An approach to develop bioremediation by isolation and characterization of microorganisms from soil contaminated with used lubricating oil.

Soil contamination with used lubricating oil (ULO) is an emerging environmental threat in many parts of the world. Bioremediation is a cost-effective and green, technological approach with the potential to remediate soil contaminated with ULO. Therefore, as an attempt to develop a bioremediation technique, the present study aimed to isolate and characterize microorganisms from soil contaminated with ULO. Bacteria and fungi were isolated from soil exposed to ULO for a long period, by enrichment culture in a mineral salt medium (MSM). Biodegradation assays and total microbial activity (TMA) studies were carried out for the microbial isolates in laboratory-scale microcosms with 1-4% w/w contamination levels of ULO. The initial screening experiment confirmed that two novel strains, RUH-K01 and RUH-F07 were efficient ULO degraders. They were identified as Pseudomonas aeruginosa RUH-K01 and Aspergillus fumigatus RUH-F07 with respect to their morphological characteristics and 16S rRNA gene sequences. Microcosm experiments revealed the biodegradation percentage in soil with 1% w/w ULO was 82.27% and 70.09% for P. aeruginosa and A. fumigatus, respectively. A slight reduction in ULO degradation was observed by both strains when the ULO contamination level increased. At 4% w/w ULO contamination level, the degradation was 56.91% for RUH-K01 and 50.25% for RUH-F07. The potential to produce bio-surfactants and other species-specific metabolic activities may be reasons for the efficient biodegradation of ULO by P. aeruginosa. The resulting significant negative correlation (p < 0.05) between the residual total petroleum hydrocarbon (TPH) content and TMA of both strains confirmed the applicability of the FDA assay as an appropriate method to characterize the ULO degradation efficiency of microorganisms. In conclusion, the overall results indicate the potential of P. aeruginosa RUH-K01 and A. fumigatus RUH-F07 to be used in bioremediation of ULO contaminated soils. [ABSTRACT FROM AUTHOR]