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Isolation, Identification and Degradation Characteristics of a Benazolin-Ethyl Degrading Bacteria and Degradation Pathway

Author: QianLiHua
Tutor: CaiTianMing
School: Nanjing Agricultural College
Course: Environmental Engineering
Keywords: benazolin-ethyl degrading bacteria degradation characteristics degradation pathway immobilized bacteria
CLC: X172
Type: Master's thesis
Year: 2011
Downloads: 16
Quote: 0
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Abstract


A highly efficient benazolin-ethyl degrading strain was isolated from pesticide wastewater treatment pool,this strain could use benazolin-ethyl as the sole carbon source for growth.It was identified as Methyloversatilis sp. according to its physiological and biochemical properties, and 16S rRNA gene sequence analysis,and the strain was designated as cd-1.The optimum growth condition was temperature 30℃and pH 8.0 in R2A culture medium. In liquid cultures, cells of stain cd-1 tended to clump together, and forming white flakes, and using organic carbon source and organic nitrogen source grew best; Ventilation had on effect on the growth of the strain; Concentration of NaCl had great impact on the growth of stain cd-1, when the concentration of NaCl was 0~5g/L,the strain grows best; Strain cd-1 was resistant to chloramphenicol and ampicillin.Results showed that the strain degraded benazolin-ethyl best at 30℃and pH 8.0.When the inoculation rate was 2% and the concentration of benazolin-ethyl was 100mg·L-1, the residue concentration of benazolin-ethyl was only 0.85mg·L-1 in salts liquid medium after 48h by the strain cd-1, the degradation of benazolin-ethyl could reach 99%; Improving inoculation rate from 0.5% to 8% speeded up the degradation of benazolin-ethyl; When the concentration of benazolin-ethyl was 25mg·L-1, the residue concentration was only 1.44mg·L-1 after 16h by the strain cd-1, and when the concentration of benazolin-ethyl was up to 400mg·L-1, the residue concentration was still 284.56mg·L-1 after 48h, showing that increasing concentration of benazolin-ethyl produced toxic effects on the strain,inhibited the degradation of benazolin-ethyl;The strain was easy to use organic nitrogen, and degraded benazolin-ethyl the fastest; Ventilation had no effect on the degradation of benazolin-ethyl;Added peptone, yeast extract and LB solution was beneficial to the degradation of benazolin-ethyl.Degradation in soil inoculated with bacteria cd-1 could accelerate the degradation of benazolin-ethyl,because the indigenous microbiology and the exogenous degradation bacteria degraded benazolin-ethyl in a synergy way, and improved the soil degradation rate of benazolin-ethyl.The degradation pathway of benazolin-ethyl in the effect of the benazolin-ethyl degrading strain cd-1 cd-1 had been learned, and three new metabolites had been detected by MS/MS and GC-MS combined detection. Benazolin、7-chloro-3-Methylbenzo[d] thiazol-2(3H)-one and 2-chloro-6-(methyle-neamino)benzenethiol were successfully detected and identified based on mass spectrum analysis and transformation between metabolite accumulation.A biochemical degradation pathway of benazolin-ethyl was proposed, benazolin-ethyl first changed into benazolin,and then benazolin changed into 7-chloro-3-methylbenzo[d]thiazol-2(3H)-one,last changed into 2-chloro -6-(methyle-neamino) benzenethiol。In order to facilitate the practical application of the strain, the immobilization of the strain was also studied. Used sodium alginate embedding the benazolin-ethyl degrading strain cd-1,results showed that mechanical strength of immobilized beads best and the degradation of benazolin-ethyl effect was best when the concentration of sodium alginate was 3%, the concentration of CaCl2 was 3% and immobilized time was 12h.The degradation rate of immobilized bacteria was slower than the free bacteria, but immobilized bacteria could tolerance pH and temperature in a wider range.Immobilized degrading bacteria could keep high stability and reactivity in a suitable number of reuse, and coula be used for immobilized reactor building.

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