Abstract:
Contamination of soil with Used Lubricant oil (ULO) has become an emerging
environmental threat due to possible negative impacts of ULO on different
ecological receptors. Therefore, remediation of ULO contaminated soils using novel
and economically feasible technique is an urgent requirement. However, drawbacks
in the conventional soil remediation measures have led the development of
bioremediation techniques using naturally found microorganisms isolated from ULO
contaminated soil. Hence, the present study aimed to characterize the isolated fungal
strain with ULO degrading potential. Further, a comparative analysis of the ULO
biodegradation ability of the isolated strains, Aspergillus fumigatus RUH8 and
Brachybacterium conglomeratum RUH1, total microbial activity (TMA), and Allium
cepa toxicity assay was performed for bioremediated soil. The experiments were
carried out under laboratory-scale microcosms with 1-5% w/w contamination levels
of ULO. Results indicated that a time-dependent increase in the biodegradation
percentages of B. conglomeratum and A. fumigatus inoculated treatments. Following
35 days, the highest biodegradation percentages of B. conglomeratum and A.
fumigatus were 77.63% and 70% respectively at 1% contamination levels. A
concentration-dependent reduction of TMA was observed in two individual strains,
A. fumigatus and B. conglomeratum.. Compared to A. fumigatus, the lowest root
growth inhibition (REI) and chromosomal inhibition (CA) was observed in B.
conglomeratum mediated bioremediated soil. The calculated percentages of REI and
percentages of CA in B. conglomeratum mediated bioremediated soil were, 18.27,
41.83, 43.27, 49.52, and 59.89 and 1.0, 1.5, 2.25, 3.0, and 3.5 respectively at 1-5%
w/w contamination level. Therefore, the findings of the study concluded that B.
conglomeratum has the potential to biodegrade and reduce the toxicity of ULO
compared to A. fumigatus highlighting the species-specificity of the biodegradation
efficiency.
