Aims: This study aimed to isolate active substances from metabolites of Bacillus amyloliquefaciens SJ100001 and examine their antifungal activity against Fusarium oxysporum (F. oxysporum) SJ300024 screened from the root-soil of cucumber wilt. Methods and Results:An active substance, anti-SJ300024, was obtained from the fermentation broth of strain SJ100001 by reversed-phase silica gel and gel chromatography, and further got its chemical structure as cyclic lipopeptide Epichlicin through nuclear magnetic resonance (NMR) and mass spectrometry (MS). In vitro experiments showed that Epichlicin had a better inhibitory rate (67.46%) against the strain SJ300024 than the commercially available fungicide hymexazol (45.10%) at the same concentration. The MTT assays proved that Epichlicin was non-cytotoxic, besides it also had good free radical scavenging ability and total reducing ability. Conclusions:Epichlicin isolated from strain SJ100001 can effectively control F. oxysporum SJ300024 screened from the root-soil of cucumber wilt.Significance and Impact of the Study: Epichlicin may be used as an environmentally friendly and efficient biocontrol agent for controlling Fusarium wilt of cucumber and reducing crop losses. More importantly, the non-cytotoxicity of Epichlicin can avoid harm to consumers. Additionally, Epichlicin has broad application prospects in medicine due to its antioxidant properties.

Background Postharvest gray mold induced by Botrytis cinerea seriously affects cherry quality, resulting in huge economic losses. The aim of this study was to isolate and purify a novel antifungal compound from the endophytic Bacillus velezensis SJ100083 of cherries to prevent postharvest gray mold. Results In this study, Baelezcin A, extracted and purified from Bacillus velezensis SJ100083, was found effective in suppressing gray mold on cherries. Furthermore, the structure of Baelezcin A was identified as a novel cyclic lipopeptide with molecular formula of C52H91N7O13 through ultra‐high‐performance liquid chromatography quadrupole Orbitrap high‐resolution mass spectrometry (UHPLC‐Q‐Orbitrap‐HRMS) and nuclear magnetic resonance (NMR). Baelezcin A treatment at 25 mg L−1 significantly decreased the disease incidence and severity of cherry gray mold, the antifungal mechanism of which was attributed to the accumulation of reactive oxygen species within the spores and the leakage of mycelium cytoplasmal contents, resulting in a low rate of spore germination. Moreover, it was proven to be biologically safe within a certain range by MTT assays. Conclusion Our study demonstrated that Baelezcin A from the culture of Bacillus velezensis SJ100083 may be a promising fruit preservative for controlling postharvest gray mold caused by Botrytis cinerea. © 2023 Society of Chemical Industry.