Biorefining brewery spent grain polysaccharides through biotuning of ionic liquids

•Cholinium-based ionic liquids are efficient pretreatments of brewery spent grain.•This IL yields better results in comparison to conventional imidazolium-based IL.•Stronger lignin reductions can be obtained when raw BSG is treated at 90 °C.•ATR-FTIR and FE-SEM are useful tools to monitor the structural changes exerted.•The results make up the basis for a rational delignification of lignocellulosics. Brewery spent grain (BSG), a relevant waste from beer industry mainly composed of polysaccharides and lignin, is experiencing a surge in the production with its associated environmental impact. Thus, this manuscript bets in the application of aqueous solutions of a cholinium-based ionic liquid (IL) containing glycinate as anion ([N1112OH][Gly]) for an efficient delignification pretreatment. The operation at 90 °C yielded drastic lignin reduction (75.89%), greater than the levels attained when a traditional imidazolium-based IL (1-ethyl-3-methylimidazolium acetate, [C2C1im][C1COO]), was used (40.18%). The advantages of this pretreatment positively impacted the subsequent saccharification reaction, as the levels were increased up to about 1.5 times regarding the control (no IL) or the imidazolium-based pretreatment. ATR-FTIR spectrometry and scanning electron microscopy turned out to be useful tools to monitor the structural changes exerted. The results presented in this work make up the basis for a rational design of bio-ILs for delignification of lignocellulosic materials.