Regioselective Biocatalytic Aromatic Hydroxylation in a Gas–Liquid Multiphase Tube‐in‐Tube Reactor

Abstract

Abstract Microreactors provide higher mass transfer rates than do conventional batch reactors. A tube‐in‐tube microreactor was used for the NADH‐dependent in vitro conversion of 2‐hydroxybiphenyl to 3‐phenylcatechol that was catalysed by 2‐hydroxybiphenyl 3‐monooxygenase. A biphasic reaction system allowed high substrate loadings, whereas the microreactor ensured excellent mass transfer rates between the organic and aqueous phases. Oxygen was supplied continuously by membrane aeration across the whole reaction compartment. The productivities achieved in the tube‐in‐tube microreactor were 38 times higher than those in previously described batch reactors and almost 4 times higher than for the same reaction in a microreactor in which aqueous, organic, and air phases were delivered through consecutive segments. This set‐up is a promising concept for oxygen‐dependent biocatalytic reactions in microreactors and is developing as a basis for applications in gram‐scale organic biosyntheses.