Thyme/garlic essential oils loaded chitosan–alginate nanocomposite: Characterization and antibacterial activities

Abstract

For controlling pathogenic bacteria using nanopolymer composites with essential oils, the formulation of chitosan/alginate nanocomposites (CS/ALG NCs) loaded with thyme oil, garlic oil, and thyme/garlic oil was investigated. Oils were encapsulated in CS/ALG NCs through oil-in-water emulsification and ionic gelation. The CS/ALG NCs loaded with oils of garlic, thyme, and garlic–thyme complex had mean diameters of 143.8, 173.9, and 203.4 nm, respectively. They had spherical, smooth surfaces, and zeta potential of +28.4 mV for thyme–garlic-loaded CS/ALG NCs. The bactericidal efficacy of loaded NCs with mixed oils outperformed individual loaded oils and ampicillin, against foodborne pathogens. Staphylococcus aureus was the most susceptible (with 28.7 mm inhibition zone and 12.5 µg·mL−1 bactericidal concentration), whereas Escherichia coli was the most resistant (17.5 µg·mL−1 bactericidal concentration). Scanning electron microscopy images of bacteria treated with NCs revealed strong disruptive effects on S. aureus and Aeromonas hydrophila cells; treated cells were totally exploded or lysed within 8 h. These environmentally friendly nanosystems might be a viable alternative to synthetic preservatives and be of interest in terms of health and food safety.

Keywords

• antimicrobial
• biopolymers
• nanocomposites
• natural products
• foodborne pathogens