Degradation of used engine oil by alcaligenes sp. strain isolated from oil contaminated site: Isolation, identification, and optimization of the growth parameters

Bioremediation process is one of the most effective methods which facilitates the cleaning of contaminated sites and restores contaminated sites through the broad biodegradative capabilities evolved by microorganisms towards undesirable organic compounds. In this study, Alcaligenes sp. with potential to degrade and utilize used engine oil as its source of carbon and energy was isolated, identified and its growth parameters optimized for efficient and better breakdown of the pollutant. Alcaligenes sp. was isolated from a used engine oil contaminated soil in an old mechanic shop, after enrichment using a carbon free (Bush-Nell Haas) media which was supplemented with used engine oil. The bacterium was identified (morphologically, biochemically, and molecularly) and studied for its ability to extract carbon from used engine oil hence degrading used engine oil. Thereafter, the various growth parameters of the bacterium isolate were optimized. Data obtained showed optimum growth parameter of 2% (v/v) used engine oil (carbon source), pH 7, temperature 37 °C, inoculum size 2 ml and incubation time 240 hours. Also, measured ribosomal RNA (16S RNA) sequence and phylogenetic analysis revealed that the isolate is a very close relative of Alcaligenes species. The degradation potential of the isolate was assessed using gravimetric analysis, and a percentage degradation of 92.5% was discovered. Overall, the results of this study suggest that Alcaligenes sp. can effectively degrade used engine oil, hence, a potential remediation organism against engine oil contamination and spills on soils or water surface.