Date Published: April 8, 2016
Publisher: Springer Berlin Heidelberg
Author(s): Lateef B. Salam.
Two bacterial strains phylogenetically identified as Pseudomonas aeruginosa strains RM1 and SK1 displayed extensive degradation ability on waste engine oil (SAE 40W) in batch cultures. Spectrophotometric analysis revealed the presence of various heavy metals such as lead, chromium and nickel in the waste engine oil. The rate of degradation of waste engine oil by the isolates, for the first 12 days and the last 9 days were 66.3, 31.6 mg l−1 day−1 and 69.6, 40.0 mg l−1 day−1 for strains RM1 and SK1, respectively. Gas chromatographic (GC) analyses of residual waste engine oil, revealed that 66.58, 89.06 % and 63.40, 90.75 % of the initial concentration of the waste engine oil were degraded by strains RM1 and SK1 within 12 and 21 days. GC fingerprints of the waste engine oil after 12 days of incubation of strains RM1 and SK1 showed total disappearance of C15, C23, C24, C25 and C26 hydrocarbon fractions as well as drastic reductions of C13, C14, C16 and PAHs fractions such as C19-anthracene and C22-pyrene. At the end of 21 days incubation, total disappearance of C17-pristane, C22-pyrene, one of the C19-anthracene and significant reduction of C18-phytane (97.2 %, strain RM1; 95.1 %, strain SK1) fractions were observed. In addition, <10 % of Day 0 values of medium fraction ranges C13, and C16 were discernible after 21 days. This study has established the potentials of P. aeruginosa strains RM1 and SK1 in the degradation of aliphatic, aromatic and branched alkane components of waste engine oils.
Waste engine oil is a brown to black oil removed from automobiles when oil is changed. It markedly differs from fresh engine oil as it contains minute quantities of additives and metallic salts. It also contains higher concentrations of heavy metal contaminants that are dangerous to living organisms such as lead, zinc, calcium, barium and magnesium as well as lower concentrations of iron, sodium, copper, aluminum, chromium, manganese, potassium, nickel, and molybdenum resulting from engine wear (Mumford et al. 1986; Vazquez-Duhalt and Greppin 1986).
Biodegradation is a process by which microorganisms transform or mineralize the molecular structure of an environmental pollutant through metabolic or enzymatic processes into less harmful, non-hazardous substances, which are subsequently integrated into natural biogeochemical cycles. The mechanisms of adaptation of autochthonous microorganisms to hydrocarbon perturbations includes synthesis of inducible enzymes, mutations such as single nucleotide change or DNA rearrangement that results in degradation of the compound and acquisition of genetic information from closely related or phylogenetically distinct population within the hydrocarbon-challenged community through horizontal gene transfer (HGT) (Top and Springael 2003; Salam et al. 2011).
This study has established the biodegradative ability of two P. aeruginosa strains RM1 and SK1 on waste engine oil and their propensity to degrade various hydrocarbon fractions of the oil. It also bring to the fore the potentials of these isolates for bioremediation of spent engine oil affected compartments. Further works to determine the optimum environmental conditions favorable for their application in bioremediation will be the focus of our future research.