Unraveling the antibacterial mechanism of Lactiplantibacillus plantarum MY2 cell-free supernatants against Aeromonas hydrophila ST3 and potential application in raw tuna

Aeromonas hydrophila is a pathogenic and spoilage bacterium, frequently found in aquatic products, demonstrated to cause foodborne illness and food spoilage. Cell-free supernatant (CFS) of Lactiplantibacillus plantarum can act as an efficient antibacterial agent against foodborne pathogens and food spoilage bacteria. The objective of this study was to evaluate the antibacterial mechanism of CFS of L. plantarum MY2 against A. hydrophila ST3 and potential application in raw tuna. Herein, the inhibitory activity of CFS against A. hydrophila, causing damage to the membrane structure of the cell with 10% minimum inhibitory concentration (MIC), has been revealed. Changes in the key enzyme activity of TCA cycle (tricarboxylic acid cycle) and changes of 114 significant metabolites revealed the disordered metabolism of A. hydrophila under CFS treatment. The significant different metabolites (VIP values > 1 and P-value < 0.05) were mainly involved in amino acids metabolism, carbohydrate metabolism, and nucleotide metabolism. Challenge tests demonstrated the CFS could inhibit the growth of A. hydrophila in raw tuna effectively, with 2.03 log CFU/g and 2.44 log CFU/g populations reduction for 4 days of storage at MIC and 2MIC treatment groups compared to control groups, respectively. This study thus confirmed the antibacterial efficacy of CFS of L. plantarum MY2, and suggested the potential of CFS as an antibacterial agent for application in the seafood sector to reduce the food poisoning and spoilage caused by A. hydrophila.