Screening Carbendazim Degradation Bacterium And Study Degradation Characteristics

To deal with the international situation of increased global economic integration and growing competition, Pesticides are needed in order to control harmful microorganisms against agriculture, thus to improve the crop yields and ensure adequate supply of agricul- tural products. Pesticides are becoming an important means to ensure a good harvest and promote agricultural development, thus to meet the needs of people's living.Though it has played an important role on the development of agriculture,the negative impact of pesticide on the environment should not be ignored. Pesticide has an effect on the killing of plant diseases and insect pests, but it also has a variety of toxicity to human beings. Sometimes, this effect occurred directly, in other cases, it occurred through media such as the air, water, soil, etc. Acute, ubacute, chronic and specialty poisoning incidents occurred frequently in the process of using pesticide. Some of The symptoms of poisoning can be cured such as vomiting and dizziness, but some are for life, such as carcinogenesis, teratogenesis, mutagenesis, reproductive toxicity and embryonic toxicity. Pesticide used in excess by farmers consciously or not can damage the environment, pollute groundwater, threaten biological survival, and also enhanced the resistance of plant diseases and insect pests to pesticides. Therefore, scientific and rational use of pesticides, and dealing with environmental pollution and excessive residual caused by pesticides have become serious problems that need to be solved urgently.In this experiment, we got bacteria that can degrade Carbendazim after a month of domesticating and concentrating from the sewage sludge samples of Hunan Haili Pesticide Factory. The degradation effect was detected by three wavelength correction method using ultraviolet spectrophotometer. Then the degradation conditions and culture medium were dually optimized. Finally pot experiment was taken to verify the actual degradation effect of the Carbendazim degrading bacteria. The main contents and results are as follows:(1)After enrichment and plate streaking experiments, 17 strains that can grow on the plate medium with Carbendazim were picked out, All of them can degrade Carbendazim. Among these 17 strains, L-1 is the best one for it can degrade 200mg/L Carbendazim in 72h with the degradation rate of 70.23±0.55%. Then we identified it from morphological, physiological and biochemical characteristics and BLAST sequence alignment of 16SrDNA and got to know that L-1 belonging to Rhodococcus erythropolis.(2)We took the single factors and four factors and three levels of the orthogonal design experiments on the L-1 degrading conditions such as temperature, initial pH, inoculum, initial concentration. The results are as follows: L-1 showed good adaptability to temperature, but adaptability to a narrow pH range. The optimum temperature is 30℃, the optimum pH value is 6.0, Inoculum can also affect the growth and degradation activity of L-1, with the best inoculum as 5%. The best initial concentration of Carbendazim was 100mg/L. The best combinations of degradation conditions that obtained by the orthogonal design are as follows: temperature 30℃, pH 5.5, inoculum 5%, initial concentration 100mg/L.(3)Experiments using Design-Expert analysis software to establish glucose, K2HPO4 and KH2PO4 interaction of three factors on the degradation of carbendazim strain L-1-related effects of three-dimensional mathematical model. Analysis of variance of the model to determine the bacterial L-1's the medium: glucose 6.4%, K2HPO4 0.2%, KH2PO4 0.09%. That ultimately determine the degradation of L-1 strain with the medium is: glucose 6.4%, peptone 3%, K2HPO4 0.2%, KH2PO4 0.09%, MgSO4·7H2O 0.02%, NaCl 0.1%.(4) Experiment's materials is spinach which is widely cultivated, By the results, we know treatment by spray bacteria 3, 4, 5, 6d, the carbendazim residual decomposition rate respectively is 24.97%, 56.43%, 83.75%, 92.46%. the degradation rate of growth continues to increase. In the 6d after spraying bacteria, the carbendazim in the treatment leaves residues of 0.48 mg/kg, below the limit 0.5 mg/kg, that's show L-1 can be applied to degrading carbendazim.