Inhibitory mechanisms of 3-methyl pentanoic acid combined with 2-methyl butyric acid and 3-hepten-2-one on Bacillus and their application in Lanzhou lily preservation

AimsLanzhou lily (Lilium davidli var. unicolor) possesses both nutritional and medicinal value, however, its bulbs are highly susceptible to postharvest physical damage. Pathogenic bacteria readily infiltrate through these wounds, resulting in extensive decay and consequent economic losses. This study demonstrates that optimized volatile organic compound (VOC) combinations can significantly reduce effective antimicrobial concentrations and broaden the antimicrobial spectrum through synergistic effects, while exhibiting excellent preservation potential.Methods and ResultsFrom decayed lily bulbs, this study isolated and identified two bacterial strains, Bacillus cabrialesii SH-3 and Bacillus amyloliquefaciens SH-5, both exhibiting opportunistic pathogenicity. Fifteen binary VOC combinations were evaluated using fractional inhibitory concentration index (FICI), identifying QM (1/8 MIC 2-methylbutyric acid + 1/8 MIC 3- methylpentanoic acid, FICI = 0.25) and QH (1/2 3-methylpentanoic acid + 1/8 3-hepten-2-one, FICI = 0.625) as optimal formulations. Mechanistic studies revealed these combinations disrupt bacterial membrane integrity, induce protein/nucleic acid leakage, and trigger oxidative stress and metabolic dysfunction.ConclusionsAgainst SH-3, only QM showed synergistic effects, reducing required concentrations by 87.5% compared to individual minimum inhibitory concentration (MIC). For SH-5, all combinations demonstrated additive effects, with QH achieving potent inhibition at 50% and 87.5% reduced concentrations for respective components. Applied at MIC levels, both formulations significantly suppressed postharvest decay while maintaining bulb quality.