Abstract
Optically pure chiral amines represent ubiquitous pharmacophores in the synthesis of pharmaceuticals, agrochemicals, and fine chemical intermediates. While ω-transaminases (ω-TAs) offer an environmentally benign and stereochemically superior route to these molecules, batch biocatalysis is frequently hampered by thermodynamic equilibrium constraints, severe product inhibition, and limited operational enzyme stability. In this study, an engineered (S)-selective ω-transaminase from Chromobacterium violaceum was covalently immobilized onto glutaraldehyde-functionalized magnetic core-shell mesoporous silica nanoparticles (M-MSNs) and incorporated into a continuous-flow packed-bed microfluidic reactor. The immobilized biocatalytic nanocomposite exhibited an immobilization efficiency of 88.4% and maintained over 82% of its native catalytic activity. Under continuous-flow microfluidic operation, residence times were systematically optimized between 5 and 45 minutes for the asymmetric amination of various prochiral ketones, utilizing isopropylamine as an abundant amine donor. The microreactor system achieved remarkable conversions of up to 96.2% with exceptional enantioselectivity (>99% ee) for model pharmaceutical precursors, including (S)-1-phenylethylamine and fluorinated phenylpropan-2-amine derivatives. Continuous operation for 72 hours revealed superior catalytic durability, retaining >90% of initial conversion without significant leaching or pressure drop. The platform yielded a space-time yield of 48.6 g·L-1·h-1, outperforming conventional batch reactors by an order of magnitude. These findings demonstrate that coupling nanostructured biocatalysts with microfluidic process intensification provides a robust, scalable pathway for the continuous asymmetric synthesis of pharmaceutical building blocks.
