Isolation and characterisation of hydrocarbon-degrading microorganisms from soils contaminated with used engine oil

Abstract

Soil contamination with used engine oil is a widespread environmental issue, posing risks to ecosystems and human health. The high levels of noxious compounds, such as trace elements and organic compounds that are composed of polycyclic aromatic rings (PAHs), immediately in used engine oil can disrupt various ecosystem reformations, like biogeochemical cycling, carbon sequestration, and the degradation of humus.  Soil samples were collected from mechanic workshops where there are traces of hydrocarbons, and microorganisms were isolated using enrichment techniques with used engine oil as the sole carbon source, and the isolates were subjected to some biochemical tests. The results obtained revealed that the mean count of heterotrophic bacteria ranged from 2.0 x10⁸ ± 0.1 to 1.1 x 10⁸ ± 0.2 CFU/g while the mean count of hydrocarbon-utilising bacteria varied from 5.4 x 10⁷ ± 0.07 to 1.3 x 10⁷ ± 0.05 CFU/g, and the fungal populations ranged from 2.9 x 10⁷ ± 0.4 CFU/g to 1.0 x 10⁷ ± 0.1 CFU/g. A total of 12 hydrocarbon-degrading bacterial species and 16 filamentous fungi were isolated, characterized and identified. Some of the characterised isolates were Alcaligenes aquatilis > Pseudomonas sp. > Acinetobacter >Bacillus subtilis > Corynebacterium sp., and Flavobacterium sp. These oil-degrading organisms revealed hydrocarbon-degrading potential and bioremediation of the oil-contaminated sites.