Laccase‐Mediated Grafting on Biopolymers and Synthetic Polymers: A Critical Review

Abstract

Laccase‐mediated grafting on lignocelluloses has gained considerable attention as an environmentally benign method to covalently modify wood, paper and cork. In recent decades this technique has also been employed to modify fibres with a polysaccharide backbone, such as cellulose or chitosan, to infer colouration, antimicrobial activity or antioxidant activity to the material. The scope of this approach has been further widened by researchers, who apply mediators or high redox potential laccases and those that modify synthetic polymers and proteins. In all cases, the methodology relies on one‐ or two‐electron oxidation of the surface functional groups or of the graftable molecule in solution. However, similar results can very often be achieved through simple deposition, even after extensive washing. This unintended adsorption of the active substance could have an adverse effect on the durability of the applied coating. Differentiating between actual covalent binding and adsorption is therefore essential, but proves to be challenging. This review not only covers excellent research on the topic of laccase‐mediated grafting over the last five to ten years, but also provides a critical comparison to highlight either the lack or presence of compelling evidence for covalent grafting.

Polymerization of Horseradish Peroxidase by a Laccase‐Catalyzed Tyrosine Coupling Reaction

“…To the best of our knowledge, until now, researchers have used mediators to assist laccase in the oxidation reaction of phenolic compounds and to initiate the protein polymerization. Most of the mediators are phenolic acids and their derivatives including ferulic acid, p‐ coumaric acid, caffeic acid, vanillic acid, and hydrolyzed oat spelt xylan (hOSX) . The mediators are small molecules and possess high reactivity against laccase to form radicals.…”

“…Recently, we fused tyrosine‐tags (Y‐tags) with target proteins and polymerized them via tyrosyl radicals to form a dityrosine‐based protein polymer backbone . The Y‐tags can be recognized by some enzymes, such as peroxidases, tyrosinase, and laccases . Among these enzymes, laccase is a promising enzyme for post‐translational modifications (PTMs) targeting Y‐tagged proteins.…”

Laccase‐Mediated Catalyzed Fluorescent Reporter Deposition for Live‐Cell Imaging

“…Moreover, laccase has been suggested as a useful agent for treating contaminated water, and removing phenol constituents in various food or beverages . In academic research, laccase has been used for the chemical transformations of small molecules, production of polymers, as an enzyme in ELISA, and in biosensing applications . This research has led to the development of modified laccases with a variety of properties, including stability in organic solvents and improved reactivity in biological media …”

Enzyme biotechnology in degradation and modification of plant cell wall polymers

“…The redox enzymes, most commonly laccases, have been applied in grafting of different compounds on fiber surfaces, typically by radical coupling between the fiber surface lignin and a phenolic compound (Table ). The laccase‐mediated grafting of natural and synthetic polymers has been recently been thoroughly reviewed by Slagman et al (). The common goals in grafting have been to introduce antimicrobial properties, increase hydrophobicity or alter charge properties of fibers and other wood products (Table ).…”