Lipid analysis: a way to improve the production of sophorolipids by Starmerella bombicola

The yeast Starmerella bombicola is known for the commercial production of the biosurfactant sophorolipids. Sophorolipids are surface-active molecules consisting of a disaccharide and a fatty acyl chain. The yeast can utilize various lipophilic substrates such as vegetable oils, alkanes and fatty acid esters and converts them to free fatty acids; the substrate of the sophorolipid biosynthetic pathway. In addition, the yeast has a very active de novo fatty acid synthesis; also in the absence of a lipophilic carbon source reasonable amounts of sophorolipids are obtained. While the production level of sophorolipids is already high; some efforts are still necessary for the synthesis of new-to-nature sophorolipids. The production of these molecules by modified Starmerella bombicola strains or by using special substrates is in some cases less efficient and requires further optimization. On the one hand, the efficiency is lower because special substrates are lost due to catabolic pathways. On the other hand, some modified strains are less productive than the wild type yeast. The blockage of these catabolic pathways and a better availability of lipophilic carbon sources can be a solution. Because uptake, transport and storage of lipophilic molecules are very important in the production process of sophorolipids, the lipid composition of different compartments are examined and compared with other (oleaginous) yeasts. By gaining knowledge on how these molecules are converted, new metabolic engineering strategies can be found to target specific genes. The fundamental knowledge about the lipid metabolism of Starmerella bombicola will hence lead to a better production platform for the synthesis of economic valuable new-to-nature sophorolipids.