| Polychlorinated biphenyls(PCBs)are a large kind of compounds,in which there are nearly 200 kinds of derivatives at present.The 4-chlorobiphenyl,which belongs to the PCBs,had harmed the natural environment and human health for its wide usage in industry,high toxicity,bioacumulation,polluted persistence and carcinogenicity.The remediation of 4-chiorobiphenyl pollution has attracted attentions of scholars.Compared to the physical and chemical remediation,bioremediation remediate this pollution more safely and economical.In this study,two degrading strains had been isolated from chemical soil.One strain,named as CB-3,could degrade 4-chiorobiphenyl to 4-chlorobenzoic acid.Another strain,named as CD-2,could use 4-chlorobenzoyl acid as the sole carbon source for growth.4-chlorobiphenyl at the concentration of 50 mg/L could be degraded completely by the combined action of these two strains in 10 huors.By analyzing of the morphology,physiological and biochemical characteristics,and phylogeny analysis,strain CB-3 was identified as Pseudomonas sp.and strain CD-2 was identified as Comamonas sp..Strain CB-3 is an aerobic gram-negative bacterium.The colony is yellow,rod-shaped,flagellated,and the size of cell is 0.59?0.60 ?m×0.9?1.1?m.The optimum growth condition of strain CB-3 was 30?,salt concentration was 1%,and pH was 7.0.Strain CD-2 is an aerobic gram-negative bacterium.The colony is canary yellow,ellipse shaped,non-fiagellated,and the size of cell is 0.96?1.10 ?m×2.0?2.3?m.The optimum growth condition of strain CD-2 was 30?,salt concentration was 1%,and pH was7.0.The degradation characteristics of strain CB-3 were studied.The results showed strain CB-3 with the inoculation amount of 3%could completely degraded the 4-chlorobiphenyl at the concentration of 50 mg/L at 30? within 10 hours.The optimum degradation temperature of the strain CB-3 was 30? and the pH value was 7.0.The strain CD-2 with the inoculation amount of 3%could completely degrade the 4-chlorobenzoicacid at the concentration of 30 mg/L at 30? within 8 hours.The optimum degradation temperature of strain DC-2 was 30? and the optimum pH value was7.0.The final metabolite from 4-chlorobiphenyl degraded by strain CB-3 was identified by HPLC-MS.The analysis result of HPLC-MS showed that the metabolic product's molecular ion peak was 155.01,and the final metabolite was identified as 4-chlorobenzoic acid.The whole genome of CB-3 was sequenced to analysis the functions of genes and verify the metabolic pathway.After results analyzed,the strain CB-3 contained bphABCD and benABCD and the degradation pathway of 4-chlorobiphenyl was preliminarily estimated.The whole genome of strain CD-2 was sequenced,The complete degradation of 4-chlorobenzoic was realized under the action of related enzymes.The bioremediation of 4-chlorobiphenyl by strain CB-3 was tested in laboratory.At 30?,strain CB-3 with the inoculation amount of 109 cfu/g soil could degrade 56.68%of 4-chlorobiphenyl at the concentration of 10 mg/kg in 30 days.The degradation rate of 4-degradation by strain CB-3 was positively correlated with the inoculation amount.The optimum temperature for degradation of 4-chlorobiphenyl in soil was 30?,and the degradation rate was 55.48%.Strain CB-3 had better degradation ability when the concentration of 4-chlorobiphenyl ranges from 3 to 10 mg/kg in soil,but the degradation efficiency decreased when the concentration was 20 mg/kg in soil.The degradation rate was 65.84%by adding peptone into soil.At 30?,the degradation rate of 10 mg/kg biphenyl was 63.29%with the inoculation of 109 cfu/g strain CB-3.The experimental results of soil remediation under laboratory conditions provided theoretical reference for the practical application. |
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