Lauric Acid Microemulsions Inhibit Staphylococcus aureus Through Cell Membrane Disruption and Potential Interference with Peptidoglycan Biosynthesis

Staphylococcus aureus (S. aureus) is a prominent foodborne pathogen that poses a continuous threat to global public health and food safety due to its possession of a variety of toxins and its multidrug resistance. Medium-chain fatty acids (MCFAs), notably lauric acid (LA), exhibit strong antimicrobial properties, but their application is heavily constrained by poor water solubility. In this study, optimized LA emulsions stabilized by chitosan (CS) and polyvinyl alcohol (PVA) were evaluated for their antibacterial activity and detailed mode of action against S. aureus ATCC 6538. The antibacterial activities were evaluated by the maximum inhibition zone, with the 20 CS-PVA/DLTA-LA formulation exhibiting stable dispersion and potent antibacterial activity at 1%. The underlying antibacterial mechanisms against S. aureus were specifically focused on cell membranes and peptidoglycan. Therein, the binding of emulsion droplets to the anionic bacterial surface was driven by electrostatic attraction. Membrane degradation was also observed with membrane dysfunctions involving membrane depolarization, increased permeability, and fluidity reduction triggered by their subsequent insertion into the lipid bilayer, which may cause cell dysmetabolism, disintegration, and eventual cell death. Overall, these findings substantiate that LA emulsions disrupt S. aureus by operating potentially multi-targeted effects involving cell membrane disruption and peptidoglycan interference, offering a promising alternative approach warranting further investigation for foodborne pathogen control.