PETROLEUM DEGRADING POTENTIALS OF BACTERIA SPECIES ISOLATED FROM PETROLEUM REFINERY SLUDGE

ABSTRACT

Crude oil is a common environmental pollutant composed of a large number of aromatic and aliphatic hydrocarbons. The intrinsic biodegradability of hydrocarbons and distribution in the environment of competent degrading microorganisms are critical to the implementation of bioremediation processes. In the present study, the petroleum degrading potentials of bacteria species isolated from petroleum refinery sludge was evaluated. The bacterial species were isolated and identified using standard microbiological methods. The petroleum degrading potentials of isolates was determined by a 14-day enrichment assay using basal salt medium (BSM) supplemented with 2% Escravos Light Crude Oil (ELCO) and assessed by gas chromatography (GC). The petroleum degrading isolates were identified as Micrococcus sp., Bacillus sp., Arthrobacter sp., Bacillus sp., Staphylococcus sp. and Streptomyces sp. The mean bacterial counts during enrichment assay ranged between 0.95 × 10¹cfu/ml (Micrococcus sp.) and 9.7 × 10¹cfu/ml (Bacillus sp.). Staphylococcus sp. exhibited the highest (96.20%) total petroleum hydrocarbon (TPH) degrading potential; while Micrococcus sp. showed the least (35.42%) TPH degrading capacity. The isolates were also remarkable in the degradation of PAH, removing between 4 and 10 PAH compounds after treatment in the following order (based on number of PAH compounds removed (highest to lowest): Staphylococcus sp. >Streptococcus sp. >Arthrobacter sp. >Bacillus sp. (sample 2) >Micrococcus sp. >Bacillus sp. (sample 4). The study demonstrated that the bacterial isolates in this study were good petroleum degraders and therefore could be employed as candidates for bioremediation of petroleum polluted sites.