Exploring the Modulation of Extracellular Metabolites in Different Listeria monocytogenes Strains under Cold-Stress.

This study investigated the modulation of extracellular metabolites in Listeria monocytogenes NCCP 15743 (L5), NCCP 16594 (L6), and ATCC 19111 (L9) strains in cold-stressed culture. The strains were cultured in Mueller Hinton broth at 8°C for 22 d. Extracellular metabolites were extracted at five growth phases (initial, lag, log, early saturate, and saturate) of each strain. Under cold-stress, growth phases of L5 and L6 exhibited similarities, while L9 displayed a distinct pattern. The change in extracellular metabolites under cold-stress was dependent on growth phase and strain. The presence of L. monocytogenes was distinguished based on the concentrations of trehalose, isoleucine, arginine, and phenylalanine. During extended cold-stressed culture, all strains enhanced two metabolic pathways at the lag and log phases: energy metabolism (trehalose, lactate, propanoate, acetate, ethanol, and formic acid) and glutathione-related metabolism (acetate, histidine, arginine, proline, glutamate, glycine, serine, and methionine). The expression of these extracellular metabolites provides crucial insights into the complex metabolic adaptations of L. monocytogenes during cold-stress culture. This study introduces a distinctive approach to identifying L. monocytogenes under cold-stress, offering potential application for safety enhancement in the food industry.