'Classical' biosurfactants produced by Starmerella bombicola contain oleic acid as the incorporated hydrophobic group. However, other chain lengths can (to a certain content) be incorporated by feeding the yeast with substrates of alternative chain lengths, be it with a lower efficiency. This is defined by the substrate specificity of the first enzymatic step in sophorolipid biosynthesis, i.e., the cytochrome P450 enzyme CYP52M1. To increase product uniformity and diversity at the same time, a new strain of S. bombicola was developed that produces sophorolipids with a palmitic acid acyl chain. This was achieved by heterologous expression of the cytochrome P450 cyp1 gene of Ustilago maydis and feeding with palmitic acid. Optimization of the production was done by protein and process engineering. You can find the full article here.