Screening Of Producing Organophosphorus Hydrolase Strains And Characterization Of The Enzyme

It has been known that organophophate can be degraded by somemicroorganisms. By using dichlovos as the sole carbon source, 7organophophate-degrading strains were isolated from the pesticide-pollutedsoil, and one of which (strain OPD7, enzyme activity is 196U/ml) was selectedfor further study, The optimal fermentation conditions for producingorganophosphorus hydrolase by strain OPD7 were determined. The optimalcomposition of fermentation medium is as follow: Glucose 1.5%, Tryptone 1%,MgSO₄·7H₂O 0.2%, KH₂PO₄ 0.5%, Na₂HPO₄ 0.5%, pH7.0. The optimal volumeof inoculum is 1%, cultivation temperature is 37℃, and the optimal shakingspeed is 180rpm when 250mL flask contains 100mL medium. Under theseconditions for 24h, the activity of organophosphorus hydrolase reach 238 U/mL,just 1.2 fold as before.The characterization of the organophosphorus hydrolase from OPD7 wassdudied. It was found that the optimal temperature and pH for the emzyme activity was 42℃and pH 7.0 respectively.The enzyme was stable within pH 6-8and up to 47℃at pH 7.0. Some metal ions like Mg²⁺,Ba²⁺, Mn²⁺ have positiveeffect on the enzyme, while other metal ions, such as Zn²⁺, Cu²⁺, slightly inhibitthe enzyme. The enzyme can not only degrade dichlorvos, but alsoacephate,methamidophos,dimethoate and omethoate.In order to protect crops from insects, pesticides have been using in fruitsand vegetables, as a result, the residual levels of pesticides on many fruits andvegetables are very high. The pesticides on vegetables were degraded by usingthe crude organophosphorus hydrolase.The results indicated that the crudeorganophosphorus hydrolase could effectively degrade organophosphoruspesticides.