Research On The Characteristics Of Cypermethrin Degradation

As a kind of pyrethroid pesticides,cypermethrin?CP?was efficient,broad-spectrum,and potential.However,it can threat to human survival environment and health with its environmental problems and agricultural remains.Especially the second generation pyrethroids have the characteristic of optical,thermal stability.Therefore,its degradation is difficult under natural conditions and exacerbated by the threat to the environment.This thesis screened with degrade cypermethrin strain from the long-term ability of CP pesticide spraying in orchard soil by inducing acclimation after separation to obtain tolerable CP 20 strains.Among ideal strains,strain N-02 able to degrade CP was identified as Aeromonas punctata by the morphological,physiological and biochemical analysis 16SrDNA.Effects of medium composition on Aeromonas punctata N-02 degradation results showed that tryptone and yeast extract powder provided carbon and nitrogen sources.Zn²⁺stimulated the degradation ability of Aeromonas punctata N-02.To investigate the effect of different factors on content of degradation of CP in the system,the volume of liquid,substrate concentration,initial pH and temperature have great influence on the degradation rate.The results of the degradation condition were optimized by the relevant surface method:liquid volume 21.61 mL,CP concentration 26.84 mg/L,initial pH 7.14,peptone 0.30%content?w/v?,0.15%yeast extract powder content?w/v?,0.05%?w/v?zinc chloride content,the culture temperature 35?,inoculation amount was 5%?v/v?,shaking speed 180 r/min,culture time 96 h and the degradation rate of CP was 63.36%,which corresponded with degradation rate in theory?62.10%?.The characteristics of CP degradation by Aeromonas punctata N-02showed that strain N-02 has higher degradation,Aeromonas punctata N-02 degradation curve was corresponding to growth curve and the degradation rate of CP.Aeromonas punctata N-02in the logarithm growth period,the degradation rate of CP reached the fastest.By the time of culture prolonged,the degradation of 20 mg/L CP was 62.31%at the 96h.The degradation spectrum of pyrethroid pesticides by Aeromonas punctata N-02 was wide.Besides the degradation of CP,Aeromonas punctata N-02 could degradate Cypermethrin,permethrin,deltamethrin,Cypermethrin and cyfluthrin.The main metabolites of CP were analyzed by GC-MS.The results indicated that Aeromonas punctata N-02 could secrete carboxylesterase,which could break the carboxylic ester bond of CP specificly into 3-phenoxy benzaldehyde and dichloro-chrysanthemum acid.The biodegradation pathway was determined by analyzing the main metabolites of 3-phenoxy benzoic acid?3-PBA?showed that there were phenol and benzoic acid in the biodegradation system.The results of this research has enriched the date base of pyrethroid pesticides degrading bacterium,which laid a foundation for the further study of pyrethroid pesticides degradation and bioremediation with important theoretical significance and practical value.