Sacrificial Substrate-Free Whole-Cell Biocatalysis for the Synthesis of 2,5-Furandicarboxylic Acid by Engineered Escherichia coli

2,5-Furandicarboxylic acid (FDCA) is a promising biobased building block for the synthesis of polymers. In this work, a novel whole-cell biocatalyst was constructed by coexpressing vanillin dehydrogenase (VDH1) and HMF/furfural oxidoreductase (HmfH) in Escherichia coli for cascade catalytic oxidation of 5-hydroxymethylfurfural (HMF) to FDCA under sacrificial substrate-free conditions. HMF was rapidly transformed to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) by VDH1, followed by subsequent oxidation to 5-formyl-2-furancarboxylic acid (FFCA) by HmfH, and finally, FFCA was converted to FDCA by VDH1 and/or HmfH. Under pH-controlled conditions, the biocatalyst enabled efficient synthesis of FDCA from 150 mM HMF in a 96% yield. Besides, FDCA was prepared in the gram scale with a productivity of around 0.4 g/L h.