| Locoweeds cause widespread poisoning of livestock in most of the world, People invest the ecology, biology and toxicology of locoweed, and other areas after a decade, but has not yet found an effective preventive measures. The relationship between grass and endophyte is inspired people to invest the endophyte of locoweeds. Successfully, people achieved isolated endophyte which produce SW from locoweed. Initially it identified as Embellisia sp. But, the investing on the optimization of endophyte, and the production conditions of SW are less.To finding endophyte best growth conditions, we invest endophytic fungi-FEL3 which isolated from O.kansuensis. We cultured solid medium at different temperatures, carbon, nitrogen and initial pH. The results showed that the best growth condition in the test is temperature for 20℃and the initial pH for 6.5, oatmeal as carbon source of mycelia growth was the fastest among different carbon sources in culture medium, coming to 8.76 mm length of mycelia after 20 days, Different nitrogen source medium, Peptone as nitrogen source at the fastest growth, achieving 6.47 mm after 20 days. The study explored promoting liquid culture conditions of different carbon source, nitrogen source, Inorganic salts, initial pH and inoculum. The results showed that the best condition in the test are oatmeal as carbon source, soybean meal as nitrogen source, CUSO4 as Inorganic salt, optimum initial pH is 6.5, inoculation was 8%, the wet weight and dry weight are best.We study the concentrations of SW of different liquid culture medium. The results show that which inhibit the activity of AMA stronger, which prouduce SW more. Under normal circumstances, a better medium for mycelial growth, the culture medium inhibited the activity of the AMA also strong. Occasionally the mycelial growth more, but the medium had little effect on the AMA isolated. SW shows the production and mycelial growth is not proportional. The experimental results showed that the best culture medium:mycelia as carbon, soy flour as nitrogen ferric, sulfate as inorganic salt, amount of inoculum is 10%, initial pH is 7.0.To analysis FEL3 liquid culturing the best carbon and nitrogen ratio, at the basement of single factor experiments, we use Response Surface Methodology to study, CCD experimental design on the FEL3 best carbon and nitrogen ratio produce SW is made. The results showed that when sucrose is 1.16 g/L, peptone was 0.23 g/L, the dry weight were maximum 0.097 g, which is 5.57 mg/mL; Sucrose is 1.23 g/L, peptone is 0.22 g/L,SW of mycelium is 67.77μg; Sucrose is 1.47 g/L, peptone,0.29 g/L when, SW maximum concentrations of 6.71×10-4 mol/L.The experiment using response surface analysis in the Box-benken experimental design method on different initial pH, medium volume and the inoculation interaction among the dry weight and the concentration of SW were studied. When the initial pH6.54, inoculum was 7.52%, liquid volume is 21.21 mL, the dry weight is 0.098 g; when the initial pH was 6.25, 7.76% inoculation, when the liquid volume 21.66 mL, SW of mycelium is 56.68μg; when the initial pH was 6.73,8.4% inoculation, when the liquid volume 20.56mL, SW of reached the maximum concentration of 6.21×10-4mol/L.
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