Fermentative Production, Characterization and Antimicrobial Activity of Chitosan from Some Zygomycetes Fungi

Modern trends in natural techniques research have been elevated recently to avoid the utilization of chemical materials in agriculture which let to explore and use the biopolymers-reliant materials instead. , Biopolymer chitosan which exhibited high activity against plant pathogens is one of these certified bio-substances. The mycelia of several fungi including Zygomycetes were used as an alternative source of chitin in large quantities which transformed to chitosan by deactylation. The present work aimed to extract of chitosan from fungal mycelium by submerged fermentation and to study its antimicrobial activity. Six fungal strains were used for economical production of chitosan. Firstly, the different fungal strains were screened for its growth rate and chitosan yield. The obtained Chitosan was characterized using the methods of vibrational spectroscopy in the infrared region and molecular weight determination. Rhyzopus oryzea was found to produce the highest biomass (11.6 g/l) and chitosan yield (670.0 mg/l) among the tested fungi on Potato Dextrose Broth (PDB). The suitable medium for mycelia growth and chitosan production by R. oryzae, in shake-flask submerged culture was Cheng broth medium with the highest chitosan yield (749.7 mg/l). Eight days of incubation in Cheng broth was the optimum time for chitosan production (73.94 mg/g biomass) . Among the tested carbon/nitrogen (C/N) ratios during submerged fermentation (SMF) of R. oryzae at, 9.0 C/N ratio was efficiently the best regarding to the fungal biomass (13.8 g/l) and chitosan yield (1008.17 mg/l). Antimicrobial activity was carried out against 5 pathogenic bacteria and 6 plant pathogenic fungi. At 5 mg/ml of fungal chitosan, the highest antibacterial activity was observed against Escherichia coli with 10.7 mm inhibition zone, whereas the highest antifungal activity was 12.8 mm for Penicillium verrucosum,. The minimum inhibitory concentration (MIC) of chitosan extract for both bacteria and fungi strains ranged from 0.067- 2.0 mg/ml. The results revealed that fugal chitosan has multiple advantages as plant protection against the infection with pathogens, and as a bio-preservative by extension the shelf life of food.