Engineered PQQ-Dependent Alcohol Dehydrogenase for the Oxidation of 5-(Hydroxymethyl)furoic Acid

Furan-2,5-dicarboxylic acid (FDCA) is a bio-based platform chemical with the potential to replace terephthalic acid in the production of polymers. A critical step for enzymatic and whole-cell production of FDCA from 5-(hydroxymethyl)furfural (HMF) is the transformation of 5-(hydroxymethyl)furoic acid (HMFA) into 5-formylfuroic acid (FFA). Here, we establish periplasmic pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases (ADHs) as biocatalytic tools for the oxidation of HMFA, HMF, and 5-formylfurfural (FFF). Further, we identify several amino acid residues including the "lid loop" of the substrate channel as promising targets for future engineering steps toward a fully periplasmic oxidation pathway to FDCA.