Method for producing of chitosan from chitin of cancerous

The invention relates to the fishing industry, namely the production of edible chitosan from crustacean chitin.

A method of obtaining chitosan from freshwater crustaceans electrochemical method (see Integrated reagent-free technology for the production of chitin and chitosan from crab by-products of aquatic organisms by electrochemical method. Maslova GV and other Theses of the Fourth all-Russian conference. M., 1995, ed. VNIRO, p.74-77).

The disadvantages of this method are significant energy consumption and high consumption of salt to create the electric field.

A method of obtaining chitosan by treating chitin with 50%sodium hydroxide solution at a temperature of 105-110°C for 40-60 min (Ed. St. USSR №1424157, class. And 22 With 29/02, 1986).

However, stringent conditions are the disadvantage of this method of deacetylation.

A method of obtaining dietary chitosan from crustacean shell, including activation of dry or wet chitin by grinding in a colloid mill, deacetylation, washing the finished product and partial dehydration, followed by drying, grinding and pelleting (see RF patent 2115344, A 23 L 1/33, 1998).

This method requires expensive equipment and complicated to maintain.

The closest analogue is the way to obtain chitosan is of crustaceans by deacetylation, including the preparation of a 50%aqueous sodium hydroxide solution, cooling it to a temperature of 18-22°With the introduction of dry chitin in the ratio of chitin: the alkali solution 1:10-1:15 until a homogeneous suspension and maintaining the latter at room temperature for 5-20 days (see RF patent 2116733, A 23 L 1/33, 1996).

However, this method involves the use of high alkali concentration, which leads to a significant consumption of alkali and partial destruction of the target product.

The technical objective of the claimed invention is the production of chitosan from crustacean chitin with a high degree of deacetylation while maintaining the native properties of the natural polymer, without breaking his chains by glycosidic linkages.

The problem is solved by the implementation of the method of producing chitosan from crustacean chitin by deacetylation of raw materials pre-cooled solution of alkali, washing and drying, while the deacetylation is carried out in three stages, the first of which are within 7 days, followed by 2 hours of heat treatment at a temperature 55-59°C, and washing is carried out after each step.

The selected process mode deacetylation process of removal of acetyl groups contribute to the preservation of the native properties of the polymer without destroying its circuit glycosidic linkages benefit is are stages of the process. Preliminary maintaining the suspension for 7 days facilitates the access of the reagent (alkali solution) to the structural units of the polymer, and the use of temperatures equal 55-59°allows to reduce the degree of crystallinity of chitin, amortizati its structure, to intensify the process of removal of acetyl groups and to obtain a chitosan with a high degree of deacetylation.

The method is as follows.

Pre-prepare a 40%solution of alkali, prispa dry sodium hydroxide in the desired amount of cold water with continuous stirring until complete dissolution. In the first phase after cooling a solution of alkali in it loads the dry chitin in the ratio of an alkaline solution of chitin 7:1 and incubated for 7 days at a temperature of 18-20°C. Then, the suspension is separated into solid and liquid parts (alkali); alkali reinforce and sent for reuse, and the solid part was washed with cold water until neutral wash water and wring out. In the second stage, moist cake mix pour the alkaline solution of the same concentration, is heated to a temperature 55-59°C and maintained with periodic stirring for 2 hours. After 2 hours, the suspension is separated and treated as described above. The third stage is conducted similarly, the second, after which the chitosan is washed and dried before the receiving moisture 8-10%.

Thus obtained chitosan has a high degree of deacetylation and preserves the native properties of the natural polymer (polysaccharide).

Examples of the method.

Example 1. For obtaining chitosan from crustacean chitin in pre-cooked and cooled to room temperature, 40%alkali solution add dry chitin in the ratio of an alkaline solution of chitin 7:1. In the first stage, the resulting suspension is maintained at a temperature of 18°With 7 days. The hard part is separated, washed with water until neutral wash water, wring out and again poured a 40%caustic soda solution. In the second step, the suspension is heated to a temperature of 57°C and maintained for 2 hours, after which the solid portion was separated, washed with water and wring out (centrifuged). The third stage is similar to the second wet cake mix pour a 40%caustic soda solution, heated to a temperature of 55°and incubated for 2 hours. Then the chitosan is separated from the alkali solution, washed with water until neutral wash water, wring out (centrifuged) and dried to a moisture content of 8 percent. The obtained chitosan has a high degree of deacetylation - 87%, high molecular weight 500 kDa.

Example 2. Similar to example 1, except that the chitin is treated with 50%caustic soda solution. In the first phase received suspense is maintained at a temperature of 18° With 7 days. The hard part is separated, washed with water until neutral wash water, wring out and poured 50%caustic soda solution. In the second step, the suspension is heated to a temperature of 59°C and maintained for 2 hours, after which the solid portion was separated, washed with water and wring out. The third stage is similar to the second wet cake mix pour 50%alkali solution, heated to a temperature of 58°and incubated for 2 hours.

The obtained chitosan has a high degree of deacetylation is 92%, but low 300 kDa molecular weight due to break glycosidic linkages and partial degradation of the polymer.

Example 3. Similar to example 1, except that the duration of the second and third stage reduced to 1 hour. The obtained chitosan has a low degree of deacetylation, is 72%.

A method of producing chitosan from crustacean chitin by deacetylation of raw materials pre-cooled solution of alkali, washing and drying, characterized in that the deacetylation is carried out in three stages, the first of which are within 7 days, followed by 2 h heat treatment at a temperature 55-59°C, and washing is carried out after each step.