Enhanced Antibacterial Activity of Eugenol-entrapped Casein Nanoparticles Amended with Lysozyme Against Gram-positive Pathogens

This study aimed to investigate the antibacterial efficiency and synergistic mechanisms of novel formulated eugenol-casein-lysozyme nanoparticles (ECL-NPs) against gram-positive bacteria. We obtained optimized ECL-NPs 151.9 nm in size and with an entrapment efficiency of 92.2%. ECL-NPs exhibited a satisfactory slow-release pattern, excellent storage stability (for 180 days at 4 °C), and freeze-drying stability. The synergy of low-dose lysozyme significantly enhanced the inhibitory efficiency of eugenol-casein nanoparticles against Staphylococcus aureus and Bacillus sp. by 5.83-fold and 5.53-fold, respectively; this resulted in a much lower minimum inhibitory concentration (3.75-fold and 4.16-fold) and minimum bacterial concentration (2.92-fold and 1.70-fold) values. Scanning electron microscopy clearly demonstrated that the entire cell morphological structure was broken into pieces after exposure to ECL-NPs. Furthermore, 100% microbial inhibition was observed in fresh fruits treated with ECL-NPs for 15 days. These findings suggest that ECL-NPs have an excellent potential for use in food industry against gram-positive bacteria.