better to purify the product by removing the acid contained in the reaction solution.

In the sixth step, the water-soluble chitosan solution is directly produced or water is evaporated using a freeze dryer to obtain powdered water-soluble chitosan.

Example 1

① chitosan (see Fig. 2a)

② water-soluble chitosan (see Fig. 2b)

③ Water-soluble chitosan treated with anion exchange resin (see Fig. 2c)

The above three samples were recorded with salts removed using infrared peaks.

Sample 1 (chitosan)

After completely dissolving chitosan in 1.5% acetic acid solution, the solution was cast on a glass plate and dried in a dryer, and then acetic acid was sufficiently removed in 1N-NaOH / MeOH (1: 1) solution to remove acetic acid. Thereafter, the resultant was washed with MeOH solution, dried and the infrared spectrum was measured (see FIG. 2A).

Sample 2 (Aqueous Chitosan KBr Infrared Spectrum Containing Acetic Acid)

The aqueous chitosan solution was prepared (pH 5 to 5.5), dried and the infrared spectrum was measured by the KBr method. Among these, water-soluble chitosan and acetic acid are contained. Since the amino group of the chitosan and the carboxyl group of acetic acid are electrostatically coupled, it is impossible to determine the existence of the carboxyl group using infrared rays. Thus, the data measured by infrared spectrum after adjusting to below pKa (4.8) with 0.1 N-HCl (pH 2) and drying it is attached below. Since the absorption derived from the carboxyl group exists in the vicinity of 1710 cm ⁻¹ of this infrared spectrum, it was confirmed from this peak that the CH ₃ COOH group exists in this material (see FIG. 2B).

Sample 3 (aqueous chitosan KBr infrared spectrum (after acetic acid removal))

An infrared ray was measured by preparing a water-soluble chitosan sample in the same manner as in Sample 2. As the carboxyl group (acetic acid) is removed by the ion exchange resin it can be seen that the absorption of the carboxyl group appears in the vicinity of 1710cm ^-1 . It can be seen from this that acetic acid added at the time of dissolution was removed by ion exchange resin (see FIG. 2C).

As described above, the method for preparing a water-soluble chitosan according to the present invention allows a simple reaction process to obtain pure water-soluble chitosan without salts and odors (organic acid).

Claims (3)

Method for producing a water-soluble chitosan portal in the following steps: Chitosan dissolving step of dissolving chitosan in a mixed solution of purified water and organic acid selected from the group consisting of acetic acid and lactic acid: Enzymatic digestion step of slowly progressing the reaction by adding 0.5 to 1.5 units of chitosanase to the chitosan solution: Reaction step of terminating the chitosanase reaction by heating the temperature of the reaction solution to 85 ℃ 30 minutes when the reaction solution is not cloudy even if the pH of 6 to 7.5: Purification step of purifying the reaction solution with an anion exchange resin: And Lyophilization step of powdering the solution by lyophilization (F / D). The method for producing a water-soluble chitosan according to claim 1, wherein when the pH of the reaction solution is not clouded, the reaction solution is heated to 85 ° C. and heated for 30 minutes to terminate the chitosanase reaction. The method for purifying an aqueous chitosan solution using an anion exchange resin (quaternary amine type OH ^- form) used in the above purification step.