Efficient synthesis of 5-hydroxymethyl-2-furancarboxylic acid by Escherichia coli overexpressing aldehyde dehydrogenases

Catalytic transformation of biomass-derived furans into value-added chemicals and biofuels has received considerable interest recently. In this work, aldehyde dehydrogenases (ALDHs) were identified from Comamonas testosteroni SC1588 for the oxidation of bio-based furans into furan carboxylic acids. Of the whole-cell biocatalysts constructed, Escherichia coli expressing a vanillin dehydrogenase (E. coli_CtVDH1) proved to be the best for the oxidation of 5-hydroxymethylfurfural (HMF). 5-Hydroxymethyl-2-furancarboxylic acid (HMFCA) was obtained in the yield of approximately 92 % within 12 h using this recombinant strain when the HMF concentration was up to 200 mM. In a fed-batch process, 292 mM of HMFCA was produced within 20.5 h, thereby providing a productivity as high as 2.0 g/L h. Other furan carboxylic acids were synthesized in the yields of 83-95%. Besides, the partially purified HMF was smoothly converted into HMFCA by this recombinant strain, with a 90% yield.