Screening and Fermentation Parameter Optimization of Lipase-Producing Trichosporon asahii

Waste cooking oil is generated in large quantities during food-waste processing, and its complex composition may pose environmental and public-health risks if it is improperly managed. Lipase-mediated conversion of waste cooking oil into biodiesel offers a promising strategy for both waste-oil valorization and greener fuel production. To expand the available microbial sources of lipases, this study isolated a strain with strong lipase-producing capacity from composted food-waste samples. The isolate was identified using molecular biological methods, the enzymatic properties of the extracellular lipase were characterized, and fermentation conditions for enzyme production were optimized by response surface methodology. The strain was identified as Trichosporon asahii. The lipase showed optimal catalytic activity at 40 °C and pH 8.0. Na⁺ and K⁺ enhanced lipase activity, whereas Ca²⁺, Mg²⁺, Mn²⁺, and Fe³⁺ inhibited the enzyme. Response surface optimization showed that a maximum lipase activity of 70.816 U/mL was obtained at a fermentation temperature of 31 °C, an initial pH of 6.33, an inoculum size of 6.843%, and a fermentation time of 120 h, representing an approximately 10-fold increase compared with the non-optimized condition. These findings provide a useful basis for developing food-waste-derived oils as biodiesel feedstocks through lipase-based fermentation and support the resource-oriented utilization of food waste.