Extraction Of Chitin From Dendrolimus Punctatus Larva And Production Of Chitosan

Dendrolimus punctatus Walker is one kind of serious forestry insect pests in our country. However, it is also a beneficent biology resource with potential development value from the aspect of nutrition. Chitin is the most abundant natural polymer except cellulose. Chitosan is the deacetylated product of chitin. Chitin and chitosan, which have various functions, are used widely in many areas. Whether in our country or abroad, the demand of them will be expanded constantly.This dissertation test takes larvae of Dendrolimus punctatus Walker as raw materials. The acid alkali method (low acid concentration removing minerals, low concentration alkali removing protein, H2O2 decolour and high concentration alkali deacetylation), was applied for extraction of chitin and chitosan. When the study on the preparation of chitin, the test uses single-factor experiment, in which the influence of reaction conditions on chitin characteristics is investigated, such as acid concentration, time of acid treatment, temperature of acid treatment, alkali concentration, time of alkali treatment, temperature of acid treatment. The result showed:(1) the acid concentration and treatment temperature are higher and treatment time is longer, the effect of removing minerals is better; (2) the alkali concentration and treatment temperature are higher and treatment time is longer, the effect of removing protein is better. According to the quality index and economy, the best extraction condition was that NaOH concentration is 8%, treatment temperature is 80℃, time is 12 hours and HCL concentration is 3%, treatment temperature is 40℃, time is 8 hours. Results indicated that chitin is white or slightly yellow tabular solids, extraction ratio was 8.46%, water content is 7.85%-8.89%, ash content is 1%, nitrogen content is 6.28%-6.84%. These qualities indexes of these products are much higher than, or at least the same with those indexes of industrial chitin.The test applied correctitude design, which contains 3 factors, such as alkali concentration; treatment temperature and treatment time. Each factor had 3 levels, and treatment tempera. According to analysis of variance, alkali concentration and time were contributed much to chitin deacetylace reaction. The result showed the best preparation condition was that alkali concentration was 35%;treatment temperature was 30℃and treatment time was 10 hours. It was shown that the product is white or slightly yellow tabular solids, water content is 7.67%-9.35%, ash content is 0.89%-1%, degree of deacetylation is up to 91.58%-94.30% and viscosity is 18.7-20.7 mPa·s.These qualities indexes of these products are much higher than, or at least the same with those indexes of industrial chitosan.The influences of bleaching of chitin under different reaction conditions were systematically studied. The results show that the best bleaching condition was that peroxide concentration was 10%;treatment temperature was 40℃and treatment time was 3 hours. It was shown that the product is white or slightly yellow tabular solids, water content is 6.5%-8.76%, ash content is 0.89%-1%, degree of deacetylation is up to 91.45%-93.46% and viscosity is 19.8-20.47 mPa·s.This was the first dissertation which made systematically study on the preparation of chitin and chitosan from larvae of D. punctatus were studied with the Acid-Alkali method. The results obtained in the dissertation would be useful for the further study and development of functional foods and other products related to Dendrolimus punctatus Walker.