Preparation And Degradation Of Organophosphorus Pesticides By Chlorpyrifos Highly Effective Degrading Bacteria

Due to the advantages of high efficiency and broad spectrum for organophosphorus pesticides,it plays an important role in the control of rice borer,planthopper,cotton bollworm,and other agricultural pests.Meanwhile,most of the organophosphorus pesticides have a long half-life and are widely used in the environment,which has potential harm to the ecological environment and human health.Therefore,it is urgent to seek an environmentally friendly and efficient treatment technology for organophosphorus pesticide residues.Biodegradation has the advantages of high efficiency,rapid reproduction,and low cost.In recent years,many organophosphorus pesticide degrading strains have been screened,isolated,and identified from environmental pollution samples.However,due to the complexity of soil environmental pollution,most degradation strains are difficult to be directly used for in-situ remediation.Therefore,the microbial immobilization technology can effectively solve the problem of poor adaptability of free cells in actual environmental remediation.This is one of the effective means of environmental bioremediation.In the study,the immobilized bactericide of chlorpyrifos high-efficiency degradation strain X1T was prepared by the compound immobilization technology.The degradation performances of immobilized bactericide were determined by comparing different immobilized method.The combined degradation mechanism of immobilized materials and degrading strain was also revealed.The research contents and results are as follows:(1)Based on embedding and different composite immobilization methods,the polyvinyl alcohol,sodium alginate,diatomite and chitosan were used as embedding materials to prepare different immobilized bacterial agents.The half-lives of chlorpyrifos(20 mg/L)degradation were 9.53,8.80,7.97,and 8.67 h,respectively.The internal structures of four kinds of immobilized bactericides were analyzed by SEM and FT-IR.The results showed that the adsorption and embedding could effectively improve the immobilization performances of strain X1T.Based on the degradation experiments of polluted wastewater,the embedding materials were determined to be more stable than the free bacteria.(2)The polyvinyl alcohol-sodium alginate and chitosan-diatomite were selected as embedding and adsorption carriers,and polyvinyl alcohol,cells,chitosan,and diatomite were used as influencing factors,respectively.The orthogonal experiments of 4 factors and 3 levels were designed to prepare the immobilized bacterial agents(CTS-KLG-PS).The optimal immobilization conditions were obtained as follows:PVA concentration of 100 g/L,cells density of 50 g/L,chitosan concentration of 20 g/L,diatomite concentration of 10 g/L.Based on experimental verification,the physical properties of CTS-KLG-PS could meet the requirements of bacterial preparation,such as elasticity,strength,stability and mass transfer performance.(3)When the immobilized bacterial agents were repeated twice and three times,the degradation rates of chlorpyrifos were more than 90.0%and 80%.After repeated for 6 times,the degradation rate of chlorpyrifos was still above 60%.The results showed that the immobilized bacterial agents could be recycled and reused.(4)Based on indoor simulated soil degradation and degradation of six organophosphorus pesticides by CTS-KLG-PS,the results showed that both immobilized bacterial agents and free cells had a good degradation effects on organophosphorus pesticides.However,the degradation of organophosphorus pesticides by immobilized bacterial agents was better than that by free cells in soil.In MSM,the immobilized bacterial agents had good degradation performances for profenofos,chlorpyrifos,parathion methyl,triazophos,isocarbophos,and phoxim at 20 mg/L.Furthermore,the degradation effect of immobilized bacterial agents on chlorpyrifos,profenofos and isocarbophos was better than that of free cells..