Abstract
Sustainable catalysts for the oxidation of phenol derivatives under environmentally friendly conditions were prepared by the functionalization of lignin nanoparticles with tyrosinase. Lignin, the most abundant polyphenol in nature, is the main byproduct in the pulp and paper manufacturing industry and biorefinery. Tyrosinase has been immobilized by direct adsorption, encapsulation, and layer-by-layer deposition, with or without glutaraldehyde reticulation. Lignin nanoparticles were found to be stable to the tyrosinase activity. After the enzyme immobilization, they showed a moderate to high catalytic effect in the synthesis of catechol derivatives, with the efficacy of the catalyst being dependent on the specific immobilization procedures.
Highlights
It is assumed that renewable materials might play a key role in Circular Economy due to their unique environmentally benign properties [1]
We described the preparation of heterogeneous catalysts for the synthesis of bioactive catechol derivatives by the immobilization of tyrosinase on microcapsules of the epoxy resin Eupergit [27,28], and as an alternative, by Layer-by-layer coating of the enzyme on Multi Walled Carbon Nanotubes (MWCNTs) [29]
The secondary metabolites resembling the dimeric units of lignin, generally showed inhibitory activity against tyrosinase [44,45,46], and the catalytic effect of tyrosinase in the oxidation of milled wood lignin was found to be negligible with respect to that of laccase and horseradish peroxidase [47]
Summary
It is assumed that renewable materials might play a key role in Circular Economy due to their unique environmentally benign properties [1]. Lignin byproducts are low cost materials that perform as well as petroleum-derived counterparts, showing beneficial properties associated with their aromatic character, such as antioxidant activity [4,5], UV-shielding protection [6,7], anticorrosion effects [8], and electrochemical responsiveness in both charge storage composites [9] and electrochemical sensors [10] For this reason, lignin is emerging as a new and inexpensive raw material for the preparation of nanocapsules with increased chemical and physical properties [11,12,13,14], due to the direct consequence of “size-effect” phenomena [15]. Lignin-based tyrosinase catalysts prepared by LbL assembly showed activity and kinetic parameters of the same order of magnitude, or higher than, those previously reported for catalysts based on the use of traditional inorganic supports
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