Enhanced biodegradation of crude oil in contaminated soil by inoculation of hydrocarbon-degraders

Inoculation of hydrocarbon-degraders will be a favorable feature for bioremediation of oil-contaminated soil. In this work, enhanced biodegradation of crude oil was investigated using the process, wherein inoculation of seven active hydrocarbon-degraders were isolated from the contaminated site. Preliminary results showed that isolated seven active bacterial strains were Acinetobacter SY21, Neisseria SY22, Plesiomonas SY23, Xanthomonas SY24, Azotobacter SY42, Flavobacterium SY43, and Pseudomonas SY44, respectively. Seven active degraders belong to gram-negative bacteria. They were capable of degrading crude oil and six other hydrocarbons (normally octane, paraffin wax, benzene, methylbenzene, phenol, and naphthalene) as carbon source and energy. Their biodegradation efficiencies of oil were higher than 80% after 8 d. The highest degradation rate of 2.34 x 10(-3) mg cell(-1) d(-1) was obtained for bacterial strain SY43 (Etwinia sp.), followed by a degradation rate of 1.50 x 10(-)3 mg cell(-1) d(-1) for bacterial strain SY23 (Plesiomonas sp.). In addition, it was observed that a higher removal efficiency of TPH depends on large number of strains by more inoculums of isolates. Finally, it has been found that the adaptation of isolates was well because there was no decrease in the CFU even when the concentration of crude oil was up to 34250 mg/kg. Moreover, the removal efficiency of total petroleum hydrocarbon (TPH) was up to 88.4% after active oil degrader was inoculated while the corresponding removal efficiency of TPH was 1.4% without inoculums. These results indicated that both the SY43 and SY23 strains are easy to grow and establish a local ecology in the oil-contaminated soil. That is, biodegradation of crude oil in contaminated soil was enhanced by inoculating isolates.