Studies on relative capabilities of bacterial and yeast isolates from tropical soil in degrading crude oil

The relative capabilities of two bacterial isolates Serratia marcescens OCS-21 and Acinetobacter calcoaceticus COU-27 from Ebubu oil polluted soil of Rivers State, Nigeria and a yeast isolate, Candida tropicalis PFS-95 from unpolluted soil of the University of Calabar campus, in degrading transniger pipeline crude oil were investigated. Crude oil degradation was measured by gravimetric analysis and capillary gas chromatographic techniques. Candida tropicalis PFS-95 exhibited a more efficient ability in degrading the crude oil than either S. marcescens OCS-21 or A. calcoaceticus COU-27. The yeast isolate PFS-95 degraded 68.9% of crude oil after 16 days of incubation whereas OCS-21 and COU-27 degraded 51.5% and 45.5% of crude oil respectively over the same incubation period. Capillary gas chromatographic analysis of the degraded crude oil revealed that crude oil components of chain length C12 to C32 were extensively degraded by PFS-95 after 16 days of incubation while OCS-21 caused a moderate degradation of the crude oil components (C20 to C28) over the same period. Acinetobacter calcoaceticus COU-27 was able to degrade only C22 to C30 components of the crude oil after 16 days of incubation. Results of crude oil adherence/emulsification tests revealed that OCS-21 was unable to emulsify the crude oil but exhibited maximal adherence to the crude oil whereas PFS-95 and COU-27 exhibited minimal adherence to, but maximal emulsification of the crude oil. Results obtained suggest that C. tropicalis PFS-95 may be a better microorganism for clearing oil spills in tropical soils than either S. marcescens OCS-21 or A. calcoaceticus COU-27. ©