Isolation,Identification,Degradation Characters And Application Of Carbendazim-Degrading Bacteria

A bacterium strain 2-1 capable of utilizing carbendazim was isolated from the long-term application of carbendazim vineyard soil. When bacterial strain 2-1 was incubated in mineral salt medium at pH 7.0 and at 30℃which contained 200 mg/L carbendazim, the degradation rate of carbendazim was 80.12%, after two days shaking at speed of 200r/min. Bacterial strain 2-1 was primarily identified as Stenotrophomonas maltophilia according to its physiological & biochemical characters and the homology analysis of its 16SrDNA sequence. Bacterial strain 2-1 had a strong absorption to carbendazim in the liquid medium, so we can not refine the carbendazim by the method of extracting or centrifuging to remove bacterial cells. The method to detect carbendazim in the medium used in the text can overcome the impact of absorption, and its linear equations has a good relationship.The method's recovery is high. Its an accurate and reliable method.By tests in shaking flasks, culture temperature, initial pH, quantity of inoculum, medium volume and initial carbendazim concentration five factors's effects on carbendazim degrading rate of Bacterial strain 2-1 was studied. Take carbendazim degrading rate as the indicator, its optimal degradation conditions were at at temperature of 25℃～30℃, initial pH6.0, quantity of inoculum 5%, medium volume 20mL, and initial carbendazim concentration no more than 200 mg/L. Extracting enzyme from Bacterial strain 2-1, found the enzyme's degrading rate to carbendazim was 0%.Take the medium glucose 10.000 g, peptone 10.000 g, NaCl 5.000g, K2HPO4 1.500g, MgSO4?7 H2O 0.200g, distilled water 1000 mL, pH value of 7.0 as the initial fermentation medium, the cell growth as the indicator. Compositions and additions of Bacterial strain 2-1's culture medium had been optimized, and the results showed that the optimal formula of culture medium is peptone 5.0 g, NaCl 5.0g, K2HPO4 0.5g, MgSO4 ? 7H2O 0.2g, and distilled water 1000mL.Response surface methodology(RSM) based on a five-level four-factor central composite rotatable design of experiments was used to optimize the optimal levels of four important factors, namely culture temperature, culture time, shaker speed, quantity of inoculum. A quadratic regression model was obtained, and solved it, the greatest predicted OD600 value of the medium was 2.38, then the value of the principal factors: culture temperature 25℃, culture time 24h, shaker speed 210r/min, and the quantity of inoculum 9%.Application of bacterium strain 2-1 to remove remanent carbendazim in small Chinese cabbage in laboratories, the test result indicate: spraying with bacterium strain 2-1 for 3,4,5day, the degrading rate of carbendazim in small Chinese cabbage was respectively 12.30%,52.18% and 95.78% compared to spraying with pure water. After spraying bacterium strain 2-1, with the time increasing, the degrading rate of carbendazim in small Chinese cabbage grow accordingly. After spraying bacterium strain 2-1 for 5day, carbendazim residue in the leaves of small Chinese cabbage was only 0.39 mg/kg, lower than the national standards'limited value of 0.5 mg/kg carbendazim residues in vegetables.