Enhanced sophorolipid production and effective conversion of waste frying oil using dual lipophilic substrates

A highly efficient sophorolipid (SL) fermentation process using dual lipophilic substrates (DLS) was developed. Using DLS consisting of palm oil and oleic acid in the flask fermentation with SL-producing yeast Starmerella bombicola, the productivity and yield of SL improved 2.4 and 1.7 times, in comparison to when using palm olein alone. In the jar fermentation process with DLS, the SL productivity and yield of 127 g/L and 62.4% were achieved in 7 days, with the complete consumption of residual lipophilic substrates in the culture medium. This process was successfully applied to the effective conversion of waste frying oil to SL, maintaining a high SL productivity and yield of 142.8 g/L and 72% in 9 days. It is concluded that the newly developed fermentation process with DLS can be useful for the industrial production of SL from renewable biological sources, especially waste frying oils.