Isolation, Identification and Evaluation of Hydrocarbon Degradation Capabilities of Diesel Degrading Bacteria Isolated from Mechanic Workshop in Anambra State.

This work was aimed at isolating bacteria species capable of degrading diesel from hydrocarbon polluted soil. Mineral salt agar was used for the isolation by vapour phase transfer of diesel as the only source of carbon. Two morphologically different colonies that gave the best growth were identified using 16S rRNA sequence as Pseudomonas aeruginosa strain SI64S and Stenotrophomonas maltophilia strain H258. Shake flask degradation of 1% diesel showed that the two organisms can utilize diesel as the only source of hydrocarbon as indicated by their growth measured by optical density (OD) 600nm; 2.025 and 1.821 for Pseudomonas aeruginosa and Stenotrophomonas maltophilia respectively. On the effect of incubation time, the optimum growth for both Strains was observed at the 10th day of incubation with P. aeruginosa strain showing higher density of growth than Stenotrophomonas maltophilia strain. The optimization of growth conditions showed that pH 7 was the best for the growth of Pseudomonas aeruginosa strain S164S while Stenotrophomonas maltophilia strain H258 grew best at pH 8. The two isolates showed remarkable growth in all the nitrogen sources tested; with Ammonium nitrate giving the optimal growth for both strains. The ability to grow in higher concentrations of diesel up to 10% was also tested. The result showed that Pseudomonas aeruginosa can degrade up to 10% diesel as shown by its growth (OD 600nm, 0.452), while Stenotrophomonas maltophilia grew in up to 6% diesel with the optical density 0.316. The isolates were also tested for their ability to grow in different fractions of crude oil at 1% concentration. The result showed that Pseudomonas aeruginosa can utilize kerosene, crude oil, engine oil and condemn oil as the only source of carbon; while Stenotrophomonas maltophilia strain was able to utilize crude oil and kerosene but not engine oil and condemn oil. The result of this research shows that these two organisms isolated from our environment can conveniently be applied for bioremediation of hydrocarbon contaminated soil.