Synergistic photoinactivation of Escherichia coli and Listeria innocua by curcumin and lauric arginate ethyl ester micelles

Authors: Ryu, Victor; CHUESIANG, PIYANAN - Chulalongkorn University; CORRADINI, MARIA G. - University Of Guelph; MCLANDSBOROUGH, LYNNE - University Of Massachusetts, Amherst; Jin, Zhonglin; Ngo, Helen; Fan, Xuetong

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2022
Publication Date: 12/14/2022
Citation: Ryu, V.N., Chuesiang, P., Corradini, M., McLandsborough, L., Jin, Z.T., Lew, H.N., Fan, X. 2022. Synergistic photoinactivation of Escherichia coli and Listeria innocua by curcumin and lauric arginate ethyl ester micelles. LWT - Food Science and Technology. 173:114317. https://doi.org/10.1016/j.lwt.2022.114317.
DOI: https://doi.org/10.1016/j.lwt.2022.114317

Interpretive Summary: The emergence of sanitizer or antibiotic resistant bacteria due to improper sanitation practices is one of the main concerns of utilizing conventional sanitizers. The inactivation of bacteria using reactive oxygen species is recognized as a solution to prevent emergence of resistant bacteria as bacteria have no known defense mechanism against some of reactive oxygen species. Photosensitizer is a molecule that could absorb light and produce reactive oxygen species. In this study we used curcumin, a food-grade photosensitizer and ethyl lauric arginate (LAE), a generally regarded as safe surfactant to photoinactivate surrogates of foodborne pathogens. We were able to stabilize and encapsulate curcumin in LAE, which led to killing bacteria more efficiently at a broad pH range. The results will be of value for the food industry to decontaminate food and food contact surfaces.

Technical Abstract: This study evaluated the changes in water dispersibility, chemical stability, and antimicrobial activity of a food-grade photosensitizer (curcumin) after being encapsulated in an lauric arginate ethyl ester (LAE) micelle. Stock curcumin-LAE solutions were prepared by titrating curcumin dissolved in ethanol into LAE aqueous solutions (pH 3.5). The LAE in the stock solutions inhibited the crystallization and prevented the chemical degradation of curcumin during storage at 20°C. The antimicrobial activity of the curcumin-LAE micelles against Escherichia coli (E. coli) and Listeria innocua (L. innocua) cocktails was assessed after 5 min irradiation with UV-A light ('= 365 nm). Synergistic antimicrobial activity was observed when LAE was present with curcumin at pH 3.5 during irradiation, which could be attributed to a more effective interaction of the photosensitizer with the cell membranes as they became more permeable. The release of protein or nucleic acid from the cells indicated an increase in its membrane permeability after treatments. Although LAE could inactivate both E. coli and L. innocua within 10 min even without UV-A light irradiation, this effect was only observed at pH 7, which shows that LAE’s antimicrobial efficacy depends on the pH. Therefore, microbial inactivation by two mechanisms, photosensitization and permeability operating simultaneously, produced a curcumin-LAE solution that could inactivate Gram-positive and Gram-negative bacteria at a broad pH range.