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Environmental contamination by waste engine oil in cities all over the world constitute serious public health concern because its effects are unwholesome and unquantifiable. This study was carried out to biodegrade waste engine oil using bacterial isolates. Three bacteria were isolated from soil samples that have been contaminated with waste engine oil for over seven years in automechanic workshops at Ebelle. They were analysed using standard methods. The bacterial count was 89.4 ± 0.02cfu/g while the control was 3.6 ± 0.14cfu/g. The bacterial diversity identified in descending order were Bacillus sp. (25.41%), Pseudomonas sp. (22.13%), Corynebacterium sp. (18.44%), Acetobacter sp. (18.03%) and Aeromonas sp. (15.98%). The biodegradation efficiencies of three bacterial isolates; Bacillus, Pseudomonas and Corynebacterium species were observed taking records of change in physicochemical parameters (pH, electrical conductivity and total hydrocarbon content) for 40 days at 10 days interval with waste engine oil sample at concentrations of 10%, 20%, 30% and 40%. Corynebacterium sp. gave the highest percentage reduction in pH values of 52.92% at 10% contamination level while Pseudomonas sp. gave the highest percentage reduction of 53.04%, 52.99% and 53.01% at 20%, 30% and 40% crude oil contamination levels respectively. The pH values of the control was almost the same all through the period of incubation. Bacillus sp. gave the highest percentage increase in electrical conductivity value of 74.17%, 69.93% and 69.91% at 10%, 20% and 40% contamination level respectively while Pseudomonas sp. gave the highest increase of 70.45% at 30% contamination level. Also, the values at day 0 and the control were not so different from each other. Corynebacterium sp. gave the highest percentage reduction in total hydrocarbon content of 95.49%, 95.48%, 96.50% and 96.50% at 10%, 20%, 30% and 40% contamination level respectively. The result revealed a reduction in pH and total hydrocarbon content while there was an increase in electrical conductivity values. This indicated that biodegradation occurred. This study revealed that the bacterial isolates particularly Corynebacterium sp. possess the ability to biodegrade waste engine oil thereby guaranteeing environmental quality and sustained public health for all and sundry.
Keywords: biodegradation, Corynebacterium sp., environmental sustainability, total hydrocarbon content