Miscanthus x giganteus is currently being considered as a promising dedicated bio-energy crop. A cost-effective development of second-generation bioethanol involves energy-saving processes. We report here for the first time the feasibility to perform pretreatments of Miscanthus with successive dilute acid then hydrophilic ionic liquids in mild conditions for an efficient energy-saving of enzymatic saccharification. Indeed, short time of pretreatments (20-40 min) with 1-ethyl-3-methylimidazolium methylphosphonate or 1-ethyl-3-methylimidazolium acetate [Emim] (vertical bar) [CH3COO] of dilute acid pretreated Miscanthus can be carried out at room/mild temperature (25-45 degrees C). In these mild conditions, a significant improvement of saccharification performances was obtained in comparison with each single pretreatment (up to a factor 2) or untreated sample (about a factor 4). Synergistic effects between these two distinct pretreatments led to an efficient lignocellulosic biomass deconstruction in soft conditions, by cellulose separation from hemicelluloses and lignin. (C) 2014 Elsevier Ltd. All rights reserved.