Enhancement of cellulose saccharification kinetics using an ionic liquid pretreatment step

Abstract

Hydrolysis of cellulose to glucose in aqueous media catalyzed by the cellulase enzyme system suffers from slow reaction rates due in large part to the highly crystalline structure of cellulose and inaccessibility of enzyme adsorption sites. In this study, an attempt was made to disrupt the cellulose structure using the ionic liquid (IL), 1-n-butyl-3-methylimidazolium chloride, in a cellulose regeneration strategy which accelerated the subsequent hydrolysis reaction. ILs are a new class of non-volatile solvents that exhibit unique solvating properties. They can be tuned to dissolve a wide variety of compounds including cellulose. Because of their extremely low volatility, ILs are expected to have minimal environmental impact on air quality compared to most other volatile solvent systems. The initial enzymatic hydrolysis rates were approximately 50-fold higher for regenerated cellulose as compared to untreated cellulose (Avicel PH-101) as measured by a soluble reducing sugar assay.

Ionic liquid‐mediated selective extraction of lignin from wood leading to enhanced enzymatic cellulose hydrolysis

“…For example, cellulose reconstituted after being dissolved in [Amim][Cl] and [Bmim][Cl] had lower degrees of crystallinity than native cellulose, which resulted in greater accessibility of the polysaccharide chains to cellulases, and thus more facile hydrolysis than was achieved without initial dissolution in and reconstitution from an IL (Dadi et al, 2006(Dadi et al, , 2007Liu and Chen, 2006). More recently, several groups have reported the dissolution of full lignocellulosic materials such as corn stalks, rice straw, bagasse, pine wood, and spruce wood in ILs followed by cellulose hydrolysis with acid or enzymes (Fort et al, 2007;Kilpeläinen et al, 2007;Li et al, 2008).…”

Ionic liquid-tolerant microorganisms and microbial communities for lignocellulose conversion to bioproducts

“…As molten organic salts, ILs typically stay in a liquid state below 100°C. Most ILs have excellent chemical stability, high thermal stability up to approximately 300°C, and are almost completely non-volatile and non-flammable (Dadi et al 2006;Lee et al 2009;Yang and Pan 2005). ILs have high polarity and usually fall in the range of 0.6-0.7 on the normalized polarity scale ( !…”

“…ILs are efficient for biomass dissolution, which is typically reported as a change in crystallinity index (CrI) (Kumar et al 2009;Segal et al 1959;Thygesen et al 2005). For example, the degrees of crystallinity in cellulose reconstituted after being dissolved in 1-allyl-3-methylimidazolium chloride ([C 3 C 1 Im]Cl) and 1-butyl-3-methylimidazolium chloride ([C 4 C 1 Im]Cl) were lower than untreated cellulose, resulting in an increased accessibility of the polysaccharide chains to cellulases (Dadi et al 2007;Dadi et al 2006;Liu and Chen 2006). A reduction in crystallinity was observed after IL pretreatment of switchgrass, maple wood, yellow pine, and hardwood red oak (Lee et al 2009;Li et al 2010;Sun et al 2009).…”

Enzyme-Catalyzed Hydrolysis of Cellulose in Ionic Liquids: A Green Approach Toward the Production of Biofuels

“…3,5,7 Different catalysts have been used for this reaction, such as metal chlorides, 4,6 acids, or enzymes. 1,31,32 The most common and widely used enzyme for this saccharification of cellulose is cellulase.…”

“…35 Studies of cellulase-induced catalysis in ionic liquids are, however, still limited. 5,[36][37][38][39] The physical and chemical properties of ionic liquids vary considerably depending on their cation-anion pair. Several attempts have been made to explore the activity of enzymes in ionic liquids, and there are various issues concerning the stability of these biomacromolecules in ionic liquids.…”