Isolation & Characterization Of A Metolachlor Degrading Strain Y4-6 And Its Degrading Characteristics

Metolachlor is a selective preemergent chloroacetamid herbicide used to control graminaceous annual grasses. With the excellent characteristic of high activation and strong selectivity, it has been become one of three kinds of herbicides widely used in China. Since the metolachlor has been widely used, its herbicide residues caused a great threat to human health and ecological environment. Microbial remediation is a good and effective method to eliminate organic pollution. However, up to now, study about the microbial degradation of metolachlor was very poor. Especially, there were no reports about the identification of metolachlor by microbe and the metabolic pathway involved in metolachl or degrading.In this study, a metolachlor-degrading bacterium strain, designated as Y4-6, was isolated from sludge of a wastewater treatment facility. It was preliminarily identified as Pseudoxanthomonas sp. according to its physiological, biochemical characteristic and the similarity analysis of its 16S rRNA sequence.Strain Y4-6 can degrade about 80%of 50 mg/L metolachlor within 3 days. The optimum temperature for its biodegradability was 30℃; pH was between 7 and 8. The degradation rate of metolachlor by strain Y4-6 was related posotively to inoculum cancentation. Too high initial concentration of metolachlor would inhibit the degradation rate. CMEPA (2-methyl-6-ethyl-2-chloroacetanilide), a metabolite of metolachlor degradation by stain Y4-6 was firstly identified by HPLC and MS analysis.Strian Y4-6 can degrade 75% of 50 mg/kg metolachlor within 72 hours in soil. The optimum temperature and pH for strain Y4-6 to degrade metochlor were 30℃ and 7.0, respectively. The degradation rate was related posotively to soil moisture and inoculum cancentation.