Monolithic flow reactor for enzymatic oxidations

BACKGROUND Oxidation is among the most important reactions in organic chemistry. Enzymatic oxidation offers a greener alternative to a conventional chemo‐catalytic approach and opens the potential for new reactions. However, inefficient use of expensive enzymes and oxygen (O2) limitations represent particular challenges for biocatalytic reactor design. This work reports a new tubular reactor for continuous flow enzymatic oxidations. RESULTS The reactor comprises a thiol‐functional porous monolith (0.93 ± 0.16 m2 g−1) and an O2‐permeable wall (115 600 ± 1500 mL m−2 day−1). The monolith retains enzyme inside the reactor leading to efficient use. The wall acts as a membrane contactor providing transport of O2 from atmospheric air to the immediate proximity of the enzyme inside the reactor, without any pressure and sparging required. The reactor performance was demonstrated using oxidation of glucose by glucose oxidase (EC 1.1.3.4) coupled with in situ consumption of hydrogen peroxide by horseradish peroxidase (EC 1.11.1.7). At a constant flow rate of 0.1 mL min−1, the product concentration reached 0.10 mmol L−1 after 1.5 h and continued to be relatively high for the next ≥10 h. Overall, the reactor remained active for >40 h using only 15 μg glucose oxidase. Furthermore, the reactor could be rejuvenated by periodic injection of fresh enzyme and thus can operate continuously for extended periods. CONCLUSION We have shown here an alternative approach to efficient enzyme use and O2 delivery. Moreover, with its flexible design, the reactor can be optimized to accommodate a range of gas‐dependent biocatalytic transformations.