Endolysins as Effective Agents for Decontaminating S. typhimurium, E. coli, and L. monocytogenes on Mung Bean Seeds

Seeds are a major source of contamination by foodborne pathogens such as Salmonella typhimurium, Escherichia coli, and Listeria monocytogenes, significantly increasing the risk of foodborne diseases associated with fresh produce like sprouts. In this study, we described novel endolysins and the engineered variants that exhibited potent bactericidal activity against these pathogens. These endolysins demonstrated strong bactericidal effects independently of outer membrane permeabilizers, effectively killing S. typhimurium, E. coli, and L. monocytogenes to undetectable levels (>4-log kill) at concentrations as low as 12.5 μg/mL. The enzymes retained their activity in complex environments, such as a wide range of temperatures (4-100 °C), pH values (4-10), serum concentrations (0-50%), and sodium chloride concentrations (0-500 mM). Furthermore, their rapid bactericidal kinetics, excellent storage stability (>18 months), and broad-spectrum antimicrobial activity enhanced their potential for application. These endolysins remained effective against stationary-phase bacteria and biofilm-forming bacteria, achieving more than 99% biofilm eradication at 200 μg/mL. Notably, at concentrations as low as 50 μg/mL, these enzymes completely decontaminated foodborne pathogens in a mung bean seed model contaminated with 4-5 log CFU of bacteria. This study is the first to report the successful use of lysins to control both Gram-negative and Gram-positive pathogens on mung bean seeds.