Effects of ionic liquid/water mixture pretreatment on the composition, the structure and the enzymatic hydrolysis of corn stalk

Recently, pretreatment of lignocellulose by ionic liquids have attracted considerable attention due to their excellent pretreatment effects and their environmental sustainable properties. However, because of the high cost and viscosity, their industrial application are restricted. In this study, water was introduced to 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) to reduce both the viscosity and the cost of using pure ionic liquid. The [Bmim]BF4/water system was proved to be effective for improving the enzymatic hydrolysis of corn stalk, and the enzymatic hydrolysis efficiency (81.68%) obtained was much higher than that found with the pure ionic liquid under the same conditions (14.46%). The findings obtained from the characterization studies were in accordance with the enhancement of the hydrolysis of the lignocellulosic biomass. After pretreated by [Bmim]BF4-H2O, the formation of a porous structure, destruction of the lignin-polysaccharide interactions, and deacetylation of hemicellulose were achieved as suggested by SEM, FTIR and 13C NMR, respectively, but the crystalline structure was not damaged indicated by XRD results.