Immobilized laccase-catalyzed coupling for construction of silk fibroinlignin composite hydrogels

Laccase (Lac) is an environmentally friendly commercially available low-cost biocatalyst that can act on phenolic groups at room temperature using ambient air. In this study, Lac immobilized silk fibroin (SF)-based hydrogels were employed to simultaneously absorb alkaline lignin (AL) and graft AL on SF to fabricate SF-AL composite hydrogels. The immobilized Lac retained highly active, and mainly catalyzed inter- and intra-molecular covalent coupling between the phenolic groups of AL and the tyrosine residues of SF. Through imparting the unique structure of lignin, the SF-AL composite hydrogels exhibited improved mechanical strength and anti-ultraviolet properties over the SF-based hydrogels. By making good use of Lac and turning diffusional limitations in Lac immobilization into advantages, this study developed a new efficient approach for production of sustainable value-added materials based on silk and lignin. This study offers a promising strategy to exploit the enormous potential of these natural biopolymers and enzymes.