Structure and surfactant activities of glycolipids secreted by basidiomycetous yeasts

Sophorolipids are glycolipids with biosurfactant activities that are naturally secreted by yeasts such as Starmerella bombicola when cultivated on a sugar plus a hydrophobic substrate such as vegetable oil. Sophorolipids are produced commercially for use in household cleaners and other products, marketed as renewable, biodegradable products. Relatively high production costs limit application of sophorolipids, primarily due to high feedstock costs. The yeast species Rhodosporidium babjevae was recently discovered to secrete similar materials, when cultivated on sugar alone, without the hydrophobic substrate, reducing feedstock costs. The secreted materials are glycolipids, and have biosurfactant activities. While the chemical structure of the lipid segment of the glycolipid is quite similar to that of sophorolipids, the glycan is structurally distinct. The properties of the secreted material are also quite different from sophorolipids, including solubility in water and other solvents, critical micelle concentration, and emulsification index. The critical micelle concentration is much lower than that of sophorolipids, indicating that these glycolipids are more active at low concentrations. Antifoam properties were comparable to commercial products. These results show promise for application of R. babjevae glycolipids as surfactants for use as detergents, emulsifiers, antifoam agents, dispersants, and numerous other applications.