Determination of petroleum biodegradation by bacteria isolated from drilling fluid, waste mud pit and crude oil

Abstract

Abstract Objective In this study, the aim was to isolate and identify bacterial strains in crude oil, drilling fluid and waste mud pit samples collected from the same oil field, determine the petroleum biodegradation and find the most effective bacteria in the samples in petroleum biodegradation. Methods The contents of crude oil, drilling fluid and waste mud pit samples were enriched in appropriate conditions. Upon identification of the isolated bacteria, the incubations in petroleum containing media were performed at 150 rpm at 30°C for 7 days. Petroleum biodegradations by bacteria were measured by using colorimetric, spectrophotometric and gravimetric methods. Results Bacillus cereus, Proteus mirabilis, Bacillus subtilis, Enterococcus faecalis were isolated from the crude oil sample; Bacillus subtilis subsp.spizizenii, Bacillus cereus, Enterococcus faecalis were isolated from the waste mud pit; and Proteus mirabilis, Klebsiella pneumoniae, Bacillus tequilensis, Bacillus axarquiensis and Enterobacter cloacae were isolated from the drilling fluid. Klebsiella pneumoniae was found to degrade 60% of the petroleum in the media and Bacillus axarquiensis degraded 51%. Conclusion In literature, no study was encountered showing biodegradation efficiencies of Bacillus axarquiensis which was isolated from the drilling fluid in our study. The use of Bacillus axarquiensis can contribute to advanced bioremediation studies.