Patent ID: 7556946

Claim:
A method for preparing chitosan from fungal or yeast chitin comprising the subsequent steps of: a) isolating chitin polymers or chitin-rich chitin-glucan copolymers from fungal or yeast biomass, b) contacting said isolated chitin polymers or chitin-rich chitin-glucan copolymers with an alkaline solution at a temperature of 100 to 120° C. for 30 to 300 minutes at a weight ratio of alkali to the amount of dry chitin contained in the chitin polymers or chitin rich chitin-glucan co-polymers of step a) which is between 1 and 20 (w/w), whereby an alkali-soluble fraction and an alkali-insoluble fraction is obtained and whereby said alkali-soluble fraction is discarded and said alkali-insoluble fraction is retained, c) contacting said alkali-insoluble fraction with an acidic solution, by suspending said alkali-insoluble fraction and bringing said suspended fraction into contact with said acidic solution whereby an acid-insoluble fraction and an acid-soluble fraction is obtained and whereby said acid-insoluble fraction is discarded and said acid-soluble fraction comprising chitosan is retained.