Abstract
SummaryFungal laccases are attracting enzymes for sustainable valorization of biorefinery lignins. To improve the lignin oxidation capacity of two previously characterized laccase isoenzymes from the white‐rot fungus Obba rivulosa, we mutated their substrate‐binding site at T1. As a result, the pH optimum of the recombinantly produced laccase variant rOrLcc2‐D206N shifted by three units towards neutral pH. O. rivulosa laccase variants with redox mediators oxidized both the dimeric lignin model compound and biorefinery poplar lignin. Significant structural changes, such as selective benzylic α‐oxidation, were detected by nuclear magnetic resonance analysis, although no polymerization of lignin was observed by gel permeation chromatography. This suggests that especially rOrLcc2‐D206N is a promising candidate for lignin‐related applications.
Highlights
SummaryFungal laccases are attracting enzymes for sustainable valorization of biorefinery lignins
Lignocellulosic biorefinery concept utilizes various plant biomass resources for the production of biofuels and Laccases (EC 1.10.3.2) are copper (Cu)-containing oxidoreductase enzymes commonly present in wood-degrading fungal species
Molecular oxygen is reduced to water at the Type 2 (T2)/Type 3 (T3) site by the electrons transferred from the Type 1 (T1) site through highly conserved His–Cys–His tripeptide
Summary
Fungal laccases are attracting enzymes for sustainable valorization of biorefinery lignins. To improve the lignin oxidation capacity of two previously characterized laccase isoenzymes from the white-rot fungus Obba rivulosa, we mutated their substrate-binding site at T1. O. rivulosa laccase variants with redox mediators oxidized both the dimeric lignin model compound and biorefinery poplar lignin. Significant structural changes, such as selective benzylic aoxidation, were detected by nuclear magnetic resonance analysis, no polymerization of lignin was observed by gel permeation chromatography. This suggests that especially rOrLcc2-D206N is a promising candidate for lignin-related applications
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