title: Superior antibacterial activity of nanoemulsion of Thymus daenensis essential oil against E. coli.
abstract: Natural preservatives are being extensively investigated for their potential industrial applications in foods and other products. In this work, an essential oil (Thymus daenensis) was formulated as a water-dispersible nanoemulsion (diameter=143nm) using high-intensity ultrasound. The antibacterial activity of the essential oil in both pure and nanoemulsion forms was measured against an important food-borne pathogen bacterium, Escherichia coli. Antibacterial activity was determined by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The antibacterial activity of the essential oil against E. coli was enhanced considerably when it was converted into a nanoemulsion, which was attributed to easier access of the essential oils to the bacterial cells. The mechanism of antibacterial activity was investigated by measuring potassium, protein, and nucleic acid leakage from the cells, and electron microscopy. Evaluation of the kinetics of microbial deactivation showed that the nanoemulsion killed all the bacteria in about 5min, whereas only a 1-log reduction was observed for pure essential oil. The nanoemulsion appeared to amplify the antibacterial activity of essential oils against E. coli by increasing their ability to disrupt cell membrane integrity.
authors.affiliation: Department of Phytochemistry & Chemical Engineering, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University, Tehran, Iran.
authors.forename: Roya
authors.initials: R
authors.lastname: Moghimi
authors.affiliation: Department of Phytochemistry & Chemical Engineering, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University, Tehran, Iran.
authors.forename: Lida
authors.initials: L
authors.lastname: Ghaderi
authors.affiliation: Department of Phytochemistry & Chemical Engineering, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University, Tehran, Iran. Electronic address: H_Rafati@sbu.ac.ir.
authors.forename: Hasan
authors.initials: H
authors.lastname: Rafati
authors.affiliation: Department of Biology, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University, Tehran, Iran.
authors.forename: Atousa
authors.initials: A
authors.lastname: Aliahmadi
authors.affiliation: Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: David Julian
authors.initials: DJ
authors.lastname: McClements
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D004655:Emulsions; D004926:Escherichia coli / Q000187:drug effects*; D057927:Hydrophobic and Hydrophilic Interactions; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D009822:Oils, Volatile / Q000494:pharmacology*; D011188:Potassium / Q000737:chemistry; D046930:Thymus Plant / Q000737:chemistry*; D014465:Ultrasonics
chemical_list: D000900:Anti-Bacterial Agents; D004655:Emulsions; D009822:Oils, Volatile; D011188:Potassium
keywords: Glutaraldehyde (Pubchem CID: 3485); Mechanism of action; Membrane integrity; Natural antimicrobial; Ostwald ripening; Particle diameter; Span 80 (Pubchem CID: 5385498); Tween 80 (Pubchem CID: 52811955)