Furan Carboxylic Acids Production with High Productivity by Cofactor-engineered Whole-cell Biocatalysts

Graphical Whole-cell biocatalysis : Cofactor-engineered E. coli cells proved to be versatile catalysts to produce furan carboxylic acids from toxic biobased furans with high productivities. The introduction of NADH oxidase (NOX) into E. coli harboring aldehyde dehydrogenases (ALDHs) significantly promoted intracellular NAD + regeneration, thus enhancing ALDH-catalyzed aldehyde oxidation. A group of aromatic aldehydes was efficiently oxidized to target carboxylic acids. More importantly, these engineered whole-cell biocatalysts displayed high substrate tolerance toward toxic furans. Furan carboxylic acids are useful chemicals in various industries. In this work, biocatalytic production of furan carboxylic acids was reported with high productivities by cofactor-engineered Escherichia coli cells. NADH oxidase (NOX) was introduced into E. coli harboring aldehyde dehydrogenases (ALDHs) to promote intracellular NAD + regeneration, thus significantly enhancing ALDH-catalyzed oxidation. These engineered biocatalysts were capable of efficient aerobic oxidation of a variety of aromatic aldehydes. More importantly, they exhibited high substrate tolerance toward toxic furans. E. coli co-expressing vanillin dehydrogenase and NOX ( E. coli_ CtVDH1_NOX) enabled efficient oxidation of 250 mM of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), providing a productivity of 3.7 g/L h. With E. coli_ CtVDH2_NOX as catalyst, up to 240 mM of furfural and 5-methoxymethylfurfural (MMF) could be smoothly oxidized. 2-Furoic acid (FCA, 227 mM) and 5-methoxymethyl-2-furancarboxylic acid (MMFCA, 287 mM) were produced in fed-batch synthesis, providing the productivities of 2.0 and 5.6 g/L h, respectively.