Abstract

The biochemical conversion route in the utilization of biomass has required intensive development of processing methods for reducing recalcitrance of cellulose to enzymatic hydrolysis. Since discovering hydrophilic ionic liquids (ILs) are efficient lignocellulose solvents, considerable efforts have been made to demonstrate their potential applications in cellulose hydrolysis. However, most of the commercial lignocellulose hydrolyzing enzymes are largely deactivated or inhibited in the presence of even low concentrations of ILs. The link found between enzyme thermostability and IL tolerance leads to the consideration that hyperthermostable enzymes are good candidates to be used together with ILs. Hyperthermostable cellulases and xylanases that are highly tolerant to aqueous solutions of ILs show resistance to competitive inhibition by IL cations and have lower amounts of structural motifs (loop and helix structures) that are prone to denaturation by IL anions. In addition, they have a net negative protein surface charge that contributes to repulsion of anions. This review provides recent developments in understanding the behaviour of hyperthermostable cellulases and xylanases in ILs by elucidating protein-IL interactions. It also outlines the current research demonstrating the potential of rational enzyme engineering to improve enzyme tolerance to ILs based on comprehension of IL-induced deactivation mechanisms.

摘要

生物质利用中的生化转化路线需要深入开发加工方法，以减少纤维素对酶水解的顽固性。由于发现亲水性离子液体 (IL) 是有效的木质纤维素溶剂，因此已经做出了相当大的努力来证明它们在纤维素水解中的潜在应用。然而，即使存在低浓度的 IL，大多数商业木质纤维素水解酶在很大程度上会失活或被抑制。在酶热稳定性和 IL 耐受性之间发现的联系导致人们考虑超热稳定性酶是与 IL 一起使用的良好候选者。对 IL 水溶液具有高度耐受性的高热稳定纤维素酶和木聚糖酶对 IL 阳离子的竞争性抑制具有抗性，并且具有较少量的易于被 IL 阴离子变性的结构基序（环和螺旋结构）。此外，它们具有有助于排斥阴离子的蛋白质表面净负电荷。本综述通过阐明蛋白质-IL 相互作用，提供了在理解 IL 中超热稳定纤维素酶和木聚糖酶行为方面的最新进展。它还概述了当前的研究，证明了基于对 IL 诱导的失活机制的理解，合理的酶工程可以提高酶对 IL 的耐受性。它们具有有助于排斥阴离子的蛋白质表面净负电荷。本综述通过阐明蛋白质-IL 相互作用，提供了在理解 IL 中超热稳定纤维素酶和木聚糖酶行为方面的最新进展。它还概述了当前的研究，证明了基于对 IL 诱导的失活机制的理解，合理的酶工程可以提高酶对 IL 的耐受性。它们具有有助于排斥阴离子的蛋白质表面净负电荷。本综述通过阐明蛋白质-IL 相互作用，提供了在理解 IL 中超热稳定纤维素酶和木聚糖酶行为方面的最新进展。它还概述了当前的研究，证明了基于对 IL 诱导的失活机制的理解，合理的酶工程可以提高酶对 IL 的耐受性。