Aqueous Ionic Liquids and Deep Eutectic Solvents for Cellulosic Biomass Pretreatment and Saccharification.
Aqueous Ionic Liquids and Deep Eutectic Solvents for Cellulosic Biomass Pretreatment and Saccharification.
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DOI：
10.1039/c3ra46149a
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发表时间：
2014-01-01
期刊：
影响因子：
3.9
通讯作者：
Zhao H
中科院分区：
文献类型：
--
作者：
Xia S;Baker GA;Li H;Ravula S;Zhao H
离子液体（ILs）已被证明是预处理木质纤维素的有效溶剂，可使纤维素和半纤维素快速糖化。然而，目前大多数集成电路的高成本仍然是将这种新方法在实际规模上商业化的主要障碍。作为一种战略迂回，人们也在探索液化液水溶液作为成本更低的纯液化液的纤维素预处理替代品。然而，对一些选择的IL系统的研究是有限的，并且仍然没有对各种IL进行系统的调查，避免了对水相IL系统提供的预处理机制的深入了解。作为填补这一空白的一步，本研究展示了用20种不同IL和3种深共熔溶剂的纯溶液和水溶液（1.0 M和2.0 M）对Avicel纤维素进行预处理的结果，并将预处理后纤维素的酶解速率与各种IL性质（如氢键碱度、极性、Hofmeister排序和疏水性）相关联。纯IL的预处理效率可能与组成阴离子的氢键碱度和IL极性有松散的相关关系；然而，水相IL的预处理效果更为复杂，不能简单地与任何单一的IL性质有关。在木质纤维素预处理中，几种水相IL系统已被确定为纯IL的有效替代品。特别地，本研究揭示了1-丁基-3-甲基咪唑甲磺酸盐（[BMIM][MeSO3]）水溶液对柳枝稷（Panicum virgatum）的预处理效果，可以使纤维素和半纤维素快速糖化。通过x射线衍射，扫描电镜，热重分析和纤维素酶吸附等温线对木质纤维素样品进行综合分析，进一步提供了更完整的水相IL预处理结构变化视图。
Ionic liquids (ILs) have proven effective solvents for pretreating lignocellulose, leading to the fast saccharification of cellulose and hemicellulose. However, the high current cost of most ILs remains a major barrier to commercializing this recent approach at a practical scale. As a strategic detour, aqueous solutions of ILs are also being explored as less costly alternatives to neat ILs for cellulose pretreatment. However, limited studies on a few select IL systems are known and there remains no systematic survey of various ILs, eluding an in-depth understanding of pretreatment mechanisms afforded by aqueous IL systems. As a step toward filling this gap, this study presents results for Avicel cellulose pretreatment by neat and aqueous solutions (1.0 and 2.0 M) of 20 different ILs and three deep eutectic solvents, correlating enzymatic hydrolysis rates of pretreated cellulose with various IL properties such as hydrogen-bond basicity, polarity, Hofmeister ranking, and hydrophobicity. The pretreatment efficiencies of neat ILs may be loosely correlated to the hydrogen-bond basicity of the constituent anion and IL polarity; however, the pretreatment efficacies for aqueous ILs are more complicated and cannot be simply related to any single IL property. Several aqueous IL systems have been identified as effective alternatives to neat ILs in lignocellulose pretreatment. In particular, this study reveals that aqueous solutions of 1-butyl-3-methylimidazolium methanesulfonate ([BMIM][MeSO3]) are effective for pretreating switchgrass (Panicum virgatum), resulting in fast saccharification of both cellulose and hemicellulose. An integrated analysis afforded by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and cellulase adsorption isotherm of lignocellulose samples is further used to deliver a more complete view of the structural changes attending aqueous IL pretreatment.