[Isolation and degrading characters of chlorpyrifos degrading bacteria XZ-3]

A strain of bacterium XZ-3 capable of highly degrading chlorpyrifos was screened from the soil sample collected from a pesticide plant after taming and enrichment. Based on analysis of phenotype, physiological and biochemical characters and 16S rDNA, XZ-3 was identified as Arthrobacter sp.. The effects of carbon source, pH, temperature and chlorpyrifos concentration on degradation were determined. The growth of bacteria in culture media were measured by visible absorption spectrophotometry under 400 nm. The residual chlorpyrifos in culture media was extracted with an equal volume of petroleum ether, and then determined by ultra-violet spectrophotometry. The results showed that the degradation rate of chlorpyrifos by XZ-3 was 86.8% in 24 h. The biodegradation rates were the highest when the additional carbon source was 0.3%, pH value was 9, chlorpyrifos concentration was 100 mg x L(-1), and cultivated temperature was 30 degrees C. The growth of bacteria increased with carbon source concentration, and was higher with pH from 8.0 to 10.0, and the highest when temperature was 30 degrees C, and chlorpyrifos concentration was 800 mg x L(-1). The strain could survive when chlorpyrifos concentration was 1000 mg x L(-1) and the removed amount of chlorpyrifos increased with chlorpyrifos concentration. The optimal conditions were proposed, which could provide theoretic basis for prevention and control of pesticides pollution.