Isolation, Identification Of Chlorpyrifos Degradation Bacteria And Optimization Of Degradation Conditions

Unlike other organophosphorus compounds, CP has been reported to be resistant toenhanced degradation since its first use in1965. The objectives of the present work weremainly focused on thought worthwhile to study the effect of different media and to considervarious environmental factors like, carbon source, nitrogen source, phosphate andDegradation conditions that affect the biodegradation of chlorpyrifos.In this study, three highly chlorpyrifos-degrading bacterial strains, named HP-1, HP-2and HP-3were isolated by enrichment culture with chlorpyrifos as sole carbon source andidentified by morphology, physiological characteristice, biochemical tests and16S rDNAsequence analysis. The degradation conditions and degradation enzyme of strain HP-2werestudied. The main results were as follows:(1) Based on the morphology, physiological characteristics, biochemical tests and16SrDNA sequence analysis, the strain HP-1was identified as Ochrobactrum anthropi, the strainHP-2was identified as Pseudomonas nitroreducens, the strain HP-3was identified asStenotrophomonas acidaminiphila. Their GenBank accession numbers are KC961631,KC961632and KC961633, respectively.(2) After cultured in liquid mineral salt medium containing100mg/L of chlorpyrifos at28C, pH7.2for7days, the degrading rates of strains HP-1, HP-2and HP-3were50.6%,59.5%and45.6%.(3) The single factor tests optimal medium components for strain HP-2degradingchlorpyrifos were as follows: fructose concentration0.1g/L, yeast extract concentration0.5g/L and phosphate concentration1.5g/L. The Central composite Design experiment was usedto sure the best medium components which influences the chlorpyrifos-degrading efficiencyby strain HP-2. The optimum medium components for chlorpyrifos biodegradation were asfollows: fructose0.11g/L, yeast extract0.60g/L and phosphate1.55g/L. After cultured in liquid optimum medium containing100mg/L of chlorpyrifos at28C, pH7.2for7days, the degrading ratesof strain HP-2was76.15%. Therefore, the optimization of chlorpyrifos-degrading mediumcomponents could enhance the biodegradation efficiency of chlorpyrifos by the strain HP-2.(4) The effects of the environmental factors to the degradation rates of chlorpyrifoswere studied with single factor test. The appropriate conditions for strain HP-2degradingchlorpyrifos were as follows: the initial pH value9.0, the temperature28.0C, the initialchlorpyrifos concentration100mg/L and the inoculation amount was15%of the total volume.Under the optimum condition, the biodegradation efficiency of chlorpyrifos increased from76.15%to81.25%.(5) Degradation characteristics of chlorpyrifos were determined by the crude enzymeextracted from the isolated strains HP-2. The content of this study included the form andorientation of the degrading enzyme for chlorpyrifos; rate of degradation for chlorpyrifos byits intracellular enzyme, extracellular enzyme and cell fragment was24.01%,8.25%and13.63%. The incubation time of the intracellular enzyme was0.5h,6h and12h; rate ofdegradation for chlorpyrifos was24.01%,50.25%and69.50%, respectively.