Screening of hydrocarbonoclastic bacteria using redox indicator 2, 6-dichlorophenol indophenol.

Petroleum products are used in different forms in auto-mechanic workshops every day. Spent motor oil disposed-off improperly contains potentially toxic substances which can seep into the water tables and contaminate ground water. This study involved isolation and screening of bacterial species capable of utilizing hydrocarbons from three auto-mechanic workshops in Abeokuta, Ogun State. Total Heterotrophic Bacterial Counts ranged from 1.03 × 10⁶ to 2.81 × 10⁶ CFU/g. Total Oil Degrading Bacterial Counts varied between 4.0 × 10⁵ and 2.01 × 10⁶ CFU/g while Surface Active Bacterial Counts were from 1.2 × 10⁴ to 2.76 × 10⁵ CFU/g. Twenty-four bacteria species capable of utilizing petroleum as a carbon source were isolated from various contaminated soils using enrichment technique. Isolated bacteria include: Bacillus spp., Pseudomonas aeruginosa, Micrococcus spp., Proteus mirabilis, Proteus vulgaris and Enterobacter spp. Redox indicator 2, 6-dichlorophenol indophenol (DCPIP) was used to screen for efficient hydrocarbon (Kerosene, Premium Motor Spirit, and Engine oil) degradation by bacteria. Degradation efficiency was measured by optical density at 600 nm. Micrococcus spp., Proteus mirabilis, and Pseudomonas aeruginosa were found to be the best isolates growing on majority of hydrocarbons due to their high utilization value when growing on the hydrocarbons tested.