Structural characterization of exopolysaccharide from Leuconostoc mesenteroides P35 and its binding interaction with bovine serum albumin using surface plasmon resonance biosensor

This paper describes the structural elucidation of Leuconostoc mesenteroides P35 exopolysaccharide (EPS-LM). Ln. mesenteroides P35 strain was isolated from a French goat cheese for its capacity to produce EPS increasing the viscosity of a whey-based fermentation medium. The chemical structure of EPS-LM analysis was elucidated by determination of optical rotation degree, macromolecular characterization, sugar units and methylation analyses, FT-IR, 1D NMR spectroscopy (1H and 13C NMR), 2D NMR spectroscopy (1H1H COSY, HSQC and HMBC). EPS-LM was a high molecular weight (ranging from 6.7 × 106 Da to 9.9 × 106 Da) dextran that is composed of only d-glucose units containing α (1 → 6) linkages and paltry α (1 → 3) branches. Since polysaccharide-protein interactions can be exploited to control and design food matrices, EPS-LM interactions with bovine serum albumin (the main constituent of bovine plasma) were investigated by surface plasmon resonance (SPR). Kinetic properties of EPS-LM binding with immobilized BSA via showed an increase of EPS-LM affinity (equilibrium constant (Kd)) for BSA from (2.50 ± 0.01) × 10-5 M-1 at 298 K to (9.21 ± 0.05) × 10-6 M-1 at to 310 K. The thermodynamic parameters revealed that van der Waals and hydrogen binding forces play a major role in the interaction of EPS-LM with BSA. However, EPS-LM-BSA interaction was non-spontaneous, entropy driven and an EPS-LM - BSA binding process was endothermic (ΔG > 0). The structural findings suggested that Ln. mesenteroides P35 α-D-glucan might find widespread technological applications in the biopolymer, medical and food industries.