Staphylococcus saprophyticus L-38 produces volatile 3,3-dimethyl-1,2-epoxybutane with strong inhibitory activity againstAspergillus flavus germination and aflatoxin production

Abstract

Controlling proliferation and aflatoxin production byAspergillus flavus is a pressing challenge for global food safety and security. Marine bacteriumStaphylococcus saprophyticus strain L-38 showed excellent antifungal activity towardA. flavus in vitro andin vivo. In sealed, non-contact confrontation assays, L-38 completely inhibited conidial germination and mycelial growth ofA. flavus through the production of volatile organic compounds (VOCs). Gas chromatography-mass spectrometry identified 3,3-dimethyl-1,2-epoxybutane (3-DE) as the most abundant VOC (32.61% of total peak area, 78% matching). Exposure ofA. flavus cultures to synthetic 3-DE similarly demonstrated strong inhibition of growth. Moreover, culture of L-38 in a sealed chamber with maize or peanuts artificially inoculated withA. flavus, at high water activity, resulted in significant inhibition ofA. flavus germination and aflatoxin biosynthesis. Scanning electron microscopy of these samples revealed severe damage to conidial cells and hyphae compared to samples not exposed to L-38. L-38 also showed broad and effective antifungal activity toward eight other phytopathogenic fungi includingAspergillus niger, Fusarium verticillioides, Fusarium graminearum, Sclerotinia sclerotiorum, Rhizoctonia solani, Alternaria alternata, Monilinia fructicola, andBotrytis cinerea. This work introducesS. saprophyticus L-38 as a potential biocontrol agent and demonstrates the efficacy of the volatile 3-DE in the control ofA. flavus and other destructive plant pathogens for post-harvest food safety.