Structural models of β-glucosidases Unglu135B12 characterised in the present work and its substrate docking. A. The pNPG-binding model of Unglu135B12 derived from Thermotoga neapolitana β-glucosidase 3B (PDB ID 2X40). The three protein domains: α/β barrel, α/β sandwich and fibronectin-like, were coloured cyan, kelly and red, respectively. B. Closeup of the catalytic centre. C. The key residues in the catalytic pocket around pNPG.