Preliminary Study of Crude Oil Degradation by Microorganisms Isolated from Polluted Soil in Okarki, River State, Nigeria

Abstract

Pollution of the environment by hydrocarbon compounds has become a significant management challenge in oil-producing countries. Presently, the use of biological means for the reclamation of polluted sites is the most acceptable technique owing to its eco-friendliness. This study was carried out to assess the crude oil degradation potential of indigenous microorganisms in polluted soil. The polluted soil was obtained from a crude oil-ladened site in Okarki, River State, Nigeria. Bacterial and fungal organisms present in the polluted soil were isolated on Nutrient agar and Saboraud dextrose agar plates respectively. The isolates were identified based on their morphological, microscopic and biochemical characteristics. Gravimetric analysis of the crude oil degradation by the isolates was done in Bushnell Hass medium supplemented with 5% crude oil as the only carbon source. A total of 6 bacterial genera namely, Staphylococcus, Citrobacter, Micrococcus, Pseudomonas, Bacillus and Corynebacterium were identified while the fungal isolates were Aspergillus niger, Aspergillus flavus and Penicillium sp. Bacterial and fungal counts were 2.57±0.01 Log cfu/g and 2.08±0.07 Log cfu/g respectively. Bacillus sp. had the highest relative abundance (27.3%), while Micrococcus sp. and Corynebacterium sp. had the least occurrence (9.1%). Among the fungal group, A. niger showed the highest percentage occurrence in the polluted soil. All the indigenous organisms isolated from the polluted soil showed varying potentials for crude oil degradation. Bacillus sp. and Penicillium sp. were the highest crude oil-degrading bacterium and fungus respectively. The degradation potential of the bacterial consortium was significantly higher (P < 0.05) than the other consortia tested. This study has shown that indigenous organisms possess the potential for crude oil degradation.