title: Cationic antimicrobial (ε-polylysine)-anionic polysaccharide (pectin) interactions: influence of polymer charge on physical stability and antimicrobial efficacy.
abstract: The cationic biopolymer ε-polylysine (ε-PL) is a potent food-grade antimicrobial that is highly effective against a range of food pathogens and spoilage organisms. In compositionally complex systems such as foods and beverages, cationic ε-PL molecules may associate with anionic substances, leading to increased turbidity, sediment formation, and reduced antimicrobial activity. This study therefore characterized the interactions between cationic ε-PL and anionic pectins with different degrees of esterification (DE) and then investigated the influence of these interactions on the antimicrobial efficacy of ε-PL. The nature of the interactions was characterized using isothermal titration calorimetry (ITC), microelectrophoresis (ME), and turbidity measurements. High (DE 61%), medium (DE 51%), and low (DE 42%) methoxyl pectins interacted with ε-PL molecules through electrostatic forces, forming either soluble or insoluble complexes with various electrical charges, depending on the relative mass ratio of pectin and ε-PL. The interaction of pectin with ε-PL increased as the negative charge density on the pectin molecules increased, that is, with decreasing DE. The antimicrobial efficacy of ε-PL against two acid-resistant spoilage yeasts (Zygosaccharomyces bailii and Saccharomyces cerevisiae) decreased progressively in the presence of increasing levels of all three pectins. Nevertheless, the low DE pectin decreased the antimicrobial efficacy of ε-PL much more dramatically, likely due to strong electrostatic binding of ε-PL onto low DE pectin molecules reducing its interaction with anionic microbe surfaces. This study provides knowledge that will facilitate the rational application of ε-PL as an antimicrobial in complex food systems.
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, Massachusetts 01003, United States.
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Chang
authors.forename: Lynne
authors.initials: L
authors.lastname: McLandsborough
authors.forename: David Julian
authors.initials: DJ
authors.lastname: McClements
mesh_terms: D000838:Anions; D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology*; D002412:Cations; D004347:Drug Interactions; D004355:Drug Stability; D010368:Pectins / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000187:drug effects; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D020068:Zygosaccharomyces / Q000187:drug effects
chemical_list: D000838:Anions; D000890:Anti-Infective Agents; D002412:Cations; D011108:Polymers; D011107:Polylysine; D010368:Pectins