Effective Concentration of Ionic Liquids for Enhanced Saccharification of Cellulose

Abstract

In an aqueous enzymatic saccharification using cellulase, the dissolution of crystalline cellulose is one of the rate-limiting steps. Insoluble cellulose powder was preliminarily heat-treated with ionic liquids (ILs), such as [Bmim][Cl] (1-butyl-3-methylimidazolium chloride) and [Amim][Cl] (1-allyl-3-methylimidazolium chloride), which enable the production of soluble cellulose. On the other hand, the presence of ILs leads to a denaturation of enzymes. Using cellulase from Trichoderma viride, the effects of [Bmim][Cl] and [Amim][Cl] in the enzymatic saccharification were compared. The production of glucose was optimized with 5 wt%-ILs, both for [Bmim][Cl] and for [Amim][Cl]. The significant inhibiting effects of ILs (IL concentration >10 wt%) could be due to the denaturation of cellulase, because the peak shifts of intrinsic tryptophan fluorescence were observed in the presence of 7.5 wt%-ILs. To analyze kinetic parameters, the Langmuir adsorption model and the Michaelis-Menten model were employed. The investigation suggests that [Amim][Cl] can provide soluble cellulose more efficiently, and can promote enzymatic saccharification in the IL concentration below 5 wt%.

Characterization of Ionic Liquid Aqueous Two-Phase Systems: Phase Separation Behaviors and the Hydrophobicity Index between the Two Phases

“…The application of IL-ATPSs in bioconversion using the cellulose enzyme has also been reported. − In these IL-ATPSs, the top phases are enriched in IL, whereas the bottom phases are enriched in salt (lower IL content). These systems seem to be suitable for the enzymatic saccharification (hydrolysis) of cellulose because a high concentration of IL is required for the dissolution of cellulose . However, the IL itself presents the risk of inactivating the enzymes. , In general, most water-soluble proteins (or enzymes) are localized in the bottom phase of ATPSs due to their hydrophilic surface properties .…”

“…These systems seem to be suitable for the enzymatic saccharification (hydrolysis) of cellulose because a high concentration of IL is required for the dissolution of cellulose. 17 However, the IL itself presents the risk of inactivating the enzymes. 18,19 In general, most watersoluble proteins (or enzymes) are localized in the bottom phase of ATPSs due to their hydrophilic surface properties.…”