Fast dissolution pretreatment of the corn stover in gamma-valerolactone promoted by ionic liquids: Selective delignification and enhanced enzymatic saccharification.

The dissolution of corn stover was investigated in gamma-valerolactone (GVL) assisted by ionic liquids. An enhanced subsequent enzymatic saccharification was reached with a total reducing sugar yield of 0.69 g.g-1 and a glucose of 0.38 g.g-1 within 24 h. The treatment effects on the physical-chemical features of corn stover in terms of the natural recalcitrance to the subsequent biological digest were systematically investigated using composition analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The structures of the associated enzymatic hydrolysis lignin (EHL) and ionic liquid extracted lignin (IEL) were characterized by gel permeation chromatography (GPC), fourier transform infra-red spectroscopy (FTIR), phosphorous nuclear magnet resonance spectrometry (31P NMR), and heteronuclear single quantum coherence spectroscopy (HSQC) for an in-depth understanding of the delignification process and the basic structural information for further lignin valorization.