Production of Value-Added Microbial Metabolites: Oleaginous Fungus as a Tool for Valorization of Dairy By-products

Mucor circinelloides is a filamentous fungus capable of producing mycelium-bound lipase and lipids and able to assimilate a wide array of substrates, like agricultural wastes and industrial effluents. A biotechnological valorization of cheese whey is described herein, in which simultaneous reduction of the organic loading and conversion of the various compounds of the by-product into added-value microbial metabolites is obtained. M. circinelloides URM 4182 was tested for the ability of producing biomass containing lipids and mycelium-bound lipase using raw cheese whey as culture medium. The fungal cultivation assays were performed in non-supplemented cheese whey at pH 4.5, 26 °C, 250 rpm for 120 h providing biomass concentration of 4.7 g L−1 containing lipids (22.5% of dry biomass weight) and lipolytic activities up to 160 U g−1. The mycelium-bound lipase was characterized in terms of its biochemical and kinetic parameters and tested on biogas production assays of cheese whey as a way to enhance the lipid hydrolysis, the limiting step in anaerobic digestion. Results demonstrate that the addition of M. circinelloides lipase on cheese whey reduced the lag phase of anaerobic digestion up to 43.7%, and the biogas production was increased by up to ninefold when compared with the control experiments.