关键词: 乙草胺；鞘胺醇单胞菌属；N\, 脱烷基；代谢途径

Abstract:

An acetochlor herbicides\|degrading strain, designated as DC\|6, was isolated from activated sludge of the wastewater outfall of a factory from Kunshan City. According to the morphological, physiological and biochemical characteristics and the phylogenetic analysis of 16S rDNA sequence, the strain was identified preliminarily as Sphingomonas sp.. Strain DC\|6 could degrade alachlor，acetochlor and butachlor, but could not degrade metolachlor, pretilachlor and propisochlor. Within 48 hours of incubation, about 76.7% of butachlor, 93.6% of acetochlor and 986% of alachlor were degraded by strain DC\|6, respectively. The degradation rates followed the order of alachlor > acetochlor > butachlor. These results indicated that the factors influencing the biodegradability of these herbicides were the length and complicated of amide nitrogens alkoxymethyl: the longer and more complicated the alkyl was, the slower the degradation efficiencies occurred. The pathway of acetochlor degradation was elucidated based on the results of metabolites identification by GC\|MS. Acetochlor was firstly degraded to 2\|chloro\|N\|(2\|methyl\|6\|ethyl) phenyl\|acetamide (CMEPA) by N\|dealkylation, and then it subsequently transformed to 2\|methyl\|6\|ethylaniline (MEA). MEA was further completely degraded via unknown metabolites. However, aniline dioxygenase, which was the key enzyme in the degradation of aniline and aniline derivatives, did not involve in the degradation of MEA. This indicated that the degradation of MEA by strain DC\|6 was different from the reported aniline degradation pathway.

Key words: acetochlor, Sphingomonas sp., N\, dealkylation, metabolic pathway