Characterization of Oil-Degrading Bacteria from Oil-Contaminated Soil and Activity of their Enzymes

Ten bacterial strains were isolated from long-term petroleum contaminated soil from the Daqing oilfield. The strains were preliminarily identified based on 16S rDNA sequence analysis combined with morphological observation, physiological and biochemical tests, in which strain X2 was identified as Bacillus pumilus, strain Z as Rhizobium sp, strain Y as Microbacterium oxydans, strain H as Arthrobacter sp., and strains X1, X3, X4, X5 X6, and X7 as Bacillus spp. The crude-oil degradation ability and activity of degradation-related enzymes of the strains were also studied, including dehydrogenase, catechol 2,3-dioxygenase, and lipase. The results showed that strain X6 has the highest oil-degradation rate in both liquid medium and contaminated soil, which reaches 54.4% and 51% in 28 d treatment. The GC-MS analysis showed that all tested strains could totally degrade chain hydrocarbons with C11∼C18, and partially degrade chain hydrocarbons with C19 ∼ C24. Most strains showed preference for growth in alkaline conditions ranging from pH 7.0 to pH 8.0, with strains X2, X6, and Z demonstrating stronger tolerance to saline and alkaline conditions than the other strains, and hence, displaying better environmental adaptability.