Interaction between structurally different heteroexopolysaccharides and β-lactoglobulin studied by solution scattering and analytical ultracentrifugation

Abstract

Despite a very large number of bacterial exopolysaccharides have been reported, detailed knowledge on their molecular structures and associative interactions with proteins is lacking. Small-angle X-ray scattering, dynamic light scattering and analytical ultracentrifugation (AUC) were used to characterize the interactions of six lactic acid bacterial heteroexopolysaccharides (HePS-1-HePS-6) with β-lactoglobulin (BLG). Compared to free HePSs, a large increase in the X-ray radius of gyration R, maximum length L and hydrodynamic diameter d of HePS-1-HePS-4 mixed with BLG revealed strong aggregation, the extent of which depended on the compact conformation and degree of branching of these HePSs. No significant effects were observed with HePS-5 and HePS-6. Turbidity and AUC analyses showed that both soluble and insoluble BLG-HePS complexes were formed. The findings provide new insights into the role of molecular structures in associative interactions between HePSs and BLG which has relevance for various industrial applications.

Binding Sites for Oligosaccharide Repeats from Lactic Acid Bacteria Exopolysaccharides on Bovine β-Lactoglobulin Identified by NMR Spectroscopy

“…Previously, binding of BLGA and other prominent milk proteins to seven EPS from lactic acid bacteria has been assessed by surface plasmon resonance analysis, and the two EPS selected here bound most strongly to native BLGA, as demonstrated in that study . Generally, the interactions with purified milk proteins vary with EPS monosaccharide composition, glycosidic linkage patterns, branching, and molecular weight. − Recently, it was suggested that the affinity for EPS is governed by polar interactions with only a smaller contribution from hydrophobic interactions and involves avidity between sites. , However, as the large molecular size of EPS hampers structural characterization of the protein complexes, the role of distinct EPS structures and the mechanisms of EPS–BLG interactions are poorly understood.…”

“…41−51 Recently, it was suggested that the affinity for EPS is governed by polar interactions with only a smaller contribution from hydrophobic interactions and involves avidity between sites. 41,51 However, as the large molecular size of EPS hampers structural characterization of the protein complexes, the role of distinct EPS structures and the mechanisms of EPS−BLG interactions are poorly understood.…”