Screening And Characterization Of Methamidophos-Degrading Bacterial Strains

Methamidophos is one of the species of organic phosphorus pesticide which isbeing largely and widely used in our country. Insecticidal Mechanism ofMethamidophos，which are widely used in the control of rice, cotton, corn and othercrop pests. is inhibited insect pest in vivo cholinesterase activity, in order to achievethe purpose of destroying or inhibiting bacteria, At the same time, the toxicity of thepesticide on human and animal is strong. It has a stomach poison, killing and suckingaffect and it is also one of the pesticides which can cause serious environmentalpollution.With the use of the principle of separation of CO metabolism tomethamidophos degrading W, Y bacteria, this study intends to study on the twostrains of degrading phenol strain and the two characteristics of the optimization ofsynergetic degradation of Methamidophos in optimal conditions. The paper obtainedthe following results.1. With the use of co-metabolism substrate gradient acclimation and screening toefficient degradation of Methamidophos by microbial strains W and Y, theconventional identification and16srDNA identification showed that there is goodcompatibility between the growths of two strains of bacteriawhich were Pseudomonassp. and Flavobacterium.2. With the help of Mintab statistical software using Plackett-Burman andBox-Behnken central composite design, people can quickly and reliably carry out themethamidophos degrading nutrition condition optimization experiment. Theexperimental results will be the basis of medium KH2PO4adding amount to3.25g/L,NH4C1addition was0.9g/L, MgSO4.7H2O0.045g/L,40h strains can make theMethamidophos degrading rate increase to87%,6%higher than the optimization(81%) before.3. The experiments showed that strains W degradating methamidophos havesignificant effect. The volume proportion of vaccinated of W strain and the Y strainis1:0.8have the fastest degradation rate in300mg/L methamidophos. W and Y strains have similar degrading Methamidophos curve. The best conditions for W, Ystrain degrade into Methamidophos are concentration of300mg/L, temperature of30℃, pH7.0-7.5, speed180r/m. Y strain growth lags behind, the degradation rate isrelatively slow, but in the700mg/L high concentration of Methamidophos had higherremoval efficiency. Two strains in300mg/L pH7.0-7.540h residual methamidophosrate can reach to8.5%and11.3%. With low liquid volume (50-75mL/250mL) Ystrain has the degrading effect (4.75%-5.238%) which was higher than that of Wstrain (6.54%-7.45%).4. The adding of sucrose, glucose, and glycerol, maltose and galactose onmethamidophos degrading have certain effect, but mannose will have bad effects.Arginine and urea as nitrogen source will extend the auxiliary of Methamidophosdegrading period. Potassium nitrate, ammonium sulfate, casein and peptone asnitrogen source can make auxiliary Methamidophos Residue rate reduce to6.87%-10.42%.5. Among the combination strains W strain has significant impact on the results. Thestrain inoculum for W strain is2.5mL and the Y strain is1.5mL. They are best mixedin700mg/L concentration of Methamidophos environment. It will still have the higherremoval efficiency of illustrated flora of Methamidophos, combination can improvethe degradation of Methamidophos concentration, mixed strains at32℃,40hmethamidophos residue rate was11.5%, with less than2%of low concentrations ofsodium chloride at Methamidophos Residue rate below4.67%).6. CPO Methamidophos has certain transformation ability. Different concentrations ofMethamidophos Residue rate within4h range from74.77%to83.9%. However, atlow concentrations, the Methamidophos degrading rate is not high, and higherconcentration conversion rate is not high too, only in the100-150mg/L residue therate reached74.77%, the optimal concentration of CPO in2400U/ML is mostsuitable. The pH6.5CPO conversion by the fitness and oxidizing agent can improvethe Methamidophos transformation to add trace. The chlorine ion on Methamidophostransformation has a small role while using chloroperoxidase can effectively removethe Methamidophos content. The optimum reaction of Methamidophos concentration is100-150mg/L and the optimum enzyme concentration is2400U/L, the mostsuitable pH has a value of6.5, H202and chloride addition on Methamidophostransformation should play no special role, when excessive usage will cause anadverse impact.This paper offers a method on how to use an "oxidase plus compound bacteria"biological method to solve the problem of environmental damage caused byMethamidophos pollution, thus, it has an excellent ecological value.