Lipid and exopolysaccharide production during hydrocarbon growth of a marine bacterium from the sea surface

Abstract

The marine bacterium Alcaligenes sp. PHY 9 L.86 was isolated from hydrocarbon-polluted sea-surface waters and grown on 0.1 % tetradecan in batch cultures. Lipid composition of cell pellets and supernatants were examined throughout growth, using thin layer chromatography coupled with flame ionization detection Cellular and extracellular carbohydrate and protein contents were estimated. Bacterial growth on hydrocarbon induced the production of extracellular emulsifying agents (biosurfactants). Formation of foams was observed in the culture medium at early stationary phase; it was related to high emulsifying activity and maximum extracellular lipid production (in particular, free fatty acids and triglycerides). Specific staining for acid polysaccharides revealed the formation of exopolysaccharid fibers associated with vesicles, the size of which depended on the growth phase. Surface-active agents produced by Strain PHY 9 L.86 explain the foam formation. Our results stress the role of biosurfactants in the biodegradation of hydrocarbon in the marine environment.