Isolation, identification and degrading properties of PAHs-degrading bacteria

Abstract:

[Objective] Polycyclic aromatic hydrocarbons (PAHs) are known as high-toxic and persistence organic contaminants in the environment. Screening highly efficient degrading bacteria is important for bioremediation of PAHs-contaminated environment. This study aimed to isolate and identify high efficient PAHs-degrading bacteria from the candidate strains, then to characterize degrading properties of these target strains. [Methods] PAHs-degrading bacteria were screened by the plate-culture method, and then these target strains were identified by the 16S rRNA gene phylogenic analysis. Degrading properties of PAHs-degrading bacteria were determined by single factor experiments. [Results] Three PAHs-degrading bacterial strains SL-1, 02173 and 02830, which utilized phenanthrene and pyrene as the sole carbon and energy source for growth, were obtained from the candidate strains. The strain SL-1 was the type strain of Rhizobium petrolearium. 02173 and 02830 were highly homologous to Pseudomonas alcaliphila and Pseudomonas corrugate, respectively. The strain SL-1 could degrade 100% of single phenanthrene (100 mg/L) and 48% of single pyrene (50 mg/L) in 3 days, and the degradation rate of pyrene was up to 74% in 5 days; it also could degrade 75.89% and 81.98% of mixed phenanthrene and pyrene within 3 days. The strain 02173 and 02830 could degrade a mixture of PAHs completely in 3 days, including naphthalene (200 mg/L), fluoranthene (50 mg/L), phenanthrene (100 mg/L) and pyrene (50 mg/L). [Conclusion] Three PAHs-degrading bacterial strains SL-1, 02173 and 02830 have high-efficient degradation ability not only for low-molecular-weight PAHs but also high-molecular-weight PAHs. These strains were the ideal candidates for bioremediation of PAHs-contaminated environment. Low-molecular-weight PAHs can promote high-molecular-weight PAHs degradation due to con-metabolism effect, while the biodegradation of low-molecular-weight PAHs will be suppressed.