Lignin holds tremendous potential as a renewable feedstock for upgrading to a number of high-value chemicals and products that are derived from the petroleum industry at present. Since lignin makes up a significant fraction of lignocellulosic biomass, co-utilization of lignin in addition to cellulose and hemicelluloses is vital to the economic viability of cellulosic biorefineries. The recalcitrant nature of lignin, originated from the molecule's compositional and structural heterogeneity, however, poses great challenges toward effective and selective lignin depolymerization and valorization. Ionic liquid (IL) is a powerful solvent that has demonstrated high efficiency in fractionating lignocellulosic biomass into sugar streams and a lignin stream of reduced molecular weight. Compared to thermochemical methods, biological lignin deconstruction takes place at mild temperature and pressure while product selectivity can be potentially improved via the specificity of biocatalysts (lignin degrading enzymes, LDEs). This review focuses on a lignin valorization strategy by harnessing the biomass fractionating capabilities of ILs and the substrate and product selectivity of LDEs. Recent advances in elucidating enzyme-IL interactions as well as strategies for improving enzyme activity in IL are discussed, with specific emphases on biocompatible ILs, thermostable and IL-tolerant enzymes, enzyme immobilization, and surface charge engineering. Also reviewed is the protein engineering toolsets (directed evolution and rational design) to improve the biocatalysts' activity, stability and product selectivity in IL systems. The alliance between IL and LDEs offers a great opportunity for developing a biocatalytic route for lignin valorization.

木质素作为可再生原料具有巨大的潜力，可用于升级到目前从石油工业中提取的许多高价值化学品和产品。由于木质素占木质纤维素生物质的很大一部分，因此除纤维素和半纤维素外，木质素的共同利用对纤维素生物精炼厂的经济可行性至关重要。木质素的顽固性源于分子的组成和结构异质性，然而，对有效和选择性的木质素解聚和增值构成了巨大挑战。离子液体（IL）是一种功能强大的溶剂，已证明在将木质纤维素生物质分馏成糖流和分子量降低的木质素流中具有很高的效率。与热化学方法相比，通过生物催化剂（木质素降解酶，LDEs）的特异性。这篇综述着重于利用IL的生物质分馏能力以及LDE的底物和产物选择性，对木质素进行价值化策略。讨论了阐明酶与IL相互作用的最新进展以及改善IL中酶活性的策略，并重点关注了生物相容性IL，热稳定和耐IL的酶，酶的固定化和表面电荷工程。还回顾了蛋白质工程工具集（定向进化和合理设计），以改善IL系统中生物催化剂的活性，稳定性和产物选择性。IL和LDE之间的联盟为开发木质素增值的生物催化途径提供了巨大的机会。