Optimization of medium composition for production of antifungal active substance from Streptomyces hygroscopicus BS-112

Streptomyces hygroscopicus BS-112 was isolated from forest land on Mountain Tai, Shandong Province, China. This bacterium showed broad-spectrum antifungal and antibacterial activities. The medium that was necessary for the production of antifungal active substances from S. hygroscopicus BS-112 was optimized by the Plackett-Burman design (PBD) and response surface methodology (RSM). Initially, glucose, soybean powder and KH2PO4 were tested using the PBD and were found to be important factors that affected the production of active substances. The steepest ascent method was then used to determine the optimal region of each factor to include in the medium. The concentrations of important factors were subsequently optimized by using a central composite design (CCD). The results obtained demonstrated that the optimal media was composed of the following factors (g/l): corn meal, 5.00; glucose, 18.61; soybean powder, 31.15; KH2PO4, 0.38 and MgSO4, 0.85. This optimization strategy enhanced the production of active substances nearly 2.8 times (4956.28 mu g/ml) compared to the yield of active substances that were produced using the basal medium. The antifungal active substances showed strong antimicrobial activity against Aspergillus flavus with minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of 3.13 and 6.25 mu g/ml, respectively.