Mucor assisted degradation of sulfosulfuron in irrigation water

Abstract

Sulfosulfuron is a widely used wheat herbicide, which has two major environmental issues, viz. carryover effect to succeeding crops, and groundwater and surface water contamination. The safer aquatic environment requires the degradation of the herbicide. In this present investigation, we have attempted to isolate an efficient fungus naturally abundant in water, which can degrade sulfosulfuron in aqueous phase. Mucor sp., a fungus isolated from irrigation water was characterized as a sulfosulfuron-degrading microorganism. It survived in the minimal broth having sulfosulfuron at a level of 2000 mgL-1. It was able to degrade entire amount of sufosulfuron applied to water within 27 days. Two major routes of degradation were established. One route involved the cleavage of sulfonylurea bridge resulting in the formation of a couple of major metabolites, viz. 2-amino-4,6-dimethoxypyrimidine (I) and 2-ethylsulfonylimidazo{1,2-a}pyridine-3-sulfonamide (II). The other route was the cleavage of sulfonylamide linkage, which formed the metabolite N-(4,6-dimethoxypyrimidin-2-yl)urea (III). Three other metabolites, N-(4,6-dimethoxypyrimidin-2-yl)-N'-hydroxyurea (IV), N,N'-bis(4,6-dimethoxypyrimidin-2- yl)urea (V) and N-(4,6-dimethoxypyrimidin)-N-(4-hydroxy-6-methoxy pyrimidin-2-yl)urea (VI) were also identified. The survival of Mucor sp. at a very high concentration of sulfosulfuron and its ability to degrade the herbicide through various biochemical mechanisms showed its potential in the bioremediation process of sulfosulfuron contaminated water.