Harnessing Deep Eutectic Solvents and Mesoporous Silica Nanospheres Immobilization for Supercharged Amine Dehydrogenase Catalysis in Continuous Flow

Abstract

Chiral amines are key building blocks in pharmaceuticals, yet their efficient and sustainable synthesis via amine dehydrogenase (AmDH) remains challenging due to limitations in substrate loading, enzyme stability, and process scalability. Herein, we report an integrated biocatalytic platform for asymmetric reductive amination (ARA) that synergistically combines a bienzymatic system (CalAmDH for ARA and GDH for cofactor regeneration) with green solvent engineering, enzyme co-immobilization, and continuous-flow technology. A deep eutectic solvent (DES) buffer system based on betaine and acetic acid (Bet–HAc) was designed to enable high substrate concentrations, with molecular dynamics simulations revealing that the DES enhances CalAmDH activity and stability by suppressing an unfavorable helix-to-loop transition. Co-immobilization yielded a robust catalyst that, in a continuous-flow reactor, achieved high conversion, excellent enantioselectivity (>99% ee), and a space-time yield (STY) of 49.11 g·L⁻¹·h⁻¹. This represents a 185-fold enhancement over prior reports and demonstrates the power of combining DES-mediated stabilization with process intensification for the green, scalable synthesis of chiral amines.