Fungal degradation of chlorpyrifos by Verticillium sp DSP in pure cultures and its use in bioremediation of contaminated soil and pakchoi

Pesticides residues in soils and on vegetables are a public safety concern. Pretreatment with microorganisms degrading pesticides has the potential to alleviate the conditions. For this purpose, the degradation characteristics of chlorpyrifos by an isolated fungal strain Verticillium sp. DSP in pure cultures, soil, and on pakchoi (Brassica chinensis L.) were investigated. Degradation rate of chlorpyrifos in the mineral salts medium was proportional to the concentrations of chlorpyrifos ranging from 1 to 100 mg l(-1). The rate of degradation for chlorpyrifos (1 mg l(-1)) in the mineral salts medium was 1.12 and 1.04 times faster at pH 7.0 than those at pHs 5.0 and 9.0, and the degradation at 35 degrees C was 1.15 and 1.12 times faster, respectively, than those at 15 and 20 degrees C. The addition of the fungal strain DSP into the contaminated soils was found to significantly increase the degradation of chlorpyrifos. Degradation rates of chlorpyrifos in inoculated soils were 3.61, 1.50 and 1.10 times faster in comparison with the sterilized soil, previously chlorpyrifos-untreated soil, and previously chlorpyrifos-treated soil under laboratory conditions. In contrast to the controls, the half-lives of chlorpyrifos were significantly shortened by 10.9% and 17.6% on treated pakchoi, 12.0% and 37.1% in inoculated soils, respectively, in the greenhouse and open field. The results indicate that the fungal strain DSP can be used successfully for the removal or detoxification of chlorpyrifos residues in/on contaminated soil and vegetable. (C) 2007 Elsevier Ltd. All rights reserved.