The invention provides a
chitosan preparation method, which comprises: (1) crushing the shell of the insects, placing in
dilute acid, carrying out dipping cooking, filtering, taking the
filter cake, and carrying out
water washing-
drying on the
filter cake to obtain a decalcified product A; (2) placing the product A, a compound
enzyme and water into a reaction container, hydrolyzing for 2-3 h under a weak alkali condition, filtering, taking the
filter cake, and carrying out
water washing-
drying on the filter cake to obtain a
protein removing product B; (3) placing the product B in a mixed
solvent, adding a neutral salt, carrying out stirring dissolving for 1-3 h, filtering, carrying out pressure reducing
drying on the filtrate to remove the
solvent, and carrying out
water washing-drying to obtain
chitin; and (4) placing the
chitin and a NaOH
aqueous solution under
ultraviolet light, irradiating for 2-3 h while carrying out an ultrasonic treatment, carrying out
centrifugation, carrying out water washing on the precipitate to achieve a
neutral state, and drying to obtain the
chitosan. According to the present invention, the preparation method has advantages of simple preparation process, regular equipment, low production of acid and alkali waste water, and meeting of the green
environmental protection production requirement, and the obtained
chitosan has advantages of high purity, high molecular weight and high deacetylation degree.