Study On Isolation, Screening Of Parathion-Degrading Bacterial Strain And Improving The Degradation Effects

Parathion was used to control of plant diseases and insect pests in agriculture widely. But it also destroyed the environment seriously and was of great residual toxicity to human heath. Biodegradation, especial the degradation by microorganism, could eliminate this kind damage.A strain D5-2 of parathion-degrading was obtained by selective enrichment culture from pesticides-contaminated soil. Parathion could be used by D5-2 as the sole source of carbon. The character analysis of morphological and physiochemical showed that strain D5-2 belonged to Acinetobacter sp. The optimum growth condition were determined for D5-2 with temperature 28℃, pH 5-8, and the optimum carbon and nitrogen source was sodium citrate and yeast respectively. Oxygen could make the strain grow better. It was strongly inhibited by high concentration NaCl in the medium.D5-2 could grow in parathion salt medium (800mg/L, parathion), however, the degradation by the strain was low (the degradation rate was only 25%).In order to improve it's degradation, the mutation and refreshing were used. After reacting with UV,0.8%nitrous acid and 60% soil extract liquid, the degradation rate reached 49.1%,69.6%, and 53.9% respectively. Finally, the degradation rate reached 82.8% after treated with multiplex mutations.The biodegradation of parathion-contaminated simulation sample with sterilized soils by D5-2 was studied. The results showed that the degradation rate was 66.7% with 100mg/kg parathion concentration after 7 days. It was of very important and large value for D5-2 to apply practically in parathion concentration soil.Furthermore, a more exact measure with ultraviolet spectrophotometer was found to examine the biodegradation of parathion. Compared with gas chromatography measures, it showed better fitting to analysis results.