Degradation of a non-phenolic β-0-4 lignin model dimer by Cerrena unicolor laccase and mediators, acetovanillone and acetosyringone

This study focuses on the laccase and mediator co-operation in modelling lignin dimer veratrylglycerol-β-vanillate ether (WE) oxidation. Earlier we stated that constitutive laccase isolated from Cerrena unicolor can cooperate with acetovanillone (AV) and acetosyringone (AS) in degradation of high molecular fraction of lignosulfonates. The fungus C. unicolor is known as a very good producer of cheap constitutive laccase. Its cultivation for this reason does not require stimulation by the expensive and toxic inducer like 2,5-xylidine. The main purpose of present study is to examine capability of C. unicolor laccase to oxidize VVE, which is a non-phenolic lignin model compound with external mediator HBT, and AV and AS in order to choose one, most efficient system. In the presence of laccase, generation of monomeric aromatic acids from non-phenolic lignin model dimer veratrylglycerol-β-vanillate ether (WE) was observed. The addition of acetovanillone (AV) or acetosyringone (AS) intensified this process, i.e. transformation was more extensive than in the experiments omitting mediators. Among the products, isovanillic (IA) and vanillic (VA) acids were identified.