HKUST-1 catalyzed efficient in situ regeneration of NAD+ for dehydrogenase mediated oxidation

Abstract

The combination of enzymatic and chemical reactions to achieve co-operative chemo-enzymatic processes has presented many challenges for decades. In this work, alcohol dehydrogenase (ADH) was encapsulated into metal-organic framework HKUST-1 crystals through an in situ approach to construct a synergistic chemo- and bio-catalysis system, where ADH was for the conversion of benzyl alcohol to benzaldehyde, and HKUST-1 was in charge for the regeneration of β-nicotinamide adenine dinucleotide (NAD+, the oxidized cofactor). It was found that HKUST-1 was a versatile catalyst for efficient oxidation of NADH in different buffers. The Michaelis-Menten kinetic parameters of immobilized ADH exhibited an increased KM (approximately 1.3-fold) and a decreased Vmax (approximately 4.7-fold) compared to free ADH. Due to the protection of HKUST-1, the immobilized enzyme showed a better resistance against urea and organic solvents compared with free enzyme, and still maintained 93% of its original activity after 6 cycles. The immobilized enzyme was successfully applied to the enzymatic transformation of benzyl alcohol to benzaldehyde in aqueous media at room temperature. Owing to the oxidized cofactor regeneration by HKUST-1, ADH@HKUST-1 composites achieved a benzaldehyde yield of 28.5%, which was approximately 4.3-fold higher than that of the individual bio-catalysis. This concept of combining chemo- and bio-catalysis may provide a novel and versatile technique for applications in biochemical catalysis, biosensors and drug delivery.