Synthesis of polymerizable quaternary ammonium bromides and their efficacy against pathogenic and food spoilage bacteria

Abstract

Despite rigorous cleaning and sanitization protocols, food manufacturing facilities can harbor persistent microorganisms that can cause post processing contamination leading to food safety and food spoilage issues. Of particular concern are ‘growth niches’, regions within a manufacturing facility more likely to accumulate water and debris because they are outside the zones of routine cleaning and sanitization. Such growth niches present a challenge in controlling post-processing microbial contamination which can affect the safety and shelf life of foods and beverages. In recent years, researchers have explored using antimicrobial and nonfouling coatings to control microbial persistence and cross contamination. A challenge in identifying effective coatings is the limited research on efficacy of antimicrobial monomers (suitable for polymerization into antimicrobial coatings) on microorganisms relevant in food safety and spoilage. In this work, we synthesize and characterize the efficacy of five antimicrobial quaternary ammonium bromide (QAB) monomers against pathogenic and food spoilage organisms. The QAB monomers are end-capped with dihydroxy moieties suitable for subsequent polymerization into antimicrobial polyurethanes and polyesters. N,N-bis(2-hydroxyethyl)-N-methyl-N-R-1-ammonium bromides (R= -octan {C8QAB}, -decan {C10QAB}, -dodecan {C12QAB}, -hexadecan {C16QAB}, -octadecan {C18QAB}) were synthesized and characterized using spectral techniques (Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy). Minimum inhibitory concentrations were determined against relevant food safety and food spoilage bacteria Listeria monocytogenes, Salmonella Typhimurium, Escherichia coli, and Pseudomonas poae. Sixteen and eighteen carbon length QAB monomers inhibited growth of L. monocytogenes and P. poae at a concentration of 3 ppm, while sixteen carbon length QAB monomerinhibited growth of Salmonella Typhimurium at 26 ppm and against Escherichia coli at 13 ppm. Quaternary ammonium compounds capped with polymerizable end groups such as those reported here offer an opportunity to reduce persistence and cross-contamination of food pathogens and food spoilage bacteria with particular relevance in growth niches outside of routine cleaning and sanitization regimens.