RU2067588C1 - Process for preparing chitozane - Google Patents

Abstract

FIELD: agriculture, medicine, textile, pulpa and-paper, and food industries. SUBSTANCE: chitan of cuticle shells is ground to particle size of 0.2-0.3 mm, treated with 40% caustic alkali solution at 100-110 C and liquid modulus of 1:20 for 3- 3.5 h and is simultaneously subjected to ultrasound treatment at frequency of 15-35 kHz. EFFECT: more efficient preparation process.

Description

 The invention relates to the field of chemistry of natural compounds and biotechnology and can be used in medicine, textile, paper and food industry.

Chitosan is a deacetylated derivative of the natural chitin polysaccharide (poly-N-acetyl-D-glucosamine) (C ₆ H ₁₂ O ₅ N) n.

 The widespread use of chitosan is associated with its unique sorption properties. The raw material for chitosan is chitin, obtained mainly from shellfish. In principle, chitin from the cell walls of bacteria, fungi, and also the chitin cover of insects can be used as a raw material.

 Chitin obtained from different types of raw materials is slightly different: for example, due to the fact that the shells of crustaceans are highly mineralized, the chitin obtained after demineralization has a loose, spongy structure, while the structure of chitin from the outer skeleton of insects that does not have mineral salts, differs in dense packaging. When treated with chemicals, this structure prevents the penetration of reagents deep into the particles of chitin.

A known method of producing chitosan, which consists in the deacetylation of chitin obtained from crustaceans when treated with 40-60% NaOH and KOH solutions at a temperature of 80-150 ^o C for 1-16 hours with limited access to air, or in an atmosphere of inert gases / 1 / .

However, when using other raw materials of the cuticular membranes of insect larvae (Musca domestica and Bombyx mori), this method was not effective enough: for example, when chitin is treated with a 40% KOH solution at 120 ^° C for 3 hours, only 5% of the processed material becomes soluble in 1% acetic acid .

Closest to the proposed technical essence is a method of producing chitosan by deacetylation of chitin of crustacean shells with a 5-10-fold excess of 40-50% solutions of caustic alkali at 120-180 ^o C, in an inert atmosphere, for 0.5-16 hours / 2 /.

 The objective of the invention was the creation of a technologically advanced method for producing chitosan from insect chitin.

This problem is solved by the method of producing chitosan, including the treatment of chitin with a 40% solution of caustic alkali at an elevated temperature, which uses chitin from the cuticular shells of insects, crushed to particles with a size of 0.2-0.3 mm, and processing is carried out at 100- 110 ^o C, the liquid module 1: 20, for 3-3.5 hours while exposure to the reaction mixture with ultrasound at a frequency of 15-35 kHz.

 Chitin cuticle flies, unlike crustacean chitin, do not contain calcium salts. When comparing the process of deacetylation of crustacean and insect chitin, there are the following differences: deacetylation of crustacean chitin (after Ca removal by acid treatment) successfully passes through the entire particle thickness, and as a result, the resulting chitosan has a fairly uniform molecular weight. The process of deacetylation of chitin from insect larvae is much slower. With prolonged treatment of insect chitin, its particles decrease in size, dissolving in alkali, but the inner layers are not fully deacetylated. This is confirmed by comparing the surface of sections of demineralized and deproteinized chitin of crustaceans and deproteinized chitin of cuticular shells of flies in a scanning electron microscope. The chitin of crustaceans has a spongy structure, while the chitin of flies larvae has a rather smooth relief of the cut surface. The chitin in the cuticle of flies is packed very tightly. To facilitate the penetration of alkali into the inner layers of insect chitin, it is necessary: firstly, grinding, maximizing its surface, and secondly, sonication of the entire reaction mixture; all this is necessary in order to create conditions for the continuous flow of unreacted alkali into the inner layers of insect chitin particles.

The fulfillment of these conditions, i.e., grinding the chitin of the cuticular shells of the larvae to particles with a limiting size of 0.2-0.3 mm and processing the reaction mixture with ultrasound of 15-35 kHz, significantly accelerates the deacetylation process, reduces losses, improves the quality of the product, because The process proceeds at relatively low temperatures (100-110 ^o C). The chitin of the cuticular membranes of the larvae, crushed to the indicated size, after treatment with a 40% KOH solution (100-110 ^o С), followed by ultrasonic treatment with 15-35 kHz for 3-3.5 hours, after washing with water and drying, is completely soluble in 1% acetic acid. The degree of its deacetylation, determined by infrared spectroscopy, 80-85% Molecular weight of about 900 kilodaltons.

