Evaluation of the degrading potentials of plasmid and non–plasmid borne soil bacterial strains on bonny light crude oil

Abstract

This study was undertaken to evaluate the degrading potentials of plasmid and non–plasmid borne soil bacterial strains on Bonny light crude oil. Enrichment technique, turbidometric test, plasmid curing test as well as gas chromatographic flame ionization detection technique was adopted for isolating and evaluating the oil degrading capabilities of the selected bacterial strains. The preliminary physicochemical results revealed that pH was recorded slightly neutral, higher conductivity (0.41 to 0.44 μS/cm), higher organic carbon (2.32 to 4.34 %) but lower nitrogen and phosphorus contents (0.27 % and 10.11 kg) as well as lower water holding capacity was noted, respectively. The results indicated that 22 out of the 60 isolated bacterial strains had high crude oil degrading potentials (A600nm > 0.3). The result further indicated that bacterial strains belong to various species which are Bacillus cereus C12, Pseudomonas aeruginosa KAVK01, Bacillus licheniformis 126, Ochrobacterium intermedium E85b, Bacillus subtillis SDDlas, Bacillus subtillis LK4.5, Enterobacter cloacae GEBRI III and Bacillus cereus So24. Plasmid borne P. aeruginosa strain KAVK01 was the best degrader with 88 % remediation efficiency within the period while the plasmid cured P. aeruginosa strain KAVK01 had 65 % degradation with the order of n – alkane hydrocarbon degradation: (n-C8 - n-C17) > (n-C18 - n-C25) > (n-C26 - n-C32). The data obtained from the current study could help in the selection of bacterial species, most especially plasmid borne bacteria that can be employed in the restoration of oil contaminated soil ecosystem in the Niger Delta region of Nigeria.