Isolation and Purification of Extracellular Inhibitory Products from Bacillus velezensis YJ0-1 and Optimization of Fermentation Medium

Soybean, as a globally important economic crop, is severely threatened by Sclerotinia sclerotiorum, the causative agent of Sclerotinia stem rot (SSR), a major disease in soybean production worldwide, leading to significant yield losses and quality deterioration. Traditional chemical control methods face challenges such as environmental pollution, pesticide resistance, and limited efficacy. Bacillus velezensis YJ0-1, identified through plate confrontation assays, demonstrated significant inhibitory effects on S. sclerotiorum via acid-precipitated crude extracts from its fermentation broth. A key antimicrobial substance, fengycin (C72H110N12O20, molecular weight 1463.8 Da), was isolated and characterized through acid precipitation, protein purification system separation, and mass spectrometry (MS). Further optimization of the PDB medium using single-factor experiments and Box–Behnken design yielded an optimal formulation: peptone 66.62 g/L, sucrose 32.68 g/L, and pH 6.5. Validation experiments showed an actual yield of 2.03 g/L, with a relative error of only 0.49% compared to the predicted yield of 2.04 g/L, significantly enhancing the synthesis efficiency of fengycin. This study provides novel microbial resources and a theoretical basis for the biological control of SSR in soybeans, while also laying a technical foundation for the industrial production of fengycin, contributing to the advancement of sustainable agriculture.