Optimization of Fermentation Conditions for Endophytic Fungi from Schisandra chinensis and Investigation of Their Antibacterial Mechanisms Against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) is a highly pathogenic bacterium for which safe and effective prevention as well as treatment methods are currently lacking. In this study, <i>Rhizoctonia bicornis</i> S10 was isolated from <i>Schisandra chinensis</i> and used to inhibit MRSA. Through single-factor experiments and response surface methodology, the optimal culture medium and fermentation conditions for <i>Rhizoctonia bicornis</i> S10 were determined. The results demonstrated that optimal growth conditions for <i>Rhizoctonia bicornis</i> S10 were achieved using corn meal as the culture medium. Furthermore, the extract of <i>Rhizoctonia bicornis</i> S10 showed maximal inhibitory activity against MRSA under the following optimized conditions: moisture content of 150%, time of 2.5 d, temperature of 30 °C, and pH 5.0. Antagonistic experiments demonstrated that the crude extract of <i>Rhizoctonia bicornis</i> S10 exhibits significant inhibitory activity against MRSA. During the growth of MRSA, the crude extract effectively suppressed its proliferation. Measurements of alkaline proteinase and membrane potential confirmed the disruption of the MRSA cell membrane, which was further visually validated by scanning electron microscopy. Additionally, the crude extract was shown to inhibit the formation of MRSA biofilms. These findings suggest that <i>Rhizoctonia bicornis</i> S10 should hold promise as a novel approach for the prevention and treatment of MRSA infections, providing new strategies and insights for combating this pathogen.