New two-stage pretreatment for the fractionation of lignocellulosic components using hydrothermal pretreatment followed by imidazole delignification: Focus on the polysaccharide valorization.

•Two-stage pretreatment proved to favor the selective fractionation of elephant grass.•The realization of two-stage pretreatment allows to use milder process conditions.•Sequential pretreatments allowed greater recovery of biomass constituents.•Imidazole is an effective solvent for delignification in sequential pretreatments.•Two-stage fractionation increases the enzymatic conversion of cellulose.