Evaluation of biodegradation rate of oil degrading microorganisms to degrade lubricant oil contaminated soil.

Abstract

Soil, an important natural resource facilitating numerous ecosystem services and interactions and anthropogenic impact on soil has altered the natural functioning of soil. Soil contamination with used lubricating oil (ULO) has emerged as a significant environmental issue in developing countries due to the growing demand for lubricating oil in both industrial and societal contexts. Consequently, there is an immediate requirement for the creation of innovative, ecofriendly, costeffective methods to remediate soils contaminated with ULO. Nevertheless, the limitations of traditional soil remediation approaches have driven the exploration of bioremediation techniques that make use of naturally occurring microorganisms, including bacteria and fungi, which have been isolated from ULO contaminated soil. The present study was focused to investigate the biodegradation rate of used petrol engine oil contaminated soil using the Pseudomonas aeruginosa ATCC 27853, Bacillus cereus ATCC 10876, and co-culture between two strains while optimizing environmental conditions. Total petroleum hydrocarbon determination was carried out by using spectrophotometric method to analyze various environmental conditions that can impact their biodegradation activity including ULO concentration (ranging from 1% to 3% v/v), inoculum size (between 1% and 3% v/v), initial pH levels (7 or 7.5), incubation temperature (ranging from 25°C to 37°C), and rotation speed (0 to 150 rpm). The optimal conditions were determined to be 1% ULO, a 2% inoculum size, pH 7, incubation at 37°C, and rotation at 150 rpm. Under the optimized conditions P. aeruginosa, B. cereus, and their mixture efficiently degraded ULO and they achieved 31.95%, 33.1%, and 40.5% respectively, after 30 days of incubation. The utilization of P. aeruginosa and B. cereus strains presents an opportunity to create a cost-effective approach for remediating soil contaminated by used engine oil. Therefore, based on the findings of the study, it is evident that both strains effectively degrade ULO in contaminated soil, with the degradation capacity being strain specific. Future studies should assess strain compatibility with ecosystem functioning, particularly in terms of reducing post-treatment toxicity. Additionally, future research should explore the degradation capacity of these strains in conjunction with natural microbial communities in oil-contaminated sites to better understand their ecological interactions and optimize remediation strategies.