Ethanol-water organosolv delignification of liquid hot water (LHW) pretreated sugarcane bagasse enhanced by high-pressure carbon dioxide (HP-CO2)

Organosolv delignification assisted by high-pressure carbon dioxide (HP-CO2), a low cost, non-corrosive and recoverable compound was evaluated as a potential green pretreatment technology for lignin extraction from liquid hot water (LHW) pretreated sugarcane bagasse to produce fermentable sugars in a lignocellulosic biorefinery concept. In this study, LHW pretreated bagasse (180 °C for 20 min with a liquid-to-solid ratio (LSR) of 9 (v/w)) was delignified with an ethanol-water mixture (1:1, v/v) and HP-CO2 as a co-solvent at milder temperatures (111.7-168.3 °C) and times (23.8-66.2 min) at a LSR of 5 (v/w). To evaluate the effects of varying operational conditions on the lignin content and delignification extent, while preserving the glucan fraction, a 22 central composite design was used as a factorial planning. Solid fractions with low lignin contents (7.35% and 10.78%) and high delignification extents (82.5% and 72.2%) with good glucan preservations (84.6% and 85.3%) were obtained at 140 °C for 45 min and 111.7 °C for 45 min, respectively. These solid fractions were subjected to enzymatic hydrolysis, yielding enzymatic conversions of 60.8% and 63.7%, respectively.