EFFECT OF INOCULATION ON THE BIODEGRADATION OF WEATHERED PRUDHOE BAY CRUDE-OIL

Enrichment cultures from oil-contaminated beach material from Prince William Sound, Alaska. generated both a mixed bacterial community of indigenous, oil-degrading marine microorganisms and a pure culture oil-degrader, strain E12V. The mixed and axenic cultures were used in comparative shake flask studies of inoculation on biodegradation of Prudhoe Bay crude oil. Within 12 h following inoculation of homogenized, oiled beach material with the mixed culture, total CO2 production was increased 2-fold relative to a noninoculated control. Moreover, measurements of phenanthrene degradation (as determined by the release of (CO2)-C-14 from [9-C-14]phenanthrene) showed a 2- or 3-fold greater degradation when inoculated with either strain EI2V or with the mixed culture, respectively. However, as medium was replaced by a simulated tidal cycle, the observed stimulation of CO2 production decreased, and the addition of strain E12V had no greater effect on total CO2 production than the addition of inorganic nutrients alone. Chemical analysis of oil recovered after 7 days incubation also suggested that, while these cultures are capable of efficient biodegradation of Prudhoe Bay crude in liquid culture, inoculation of beach material with high numbers of these microorganisms had little effect on the rate and extent of biodegradation of weathered crude oil. Overall, the sustained stimulatory effect was no greater than that observed with the addition of inorganic nutrients alone.