Selective cleavage of lignin β-O-4 aryl ether bond by β-etherase of the white-rot fungus Dichomitus squalens.

Production of value-added compounds from a renewable aromatic polymer, lignin, has proven to be challenging. Chemical procedures, involving harsh reaction conditions, are costly and often result in nonselective degradation of lignin linkages. Therefore, enzymatic catalysis with selective cleavage of lignin bonds provides a sustainable option for lignin valorization. In this study, we describe the first functionally characterized fungal intracellular beta-etherase from the wood-degrading white-rot basidiomycete Dichomitus squalens. This enzyme, Ds-GST1, from the glutathione-Stransferase superfamily selectively cleaved the beta-O-4 aryl ether bond of a dimeric lignin model compound in a glutathionedependent reaction. Ds-GST1 also demonstrated activity on polymeric synthetic lignin fractions, shown by a decrease in molecular weight distribution of the lactase -oxidized guaiacyl dehydrogenation polymer. In addition to a possible role of DsGST1 in intracellular catabolism of lignin-derived aromatic compounds, the cleavage of the most abundant linkages in lignin under mild reaction conditions makes this biocatalyst an attractive green alternative in biotechnological applications.Peer reviewe