Journal
INNOVATIVE FOOD SCIENCE & EMERGING TECHNOLOGIES
Volume 75, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ifset.2021.102902
Keywords
Thyme essential oil; Nanoemulsions; Ultrasonication; S; aureus; Antibacterial mechanism; Cell membrane characteristics; E coli
Categories
Funding
- Natural Science Foundation of Zhejiang Province, China [LQ20C200014]
- National Natural Science Foundation of China [32001799]
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The antibacterial activities of thyme essential oil nanoemulsions prepared by ultrasonication and high-pressure homogenization were evaluated, with superior bacteriostatic and bactericidal effects observed for the ultrasonicated samples. The underlying antibacterial mechanisms targeting cell membranes of both Gram-negative and Gram-positive bacteria were investigated, revealing membrane disintegrations and dysfunctions associated with fatty acid composition modifications upon exposure to the nanoemulsions. These results provide insights into the mode of action of the nanoemulsions, laying a critical theoretical basis for their future application in food matrix.
In this study, the antibacterial activities of thyme essential oil nanoemulsions (TEON) prepared by ultrasonication (US) and high-pressure homogenization (HPH) were evaluated via minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-killing curve analyses. TEON-US presented superior bacteriostatic and bactericidal effects, which was found to be correlated with its better physicochemical characteristics (including smaller droplet size and higher zeta potential) compared to TEON-HPH. The underlying antibacterial mechanisms were specifically investigated targeting cell membranes of Escherichia coli O157:H7 (Gram-negative bacterium) and Staphylococcus aureus (Gram-positive bacterium). Thereinto, membrane disintegrations were observed followed by massive leakage of cytoplasmic inclusions. Furthermore, the membrane dysfunctions (involving membrane potential depolarization and fluidity reduction) were likely associated with the modifications seen in the fatty acid composition upon TEONs exposure, and ultimately causing bacterial death. These results deciphered the mode of antibacterial action of TEONs, providing a critical theoretical basis for their future application in food matrix.
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