Isolation, Identification Of Aldicarb Degrading Bacteria And Its Biodegradation Characteristics

In this dissertation, several soil samples were collected in Shandong province, where aldicarb was used long-term in the different environments. Dominant strains whose degradation rates were high and stable were selected. The effects of temperature, pH value, nitrogen source concentration, and substrate concentration on degradation rate were studied. Its degradative enzyme were studied preliminary. The main items as following:1. Using the enrichment culture technique, ZH-1 was isolated on LB medium containing aldicarb, and selected for further research for its high degrading efficiency. The strain could utilize aldicarb as its sole nitrogen source. Biochemical characteristics, physiological tests with analysis of its16SrDNA sequence indicated that the strain had high similarity with the genus Sphingobacterium. Growth determinations demonstrated that sucrose and sodium nitrate were the best carbon source and nitrogen source for growth and degradation of ZH-1, and C:N ratio 1:1 was appropriate for it cultured in mineral salts medium, respectely.2. By using UV, its growth and aldicarb degradation were detected respectely and the effects of temperature, pH value, nitrogen source concentration, and substrate concentration on degradation rate of the strain ZH-1 were also studied. The result suggested: 68% of aldicarb was degraded by the isolate strain after 5 days of incubation at 30℃, 120 rpm in liquid mineral salts medium. The culture temperature and pH had great effects on the biodegradation of aldicarb and bacterial growth. The optimal conditions for the strain's growth was culture temperature 25-30℃; pH value 6.5-8.0, and the concentration of sodium nitrate 0.3%.3. The velocity of ectoenzyme and endoenzyme of the strain ZH-1 were measured. The result showed that endoenzyme had higher velocity than ectoenzyme. The optimal conditions for high degrading activity were temperature 30℃, pH value 7.0, respectely. Its Km and Vmax of the enzyme was 28.41nmol/mL, 227.67nmol/min, respectely. 4. The effects of carbendazim, myclobutanil, tebuconazole and mancozeb fungicides, commonly used in field, on the strain's growth and aldicarb degradation were also determined. Results showed that the growth of ZH-1 strain and aldicarb degradation were not obviously inhibited at different concentrations of these fungicides. It can be assumed that the application of some fungicides would not affect on the growth of the strain and its capacity on the degradation of aldicarb in theory.