Status of Biocatalysis in the Production of 2,5-Furandicarboxylic Acid

2,5-Furandicarboxylic acid (FDCA) is an increasingly important platform chemical that may be produced via thermochemical, photochemical, electrochemical, or biocatalysis. Biocatalysis is preferred as it can be performed under mild reaction conditions, in an aqueous environment, and can involve benign oxidants (molecular oxygen) and biodegradable catalysts (enzymes and cells). Whole cells and isolated enzymes have both been demonstrated effectively catalyze the biotransformation of HMF (5-(hydroxymethyl)furfural) to FDCA. Whole cell biocatalysts are robust and benefit from endogenously produced cofactors (which are otherwise expensive stoichiometric reagents). However, wild-type organisms suffer from catabolic pathways which yield many side products and catabolize FDCA. Thus, whole cells require metabolic modification to favor certain pathways and eliminate others to be viable. With clear pathways and simple reaction conditions, isolated enzymes allow for better control and easier product recovery. However, no individual enzyme effectively catalyzes the full oxidation of HMF to FDCA, and thus, cofactors, mediators, immobilization, mutation, or cooperation with other enzymes is employed to achieve complete oxidation. Herein, a comprehensive review of the biocatalytic methods for converting HMF to FDCA is presented. Moreover, general strategies for alcohol and aldehyde oxidation are also discussed to provide a more complete context.