Screening,Identification And Characterization Of Prothioconazole-degrading Bacteria

While prothioconazole is popularized in agricultural production activities,the residual pesticides in the environment pose a threat to the natural environment and human health.Green and efficient removal of pesticide residues in the environment has received extensive attention from researchers at home and abroad.Separation and domestication of high-efficiency degradation strains from polluted environments and the use of microorganisms to biodegrade pollutants are one of the main ways to repair residual pesticide pollution.This study screened and isolated prothioconazole highefficiency degradation bacteria from the activated sludge of pesticide plants.Observe the morphological characteristics of the strains through optical microscope and electron microscope scanning,combined with Biolog Microbial Identification Manual and 16 s r RNA sequence analysis.And through the response surface design,the optimal conditions for the degradation of prothioconazole were explored,and the degradation kinetic model at multiple concentrations was established.The results of the study are as follows:1?By High Performance Liquid Chromatograph,set the mobile phase as acetonitrile and 0.1% phosphate buffer(65 and 35);the flow rate is 1m L/min;the column temperature is 30?;the detection wavelength is 220nm;the column is TC-C18,5?m,4.6x250 mm.Prothioconazole and prothioconazole peak at approximately 8.639 min and6.352 min respectively.Within the range of 0.1?5mg/L,the drug standard curve has a good linearity,and the recovery rate of adding to the medium is 93%?116%.2?From the activated sludge samples,7 strains with a certain degradation effect of prothioconazole were selected;among them,strain W-313 has the best degradation ability.W-313 is a highly efficient degrading bacterium that can use prothioconazole as the sole carbon source,and it also has a degradation effect on prothioconazole-desthio.The colonies on the LB plate are gray-green,and the rods appear under the scanning electron microscope.Physiological and biochemical characteristics combined with16 Sr DNA gene sequence identified as Pseudomonas,named Pseudomonas aeruginosa W-313.Y-2625 is a degradation effect that can be degraded with prothioconazole as a single carbon source,and degradation effects on the prothioconazole-desthio.A short rod shape is presented under the LB plate.Physiological and biochemical characteristics combined with 16 Sr DNA gene sequence identified as Enterobacter,named Enterobacter Cloacae Y-2526.3?Using the controlled variable method,explore the effects of initial temperature,initial p H,inoculum,salinity,and exogenous carbon sources on the degradation of prothioconazole.Within a certain range,the inoculum amount and salinity have no obvious influence on the degradation effect;under the influence of the initial temperature,initial p H and amount of exogenous glucose,the degradation effect shows a trend of increasing first and then decreasing.Combined with Plackett-Burman experiment,it is determined that the initial temperature is the main environmental factor that affects the degradation of prothioconazole by the strain W-313,and the overall impact turned to be that initial temperature>>initial p H>exogenous glucose amount>salinity>inoculation amount.The results of Placket-Burman experiments in strain Y-2625 are: initial temperature> Initial acid alkaline >> Exogenous glucose content> Salinity> inoculation amount.4?The conditions for Pseudomonas aeruginosa W-313 to degrade prothioconazole were optimized by response surface methodology.When the initial p H was 7.40,the temperature was 32.0?,and the glucose content was 0.60%,W-313 had the best degradation effect on prothioconazole that the degradation rate can reach 65.12% in 48 hours.And when the initial p H was 6.83,the temperature was 34.0?,and the glucose content was 5.60%,Y-2625 had the best degradation effect on prothioconazole that the degradation rate can reach 64.62% in 48 hours.5?Set the concentration of 20,50,100,200,500mg/L of prothioconazole to optimize the fermentation medium,and the degradation of prothioconazole at different concentrations over time is simulated by the first-order kinetic model.The first-order kinetic model fits the degradation status of strains within 50mg/L well.When the initial amount of substrate exceeds 100mg/L,the degradation of the strain will be delayed obviously,and it will be delayed with the increase of substrate concentration.As the initial substrate concentration increases,the degradation half-time gradually increases.