Multifunctional alkyl ferulate esters as potential food additives: Antibacterial activity and mode of action against Listeria monocytogenes and its application on American sturgeon caviar preservation

The alkyl ferulate esters were prepared through lipase-catalyzed reactions by using green deep eutectic solvent-water binary mixtures. Antibacterial effects screening of alkyl ferulate esters against Listeria monocytogenes demonstrated that hexyl ferulate (FAC6) exerted both bacteriostatic and bactericidal effects on Listeria monocytogenes (minimum inhibitory concentration: 0.1 mM, minimum bactericidal concentration: 0.2 mM). The antibacterial mechanism of FAC6 were further investigated to provide more information on practical applications as a multi-functional food additive. The growth curves and time-kill assay also showed the occurrence of cell lysis and significant inhibition of the growth of L. monocytogenes caused by FAC6. PI uptake analysis and massive leakage of cell constituents (K+, proteins and nucleotide) demonstrated that the membrane integrity and permeability were undermined by FAC6. Alterations in morphology and membrane hyperpolarization of L. monocytogenes cells treated with FAC6 further clearly confirmed that it disrupted the cell membrane. Meanwhile, FAC6 interacted with membrane proteins and affected the protein expression system, causing a significant change in contents, constitution and conformation of membrane proteins. Moreover, FAC6 could bind to L. monocytogenes DNA grooves to form complexes. Overall, this research highlights the effectiveness of FAC6 against L. monocytogenes, suggesting that FAC6 with both antioxidant and antibacterial activities can be used as an effective and safe multifunctional food additive for American (Amer) sturgeon caviar preservation.