Enzymatic decomposition and electrochemical study of alkali lignin by laccase (Trametes versicolor) in the presence of a natural mediator (methyl syringate)

Abstract

The electrochemical oxidation mechanism of alkali lignin in the presence of a laccase–mediator system (LMS) in an aerobic environment.

Greener Routes to Biomass Waste Valorization: Lignin Transformation Through Electrocatalysis for Renewable Chemicals and Fuels Production

“…Although copper-containing oxidases such as laccases can degrade lignin, they are not as effective for ECO due to their low electrochemical reduction potential [131][132][133][134] and their large size [135] and will require lower molecular weightm ediators as electron carriers.Y ao et al conducted two studies to investigate the effects of am ediator (methyl syringate) and ac ombined laccase-mediator system (LMS) (Myceliophthora thermophila [134] and Trametes versicolor [136] )o nt he electrochemical degradation of alkali lignin deposited on ag lassy carbon electrode disc. Interaction of the lignin with the LMS caused morphological changes on the lignin structure and significantly increased the surface area.…”

“…Studying lignin ECO in aerobic and anaerobic environments, four major mechanisms were proposed.I nt he absence of LMS under aerobic conditions, direct oxidation of lignin can be promoted by the oxygen reduction reaction( ORR). [134,136] In the presence of laccase (a known biocatalyst), surfacep henolic groups on the lignin structure can also be oxidized at high potentials and can be enhanced in aerobic environments aided by ORR. [136] In the presence of just the mediator,u nder aerobic conditions, both the surface phe-nolic groups and the more internal b-O-4 linkages can be oxidized as the small mediator radical formed at lower potential can access the internal lignin linkages via mesopores.…”

“…[134,136] In the presence of laccase (a known biocatalyst), surfacep henolic groups on the lignin structure can also be oxidized at high potentials and can be enhanced in aerobic environments aided by ORR. [136] In the presence of just the mediator,u nder aerobic conditions, both the surface phe-nolic groups and the more internal b-O-4 linkages can be oxidized as the small mediator radical formed at lower potential can access the internal lignin linkages via mesopores. [136] Finally,t he laccase-mediator combination has as ynergistic effect whereby charget ransfer between the laccase and the mediator promoted by ORR in an anaerobic environment resultsi n lignin oxidation at the lowest potential.…”

“…[136] In the presence of just the mediator,u nder aerobic conditions, both the surface phe-nolic groups and the more internal b-O-4 linkages can be oxidized as the small mediator radical formed at lower potential can access the internal lignin linkages via mesopores. [136] Finally,t he laccase-mediator combination has as ynergistic effect whereby charget ransfer between the laccase and the mediator promoted by ORR in an anaerobic environment resultsi n lignin oxidation at the lowest potential. [136] More recently,R afiee et al studied the aminoxyl-mediated (TEMPO and 4-acetamido-TEMPO (ACT)) ECO of primary alcohol functionalities found in lignin model compounds and mild acidolysis extracted poplarl ignin to carboxylic acid.…”

Sponge-like N-doped carbon materials with Co-based nanoparticles derived from biomass as highly efficient electrocatalysts for the oxygen reduction reaction in alkaline media

“…Soybean straws are abundant renewable biomass riched in celluloses, hemicelluloses and lignin 37,38 and these contents can contribute to enhancing the activity of ORR catalysts. 39,40 To the best of our knowledge, there is no report about a facile method to synthesize ORR catalysts derived from soybean straws. Herein, the electrocatalysts (CoNASS) with N and Co co-doped spongiform porous carbon materials were prepared by a two-step method.…”