Redox-Switchable Biocatalyst for Controllable Oxidation or Reduction of 5-Hydroxymethylfurfural into High-Value Derivatives.

Biocatalytic upgrading of biomass-derived 5-hydroxymethylfurfural (HMF) into high-value derivatives is of great significance in green chemistry. In this study, we disclosed the successful utilization of whole-cell F18 for its switchable catalytic performance in the on-demand catalysis of HMF to different value-added derivatives, namely, selective reduction to 2,5-bis(hydroxymethyl)furan (BHMF) or oxidation to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). Based on the fine-tuning of biochemical properties, the biocatalyst can proceed an efficient hydrogenation reaction toward HMF with a good selectivity of 97.6% to yield the BHMF at 92.2%. Noteworthily, BHMF could be further oxidized to HMFCA and 2,5-furandicarboxylic acid (FDCA) by the whole cell. To realize the on-demand syntheses of HMFCA, the genes encoding HMF oxidoreductase/oxidase of whole-cell F18 were then deleted to prevent the further conversion of HMFCA to FDCA, which led to a 10-fold decrease of FDCA. Thus, an HMF conversion of 100% with an HMFCA yield of 98.3% was finally achieved by the engineered whole cell at a substrate concentration of 150 mM. Moreover, HMFCA synthesis was efficiently prepared with an excellent selectivity of 96.3% and a yield of 85.1% even at a high substrate concentration of up to 200 mM.