Screening Of Dominant Degrading Bacteria And Chiral Degradation Of Pyrethrins In Soil

Pyrethroid pesticides are important species of chiral pesticides,they are widely used in modern agricultural production because of their high efficiency,low toxicity characteristics,but their pollution to the environment is also one of the difficulties faced by human beings.Microbial remediation of pesticides has been an important topic in scientific research.The structure of the pyrethroid insecticides is more complex,which contain many chiral centers and many enantiomers,different isomers often show different insecticidal activity and degradation behavior in the environment.Knowledge on enantioselective degradation behavior of pyrethroids are useful for better understanding the chiral profiles as well as accurate evaluation of ecological risks of pyrethroid pesticides.In this paper,?-cyfluthrin and permethrin,two important pyrethroid insecticides,were selected to systematically study their stereo and enantioselective degradation behavior in soil and by screened dominant microbial strains.the experimental contents were as follows:1)Isolation of degrading microorganisms from permethrin,and study on the selective degradation of enantiomersFive dominant microbial strains of PM-A,PM-B,red-A,red-B and red-C,capable of degradation of permethrin were isolated from Shijiazhuang yellow soil and Wuhan red soil.PM-A was identified as Curtobacterium flaccumfaciens.PM-B was idenfied as Micro Bacillus.Red-A was identified as staphylococcus sciuri.Red-B and Red-C were identified as Bacillus sp.and Sphingobacterium spiritivorum.On the basis,the stereo and enantioselective degradation of permethrin by the five strains were studied in details.The results showed the cis-isomer was degraded faster than the trans-isomer with strains red-A and red-C,whereas the trans-isomer showed higher degradation rate for strain PM-B.Moreover,the cis-isomer exhibited some enantioselectivity when permethrin was degraded by strain PM-B,the trans-isomer exhibited some enantioselectivity when permethrin was degraded by strain PM-A,red-A,red-B and red-C.But,red-A preferentially degraded 1R-trans isomers,PM-A?red-B and red-C preferentially degraded 1S-trans.2)Microbial screening,identification and enantioselective biodegradation of ?-cyfluthrinTwo bacterial strains Jin-B and Jin-D,capable of degradating ?-cyfluthrin,was isolated from sludge by enrichment culture.Jin-B was identified as Pseudomonas plecoglossicida and Jin-D was Pseudomonas sp based on analysis of physiological properties and 16 S rDNA sequence.The results showed the degradation followed first-order kinetics,and no enantioselectivity was observed for the two enantiomers of ?-cyfluthrin.But,strain Jin-D exists in cis and trans isomerization degradation about ?-cyfluthrin,it preferentially degraded cis isomers.