Pretreatment of corn stover by acidic and basic choline chloride solutions for enzymatic hydrolysis

As a cheap, biodegradable, and nontoxic chemical, choline chloride (ChCl) is widely used in animal feed. In this study, acid and alkali catalyzed ChCl pretreatments of corn stover (CS) were investigated. Compared with single aqueous ChCl pretreatment, H 2 SO 4 acidified aqueous ChCl pretreatment was more effective in removing lignin (69.5%) and xylan (84.9%). NaOH alkalified aqueous ChCl pretreatment demonstrated better performance of delignification (76.8%) but weaker capability of removing xylan (46.2%) than acidified aqueous ChCl pretreatment. Following enzymatic digestibility of pretreated CS, glucose yield from acidified ChCl pretreatment was 72.1%, significantly lower than that of alkalified ChCl pretreatment (89.4%). However, the highest glucose yield of 98.6% resulted from solitary alkali pretreatment. Correlation studies between change in physico-chemical properties of pretreated solids and corresponding enzymatic digestibility indicated high delignification and bigger cellulose crystallite size were mainly responsible for high enzymatic hydrolysis efficiency. Additionally, the properties of extracted lignin from single and combined pretreatments with ChCl and alkali or acid were analyzed. Acidified ChCl pretreatment increased, whereas alkaline ChCl pretreatment decreased molecular weight and phenolic hydroxyl groups of separated lignin in comparison to individual acid and alkali pretreatment. These findings would provide useful information in understanding biomass pretreatments with aqueous ChCl.