Isolation And Characteristics Of Efficient Carbendazim Degradation Bacterium

Object:Carbendazim degradation bacterium were isolated from grape vineyard soil in Xinjiang province of China and the degradation characteristics of bacterium were also evaluated with laboratory experiment. This study may be useful for the bioremediation of pesticide contaminated soil in this area.Methods:In this experiment, carbendazim degradation bacterium were isolated from grape vineyard soil under continuous enrichment culture conditions. Identification of bacterial strain was completed with Biolog analysis and comparison sequences of 16S rDNA and phylogenetic analysis. The residue of carbendazim in soil was analyzed with HPLC for investigating the degradation characteristics of carbendazim degrading bacterium.Results:1. There were 16 species of microorganism isolated from the isolation and purification medium. All of colonies can survive in culture medium with carbendazim concentration from 400 to 1000 mg/L. Two isolates XJ-D and XJ-H were selected because of its high carbendazim degrading rate. Carbendazim, 600 mg/L, could almost be degraded completely within 15 days by the strain XJ-D and XJ-H.2. Identification of bacterial strain were completed with Biolog analysis and comparison sequences of 16S rDNA and phylogenetic anlaysis. Bacterial strains of XJ-D and XJ-H were identified as Rhodococcus erythropolis and Azospirillum brasilense, respectively.3. Both XJ-D and XJ-H could use carbendazim as sole carbon or nitrogen source. Carbendazim at concentration of 600 mg/L were degraded with 99.0% and 95.6% and the high average degradation rate were 52.87mg/(L·d) and 52.24 mg/(L·d) for XJ-D and XJ-H within 11 d in mineral salts medium, respectively. However, when the carbendazim at the level of 1000 mg/L, about 27.68% and 60.44% of carbendazim was removed for XJ-D and XJ-H, respectively. The adaptability of strain XJ-H was better than that of XJ-D under the high carbendazim concentration conditions.4. In the simulation test of soil, the strain XJ-D can degrade 82.81% of carbendazim at concentrations of 200 mg/kg within 15 d. The average degradation rate and the half-lives of carbendazim in soil inoculate XJ-D were 11.04 mg/(kg-d) and 6.28 d, respectively. For the control, the degrade rate and the average degradation rate were 25.27% and 3.37 mg/(kg-d), respectively. The half-lives of carbendazim in control soil was 34.58 d. It suggested that the degradation of carbendazim in soil were promoted significantly by XJ-D. The strain XJ-H can not survive when it was inoculated to the soil.5. The suitable conditions of carbendazim degradated with XJ-D were studied in a laboratory experiment.the strain XJ-D showed a good characteristics of degradation in soil, when the concentration of carbendazim at 200 mg/kg; inoculation rate of stains at 109 cells/g dry soil, soil temperature at 23～28℃, and soil moisture at 60%-80%.