Identification Of Chloroacetamide Herbicides Degradating Bacterium Microbacterium Sp. T4-7and Characterization Of Its Degradation Enzyme

Acetochlor and propanil both are the chloroacetamide herbicides.2-Methyl-6-ethyl-2-chloroacetanilide (CMEPA) is metabolic intermediate of acetochlor. This paper studied an acetochlor-degrading strain T4-7, which was isolated from the herbicide polluted soil by acetochlor, was capable of degrading CMEPA. Strain T4-7can degrade CMEPA to2-methy-6-ethylaniline (MEA). Strain T4-7was identified as Microbacterium sp. based on its phenotypic characterization, physiological and biochemical characters and the result of the16S rDNA gene sequence alignment.The optimum temperature for growth was30℃. Below or above30℃, its growth would be inhibited. The optimal pH for the growth of strain T4-7was6-9. Growth of strain T4-7was significantly inhibited when the pH was lower than6or higher than9. Strain T4-7could endure a NaCl concentration of5%. The optimal carbon source for the growth of strain T4-7was glucose, and peptone was the opptimal nitrogen source. The strain had resisitance to kanamycin, ofloxacin and polymyxin antibiotics.The strain could degrade CMEPA and propanil completely in10hours. There was a wide temperature and pH range of degrading CMEPA or propanil for the strain. The degradation rate could still reach up to50%at20℃. Compared with other pH value, the degradation rate had a significant effect on pH6, and it was the highest. The CMEPA degradation of curves showed on a descenting trend at pH values below or above6. The degradation rate decreased significantly when the strain T4-7degraded propanil in the acidic environment. The degradation rate could approach80%on degradation of propanil in neutral or alkaline environment. With the increase of initial concentration of CMEPA and propanil, the degradation rate became lower. The degradation rate was related positively to inoculation level. Copper ion had a significant inhibition effect on degradation of CMEPA and propanil. There was no chlorine detected during the whole degradation of CMEPA. Strain T4-7could convert catechol into new compounds, but can not degrade aniline and hydroxyphenol.The optimal temperature of degrading CMEPA by crude enzyme, broken by strain T4-7, was40℃, and it was45℃for degrading propanil. The crude enzyme showed high activity at low temperatures, but the enzyme activity decreased gradually with increasing temperature. It reached the highest degradation rate at pH7. Under neutral environmental condition, the enzyme activity was the highest. Cu2+could significantly inhibit the degradation of CMEPA and propanil by crude enzyme.