Pretreatment Cellulose Lignin Ionic liquid Cellulase a b s t r a c t 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 pre-treatments 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 (20e40 min) with 1-ethyl-3-methylimidazolium methylphosphonate or 1-ethyl-3-methylimidazolium acetate [Emim] þ [CH 3 COO] À of dilute acid pretreated Mis-canthus can be carried out at room/mild temperature (25e45 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 lignocel-lulosic biomass deconstruction in soft conditions, by cellulose separation from hemi-celluloses and lignin. ª