The Degradation of Dimethoate and the Mineral Immobilizing Function for Cd2+ by Pseudomonas putida

Organophosphorus pollution and heavy metal pollution are prominent in China and have caused increasingly severe environmental pollution. This research used Pseudomonas putida to degrade dimethoate so as to induce the formation of calcium carbonate (CaCO₃) and calcium phosphate (Ca₃(PO₄)₂) in beef extract peptone medium. In addition, the mineral immobilizing function of the generated Ca₃(PO₄)₂ and CaCO₃ for Cd²⁺ was studied by adding different concentrations of Cd²⁺ to the culture solution. Meanwhile, transmission electron microscopy (TEM), scanning electronic microscopy (SEM), X-ray diffraction, gas chromatography and atomic absorption spectrophotometry were used to investigate the biodegradation of dimethoate, the concentration variation of Ca²⁺ and Cd²⁺, the mineral and chemical compositions of the precipitates. The results showed that the growth of P. Putida could increase the pH value of the culture solution and effectively degrade the organophosphorus pesticide dimethoate. Besides, the concentration of Ca²⁺ in the culture solution decreased significantly in the first four days and then tended to be stable. Moreover, the TEM and SEM results presented that there were large amounts of biogenic sedimentary CaCO₃ and a little Ca₃(PO₄)₂ in the precipitates. Furthermore, in the employed culture system, the removal rates of Cd²⁺, when added at two different concentrations (6 ppm and 15 ppm), reached 100%. Therefore, this study provided a new idea for treating wastewater polluted with organophosphorus pesticide and heavy metals by using microorganisms.