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.
