ABSTRACT
Shrimp or crab shell proteins are removed by treatment with 3-5% (w/v) NaOH aqueous solution at 80-90°C for a few hours or at room temperature overnight. Afterward, the product’s inorganic constituents are removed by treatment with 3-5% (w/v) HCl aqueous solution at room temperature giving a white to beige colored sample of chitin. The treatment of the sample with an aqueous 40-45% (w/v) NaOH solution at 90-120°C for 4-5 h results in Ndeacetylation of chitin. The insoluble precipitate is washed with water to give a crude sample of chitosan. The conditions used for deacetylation will determine the polymer molecular weight and the degree of deacetylation. The crude sample is dissolved in aqueous 2% (w/v) acetic acid, then the insoluble material is removed giving a clear supernatant solution which is neutralized with NaOH solution, resulting in a purified sample of chitosan as a white precipitate (7). Further purification may be necessary to prepare medical and pharmaceutical grade chitosan.
