Crude oil degradation by <i>Bacillus</i> and <i>Micrococcus</i> species isolated from soil compost in Kano, Nigeria

Abstract

Microorganisms capable of degrading crude oil were isolated from soil compost in Kano, northwestern Nigeria. The work was carried out with the aim of determining crude-oil biodegradation potentials of Bacillus and Micrococcus species isolated from the soil compost as well as the assessment of the applicability of compost in bioremediation of hydrocarbon-polluted soils. The physico-chemical and microbiological parameters of the uncontaminated soil compost samples were determined using standard procedures. Similarly, the microbiological properties of the crude oil-contaminated soil compost samples were determined using liquid Mineral Salt medium. The microorganisms isolated from the contaminated soil samples showed an appreciable degree of degradation of the crude oil used, among which the crude oil-utilizing potentials of Micrococcus species and Bacillus species isolated from the soil composts were further analyzed using biodegradation experiment. Here, utilization of the crude oil as a growth substrate by the two bacterial isolates resulted in increased population densities with simultaneous increase in emulsification index (EI24) value and decrease in residual crude oil concentration. The Fourier Transform Infrared Spectrometry (FTIR) analyses of the residual hydrocarbons in the liquid minimal salt (MS) medium at the end of 15 days incubation showed that Micrococcus species had the highest degradation rate of 93.7% while Bacillus species had biodegradation rate of 87.5%. Thus, the two bacterial species isolated in this study showed appreciable degrees of degradation of the crude oil used. It could therefore be concluded that bioremediation of crude oil-polluted fields could be achieved using indigenous hydrocarbon utilizers of the soil compost and the process could be enhanced by supplementing the polluted environment with compost.

Keywords: Soil compost, Crude oil-degrading microorganisms, Bioremediation, Kano.