Abstract
β-Glucosidase B (BglB) hydrolyzes β‑glycosidic bonds in complex carbohydrates, playing an important role in global carbon cycling, and diverse biofuel and biotechnological applications. This study systematically evaluated the functional and structural role of residue F397 by generating and characterizing all 19 possible amino acid substitutions. Hydrophobic and neutral substitutions expressed efficiently and retained catalytic efficiency and substrate affinity comparable to wild-type, whereas charged or polar substitutions reduced BglB expression and structural stability. Kinetic analyses showed minimal effects on K (M) , while thermal stability was generally decreased. These results indicate that F397 primarily contributes to local structural stability rather than catalysis.