PRODUCTION OF CHITOSAN BY FUNGI

Chitosan is a novel biopolymer with numerous industrial, food, and biomedical applications. Our studies examined the production of chitosan from mycelia of Absidia coerulea, Mucor rouxii, Gongronella butleri, Phycomyces blakesleeanus and Absidia blakesleeana. In batch culture, strains were screened to determine the fastest growing and greatest chitosan-yielding fungi. Optimum chitosan yields were observed for most cultures at 21-degrees and 26-degrees-C in 1% yeast extract, 0.4% glucose, and 0.3% peptone. A. coerulea ATCC 14076 and NRRL 1315 were the best producers of chitosan of the strains examined. Chitosan yields of A. coerulea, M. rouxii, G. butleri, P. blakesleeanus and A. blakesleeana were 47-50, 29-32, 21-25, 6 and 7 mg/100 mL of medium, respectively. The degree of acetylation of chitosan ranged from 6 to 15%; the lowest was from strains of A. coerulea. Viscosity average molecular weights of fungal chitosans were equivalent, approximately 4.5 x 10(5) daltons. A. coerulea 14076 yielded the most chitosan, 51 mg/100 mL of medium at pH 5.5 in 48 h. Supplementation with 0.5 mg of cobalt/100 mL medium showed an increase of approximately 20% in the chitosan yield form A. coerulea 14076. Batch fermentations were carried out in flask, airlift and stirred tank fermentors. Fermentation by continuous culture in the stirred tank reactor produced the highest amount of chitosan from A. coerulea 14076 resulting in an approximate three-fold increase in chitosan production as compared to batch culture.