Isolation,Identification And Characteristic Of A PCBs-Degrading Strain

Polychlorinated biphenyls(PCBs) are a class of typical,complex,and ubiquitous Persistent Organic Pollutants(POPs) in the environment. It was listed in Stockholm Convention in 2001. In recent years, lots of studies have been concentrated on degradation of PCBs because of their environmental persistence, bioaccumulation,semi-volatile and biological toxicity. Biodegradation of PCBs has captured great attention in the field of environmental science and technology. One of the promising solutions is to obtain microbial strains capable of removing more PCB congeners aerobically at a high biotransformation rate.A polychlorinated biphenyls-degrading bacteria was firstly isolated from soil suffering from long-term PCBs contamination and was then cultivated. 16 S rDNA sequence analysis identified the bacteria as Pseudomonas aeruginosa. Experiments were conducted to study the degradation characteristics of the bacteria for PCB77.The study revealed that the bacteria could grow with PCB77 providing the only carbon source and its 7-day degradation rate of 2 ml( OD600=1.0) for PCB77 at concentration of 1.0 mg·L-1 was 49.6 %, under pH of 7.5 and the temperature and vibration speed of thermostatic vibrating incubator set at 30 ? and 150 r·min-1respectively. The influence of co-existing pollutants, including three aromatics and two heavy metals, on the degradation rate was also studied during the experiment.The results indicated that the degradation rates changed to 58.5 %, 53.8 % and 40.8 %respectively when the same concentration(i.e. 1.0 mg·L-1) of biphenyl or phthalic acid or benzoic acid was introduced to the solution. The presence of either Cr6+ or Pb2+ both had suppressing effect on the degradation rate, and the higher the concentration, the more significant of the effect. The suppressing effect of Cr6+was demonstrated to be more obvious than that of Pb2+. With the chlorine increased from 3to 5, the degradation rate of PCBs homologue are decreased to 89.6 %, 49.6 %,23.5 % respectively. Surfactants, as carbon sources, obviously promote the biodegradation of PCBs. The degradation rates of experimental group increased by13 % than control group after adding TW-80. The degradation rate of PCB77 increased with the concentration of TW-80(0, 0.5, 1.0, 2.0 g·L-1) and increased by0 %, 12.9 %, 17.63 % and 21.38 % respectively. With the increase of the number of Chlorine atoms in PCBs(PCB18, PCB77, PCB101), degradation rate of PCBs with TW-80 increased by 10.4 %, 14.4 % and 19.1 % respectively. The toxicity of PCBs biodegradable system decreased over time and the drop rate shows the negativecorrelation with the number of chlorine atoms in PCBs.The above results show that JXJ is a efficient aerobic PCBs degrading bacteria.All these results pave the way for further research and enhance bioremediation in persistent chlorinated complex contaminated sites.