Easily measurable pH as an indicator of the effectiveness of the aqueous cholinium ionic liquid-based pretreatment of lignocellulose

Abstract

Aqueous ionic liquid (IL) solutions have recently received significant interest as promising alternatives to neat ILs for lignocellulose pretreatment because of many advantages. In this study, 39 aqueous cholinium IL solutions were used to pretreat rice straw for improving the subsequent enzymatic saccharification. Strong correlations were observed between the pH of these aqueous ILs and their respective delignification capacities, between their pH and the polysaccharide digestibility, and between their pH and the corresponding reducing sugar yields. More than 55% of the lignin was removed from rice straw after pretreatment with aqueous ILs of pH > 11.0, thus resulting in a high digestibility (88–96% for cellulose and 65–89% for xylan) during the process of enzymatic saccharification. Establishing this type of correlation between the pH of aqueous ILs and their pretreatment effectiveness may be useful for the rational design and selection of ILs for lignocellulosic biomass pretreatment.