Application of<i>Rhodococcus jostii</i>RHA1 glycolate oxidase as an efficient accessory enzyme for lignin conversion by bacterial Dyp peroxidase enzymes

Abstract

Lignin oxidation by bacterial dye-decolorizing peroxidase enzymes requires hydrogen peroxide as a co-substrate, an unstable and corrosive oxidant. We have identified a glycolate oxidase enzyme from <i>Rhodococcus jostii</i> RHA1 that can couple effectively at pH 6.5 with DyP peroxidase enzymes from <i>Agrobacterium</i> sp. or <i>Comamonas testosteroni</i> to oxidise lignin substrates without addition of hydrogen peroxide. <i>Rhodococcus jostii</i> RHA1 glycolate oxidase (RjGlOx) has activity for oxidation of a range of α-ketoaldehyde and α-hydroxyacid substrates, and is also active for oxidation of hydroxymethylfurfural (HMF) to furandicarboxylic acid. The combination of RjGlOx with <i>Agrobacterium</i> sp. DyP or <i>C. testosteroni</i> DyP generated new and enhanced amounts of low molecular weight aromatic products from organosolv lignin substrates, and was able to generate high-value products from treatment of lignin residue from cellulosic biofuel production, and from a polymeric humin substrate.