The Screening Of The Nicosulfuron-degradated Strain From Soil And The Processing Of Microorganism Agent

Nicosulfuron is widely used in corn field, which belongs to the sulfonylurea herbicides. As its longer persistence and refractory in the soil, the nicosulfuron is easier to cause environmental problems, as well as the property of leaching fast. Therefore, it’s very important and practical to research a rehabilitation program of nicosulfuron. We successfully screened out eight kinds of nicosulfuron degrades bacterial through the method of enriching culture to the three kinds of soil samples, which was found that YQ14 had the best degradation effect, and then we screened its best degradation conditions and optimized its fermentation conditions. At last, we obtained the preliminary agents. The main contents are as follows:1. In the experiment, four strains were isolated from soil sample 1, marking YQ1,YQ2,YQ3,YQ14; and two strains were marked SQ4 and SZ14, which were from soil sample 2, and then two strains from soil sample 3, which were marked HQ5 and HQ6. All the strains were cultured in medium III which adding 5 mg/L of nicosulfuron TC, and then placed them in a shaking incubator with the temperature of 30°C and speed of 150 r/min, finally the nicosulfuron content were detected after five days by using High Performance Liquid Chromatography, and the degradation rate were calculated. The results showed that YQ14 had the highest effect with the degradation rate of 84.3% while the YQ1 and YQ2 of 53.1% and 62.3%. At last, YQ14 was identified as Bacillus cereus by 16 S r DNA sequence analysis.2. Single factor method and response surface methodology were used to optimize the degradation conditions of nicosulfuron. The result showed that the best medium was basal medium III and LB, the best initial concentration and the appropriate temperature were 2~5 mg/L and 30oC, while the best inoculating quantity was 1×108 CFU/m L. The optimum degradation conditions were obtained by using response surface methodology, which contained the temperature of 33.58°C, inoculating quantity of 1×108 CFU/m L and the initial concentration of 2.87 mg/L.3.By optimizing the fermentation conditions of YQ14 strain, we determined the best fermentation medium were corn flour of 1%, peptone of 0.5%, Mg SO4?7H2O of 0.01%; and the optimum culture conditions were p H 7.5, age of 12 h, inoculum of 10%, bottling volume of 30 m L/250 m L.4. Based on the fermentation medium, a large number of strains were cultivated, and then microorganism was obtained while the bran and the fermentation broth as a carrier, whose content of bacteria was 1.8×1010 CFU/g by detecting. And then the content of bacteria was 3.6×108 CFU/g after 120 d. We chosed the indoor test of small cup and caculated the inhibition of different treatment groups. The results showed that the microorganism had reduced nicosulfuron injury on wheat at different concentration. All the results indicated that the YQ14 strain, the degradation activity was not reduced after being agents, which had the potentiality for further promotion.