Abstract: Objective: To explore the inhibitory mechanism of the fermentation products of Bacillus megaterium L2 against Erwinia carotovora subsp. carotovora EC-1 as a major soft rot pathogen of Amorphophallus konjac K. Koch during storage. Methods: The fermentation products were extracted from freeze-dried Bacillus megaterium culture and separated by silica gel column chromatography under atmospheric pressure into 7 fractions (LE4-1-LE4-7). LE4-3, which exhibited potent antibacterial activity against strain EC-1, was analyzed for chemical composition by gas chromatography-mass spectrometry (GC-MS), and its antibacterial mechanism was studied by measuring the half maximal inhibitory concentration (IC50), the conductivity of cell suspension, nucleic acid and protein leakage, soluble total sugar concentration, total cell protein concentration, phosphorus metabolism and intracellular reactive oxygen species (ROS) level. Results: The major compounds of LE4-3 included ethyl phenylacetate (32.190%), ethyl linoleate (15.819%), and methyl phenylacetate (13.793%). Its IC50 value against strain EC-1 was (1.06 ± 0.01) mg/mL, and the antimicrobial mechanism may be achieved by damaging bacterial cell structure, affecting the integrity of the cell membrane, and inhibiting protein biosynthesis and energy metabolism. Therefore, fraction LE4-3 has promising application prospects for soft rot resistance in Amorphophallus konjac K. Koch during storage.

Key words: Bacillus megaterium, Erwinia carotovora subsp. carotovora, bacteriostatic mechanism