Determination of the Minimal Inhibitory Concentration of Lauric Arginate against Three Strains of Salmonella enterica

Introduction: Lauric arginate (LAE) is a food grade cationic surfactant derived from the integration of lauric acid, L-arginine, and ethanol. Although it possesses antimicrobial capabilities, its commercial application in food and beverage systems is currently limited due to its bitter/astringent taste and low levels of solubility.

Purpose: The objective of this study was to determine the minimum inhibitory concentration of LAE on Salmonella in a broth system.

Methods: To determine the minimum inhibitory concentration (MIC) of LAE in a broth system, LAE (5%, pH 7.0, 10 mM Phosphate Buffer) stock solution was diluted to varying ppm concentrations (0, 1, 2, 4, 8, 16, 32, 64, 128, and 256) and randomly distributed in microtiter plates. A 1% inoculum of Salmonella enterica (ATCC strains BAA-708, BAA-709, and BAA 710) overnight culture was added to 2X TSB, combined with equal amounts of LAE and incubated at 32 °C and 20 °C. After 6, 24, 48, and 72 hours of incubation, O.D. at 570 nm was measured. The MIC was defined as the lowest concentration that inhibited bacterial growth (as measured by OD) after 72 h. Experiments were performed with three independent replicates.

Results: The minimum inhibitory concentration of LAE in a broth system was dependent on strain but not incubation temperature. At both temperatures, strains BAA-708 and BAA-709 were inhibited at 256 ppm, while growth of strain BAA-710 was inhibited at 128 ppm. These results indicate that the incorporation of LAE in a concentration of 256 ppm would likely be effective in inhibiting Salmonella enterica in other systems. 

Significance: By determining the MIC against multiple Salmonella enterica strains, the most appropriate amount of LAE can be selected for use in food and beverage products.