| Summary: | A strain of Bacillus subtilis strain YB1, isolated and preserved in our lab., showed a high nicosulfuron-degrading activity. Optimization of culture conditions on production of nicosulfuron-degrading enzyme from Bacillus subtilis strain YB1 was carried out through mono-factor experiments. The characterization of degrading enzyme(s) was studied in this paper. The results showed that B. subtilis YB1 can use nicosulfuron as sole carbon source under aerobic condition. The key enzyme(s) involved in the initial biodegradation of nicosulfuron was localized to extracellular proteins and showed to be induced expressed. Enzyme-specific activity was up to 89.34 U mg−1 at pH 8.0 and 30°C, incubation for 96 h, inoculum 4.5×108 CFU mL−1 in Luria-Bertani liquid medium with nicosulfuron of 40 mg L−1. The maximum degradation rate of extracellular crude enzymes on nicosulfuron was 66% at pH 9.0, 35°C in the enzymatic reaction system with nicosulfuron of 5 mg L−1. This degrading enzyme(s) was sensitive to high temperature, but kept high activity under alkaline conditions.
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