Effects of the advanced organosolv pretreatment strategies on structural properties of woody biomass

Abstract Plants have evolved their lignocellulosic cell walls through complex structural and chemical mechanisms to protect itself against microbial attacks, which makes native lignocellulosic biomass recalcitrant to enzymatic deconstruction. Pretreatment is a crucial step in the biological conversion of biomass as it can render structural changes in the plant cell wall to reduce the biomass recalcitrance, thus enhancing its sugar release performance. There have been many efforts to develop effective pretreatment technologies to overcome the biomass recalcitrance with a primary focus on the efficient conversion of biomass carbohydrates to liquid fuels, while lignin is significantly underutilized despite its bulk amount and high-value opportunities. In this study, the effects of two recent organosolv pretreatment strategies, co-solvent enhanced lignocellulosic fractionation (CELF) and γ-Valerolactone (GVL) pretreatments, on physicochemical properties of poplar were investigated and compared with the effects of conventional ethanol organosolv pretreatment. Diverse physicochemical properties of biomass including chemical compositions, molecular weights of cellulose and lignin, aromatics and inter-unit linkages of lignin, lignin hydroxyl group contents, cellulose crystallinity, and accessible surface area of cellulose were analyzed before and after pretreatments. The results revealed how each organic solvent pretreatment system affected biomass structural characteristics and recalcitrance.