Immobilized Whole Cell System with Methyl Parathion-Degrading Activity for Organophosphate Insecticide Detection

As the result of the extensive use and high contamination of organophosphate (OP) insecticides in agricultural products and the environment, especially in developing countries, a simple and convenient means for OP detection and screening was investigated. Whole cells from the recombinant clone BpGP carrying methyl parathion (MP) degrading, mpdB, gene originating from MP-degrading Burkholderia cepacia and possessing MP-degrading activity were immobilized onto the polystyrene surface of the wells of microtiter plates using adsorption method, followed by cross-linking with glutaraldehyde. The immobilized cells were used as a bio-component for spectrophotometric detection of OP compounds, with MP as a representative insecticide. Scanning electron microscope and cell count analyses revealed highly dense, rod shaped bacterial cells stably attached to the well surface. The system was most stable at 25°C and could be used to detect MP repetitively up to 46 rounds, although it was still active at about 45% until round 100. For MP analysis, the linear range of the system was 2-200 µg/mL and the detection limit was 2 µg/mL. The tests on spiked and real samples were also performed and the results revealed high detection efficiency. This immobilized cell microtiter plate system has a great potential to be utilized as an alternative for OP detection and screening with the advantages of simplicity, stability, ease and convenience for assembly and use, and low cost.