| Carbamate pesticides are novel broad-spectrum insecticides, acaricides and herbicides. Carbofuran, a carbamate pesticide with high toxicity, has been used extensively in agriculture. Presently, much awareness is created on the environmental pollution problems caused by the pesticide. Many scientists have devoted to study on pesticide residue and metabolism, and microbial degradation of pesticide residues is of particular interest.In this paper, the enrichment culture method was established to isolate and screen microorganism which could degrade carbofuran. One carbofuran-degrading strain named YM3 was isolated from activity sludge. Its physiological and biochemical characters, and biologic actions in environment were studied. The main objective of this paper is to find dominant strain with efficient carbofuran-degrading ability and provide theoretic basis for the practical application of the isolate. The main results are as follows: 1. From the activated sludge samples, several carbofuran-degrading bacterial strains were isolated. One with better growth named YM3 was selected for further study. Based on the results of phenotypic features, physiological-biochemical properties, and phylogenetic similarity of 16S rRNA gene sequences, the isolate was designated as Paracoccus sp. YM3. The 16S rRNA partial sequence was deposited in the GenBank database under the accession number EU309677.2. The optimal growth conditions of isolate YM3 were determined. YM3 was able to degrade carbofuran and use it as the sole carbon source. It was shown that 30?C and pH 7.0 were propitious to the microbial growth, and the change of aeration had an influece on degrading rate.3. The carbofuran degrading ability of the pure culture was investigated by UV-Vis, HPLC and TLC. Under the condition of 30?C and pH 7.0, strain YM3 could degrade 50 mg/L carbofuran within 6 days. Carbofuran-7-phenol was detected as the major intermediate metabolite and it accumulated without degradation. Effects of different initial carbofuran concentration, incubation temperatures, initial pH, total inocula biomass amount and additional carbon source were investigated to determine the optimal biodegradation conditions. Results showed that the isolate could effectively degrade carbofuran when provided as the sole carbon source, with pH 7.0, at 30?C. Higher inoculation amount could increase the degradation rate of carbofuran. And too high concentration of substrate had an negative effect on biodegradation. Addition of extra carbon source, such as glucose or sucrose, could greatly enhance the biodegradation of carbofuran. The study may provide theoretic basis for bioremediation of contaminated soils.4. The location of carbofuran degradation enzyme of strain YM3 was performed by the osmoic shock method, and it indicated the enzyme was intracellular. SDS-PAGE analysis of the total proteins of the strain under induced and noninduced cultures indicated that the degrading enzyme in Paracoccus sp. YM3 might be inducible.5. Biodegradation of carbofuran in soils was studied in this experiment, and we found that more than 80% carbofuran was degraded within 12 days whether in sterile soil or in non-sterile soil.In tobacco hypersensitivity experiment, no disease spots were found on the surface of tobacoo (NC89) leaves inoculated with YM3, which meant that YM3 had no pathogenic effect on the plant. The strain could also degrade methomyl andβ-Cypermethrin, showing a board substrate range, which indicated its high potential use in bioremediation of contaminated environment.
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