Crude Oil Degradation by Microorganisms in Soil Composts.

Abstract

The hydrocarbon utilizing capabilities of Micrococcus varians, Bacillus badius, Corynebacterium ulcerans and Corynebacterium amycolatum isolated from soil composts were analysed. In the biodegradation experiment, utilization of the substrate by bacterial isolates resulted in increased population densities with simultaneous increase in emulsification index (EI 24) valued from 30.0 to 48.84 and a decrease in residual crude oil concentration. The growth rate constants (u) and mean generation (h) times of Micrococcus varians, Bacillus badius, Corynebacterium ulcerans and Corynebacterium amycolatum were 0.027 and 25.5, 0.025 and 27.5, 0.019 and 36.2, 0.023 and 30.0, respectively. The gas chromatographic analysis of the residual hydrocarbons in the liquid medium at the end of 30 days incubation showed that Micrococcus varians had the highest degradation rate of 93.10%, whilst Bacillus badius, Corynebacterium ulcerans and Corynebacterium amycolatum were 0.027 and 25.5, 0.025 and 27.5, 0.019 and 36.2, 0.023 and 30.0, respectively. The gas chromatographic analysis of the residual hydrocarbons in the liquid medium at the end of 30 days incubation showed that Micrococcus varians had the highest degradation rate of 93.10%, whilst Bacillus badius, Corynebacterium ulcerans and Corynebacterium amycolatum had biodegradation rates of 89.22, 88.22 and 90.82%, respectively. The residual hydrocarbon in soil microcosm after 30 days of biodegradation was 73.75, 75.81 and 76.94% for Micrococcus varians, Corynebacterium amycolatum and a consortium of the two isolates, respectively. A substrate specificity test of the isolates on different hydrocarbons showed that the isolates had good growth on anthracene and engine oil but poor growth on pyrene, toluene, naphthalene, dodecane and xylene.