Biodegradation of bonny light crude oil by plasmid and non-plasmid borne soil bacterial strains using biostimulation and bioaugmentation techniques

A laboratory scale study was designed and conducted to assess the biodegradation of Bonny light crude oil by plasmid and non-plasmid borne soil bacterial strains using biostimulation and bioaugmentation techniques. The enrichment technique, turbidometric test, plasmid curing test, molecular identification method, biostimulation test, bioaugmentation test and gas chromatographic technique were carried out using standard analytical techniques. The physicochemical analysis result showed that the pH was slightly neutral, the organic carbon content was higher (2.32 to 4.34%), the conductivity was higher (0.41 to 0.44 μS/cm), and the water holding capacity was lower (0.27 percent and 10.11 kg, respectively). Based on their capacity to use crude oil, the results showed that 22 of the 60 isolated bacterial strains had higher pollutant degrading potentials (A600nm > 0.3).The identified potent hydrocarbon degraders includes: Bacillus spp., Pseudomonas aeruginosa KAVK01 and Ochrobacterium E85b strains. The highest degradation efficiency of 91% was found in soil that had been contaminated with 3 % (v/w) crude oil, amended with inorganic salts, and inoculated with plasmid-borne mixed cultures. The result further indicated that the consortium of plasmid borne isolates enhanced the reduction of the crude oil from the initial concentration of 10,318 ppm to 501 ppm (95 %) whereas 64 % decontamination was facilitated by the consortium of plasmid cured isolates. The information gathered from this investigation may be useful in choosing bacterial species, particularly plasmid-borne ones that can be employed to biodegrade soil contaminated by crude oil in Nigeria's Niger Delta region as well as the sample collection locations.