Title: Structural characterization of novel sophorolipid biosurfactants from a newly-identified species of Candida yeast Authors
Submitted to: Carbohydrate Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2011
Publication Date: July 24, 2011
Citation: Price, N.P., Ray, K.J., Vermillion, K., Dunlap, C.A., Kurtzman, C.P. 2011. Structural characterization of novel sophorolipid biosurfactants from a newly-identified species of Candida yeast. Carbohydrate Research. 348:33-41. DOI: 10.1016/j.carres.2011.07.016. Interpretive Summary: The annual production of detergents is about 10 million tons, mostly derived from oil-based feedstocks. ARS scientists have identified several different types of yeasts that produce bio-based detergents called sophorolipids in large quantities. As much as 20 g/L of the sophorolipids are produced by several of the yeast strains. This paper describes the chemical structures of sophorolipids from a newly identified strain of yeast from the ARS Microbial Collection, called Candida spp. NRRL Y-27208. These new sophorolipids are comprised of a sugar (sophorose) attached to a 18-hydroxyl-fatty acid. Unlike most other sophorolipids they have an open chain structure which alters their detergent properties. We also found several sophorolipid polymers. These sophorolipids are microbe-produced detergents that have value as potential replacements for increasingly expensive oil-based materials.
Technical Abstract: The 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-ß-D-glucopyranosyl-D-glucopyranose (sophorose) ß-O-glycosidically-linked to 17-L-hydroxy-delta-9-octadecenoic acid, where the acyl carboxyl often forms a 4"-lactone to the terminal glucosyl residue. In a recent MALDI-TOF/MS-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. Unlike those reported previously, the NRRL Y-27208 sophorolipids contain a terminal-hydroxy-linked acyl group (typically 18-hydroxy-delta-9-octadecenoate), and occur predominantly in a non-lactone, anionic form. In addition, seventeen dimeric and trimeric sophoroses were identified by MALDI-TOF/MS from this strain. The surfactant-like properties of these sophorolipids has value as potential replacements for petroleum-based detergents and emulsifiers.