Ionic liquid (IL)-acid pretreatment is known to not only enhance the enzymatic hydrolysis efficiency of lignocellulose but also to generate deposits on the surface of fiber by conventional water regeneration, which retard the increment. In this study, ethanol aqueous solution regeneration was developed as a new method to change the substrates characteristics for IL-acid pretreatment and their effects on the enzymatic hydrolysis were evaluated. Following the IL-acid reaction, the biomass slurry was subjected to ethanol aqueous solution at various concentration. Results indicated that anti-solvent choice significantly influenced the reconstruction of both hemicelluloses and lignin as a result of the competition between water and ethanol. The partial removal of hemicelluloses and suitable lignin re-localization contributed to a more porous structure. Consequently, the cellulose digestibility of aqueous ethanol regenerated samples was dramatically enhanced to ∼100% and approximately 11- and 2-fold higher than that of untreated and conventional water regenerated pretreated samples, respectively. A giant leap in the initial rate of enzymatic hydrolysis was also detected in 50% ethanol aqueous solution regenerated samples and only about 10 hr was needed to convert 80% of cellulose to glucose due to the appearance of cellulose II hydrate-like and more porous structure.
Keywords: Arundo donax Linn; anti-solvent; cellulose II hydrate-like structure; hemicelluloses removal; ionic liquid-acid pretreatment; lignin re-localization.
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