Effect of fructooligosaccharides in full-hydrated lactic acid bacteria membrane models during thermal stress: A molecular simulation study

Fructooligosaccharides (FOS) are a promising choice for cryoprotection of lactic acid bacteria (LAB). However, the mechanism by which this protection takes place is not well understood. Molecular simulation is a key tool for gathering insights into complex physicochemical problems like this. Existing computational studies on this topic only deal with Gram-negative bacterial membranes and disaccharides, a picture which is far from real preservation conditions involving LAB. We have used all-atom molecular dynamics simulations at different temperatures to investigate the interaction between a FOS mixture and membranes whose composition is meant to mimic three LAB strains of industrial relevance. It was concluded that the presence of FOS helps to preserve the membrane by reducing phase transition hysteresis and attenuating changes in area per lipid, thickness and lipid order upon cooling. Furthermore, a migration of FOS molecules towards the bulk region in concurrence with the migration of water molecules towards the membrane surface was identified. These findings support the exclusion hypothesis, which has been proposed to explain the mechanism of sugar-membrane interaction.