Optimization of cultivation system for Bacillus Siamese strain and its biocontrol effect on postharvest Colletotrichum gloeosporioides

In this study, we established an effective cultivation system for Bacillus Siamese (N-1), identified key antibacterial substances, and explored the underlying mechanisms of optimized N-1 fermentation for controlling pathogens. Our results demonstrate that the optimized system significantly enhanced the inhibitory effect of N-1 on five types of pathogens affecting tropical fruits. Additionally, non-targeted metabolomics analysis and ultra-high performance liquid chromatography triple quadrupole mass spectrometer system (UPLC-MS/MS) revealed the presence of lipopeptides, including Surfactin and FengycinA, in the optimized fermentation. Furthermore, in vitro experiments indicated that lipopeptide treatment (LT) at a concentration of 3.125 mg mL- 1 significantly distorted the hyphae, decreased the activity of antioxidant enzymes, increased the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and hydrogen peroxide (H2O2) 2 O 2 ) contents, and enhanced protein exosmosis rate of C. gloeosporioides. . Moreover, LT markedly reduced the activities of energy metabolism-related enzymes, including succinate dehydrogenase (SDH), Na+K+-ATPase, + K +-ATPase, and Ca2+Mg2+-ATPase, 2+ Mg 2+-ATPase, as well as ATP content, leading to apoptosis of C. gloeosporioides. . In vivo experiments revealed that LT significantly inhibited the expansion of disease spots caused by C. gloeosporioides in mango fruit. These findings suggest that the established culture system could serve as a potential strategy to enhance biocontrol efficacy and prevent fruit decay.