The influence of synergistic antibacterial saponins, sapindoside A and B, on the fatty acid composition and membrane properties of Micrococcus luteus.

Abstract

Background: Saponins from Sapindus mukorossi Gaertn. are natural surfactants with excellent foaming ability, biodegradability, and safety. However, their applications in food have been rarely reported. The aim of this work was therefore to investigate the synergistic antibacterial roles of a combination of sapindoside A and B (S_AB), which are major components of Sapindus saponins, in altering the properties and fatty acids (FAs) in the membrane of Micrococcus luteus, which has been identified as an opportunistic pathogen.

Results: Microscopy showed that S_AB destroyed the integrity of the cell membrane and internal structures and led to the leakage of the cell content. Further analysis indicated that the ratio of saturated FAs to unsaturated FAs was increased significantly, and the membrane fluidity, permeability, and integrity changed substantially. Although sapindoside A and B exerted similar synergistic effects on fatty acid composition and membrane fluidity, sapindoside A had a greater impact on membrane permeability and integrity, consistent with density functional theory.

Conclusion: The activity of M. luteus was inhibited more effectively by S_AB than sapindoside A or B alone. It attacked cell membrane FAs, resulting in changing membrane fluidity, permeability, and integrity, eventually causing leakage of the cell contents, and ultimately cell death. This helped to provide evidence for the use of S_AB as a natural antibacterial detergent additive in the food industry. © 2024 Society of Chemical Industry.