Efficient sophorolipid production with dual lipophilic substrates and its application to the upcycling of waste frying oil

Abstract: For industrial production of sophorolipid (SL), shorter time and complete consumption of lipophilic substrates are very essential. A highly efficient SL fermentation process using dual lipophilic substrates (DLS) was developed ¹⁾. 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.
With the increased efforts toward a circular economy, 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.
Furthermore, additional studies on the acid values of degraded oils to mimic waste frying oil and their effect on SL production were performed. It was confirmed that the increase in acid value as the oil degraded did not significantly decrease SL production ²⁾.
The newly developed fermentation process with DLS can be useful for the industrial production of SL from renewable biological sources, especially waste frying oils.

References:
1) Hirata Y., Igarashi K., Ueda A., Quan GL. Enhanced sophorolipid production and effective conversion of waste frying oil using dual lipophilic substrates. Bioscience, Biotechnology, and Biochemistry, 2021, Vol. 85, No. 7.
2) Ishizaki R., Matsusako, T., Araki M., Hirata Y. The effect of acid value of degraded oils on sophorolipid production. 11^th JACI/GSC Symposium, June 15-16, 2022 (virtual).