Purification and structural analysis of β-glucosidase from Lactobacillus acidophilus GIM1.208 and its interaction with rosamultin in Rosa roxburghii Tratt

Lactobacillus acidophilus GIM1.208 (LA) β-glucosidase (BGL) converts glycosides from Rosa roxburghii Tratt (RRT) to release more active aglycones. This study purified LA BGL and investigated it interaction with rosamultin in RRT. The isolated and purified BGL in the study had higher purity and activity, and the proportion of ordered structure in its secondary structure was greater than 60%, indicating better structural stability. The hydrolysis of purified BGL hydrolyzed rosamultin to tormentic acid at a rate of 25.2% (p < 0.01), and the hypoglycemic activity of tormentic acid was higher than that of rosamultin. Rosamultin causes BGL to undergo massive aggregation and enhances the hydrogen bonding network structure. Thermodynamic analyses indicate that their binding is a non-spontaneous exothermic entropy-decreasing reaction, with the main forces being hydrogen bonding, van der Waals forces, or protonation forces. Additionally, their thermodynamic binding constant Kd = 2.976 × 10 −5 mol/L and dissociation constant K D = 2.67 × 10 −5 mol/L indicate that the two have high affinity and strong interaction. In conclusion, BGL has the ability to hydrolyze rosamultin to release tormentic acid and they have a strong interaction. The results of this study can provide a reference for the study of glycoside changes and their interactions in RRT fermented by LA. • BGL was obtained with high activity and purity. • BGL hydrolyzed rosamultin to release tormentic acid. • The hypoglycemic activity of tormentic acid was higher than that of rosamultin. • The binding of BGL to rosamultin is non-spontaneous and exothermic. • BGL binds to rosamultin with hydrophobic forces.