A peptide-based conductive hydrogel capable of in situ bioelectrocatalytic NADH regeneration for sustained production of 1-propanol†

Abstract

Nicotinamide-adenine dinucleotide (NAD⁺/NADH) is a coenzyme that acts as a donor and acceptor of electrons in redox reactions within all eukaryotic cells. The reduction of NAD⁺ produces NADH that subsequently acts as the key electron carrier. However, limited stability of enzymes under operational conditions, unwanted by-products and limited external electron donors result in low efficiency of NADH regeneration to drive the downstream enzymatic reactions. Herein, we modularly designed a peptide hydrogel, which provided an appropriate physiological microenvironment for maintaining the bioactivity of alcohol dehydrogenase. Meanwhile, Bi nanoparticles were in situ synthesized and doped into nanofibers during the peptide self-assembly to afford a conductive hydrogel with enhanced bioelectrocatalytic efficiency. Both linear sweep voltammetry and chronoamperometry data unveiled excellent electrochemical performance of this hydrogel for sustained NADH regeneration at low potential (−0.37 V vs. RHE). Even at a relatively high potential of −0.79 V vs. RHE, the yield of NADH for 10 h was as high as 81%. The regenerated NADH could further drive propionaldehyde alcoholization to produce 1-propanol sustainably with a rate of 1.34 mM h⁻¹ at −0.62 V (vs. RHE). Overall, this peptide-based conductive hydrogel could achieve sustained 1-propanol production by leveraging in situ bioelectrocatalytic NADH regeneration, demonstrating a promising approach for electroenzymatic biofuel and pharmaceutical production.