Using Surface Plasmon Resonance Technology to Screen Interactions Between Exopolysaccharides and Milk Proteins

Surface plasmon resonance-based biosensors enable the interaction between biomolecules to be monitored in real time with a label-free assay format. In the present study, the technique was used to assess the interaction between exopolysaccharides (EPS) and different milk proteins. The EPS were derived from three homopolysaccharide (HoPS)-producing Lactobacilli strains; Lactobacillus sakei, Lactobacillus plantarum, and Lactobacillus salvarius. The purified milk proteins applied were β-casein, β-lactoglobulin, and κ-casein. The results show that the binding capacity depends on the pH and decreases with increasing pH. HoPS from L. salvarius and L. sakei provided the highest binding response and interacted with κ-casein at all the tested pH values, i.e. in the range 4.0−5.5, and with β-casein at pH 4.0−5.0. When examined at pH 4.0, only HoPS from L. salvarius and L. sakei interacted with β-lactoglobulin. Under the tested conditions, HoPS from L. plantarum showed always either a lower binding response or no binding at all compared with HoPS from L. salvarius and L. sakei.