Optimization of Nutrient and Fermentation Parameters for Antifungal Activity byStreptomyces lavendulaeXjy and Its Biocontrol Efficacies againstFulvia fulvaandBotryosphaeria dothidea

Abstract

AbstractThis study has been proved that statistical experimental designs offer efficient and feasible approaches for determination of culture medium and fermentation conditions ofStreptomyces lavendulaeXjy. Nutrition and cultural conditions have high influence on the antibiotic production ofS. lavendulaeXjy. Soya bean meal, NaCl and (NH4)2SO4were identified as the best ingredients for high antifungal activity of Xjy based on single variable experiments. Using response surface methodology, the best concentrations of medium ingredients were 1.46% soya bean meal, 2.25% NaCl and 1.26% (NH4)2SO4. The potential components were reduced from seven to three, and the antibiotic activity was increased by 10%. The optimized conditions for Xjy in a 250‐ml Erlenmeyer flask were initialpH5, medium volume 25 ml/250 ml and inoculation volume 10% at 30°C with 200 rpm by response surface methodology. Validation experiments carried out to check the accuracy of the models indicated that the predicted values agreed with the experimental values. The extension of necrosis lesion ofBotryosphaeria dothideawas impeded by the application of Xjy in apple fruit. In tomato plants, Xjy showed the 43.7–51.7% curative and protective effects againstFulvia fulva. The optimal medium not only gave a 20% increase in antifungal activity, but it provided a simpler formulation. The results will set a basis for further study on large‐scale fermentation volumes usingS. lavendulaeXjy and be useful for the development of more advanced control strategies on plant diseases.