Isolation, Identification And Degrading Characters Of DDT And DDE Degrading Strain Dxz9

In this dissertation, taking DDT and DDE as a model pollutant, a strain of bacterium DXZ9 capable of highly degrading DDT and DDE 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, DXZ9 was identified as Stenotrophomonas sp. Degrading-bacteria enrichment and isolation, characterization of biodegradation were studied systematically. The results could be summarized as follows:1. The author introduced the use situation, pollution, mobility in environment, degradation and metabolism, ecological toxicological characteristics and pollutant management of DDT and DDE, which has been applied extensively in the world and recently in China; accordingly author presents the issues that would be investigated.2. DDT and DDE degrading-bacteria were isolated by direct way and selective enrichment from soil exposed to pesticides and soil of pesticides production, and then researched on the bacteria in our laboratory conservation. Four high efficiently degrading DDT strains and two high efficiently degrading DDE strains were isolated by selective enrichment, and the high efficiently degrading DDT strains degrading rates under the condition of 30℃,pH 6.0 8.0 in culture media containing 10mg·L^-1 of DDT in 5d were all above 45%, the high efficiently degrading DDE strains degrading rates were all above 35% in the same condition. In contrast, we choose the strain DXZ9 for further study. We identified DXZ9 as Stenotrophomonas sp. based on analysis of phenotype, physiological and biochemical characters and 16S rDNA.3. The effects of time, pH, temperature and DDT DDE concentration on degradation was determined. The results showed that the degradation rate of DDT by DXZ9 was 55.0% in 5 days, and DDE was 39.88%. The biodegradation rates were the highest when pH value was 6.0⁸.0, DDT and DDE concentration was 10mg·L^-1 and cultivated temperature was 30℃. The growth of bacteria higher with pH from 6.0 to 10.0, and the highest when temperature was 30℃, DDT or DDE concentration was 10mg·L^-1.The strain could survive when DDT or DDE concentration was 150mg·L^-1 and the removed amount of DDT DDE increased with DDT or DDE concentration.4. Analysis of the extracted metabolites. In our research, DDT and DDE metabolites were identified in the test culture medium.