ISOLATION OF A MARINE YEAST THAT DEGRADES HYDROCARBON IN THE PRESENCE OF ORGANIC-SOLVENT

Forty-three yeast strains that tolerated organic solvents were isolated by treatment of deep-sea sediments collected at depths of 1200 m in Sagami Bay and 1977 m in Suruga Bay in the Pacific Ocean with 50% (v/v) n-hexane. With these deep-sea isolates and 58 yeast type strains purchased from culture collections, tolerance to organic solvents was tested. When n-dodecane, n-decane, n-nonane, hexyl ether, n-octane, isooctane, cyclooctane, diphenyl ether, or n-hexane was added to growth medium at the concentration of 10% (v/v), one marine yeast, strain Y-40, could grow in all media except that with n-hexane. This strain was selected as a possible degrader of petroleum hydrocarbons. From results of studies of morphology and taxonomy, it seemed to be a species of Candida. Strain Y-40 could grow well in concentrations of 50% (v/v) of four solvents. The ability to degrade hydrocarbons of kerosene dissolved in 20% (v/v) n-octane was compared for strain Y-40 and the hydrocarbon-assimilating strains C. tropicalis IFO 1400 and Yarrowia lipolytica IFO 1548. Only Y-40 could degrade n-alkanes with a carbon number of more than 8 in the presence of n-octane. The extent of degradation of n-alkanes in the presence of organic solvent which was higher than that without the organic solvent.