Degradation of chlorimuron‐ethyl by A spergillus niger isolated from agricultural soil

Abstract Chlorimuron‐ethyl, ethyl‐2‐[[[[(4‐methoxy‐6‐chloro‐pyrimidin‐2‐yl)amino]carbonyl]amino] sulfonyl]benzoate, is used as a pre‐ and postemergence herbicide for the control of important broadleaved weeds in soybean and maize. Due to its phytotoxicity to rotation crops, concerns regarding chlorimuron contamination of soil and water have been raised. Although it is degraded in the agricultural environment primarily via pH ‐ and temperature‐dependent chemical hydrolysis, microbial transformation also has an important role. Fungi such as F usarium and A lternaria are unable to survive in artificial media containing chlorimuron‐ethyl at 25 mg L −1 . However, A spergillus niger survived in minimal broth containing chlorimuron at 2 mg mL −1 . A spergillus niger degraded the herbicide to harvest energy through two major routes of degradation. One route involves the cleavage of the sulfonylurea bridge, resulting in the formation of two major metabolites, namely ethyl‐2‐aminosulfonylbenzoate ( I ) and 4‐methoxy‐6‐chloro‐2‐amino‐pyrimidine ( II ). The other route is the cleavage of sulfonylamide linkage, which generates the metabolite N ‐(4‐methoxy‐6‐chloropyrimidin‐2‐yl) urea ( III ). Two other metabolites, saccharin ( IV ) and N ‐methyl saccharin ( V ), formed from metabolite II, were also identified. A metabolic pathway for the degradation of chlorimuron‐ethyl by A . niger has been proposed.