Bioremediation And Application Of Acetocholr Degrading Strain

Acetochlor is a chloroacetanilide herbicide that is used to control broad-leaved weeds and some grasses in crops at very low application rates, because of its high efficiency and low cost, acetochlor has been widely used by many countries. Because of its high phytotoxicity and its vast use ultimately caused more serious environment pollution. Microbial remediation has been deemed to be much more advantageous method than the others, so it has been an important research item for us to exploit and utilize microbial resource to remove environment pollution. This research aimed at isolating the bacteria that could use acetochlor as sole carbon source, studied characterization of degrading strain.After enrichment, a acetochlor-degrading bacteria, named YCA1 was isolated from acetochlor-contaminated samples using selective culture medium with acetochlor as sole carbon source. The strain was identified as Bacillus sp. based on morphological, physiological and 16S rRNA phylogenetic analysis.Strain YCA1 could degrade 78.7% of 50 mg-L"1 acetochlor within 3 d. Strain YCA1 could utilize acetochlor as sole carbon resource for growth. The optimum temperature and pH for YCA1 growth was 30℃ and 7.0, respectively. There was a positive correlation with the the growth and aeration.YCA1 could utilize fructose and glucose as it’s optimal carbon source effectively, while hardly use amylase. Most of the common nitrogen source could be used by YCA1, but the optimal nitrogen source was peptone and yeast extract.YCA1 could degrade acetochlor in effect at low concentration, when concentration up to 100mg·-L-1, YCA1 could also degrade acetochlor, but the rate is slow. Large inoculation could enhance the degrading rates. The optimal pH of YCA1 for degrading is 7.0, and the optimal degrading temperature of YCA1 is 30 ℃. The degrading rate showed a positive correlation with the amount of initial inoculum size, but it showed a negative correlation with the initial concentration of acetochlor. The addition of glucose, peptone, or yeast extract could promote the degradation of acetochlor. The degradation products of acetochlor in the culture medium extracts were isolated and identified by LC-MS. Three metabolites of acetochlor degradation were identified and the degrading pathways were studied.Only 7.2% of acetochlor was degraded in sterilization soil with YCAl strain, but 57.5% with YCAl strain, respectively. In the soil without sterilization, the degradation rates are 8.8% and 64.5%, respectively. The result showed that the inoculation of YCAl to soil treated with acetochlor resulted in a higher degradation rate than in non-inoculated soil regardless of the soil is sterilized or non-sterilized. The degradation of acetochlor was affected by the size of strain YCAl and soil moisture capacity.