Biocatalysis in ionic liquids for lignin valorization: Opportunities and recent developments

Joseph C. Stevens, Jian Shi

Research output: Contribution to journalReview articlepeer-review

38 Scopus citations

Abstract

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.

Original languageEnglish
Article number107418
JournalBiotechnology Advances
Volume37
Issue number8
DOIs
StatePublished - Dec 2019

Bibliographical note

Funding Information:
We acknowledge the National Science Foundation , United States of America under Cooperative Agreement No. 1355438 and 1632854 and the National Institute of Food and Agriculture, U.S. Department of Agriculture under accession number 1003563 for supporting this work. The information reported in this paper is part of a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.

Funding Information:
We acknowledge the National Science Foundation, United States of America under Cooperative Agreement No. 1355438 and 1632854 and the National Institute of Food and Agriculture, U.S. Department of Agriculture under accession number 1003563 for supporting this work. The information reported in this paper is part of a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.

Publisher Copyright:
© 2019 Elsevier Inc.

Keywords

  • Biocatalysis
  • Directed evolution
  • Enzymes
  • Ionic liquid
  • Lignin
  • Protein engineering

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

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