In order to understand the composition and structure of herbicidal active substance from the root of Flaveria bidentis (L.) Kuntze, the isolation and structural identification were researched in this paper. The crude extract from the root of F. bidentis (L.) Kuntze was extracted by petroleum ether, ethyl acetate, and water saturation of n-butyl alcohol, respectively, and the extraction fluid was separated by using the method of TLC, then the main fraction was separated by HPLC, and the structure of the herbicidal active substance was analyzed by LC-MS, elemental analysis and 1H-NMR. The results showed that the petroleum extraction had the strongest herbicidal activity, and the purple blue stripe separated by TLC had the strongest effect on Digitaria sanguinalis. The herbicidal active substance was identified as α-terthienyl according to the data of LC-MS, elemental analysis and 1H-NMR.

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.