Q-192. Differential Degradation of Crude Petroleum Fractions by Strains of Candida parapsilosis Isolated from Tropical Oil-Bearing Environment

S. A. Adebusoye1, M. O. Ilori1, G. O. Oyetibo1, O. S. Obayori1, A. E. Omotayo1, O. Ajidahun1, C. James1, O. K. Adekeye2;
1Univ. of Lagos, Lagos, NIGERIA, 2Conoil PLC, Lagos, NIGERIA.

The continual reliance on fossil fuel as the world’s primary source of energy has made petroleum spills inevitable consequences of oil production, refining and distribution and this has remained a major issue. Since microbial degradation is known to be an efficient process in the in situ decontamination of oil-bearing environments, it is believed that development of effective bioremediation strategies will be aided by microbial sourcing of novel and competent hydrocarbon degraders with broad and unusual substrate spectrum. Thus, in keeping with this objective, two Candida parapsilosis strains (MN1 and MC1) isolated after repeated batch enrichment technique were tested for their biodegradation potentials on Nigerian crude oil. Axenic cultures of strains MN1 and MC1 grew at a rate of 1.623 day-1 and 0.586 day-1 respectively in mineral salts medium supplemented with 8.4 g/l of crude oil. Whereas strain MN1 degraded aliphatic fractions by 74.4% and the aromatics by 743.04%, the corresponding value obtained for MC1 were 97.63% and 93.48% during the 14-day incubation period. The GC fingerprinting of aliphatic fractions showed major degradation of heptadecane (C17), octadecane (C18), nonadecane (C19), cicosane (C20), dodecane (C20), tricosane (C23), hexacosane (C26), octacosane (C28) and nonacosane (C29) in less than 6 days while nearly 100% of these fractions including the isoprenoid molecules were metabolized in 14 days. Among the aromatic fractions that were nearly eliminated during the cultivation period were benzo(a)pyrene, benzo(k)fluoranthene, benzo(a)anthracene, indeno(1,2,3-CD)pyrene, chrysene, pyrene, phenanthrene, fluorene and anthracene. Interestingly, substrate uptake studies showed that both strains grew very well on petroleum cuts, biphenyl, phenol, xylene, benzene and quite a number of polyaromatic compounds including pyrene, phenanthrene and anthracene. The metabolic functions of these strains suggest their potentials for applications in oil spill cleanup as well as in single cell protein production using petroleum feedstocks.