Microbial proficiency in spent engine oil degradation of polluted soil from auto-repair facilities and industrial sites: isolation and molecular characterization of hydrocarbonoclastic microorganisms

Abstract

The disposal of spent engine oil presents a significant environmental challenge due to its toxic and persistent nature. This study aims to isolate and molecularly characterize microbes capable of degrading spent engine oil, with the ultimate goal of developing eco-friendly bioremediation strategies. Soil and water samples from auto-repair facilities and industrial sites were collected, and Mineral Salt Agar (MSA) medium was used to screen for spent engine oil degrading microorganisms. Isolated strains were screened for their ability to utilize spent engine oil through growth experiments and biochemical assays. Other parameters monitored were temperature and pH. The 16S rRNA gene sequencing was employed to identify the isolated microbes at the molecular level. BLAST program in National Centre for Biotechnology Information (NCBI) Genebank database Phylogenetic analysis revealed a diverse array of seven (5) isolates including bacterial (3) and fungal (2) taxa, suggesting a rich microbial diversity involved in spent engine oil degradation. The isolates were identified as bacteria (SA1- Bacillus thuringiensis, SA6-Bacillus cereus, and SB5-Alcanivorax borkumensis) and fungi (SA5-Aspergillus niger and SC3-Aspergillus flavus). The percentage of oil degradation rate was SA5 (43.80%) > SA1 (29.17%) > SB5 (28.82%) > SC3 (6.07%). The fungal isolate, SA5-Aspergillus niger showed a significant (p < 0.05) spent engine oil degradation rate compared to the bacteria. The study demonstrates the potential of not only bacteria but indigenous fungal communities in mitigating the environmental impact of spent engine oil. It also provides a foundation for future studies focused on optimizing the biodegradation of complex hydrocarbon pollutants.