Antifungal mechanism of Bacillus amyloliquefaciens SC-B15 and its application in cereal mildewproof and grape preservation

Microorganisms and their metabolites play vital roles in inhibiting the growth of toxic-producing fungi. Here, Bacillus amyloliquefaciens SC-B15 showed over 64% inhibition of six mycotoxin-producing fungi and the best inhibition of A. ochraceus (81%). Meanwhile, the supernatant fraction of >10 kDa showed the best inhibition against A. ochraceus and the antifungal proteins were probably cell wall hydrolytic enzymes. Our study showed that the antifungal components lead to the destruction of mycelium and spores of A. carbonarius, while also affecting gene expression of cell wall integrity signaling pathways and secondary metabolic processes, such as leading to substantial downregulation of pks genes and affecting the synthesis of OTA precursors. The antifungal fraction could markedly reduce the spot diameter (66.19%) and Ochratoxin A (OTA) accumulation (63.56%) of grape wounds, and reduce A. carbonarius growth (64.78%) and OTA accumulation (84.41%) during cereal storage. Our research indicates that the SC-B15 strain has a promising prospect in the control of Aspergillus and OTA contamination.