Biodegradation of nicosulfuron by the bacterium Serratia marcescens N80

By enrichment culturing of the sludge collected from the industrial wastewater treatment pond, we isolated a highly efficient nicosulfuron degrading bacterium Serratia marcescens N80. In liquid medium, Serratia marcescens N80 grows using nicosulfuron as the sole nitrogen source, and the optimal temperature, pH values, and inoculation for degradation are 30-35°C, 6.0-7.0, and 3.0% (v/v), respectively. With the initial concentration of 10 mg L⁻¹, the degradation rate is 93.6% in 96 hours; as the initial concentrations are higher than 10 mg L⁻¹, the biodegradation rates decrease as the nicosulfuron concentrations increase; when the concentration is 400 mg L⁻¹, the degradation rate is only 53.1%. Degradation follows the pesticide degradation kinetic equation at concentrations between 5 mg L⁻¹ and 50 mg L⁻¹. Identification of the metabolites by the liquid chromatography/mass spectrometry (LC/MS) indicates that the degradation of nicosulfuron is achieved by breaking the sulfonylurea bridge. The strain N80 also degraded some other sulfonylurea herbicides, including ethametsulfuron, tribenuron-methyl, metsulfuron-methyl, chlorimuron-ethyl,and rimsulfuron.