Bioprospecting of potential petroleum hydrocarbon degraders using bacterial strains isolated from soils around transformer installation areas

The study assessed the contamination levels of the soils around transformer installation areas in Ile-Ife, which were contaminated with transformer oil. Contamination levels are determined by using some soil physicochemical properties (pH, electrical conductivity, and organic matter) and also identifying some hydrocarbon utilizing bacteria in the oil-contaminated soils. Soil samples were collected from transformer oil-contaminated and uncontaminated soils at 5-15-cm depth. Soil physicochemical properties were determined using standard methods. The soil samples were screened for hydrocarbon-degrading bacteria; the isolates were duly identified using the matrix-assisted laser desorption/ionization-time of flight/mass spectrometry technique. The growth rate of the bacterial isolates in the hydrocarbon medium was monitored. Thereafter, the residual oil was analyzed quantitatively and qualitatively using gravimetric and gas chromatography-mass spectrometry techniques, respectively. The results of the physiochemical parameters of the oil-contaminated soils showed that the soils had mean values of pH (5.01 +/- 0.22), electrical conductivity (574.45 +/- 63.35 mu s/cm), and soil organic matter (50.53 +/- 5.67 g/kg). The chromatogram of the residual oils from the biodegradation process showed the efficacy ofProvidencia stuartii and Bacillus pseudomycoidesin degrading alkyl polycyclic aromatic hydrocarbons (PAHs), cycloalkanes, unsaturated alkanes, and unsaturated-branched alkanes, whileProvidencia rettgericould adequately degrade cycloalkenes, cycloalkanes, unsaturated alkanes, and unsaturated-branched alkanes. In this study, novel hydrocarbon-degrading bacterial isolates were identified, and the extent of their hydrocarbon and complex organic compound utilization was shown, it suggests the need for further studies to explore their potentials in bioremediation programs.