Antimicrobial Activity of Alternative Surfactants on Foodborne Pathogenic Bacteria

Abstract

This research aims to investigate the antimicrobial activity of selected surfactants that are derived from natural substances to use as a replacement for synthetic surfactants. Antimicrobial activities of the selected surfactants, including capryl glucoside (CA), coco glucoside (CG), and decyl glucoside (DG), were determined by the broth dilution method. Foodborne pathogenic bacteria, including Escherichia coli TISTR 780, Salmonella Typhimurium TISTR 292, Listeria monocytogenes Scott A, and Staphylococcus aureus TISTR 1466 were tested. The minimum inhibitory concentration (MIC) of tested alternative surfactants for Gram-positive bacteria and Gram-negative bacteria ranged between 0.003 - 0.2 and 5 - >10% (w/w), respectively. The minimum bactericidal concentration (MBC) of those bacteria ranged between 0.005 – 2 and 5 - >10% (w/w), respectively. Among tested surfactants, CG showed the strongest antimicrobial activity against L. monocytogenes (MIC=0.003% and MBC=0.005%), followed by S. aureus (MIC=0.09% and MBC=1%) and E. coli (MIC=7% and MBC=8%), respectively. However, there was no antibacterial effect on S. Typhimurium at the maximum concentration tested of 10%. The optimum pH condition for antibacterial activity was investigated via the time-kill assay. The destruction curves of L. monocytogenes against CG in different pH conditions, including 0.1M phosphate buffer saline (PBS, pH 7.2), 0.1M PBS (pH 5.6), and citrate buffer (pH 5.6), were plotted in comparison to the commercial fruit and vegetable cleaners used as a benchmark. The results showed that 0.5% CG in 0.1M PBS (pH 7.2) could reduce L. monocytogenes by 5 Log (⁓99.999% reduction) within 3 sec. After the exposure time of 5 min, the 0.5% CG in citrate buffer (pH 5.6) could reduce the number of L. monocytogenes and S. aureus by 4 Log (⁓99.99% reduction) and 3 Log (⁓99.9% reduction), respectively. Moreover, 0.5% CG in 0.1M PBS (pH 5.6) could reduce the number of L. monocytogenes by 3 Log (⁓99.9% reduction). All CG treatments could reduce the number of E. coli by 1 Log (⁓90% reduction). At the same time, the commercial cleaner could reduce the number of L. monocytogenes, E. coli, and S. aureus by 0.89 - 1.39 Log (⁓81% - ⁓90% reduction). This research demonstrated the antimicrobial efficacy of CG, which has the potential to be used as an alternative antimicrobial surfactant and can be applied to cleaners and sanitizers for household products.