Biocatalysis in ionic liquids for lignin valorization: Opportunities and recent developments
Biocatalysis in ionic liquids for lignin valorization: Opportunities and recent developments
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离子液体生物催化木质素增值：机遇和最新进展
DOI：
10.1016/j.biotechadv.2019.107418
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发表时间：
2019
影响因子：
16
通讯作者：
Shi, Jian
中科院分区：
文献类型：
--
作者：
Stevens, Joseph C.;Shi, Jian
木质素作为可再生原料具有巨大的潜力，可用于升级为目前来自石油工业的许多高价值化学品和产品。由于木质素构成木质纤维素生物质的重要部分，除了纤维素和半纤维素之外，木质素的共同利用对于纤维素生物精炼的经济可行性至关重要。然而，木质素分子组成和结构的不均一性导致了木质素的不稳定性，这对有效和选择性的木质素解聚和稳定化提出了很大的挑战。离子液体（IL）是一种强溶剂，其在将木质纤维素生物质分级分离成糖流和降低分子量的木质素流中表现出高效率。与热化学方法相比，生物木质素降解在温和的温度和压力下进行，而产物的选择性可以通过生物催化剂（木质素降解酶，LDEs）的生物活性特异性来提高。本文综述了利用离子液体的生物质分馏能力和LDEs的底物和产物选择性的木质素增值策略。阐明酶-IL相互作用的最新进展，以及提高酶活性的IL的策略进行了讨论，特别强调生物相容性IL，耐热和IL耐受酶，酶固定化，和表面电荷工程。介绍了蛋白质工程工具包（定向进化和合理设计）在提高IL系统中生物催化剂活性、稳定性和产物选择性方面的应用。IL和LDE之间的联盟为开发木质素价值的生物催化途径提供了很好的机会。
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 improvedviathe 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.