The uses of ionic liquids (ILs) to alter the performance of enzymes and to pretreat cellulosic biomass have been investigated. In the present study, the activity of beta-glucosidase from Themotoga maritime (TmBgl1A) was studied in a phosphate buffer containing imidazolium-based ILs. Among the imidazolium-based ILs that were tested, 1-butyl-3-methylimidazolium acetate [Bmim][OAc] showed the most improvement for the hydrolysis activity of TmBgl1A at pH 7.0. From the steady-state emission spectra, [Bmim][OAc] quenched the intrinsic fluorescence of TmBgl1A. The improvement in the activity of TmBgl1A induced by [Bmim][OAc] could be linked to the flexibility of the conformation of TmBgl1A. (C) 2014 Elsevier B.V. All rights reserved.