Overexpression of endogenous multi‐copper oxidases mcoA and mcoC in Rhodococcus jostii RHA1 enhances lignin bioconversion to 2,4‐pyridine‐dicarboxylic acid

Abstract To improve the titre of lignin‐derived pyridine‐dicarboxylic acid (PDCA) products in engineered Rhodococcus jostii RHA1 strains, plasmid‐based overexpression of seven endogenous and exogenous lignin‐degrading genes was tested. Overexpression of endogenous multi‐copper oxidases mcoA , mcoB , and mcoC was found to enhance 2,4‐PDCA production by 2.5‐, 1.4‐, and 3.5‐fold, respectively, while overexpression of dye‐decolorizing peroxidase dypB was found to enhance titre by 1.4‐fold, and overexpression of Streptomyces viridosporus laccase enhanced titre by 1.3‐fold. The genomic context of the R. jostii mcoA gene suggests involvement in 4‐hydroxybenzoate utilization, which was consistent with enhanced whole cell biotransformation of 4‐hydroxybenzoate by R. jostii pTipQC2‐mcoA. These data support the role of multi‐copper oxidases in bacterial lignin degradation, and provide an opportunity to enhance titres of lignin‐derived bioproducts.