| Summary: | In the submerged fermentation process, the introduction of novel nutrient media as sources of carbon and nitrogen can enhance antifungal activity. In this study, we used a submerged fermentation process to find the optimal media for the <i>Bacillus velezensis</i> BP-1 strain to grow in, and that would boost its antifungal activity against <i>Peyronellaea arachidicola</i>. By using a single-factor test and central composite design (CCD) in the response surface methodology, the optimal fermentation medium for the <i>B. velezensis</i> BP-1 strain was identified. The antagonistic potential of <i>B. velezensis</i> BP-1 was assayed against the <i>P. arachidicola</i> fungus to manage web blotch disease in peanut plant leaves. The LB medium was screened as the best medium, with a maximum antifungal activity of 90% in comparison to the other mediums. Semolina flour as the carbon source, peanut root extract as the nitrogen source, and magnesium sulfate as the inorganic salt were selected as the best nutrient components in comparison to the others. The response surface methodology was optimized by using 15 g/L of semolina flour as the carbon source, 13.68 g/L of peanut root extract as the nitrogen source, and 0.50 g/L of magnesium sulfate as the inorganic salt, achieving 90% inhibition of <i>P. arachidicola</i>. The in vitro bioassays showed that the optimized fermentation broth of <i>B. velezensis</i> BP-1 had significant antifungal activity, with an inhibition rate of 88.34% against <i>P. arachidicola</i>. In the pot experiments on disease control, the management effects revealed that the pre-inoculation spray of the <i>B. velezensis</i> BP-1 broth had significant efficiency (96%) when compared to the post-inoculation spray of the <i>B. velezensis</i> BP-1 broth. These findings suggest that the optimized fermentation broth of the <i>B. velezensis</i> BP-1 strain had strong antifungal activity. This could be a potent biocontrol tool for aiding in the early disease management of web blotch in peanut plants.
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