 The main differences between chitin, cuticle of larvae of flies and chitin of crustaceans are as follows: 1) chitin, cuticle of larvae of flies, unlike chitin of crustaceans, does not contain calcium salts. This allows us to omit one of the main technological stages of chitin deacetylation associated with its demineralization, which is an important advantage of our technology for producing chitosan; 2) the chitin of the cuticle of the larvae of flies, unlike the chitin of crustaceans, does not contain fluorine-containing compounds, which will significantly increase the life of the equipment used in the process of its cleaning and deacetylation, since volatile fluoride compounds that strongly corrode the apparatus are released during the acid treatment of shellfish shells.

 The proposed method allows the use of larvae of synanthropic flies as chitin-containing raw materials, which are the product of a new technological process for waste-free processing of manure. The chitin of insect larvae differs in nature from crustacean chitin and is unique in itself in comparison with the known sources of chitin.

 The characteristics of the insect chitin feedstock are not described in literature in contrast to crustacean chitin, which is the subject of numerous articles in the scientific and technical literature and a large number of patents.

The method is as follows. The chitin of the cuticular shells of insects is crushed to a particle size of 0.2-0.3 mm, then treated with a 40% KOH solution at 100-110 ^o C and at the same time the entire reaction mixture is subjected to ultrasound treatment with a frequency of 15-35 kHz for 3-3.5 hours. The resulting product is washed with water to a pH of 7.0, precipitated by centrifugation and dried. Under this treatment mode, the entire precipitate is completely dissolved in 1% acetic acid; its degree of deacetylation, determined by infrared spectroscopy, is 70% and higher. The method is illustrated by examples.

Example 1. 3 g of deproteinized chitin from the cuticular shells of fly larvae (Musca domestica) are crushed to a particle size of 0.2-0.3 mm, treated in 60 ml of a 40% KOH solution at 100 ^o C for 3 hours, at the same time the entire volume is treated the reaction mixture with ultrasound at a frequency of 15 kHz in cavitation mode. At the end of the procedure, the remaining product is washed with 25 volumes of water (1.5 L) to a pH of 7.0, precipitated by centrifugation. The weight of the dried residue is 2.67 g. The degree of deacetylation is above 70%. Viscosity - 800 Cf. The molecular weight of 900 kDa. Within 24 hours, 100 mg of the product is completely dissolved in 10 ml of a 1% solution of acetic acid.

Example 2. 3 g of chitin from the cuticular membranes of silkworm pupae (Bombyx mori), crushed to a particle size of 0.2-0.3 mm, are treated in 60 ml of a 40% KOH solution at 110 ^{° C.} for 3 hours. At the same time, the entire reaction volume is treated with ultrasound at a frequency of 15 kHz in the cavitation mode. At the end of the procedure, the remaining product is washed with water (1.5 L) to a pH of 7.0, then precipitated by centrifugation, dried. The weight of the dried precipitate is 2.59 g. The degree of deacetylation is 70% and higher. Viscosity 600 Avg. Molecular mass up to 900 kDa. Within 24 hours, 100 mg of the product is completely dissolved in 10 ml of a 1% solution of acetic acid.

Example 3. 3 g of deproteinized chitin from the cuticular shells of the larvae (Musca domestica), crushed to a particle size of 0.2-0.3 mm, are treated in 60 ml of a 40% KOH solution at 110 ^{° C.} for 3.5 hours. At the same time, the entire volume of the reaction mixture is treated with ultrasound at a frequency of 35 kHz in the cavitation mode. Then the remaining product is washed with water (1.5 L) to pH 7.0, precipitated by centrifugation, and dried. The weight of the dried precipitate is 2.63 g, the degree of deacetylation is 85%, the viscosity is 600 Cp, and the molecular weight is 800 kDa.

Claims (1)

A method of producing chitosan, comprising treating chitin with a 40% solution of caustic alkali at elevated temperature, characterized in that they use chitin from the cuticular shells of insects, crushed to particles with a size of 0.2 0.3 mm, and processing is carried out at 100 110 ^o С , the liquid module 1 20, for 3.0 to 3.5 hours with simultaneous exposure to the reaction mixture with ultrasound at a frequency of 15 35 kHz.