Degradative Studies of Crude-Oil Degrading Bacteria Isolated from Hydrocarbon Polluted Surface Water in Agbabu, Ondo State

Hydrocarbon-utilizing potentials of bacteria isolated from twelve different bitumen-contaminated sites in Agbabu, Ondo State were investigated. Water samples were collected and analyzed using standard microbiological techniques. The mean total bacterial count and mean total hydrocarbon- degrading bacterial counts were determined using pour plate technique. The hydrocarbon-utilizing potentials of the isolates were further determined by screening them in mineral salt broth supplemented with 2% crude-oil over a period of 10 days. The growth of the isolates was monitored by measuring the absorbance (OD600nm) and Total viable count (log10 CFU/ml). Five isolates selected based on their ability to utilize crude-oil were subjected to conventional biosurfactant screening tests: qualitatively (drop collapse) and quantitatively (oil spreading and emulsification activity). The selected five isolates were used to degrade crude-oil and percentage degradation was determined by Gas chromatography analysis. The isolates were identified by the amplification and sequencing of the 16S rRNA sequences. The Mean Total bacteria count and the Mean Total hydrocarbon-utilizing bacteria count were 7.70 (log10 CFU/ml) and 7.14 (log10 CFU/ml) respectively. Out of the isolates screened for biosurfactant production, only Pseudomonas and Bacillus species were positive for all the tests. They had a clear zone of 4 mm each and an emulsification capacity of 65.50% and 57.13% respectively. The percentage degradation of crude oil by Pseudomonas aeruginosa, Micrococcus luteus, Bacillus cereus, Acaligens faecalis and B. lichenformis were 78.67%, 68.27% 63.16%, 54.28% and 51.54% respectively. Pseudomonas aeruginosa had the highest % degradation (78.67%) while the lowest % degradation (51.54%) was observed by B. lichenformis. The identities of the isolates revealed by 16S rRNA sequences were Pseudomonas aeruginosa, Bacillus cereus, B. lichenformis Acaligens faecalis and Micrococcus luteus.