Biocontrol of tobacco leaf mold using Bacillus velezensis : effects on volatile profiles and microbial community

ABSTRACT Mold contamination causes economic losses and poses risks to human and animal health. Tobacco leaves, as a high-value agricultural product, are particularly susceptible to mold contamination during post-harvest handling. In this study, the antifungal performance of Bacillus velezensis ZD-F13 was evaluated on tobacco leaves. In laboratory-scale assays, ZD-F13 treatment reduced the fungal colony count by 84% relative to the Penicillium group. Electronic-nose and gas chromatography-ion mobility spectrometry analyses showed that the volatile profile of the Penicillium + ZD-F13 group was closer to that of the normal leaves group than to that of the Penicillium group. To further evaluate its practical applicability, B. velezensis ZD-F13 was tested on 5 kg of tobacco leaves and reduced the fungal colony count by 50% relative to the untreated group. Microbial community analysis revealed changes in bacterial and fungal community composition, including an increase in the relative abundance of Bacillus from 0.09% to 48.1%. These findings support the potential application of B. velezensis ZD-F13 for controlling tobacco leaf mold and providing a basis for further development of postharvest biocontrol strategies. IMPORTANCE Mold contamination of tobacco leaves causes substantial economic losses and can compromise product quality and safety during postharvest storage and processing. Effective control strategies remain limited, particularly those capable of suppressing mold without disturbing the natural microbial community or altering quality-related characteristics. This study showed that ZD-F13 treatment reduced fungal colony counts under controlled laboratory conditions and was associated with a lower fungal colony count in the 5-kg practical trial. ZD-F13 treatment also shifted the volatile profile toward that of healthy leaves without causing a statistically detectable loss of Shannon diversity under the tested conditions. These findings suggest that ZD-F13 has potential as a postharvest biocontrol agent for tobacco leaves.