Overexpression of Endogenous Multi-Copper Oxidases Mcoa and Mcoc in Rhodococcus Jostii RHA1 Enhances Lignin Bioconversion to 2,4-Pyridine-dicarboxylic Acid

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.