Synergistic Antibacterial Effects of ε‑Poly‑L‑Lysine and Oregano Essential Oil: In Vitro, In Vivo, and In Silico Approaches to Improve Safety and Shelf Life of Strawberries

This study developed a novel synergistic antibacterial system combining ε-poly-L-lysine (ε-PL) and oregano essential oil (OEO) as a natural, non-thermal preservation strategy for fruits. Among ε-PL combinations with seven different essential oils, OEO exhibited the strongest synergistic interaction, significantly enhancing antibacterial efficacy, compared to individual agents, likely through disruption of bacterial cell membranes and leakage of intracellular components. This effect was validated through integrated in vitro assays, in vivo application on strawberries, and in silico molecular docking analysis, which showed a binding energy of -7.8 kcal/mol. The ε-PL/OEO treatment reduced total viable counts to < 3.0 log CFU/g and extended shelf life by 5 days at room temperature. Furthermore, the treatment effectively preserved key quality parameters, including pH (2.69), titratable acidity (0.493%), total soluble solids (7.4 °Brix), and reducing sugars (0.772 g/100 g), while minimizing weight loss to < 2.0%. These findings demonstrate that the ε-PL/OEO combination represents a promising, sustainable alternative to synthetic preservatives, offering enhanced microbial safety and improved quality retention in perishable fruits.