Sustainable and Effective Chitosan Production by Dimorphic Fungus Mucor rouxii via Replacing Yeast Extract with Fungal Extract

The effects of switching morphology and replacing supplementary nutrients with fungal extract (5 and 10 g/L) on the production of major metabolites and chitosan by Mucor rouxii were investigated. This approach was supposed to promote sustainability of the fermentation process and improve its economic feasibility. Different fungal morphologies, i.e., purely filamentous (PF), purely yeast-like (PY), mostly filamentous (MF), and mostly yeast-like (MY), were evaluated. The highest ethanol yields were obtained from the media supplemented with 10 g/L fungal extract for all morphologies, while adding nutrient salts did not make any improvements in these yields, except a slight decrease in the fermentation time. Except for PF morphology, the replacement of yeast extract favored the biomass production yields. Moreover, the alkali insoluble material (AIM) yields were higher as a result of the replacement for most cases. Furthermore, the replacement resulted in increased glucosamine and decreased N-acetyl-glucosamine content of AIM for almost all the morphologies. AIM yields of at least 0.25 g/g-glucose and maximum chitin/chitosan yield of 0.78 g/g-AIM were obtained from the solids remaining after autolysis process, which were higher than that obtained from the raw biomass. The maximum yield of 0.135 g/g-AIM purified chitosan with intact molecular weight was obtained from the biomass with PF morphology supplemented with 10 g/L fungal extract plus nutrients.