Studies on two mixed strains for pyrethroids degradation

【Objective】 The study aimed to prepare efficient mixed strains for pyrethroids degradation,and provide prospect candidate biological agents for use in pyrethroid-contaminated environment.【Method】 The mixed strains were composed upon strain HU and ZH.The degradation conditions were optimized with response surface methodology(RSM).The degradation ability of the mixed strains was evaluated with high performance liquid chromatography(HPLC).The degradation process was analyzed with first-order kinetics.【Result】 The optimal conditions for biodegradation were obtained as follows:temperature 28.5 ℃,pH 7.7 and inocula biomass 0.4 g/L.The optimal inoculating rate was 1∶1 based on single strain HU and ZH.Under such conditions,the mixed strains could effectively degrade fenvalerate,deltamethrin and cypermethrin.The degradation rates were 97.5%,94.3% and 96.6%,respectively,increasing by 23.6%,12.0%,17.9% or 56.9%,15.9%,14.1%,compared with the single strain HU or ZH after 3 days of incubation.Furthermore,the degradation processes followed first-order kinetics and half lives(T1/2) were 20.7,22.2 and 21.6 h,respectively,which were shortened by 14.1,7.2,10.6 h or 72.9,12.1,15.5 h,compared with the single strain HU or ZH.It's proposed that there is a synergistic effect between strain HU and ZH on fenvalerate,deltamethrin and cypermethrin degradation.【Conclusion】 The mixed strains could greatly improve the degradation efficiency of fenvalerate,deltamethrin and cypermethrin.Obtained results showed the optimal inoculating rate of the mixed strains was 1∶1.