Functionalized Metal-Organic Framework for NADH Regeneration by Hydrogen in a Redox Flow Bioreactor

Area of Science:

• Electrochemistry
• Catalysis
• Biotechnology

Background:

• Electrochemical regeneration of reduced nicotinamide adenine dinucleotide (NADH) is crucial for industrial chiral chemical synthesis.
• Current methods face limitations due to high NADH consumption and inefficient cyclic regeneration.
• Developing robust and efficient NADH regeneration systems is essential for broader industrial application.

Purpose of the Study:

• To develop an efficient and stable system for electrochemical NADH regeneration.
• To immobilize a rhodium catalyst ([Rh(Cp*)(bpy)Cl]+) onto a metal-organic framework (NU-1000) for enhanced stability and reusability.
• To demonstrate the system's efficacy in an enzymatic electrocatalytic process for chiral chemical synthesis.

Main Methods:

• In-situ growth of 3D ordered metal-organic framework (NU-1000) on graphite felt.
• [Rh(Cp*)(bpy)Cl]+ immobilization on Zr6 nodes of NU-1000 via solvent-assisted ligand incorporation (SALI).
• Application in a flow bioreactor coupled with a gas diffusion electrode (GDE) for H2 oxidation and NADH regeneration.
• Enzymatic electrocatalytic synthesis of L-lactate using L-lactate dehydrogenase (LDH).

Main Results:

• Achieved highly efficient enzymatic electrocatalytic synthesis of L-lactate.
• Demonstrated remarkable total turnover numbers (TTN): 19600 for [Rh(Cp*)(bpy)Cl]+ and 1750 for NAD+ after 48 hours.
• Obtained high turnover frequencies (TOF): 2350 h-1 for [Rh(Cp*)(bpy)Cl]+ and 210 h-1 for NAD+.
• The immobilized catalyst exhibited high stability and reusability in the flow system.

Conclusions:

• The developed system provides an efficient and sustainable method for electrochemical NADH regeneration.
• Immobilization of the rhodium catalyst within NU-1000 enhances its stability and catalytic activity.
• This approach offers significant potential for industrial-scale enzymatic electrosynthesis of chiral chemicals.