Determination and Microbial Degradation of Lambda-Cyhalothrin

Abstract

This work presents laboratory studies on the degradation of lambda-cyhalothrin. At first, a rapid quantitative determination method of lambda-cyhalothrin in food was developed by high performance liquid chromatography. Lambda-cyhalothrin-degrading bacterium F37 was isolated from the sewage of a pesticide factory outlet and was identified as Citrobacter braakii. The effects of environmental factors including carbon and nitrogen sources, initial pH, medium volume, incubating temperature and substrate concentration on the degradation rate were investigated. The addition of sucrose and yeast extract at the concentrations of 4.0 and 3.0 g/L, respectively, was the best for the degradation of lambda-cyhalothrin. F37 showed higher degradation activity at the range of moderate pH value (pH 6.5-8.0). After 72-h stirring culture, the degradation rates of lambda-cyhalothrin reached 81.1% at pH 7.0. The degradation dynamics analysis showed that the degradation half-life times of lambda-cyhalothrin in the culture liquid of F37 were only 5.7, 1.9 and 4.9 days at pH 9.0, 7.0 and 5.0, respectively. In addition, cypermethrin and triazophos could also be degraded by F37, showing that F37 was a broad-spectrum pesticide- degrading bacterium. Application of F37 on eliminating pesticide in vegetable showed that 68% of lambda-cyhalothrin was removed after treatment for 48 h. The results indicated that Citrobacter braakii F37 is effective in the elimination of pesticide and may provide a potent application in detergent industry and environmental restoration.