A comparative study of oilseed cakes as hydrophobic feedstocks for sophorolipid production by solid-state fermentation

The sustainable production of sophorolipids (SLs) has promoted the use of alternative agricultural byproducts and residues as nutrient sources. Corn, sunflower, soybean, and rapeseed oilseed cakes have been studied as newer hydrophobic feedstocks for SL production through solid-state fermentation using the wild-type strain of Starmerella bombicola. Maximum sophorolipid production at 0.5-L bioreactors was found to be reached by corn cake (0.743 ± 0.038 gSL g⁻¹Fat_i). HPLC analysis revealed that the composition of the hydrophobic substrate influences the profile and distribution of SL congeners. Emulsification and oil displacement tests were performed for the crude extracts showing that emulsification stability is influenced by SLs crude extract concentration. The best-performing oilseed cakes were scaled-up in a 22-L bioreactor demonstrating that the increase in scale by 44 times-maintained SLs production. The temperature influence was discussed, and the reproducibility of the method was confirmed. Outcomes highlighted a linear relation between initial fat concentration and SLs crude extract production.