Synergistic integration of commercial natamycin with VOCs-producing Bacillus in zein nano-coatings for berry preservation

Blueberries and grapes are highly susceptible to fungal infections during pre-harvest, transport, and postharvest stages, leading to substantial economic losses. Conventional control methods often involve high equipment costs and contribute to the emergence of drug-resistant pathogens. Recently, the antifungal potential of volatile organic compounds (VOCs) has gained increasing attention as a sustainable alternative. Bacillus amyloliquefaciens HJ-B8 was successfully screened for its dual functionality of direct contact inhibition and volatile-mediated inhibition against Penicillium expansum . The VOCs produced by HJ-B8 were analyzed revealing a complex profile with several compounds that may contribute to its antifungal effect. The interaction between natamycin (Nata) and the HJ-B8 strain was also explored, showing a synergistic effect on fungal inhibition. A novel antifungal coating system was developed by combining HJ-B8 and Nata-loaded zein nanoparticles (HJ-B8@Nata-Zein NPs@Amy-Fe²⁺) to enhance the preservation of blueberries and grapes. The antifungal activities of this coating were evaluated in vitro and in vivo . The coating was further characterized by evaluating particle size, zeta potential, encapsulation efficiency, and light stability and assessed the antifungal efficacy. The in vivo tests demonstrated that the coating effectively reduced the decay rate, weight loss, soluble solids content and anthocyanin levels in treated blueberries and grapes. Furthermore, scanning electron microscopy (SEM) revealed improved preservation of fruit surface and flesh integrity. This opens up new possibilities for post-harvest preservation of berries using a synergistic antifungal coating system and provides a theoretical basis for related applications. • HJ-B8 produces antifungal VOCs and directly inhibits P. expansum . • Nata and HJ-B8 show novel synergy in vitro and in vivo . • An innovative HJ-B8@Nata-Zein NPs@Amy-Fe 2 + coating boosts antifungal effect. • Coating reduced disease incidence, weight loss and anthocyanin degradation.