Screening of PCBs-degrading bacteria and enhanced bioremediation of soil under low-temperature condition

Two low-temperature PCBs (polychlorinated biphenyls) -degrading strains were isolated from the long-term PCBs-contaminated soil and named strain P and strain Q which could utilize the PCBs as the sole carbon source and energy source. These two strains were identified by 16S rDNA sequence analysis. PCBs-degrading ability of these two strains was investigated by resting cell experiment and the bioremediation of PCBs-contaminated soil was simulated in laboratory. The results showed that strain P was initially identified as Sphingomonas sp. and strain Q was initially identified as Pseudomonas sp., both Strain P and strain Q had greater ability to degrade the low-chlorinated PCBs than the high-chlorinated PCBs. The highest removal rate of PCBs single-component by strain P was 77% while strain Q was 99%. The PCBs-degrading ability of strain Q was approximately 20%~30% higher than strain P. When two strains worked together in soil, the PCBs, especially the high-chlorinated PCBs could be removed more effectively. After adding surfactant hydroxypropyl-β-cyclodextrin to the bioremediation system of PCBs-contaminated soil, the growth of strain P did not change significantly while the biomass of strain Q increased obviously, and the removal rate of PCBs was twice more than not adding hydroxypropyl-β-cyclodextrin. Adding surfactant made the total removal rate of PCBs reached above 57%, which indicated that adding hydroxypropyl-β-cyclodextrin was conducive to the bioremediation of PCBs-contaminated soil.