Pretreatment of Eastern White Pine (Pinus strobes L.) for Enzymatic Hydrolysis and Ethanol Production by Organic Electrolyte Solutions

Organic electrolyte solution (OES), composed of room temperature ionic liquids (RTILs) and polar organic solvent, was applied during the pretreatment of eastern white pine (EWP), one of the most recalcitrant woody biomass. The influence of various crucial parameters that govern the dissolution and further pretreatment process were examined. A gradual reduction of the crystallinity of cellulose I, fragmentation and fibrillation, as well as lignin redistribution occurred with an increase of χ[AMIM]Cl (molar portion of [AMIM]­Cl) from 0.1 to 0.9; whereas the content of the cellulose, acid insoluble lignin as well as hemicellulose composition did not change. The efficiency of glucose released from EWP through rapid enzymatic hydrolysis (24 h hydrolysis yield) and the final hydrolysis yield (120 h hydrolysis yield) were improved remarkably by up to 460% and 500% after OES pretreatment. No negative effect of OES pretreatment on downstream ethanol fermentation was observed, and the highest ethanol productivity was 11.04 g ethanol/100 g EWP (when χ[AMIM]Cl = 0.9).