Production of Chitosan by Some Fungi and Its Industrial Applications

Abstract

The microbial production of the Chitosan biopolymer, characterization and its basic application was the main aim of this research. Seventeen fungi were isolated from agricultural soil located in Cairo, Egypt. These isolated fungi were priliminary identified and permitted to grow on peptone glucose yeast (PGY) broth fermentation medium to test their chitosan-production ability. The best chitosan producer was Rhizopus oryzae gave cell dry matter 3.77 g/l, 255.0 mg/g of chitinious matter and alkali-insoluble material (AIM) was 370.0 mg/g. Rhizopus oryzae was identified on a molecular basis using 18S rRNA. It was identified as Rhizopus oryzae 1.3.32 and the phylogenetic tree of the organism was described. Crustacean chitosan was extracted from shrimp shells to be compared with the fungal and the standard chitosans. Extracted Chitin represented 21% and crustacean chitosan 16 % from the total initial weight of crude shrimp shells. Characterization of Chitosan samples included FTIR, TEM, XRD, viscosity analysis, TGA were studied. The deacetylation degree crystal size and the molecular weight were 75.00, 79.00 and 77 % and 386, 261, 32 nm and 1086, 113.7 and 80.84 kDa, for the standard, crustacean and fungal chitosan, respectively. The transmission electron microscope analysis revealed the particle sizes were 600, 300 and 32 nm for standard, crustacean and fungal chitosan samples. To maximize R. oryzae chitosan, it was necessary to conduct a lab-scale fermentation. One way experiments were carried out to optimize the fermentation environmental conditions. The best fermentation conditions were 30C incubation temperature, 200 rpm, pH 4.5, 24 h incubation time. The inoculum was 2 ml from spore suspension concentration 2.9x107 cfu/ml and five days old. Glucose and maltose were the carbon sources of choice within the fementation medium that encouraged the chitosan production. Using the pepton