Cholinium carboxylate ionic liquids for pretreatment of lignocellulosic materials to enhance subsequent enzymatic saccharification

The present study is the first report demonstrating that ionic liquids consisting of cholinium cations and linear carboxylate anions ([Ch][CA] ILs) can be used for pretreatment of lignocellulosic materials to enhance subsequent enzymatic saccharification. Six variants of [Ch][CA] ILs were systematically prepared by combining cholinium cations with linear monocarboxylate anions ([CnH2n+1-COO](-), n = 0-2) or dicarboxylate anions ([HOOC-CnH2n+1-COO](-), n = 0-2). These [Ch][CA] ILs were analyzed for their toxicity to yeast cell growth and their ability to pretreat kenaf powder for subsequent enzymatic saccharification. When assayed against yeast growth, the EC50 for choline acetate ([Ch][OAc]) was 510 mM, almost one order of magnitude higher than that for 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). The cellulose saccharification ratio after pretreatment at 110 degrees C for 16h with [Ch][OAc] (100.6%) was almost comparable with that after pretreatment with [Emirn][OAc]. Therefore, [Ch][OAc] is a biocompatible alternative to [Emim][OAc] for lignocellulosic material pretreatment. (C) 2012 Elsevier B.V. All rights reserved.