Bacterial Inhibition Mechanism of Rhamnolipid-Modified β-Carotene/Rutinoside Complex Liposomes

In this study, a new cholesterol-free delivery system named RL-βC-Rts was developed using rhamnolipid (RL) as the surfactant and encapsulating both β-carotene (βC) and rutinoside (Rts). The purpose was to examine its antibacterial properties against four food-borne pathogenic microorganisms including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. m), and Salmonella typhimurium (S. typhimurium) and to investigate the mechanism behind the inhibition. Results from bacterial viability tests and minimum inhibitory concentration (MIC) showed RL-βC-Rts possessed antibacterial activity. Upon further examination of the cell membrane potential, it was observed that E. coli, S. aureus, L. m, and S. typhimurium exhibited a reduction in mean fluorescence intensity by 50.17%, 34.07%, 34.12%, and 47.05%, respectively. These decreases suggested damage to the structure of the cell membrane, which subsequently resulted in the discharge of proteins from the bacteria and the consequential impairment of crucial functions. This was supported by alterations in protein concentration. The results of the RT-qPCR showcased that the expression of genes associated with energy metabolism, tricarboxylic acid cycle, DNA metabolism, virulence factor formation and cell membrane formation could be suppressed by RL-βC-Rts.

The online version contains supplementary material available at 10.1007/s12088-023-01077-6.