Structural characterization of novel sophorolipid biosurfactants from a newly identified species of Candida yeast.

Sophorolipids are a group of O-acylsophorose-based biosurfactants produced by several yeasts of the Starmerella clade. The known sophorolipids are typically partially acetylated 2-O-β-D-glucopyranosyl-D-glucopyranose (sophorose) O-β-glycosidically linked to 17-L-hydroxy-Δ9-octadecenoic acid, where the acyl carboxyl group often forms a 4″-lactone to the terminal glucosyl residue. In a recent MALDI-TOFMS-based screen for sophorolipid-producing yeasts we identified a new species, Candida sp. NRRL Y-27208, that produces significant amounts of novel sophorolipids. This paper describes the structural characterization of these new compounds, using carbohydrate and lipid analysis, mass spectrometry, and NMR spectroscopy. Unlike those reported previously, the NRRL Y-27208 sophorolipids contain an ω-hydroxy-linked acyl group (typically 18-hydroxy-Δ9-octadecenoate), and occur predominantly in a non-lactone, anionic form. In addition, 17 dimeric and trimeric sophoroses were identified by MALDI-TOFMS from this strain. The surfactant-like properties of these sophorolipids have value as potential replacements for petroleum-based detergents and emulsifiers.