Biocatalytic conversion of lignin model oligomer using a laccase-mediator system

Area of Science:

• Biocatalysis and Enzyme Technology
• Polymer Chemistry
• Biomass Conversion

Background:

• Lignin, a complex biopolymer, presents challenges in biomass valorization due to its recalcitrant structure.
• Enzymatic approaches offer sustainable alternatives for lignin depolymerization.
• Understanding lignin degradation pathways is crucial for efficient biofuel and biochemical production.

Purpose of the Study:

• To investigate the biocatalytic efficacy of laccase from *Trametes versicolor* with 1-hydroxybenzotriazole (1-HBT) on a hexameric lignin model compound.
• To elucidate the degradation products and reaction mechanisms involved in this enzymatic conversion.
• To assess the potential for repolymerization of lignin fragments.

Main Methods:

• Utilized laccase enzyme from *Trametes versicolor* and the mediator 1-hydroxybenzotriazole (1-HBT).
• Applied the biocatalytic system to a hexameric lignin model compound containing common lignin linkages.
• Analyzed degradation products using mass spectrometry over a 24-hour period.

Main Results:

• Demonstrated effective cleavage of the lignin model compound, predominantly at the β-O-4 ether linkage.
• Identified a β-5 dimer intermediate, which was subsequently consumed into further degradation products.
• Observed mass spectrometric evidence of repolymerization, forming higher oligomers from degradation intermediates.

Conclusions:

• The laccase/1-HBT system is effective for lignin model compound breakdown, targeting key linkages.
• Proposed mechanistic pathways for the observed catalytic processes, including degradation and repolymerization.
• Highlights the complexity of enzymatic lignin conversion, involving both breakdown and potential re-formation of polymers.