The molecular basis of the adsorption of bacterial exopolysaccharides on montmorillonite mineral surface

Rhizospheric exopolysaccharides (EPS) spontaneously aggregate mineral particles. Molecular dynamics simulations with Cerius2 and Materials Studio programs have been performed to study the adsorption of chemical groups, monosaccharides and oligosaccharides, onto the basal surface of Na-montmorillonite. The estimated enthalpies of adsorption of chemical groups nicely reproduced the expected values. Mono- and oligosaccharides have a preferred geometry of adsorption. Monosaccharides maintained their shape upon adsorption whereas oligosaccharides flattened more or less on the surface, depending on their flexibility. The conformational adaptability was shown to be the leading factor that determined the interaction strength between the EPS and the mineral surface.