Fermentative Production of Mycelial Chitosan from Zygomycetes: Media Optimization and Physico-Chemical Characterization

Abstract

The present study focused on production of mycelial chitosan from fungal mycelium by submerged fermentation with ecologically more balanced process. Different fungal strains were screened and Absidia butleri NCIM 977 was found to produce the highest mycelial chitosan. The one-factor-at-a-time method was adopted to investigate the effect of batch time, environmental factors ( i.e . initial pH and temperature) and medium components ( i.e . carbon and nitrogen) on the yield of mycelial chitosan. Among these variables, the optimal condition to increase in yield of mycelial chitosan was found to be batch time (72 h), pH (5.5), temperature (30 ° C ), carbon source (glucose) and nitrogen source (tryptone and yeast extract). Subsequently, a three-level Box– Behnken factorial design was employed combining with response surface methodology (RSM) to maximise yield of mycelial chitosan by determining optimal concentrations and investigating the interactive effects of the most significant media components ( i.e . carbon and nitrogen sources). The optimum value of parameters obtained through RSM was glucose (1.58%), tryptone (1.61%) and yeast extract (1.11%). There was an increase in mycelial chitosan yield after media optimization by one-factor-at-a-time and statistical analysis from 683 mg/L to 1 g/L. Mycelial chitosan was characterized for total glucosamine content (80.68%), degree of deacetylation (DD) (79.89%), molecular weight (8.07 × 10 4 Da) and, viscosity (73.22 ml/g). The results of this study demonstrated that fungi are promising alternative sources of chitosan with high DD and high purity.