Direct Solid-State Fermentation of Soybean Processing Residues for the Production of Fungal Chitosan by Mucor rouxii

Abstract

The feasibility of utilizing soybean-processing residues such as soybean meal and hulls as sub-strates for chitosan production by the fungus Mucor rouxii ATCC 24905 via solid-state fermenta-tion (SSF) was investigated. The effects of the type of soybean-based substrate, length of cultiva-tion period, substrate moisture content, substrate pH, incubation temperature and extraction con-ditions on chitosan yield were determined. The results showed that a maximum fungal chitosan yield of up to 3.44% by dry substrate weight (34.4 g/kg) could be achieved using a pure soybean meal substrate with an initial moisture content of 50% (w/w) and pH of 5 -6 incubated for six days at 25˚C. A more severe heat treatment (autoclaving vs. refluxing) resulted in higher chitosan extraction yields regardless of the strength of extraction reagents. Fourier transform infrared (FTIR) analysis of the fungal chitosan revealed its degree of deacetylation (DDA) to be between 55% and 60%.