Preparation method of low-molecular chitosan

Abstract

The invention relates to a preparation method of low-molecular chitosan, which comprises the following steps: ultrasonically treating crab shells with diluted hydrochloric acid, adding deionized water to dilute the diluted hydrochloric acid, adding benzoic acid for continuous ultrasonic treatment, deproteinizing with low-concentration sodium hydroxide, washing, and thermally treating deacetylated wet chitosan with high-concentration sodium hydroxide, dissolving the wet chitosan in a diluted hydrochloric acid aqueous solution, adding into a three-electrode system which takes a graphite plate as an anode, foam titanium as a cathode and a silver / silver chloride electrode as a reference electrode, keeping a certain distance of 3-5cm between the anode and the cathode, keeping a constant point potential of-1.2 to-1.5 V, and electrolyzing for 0.5-1 hour. According to the method, the repeated deacetylation process of sodium hydroxide in the deacetylation process is simplified, the usage amount of sodium hydroxide is reduced, the deacetylation degree of the low-molecular chitosan prepared by combining one-step sodium hydroxide deacetylation with electrolysis is as high as 94.8%, the molecular weight is low and reaches about 2500, the molecular weight distribution is narrow, the molecular weight distribution coefficient is 1.13, and the content of protein impurities in the low-molecular chitosan is as low as 0.072%.

Description

technical field [0001] The invention relates to the technical field of chitosan degradation, in particular to a preparation method of low-molecular chitosan. Background technique [0002] Chitosan is a natural high molecular polymer, which belongs to amino polysaccharides. It is the only alkaline polysaccharide with cationic charge found so far. It has unique biological activity, non-toxicity, good biocompatibility and easy degradation. advantage. Chitosan is prepared by deacetylation of chitin. Generally speaking, chitin whose N-acetyl group has been removed by more than 55% can be called chitosan. The hydrogen bonds inside and outside the prepared chitosan molecule are mutually It acts to form an ordered macromolecular structure. Because its molecular weight is usually hundreds of thousands to millions, it is only soluble in dilute hydrochloric acid, nitric acid and other inorganic acids and most organic acids, but insoluble in water and alkaline solutions, resulting in ...

AI Technical Summary

Problems solved by technology

Acid degradation method is one of the main ways to prepare monosaccharide and a series of corresponding low molecular weight chitosan, but acid degradation method is not easy to control, selectivity is poor, separation and purification are difficult, and the yield is low. When preparing low molecular weight chitosan Mainly obtained monosaccharides, followed by disaccharides, it is difficult to obtain the required active low molecular weight chitosan; hydrogen peroxide oxidative degradation method is a method that has been studied more at present, but the biggest problem is that the reaction process is not easy to control, and browning occurs easily. In the degradation process, various reaction reagents are introduced, which increases the difficulty of controlling the degradation side reactions and the separation and purification of degradation products; the degradation process and product molecular mass distribution of the enzymatic degradation method are easier to control, but the disadvantage is that the enzymes used are relatively special , high cost, long production cycle, and the product contains a very small amount of complexes of sugar and enzyme protein, the complex product will cause pyrogen reaction so that it cannot be used in food, medicine and other fields

The physical degradation method mainly uses microwave, ultrasonic, γ-ray and other physical methods to degrade chitosan, but the physical degradation method also has certain limitations, and it is not easy to realize industrialization at present.

In the prior art, small molecular chitosan is prepared by electrochemically degrading chitosan, but the high degree of deacetylation of chitosan makes its crystallinity high, and chitosan with high crystallinity makes the degree of electrochemical degradation uncontrolled , the electrolyzed chitosan has a wide molecular weight distribution

[0004] In addition, the preparation of chitosan with a high degree of deacetylation in the prior art is to use a strong base such as high-concentration sodium hydroxide to repeat heat treatment many times to achieve the purpose of high deacetylation. Although this method can prepare chitosan with a high degree of deacetylation Chitosan, but the repeated use of strong alkali makes the amount of high-concentration alkali large, which is not friendly to the environment, and it takes time to repeat multiple times, and multiple strong alkali treatments will excessively destroy the molecular structure of chitosan, and greatly improve the quality of the chitosan. The crystallinity of chitosan in the subsequent degradation process leads to uncontrollable changes in the molecular weight of chitosan, and the molecular weight distribution is wide, thereby reducing the performance of chitosan

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