Simultaneous pretreatment and enzymatic saccharification of (ligno) celluloses in aqueous-ionic liquid media: A compromise

•Simultaneous IL-pretreatment and enzymatic saccharification of biomasses succeeded.•10% v/v of IL led to highest yields of saccharification without fractionation.•[C2mim][MeO(H)PO2] was more powerful than [C2mim][OAc] for one-step process.•Synergistic action of cellulases in IL-aqueous media was influenced.•A compromise between substrate accessibility and enzyme deactivation governed.

In view of decreasing the amount of IL to achieve efficient simultaneous pretreatment and saccharification, a comprehensive study was undertaken. Different types of lignocellulosic biomasses were investigated in various enzymatic aqueous-IL systems including 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) or 1-ethyl-3-methylimidazolium methylphosphonate ([C2mim][MeO(H)PO2]). To better understand how 10% (v/v) of IL in the reaction medium led to the highest yields of glucose without fractionation from sawdust, distinct cellulosic models were then used as substrates. Kinetic studies demonstrated that both ILs affect synergistic action of cellulolytic enzymes depending on both constitutive anion and cellulosic substrate. Concentrations above 10% v/v of ILs deactivated cellulase even on highly digestible model substrates. β and α Kamlet-Taft parameters constituted more physicochemical pertinent indicators than apparent pH value to investigate effects of IL on cellulase performances. Fine description of these effects was proposed onto individual EG, CBH and BG. [C2mim][MeO(H)PO2] was demonstrated a better compatible IL for enzymes up to a concentration of 30% (v/v). The efficiency of simultaneous pretreatment and saccharification was governed by a compromise between better substrate accessibility and enzyme deactivation.