Extraction and evaluation of antimicrobial activity of γ- chitosan from cell wall of Aspergillus niger (PTCC 5223)

Due to high biomass and substantial amount of chitosan in the cell wall, cultivation and production of chitosan from Aspergillus niger was studied. The fungus grown on Potato Dextros Agar (PDA) slants were inoculated in Potato Dextros Broth (PDB) and incubated (25°C, 180 rpm). To evaluate changes in biomass, chitosan and other growth parameters over a period of 21 days and the interval of 3 days these factors were measured. The results showed that maximum of fungal biomass (22.5 g/L), chitosan (7.37%) and other growth parameters in the late exponential growth phase found. The pH of the medium in this stage was the lowest (2.5). After entering the medium to stationary phase, these factors were significantly reduced. Gram positive bacteria were more sensitive to chitosan compared to gram negative bacteria (P≤0.5). But Candida albicans showed the highest sensitivity to chitosan. The antibacterial properties of chitosan were more than their antifungal properties. Due to availability, ease of cultivation and maintenance this strain and acceptable level of chitosan, can be used as an alternative for transitional source (shellfish). Based on the present finding, it could be inferred that the A. niger can be considered as an source of chitosan which have inhibitory activity against some microorganisms that require further study.