Pretreatment of corn stover by combining ionic liquid dissolution with alkali extraction

Abstract

Pretreatment plays an important role in the efficient enzymatic hydrolysis of biomass into fermentable sugars for biofuels. A highly effective pretreatment method is reported for corn stover which combines mild alkali-extraction followed by ionic liquid (IL) dissolution of the polysaccharides and regeneration (recovery of the polysaccharides as solids). Air-dried, knife-milled corn stover was soaked in 1% NaOH at a moderate condition (90°C, 1 h) and then thoroughly washed with hot deionized (DI) water. The alkali extraction solublized 75% of the lignin and 37% of the hemicellulose. The corn stover fibers became softer and smoother after the alkali extraction. Unextracted and extracted corn stover samples were separately dissolved in an IL, 1-butyl-3-methylimidazolium chloride (C(4) mimCl), at 130°C for 2 h and then regenerated with DI water. The IL dissolution process did not significantly change the chemical composition of the materials, but did alter their structural features. Untreated and treated corn stover samples were hydrolyzed with commercial enzyme preparations including cellulases and hemicellulases at 50°C. The glucose yield from the corn stover sample that was both alkali-extracted and IL-dissolved was 96% in 5 h of hydrolysis. This is a highly effective methodology for minimizing the enzymatic loading for biomass hydrolysis and/or maximizing the conversion of biomass polysaccharides into sugars.

Microbial inhibitors: formation and effects on acetone-butanol-ethanol fermentation of lignocellulosic biomass

“…Alkali salt pretreatment utilizes a 0.05-0.30 % (w/w) alkali solution to treat cellulosic biomasses at less than 100°C for 10-60 min (Feng et al 2014;Rasmussen et al 2014). Ionic liquid pretreatment is usually carried out at 70-160°C for 1-24 h (Dibble et al 2011;Geng and Henderson 2012;Li et al 2011;Uppugundla et al 2014). In addition to these pretreatment processes, conditions of enzymatic hydrolysis are 45-50°C for 48-120 h with cellulase loading rates of 4.5-60 FPU/g of glucan at pH 4.8 and about 150 rpm (Kim et al 2003;Qureshi et al 2014;Saha et al 2013).…”

Ionic liquids as a tool for lignocellulosic biomass fractionation

“…Although the disruption of the cellulose crystallinity is crucial to provide the biomass suitable for enzymatic digestion, lignin removal is even more critical for improving enzymatic hydrolysis of cellulose [72].…”

Multi-Scale Structural Studies of Sequential Ionic Liquids and Alkali Pretreated Corn Stover and Sugarcane Bagasse

“…Hence, the quantitative analysis had to be done in order to substantiate the structural changes. The results were summarised in Figure 5 improved hydrolysis in combined pretreatments may be due to the increased amorphous cellulose contents after the disruption of intra molecular and inter molecular hydrogen bonding leading to more of enzyme accessibility stemming from the effective removal of hemicelluloses and lignin [53]. The process eco-…”