Laccase as a Tool in Building Advanced Lignin-Based Materials.

Lignin is an abundant natural feedstock that offers great potential as a renewable substitute for fossil-based. Its polyaromatic structure and unique properties have attracted significant research efforts. The advantages of an enzymatic over chemical or thermal approach to construct or deconstruct lignins are it operates in mild conditions, requires less energy and usually uses non-toxic chemicals. Laccase is a widely investigated oxidative enzyme that can catalyze the polymerization and depolymerization of lignin. Its dual nature causes a challenge in controlling the overall direction of lignin-laccase catalysis. In this review paper, the factors that affect laccase-catalyzed lignin polymerization were summarized, evaluated, and compared in order to identify key features that favor lignin polymerization. In addition, a critical assessment of the conditions that enabled production of novel lignin hybrids via laccase-catalyzed grafting were presented. To assess the industrial relevance of laccase-assisted lignin valorization, patented applications were surveyed and industrial challenges and opportunities were analyzed. Finally, our perspective in realizing the full potential of laccase in building lignin-based materials for advanced applications was deduced from analysis of the limitations governing laccase-assisted lignin polymerization and grafting.