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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. © 2021 Society of Chemical Industry (SCI).

Poly­(dimethylsiloxane) (PDMS) is an attractive, versatile, and convenient material for use in biomedical devices that are in direct contact with the user. A crucial component in such a device is its surface in terms of antimicrobial properties preventing infection. Moreover, due to its inherent hydrophobicity, PDMS is rather prone to microbial colonization. Thus, developing an antimicrobial PDMS surface in a simple, large-scale, and applicable manner is an essential step in fully exploiting PDMS in the biomedical device industry. Current chemical modification methods for PDMS surfaces are limited; therefore, we present herein a new method for introducing an atom transfer radical polymerization (ATRP) initiator onto the PDMS surface via the base-catalyzed grafting of [(chloromethyl)­phenylethyl]­trimethoxysilane to the PDMS. The initiator surface was grafted with poly­[2-(dimethylamino)­ethyl methacrylate] (PDMAEMA) brushes via a surface-initiated supplemental activator and reducing agent ATRP (SI-SARA-ATRP). The use of sodium sulfite as a novel reducing agent in SI-SARA-ATRP allowed for polymerization during complete exposure to air. Moreover, a fast and linear growth was observed for the polymer over time, leading to a 400 nm thick polymer layer in a 120 min reaction time. Furthermore, the grafted PDMAEMA was quaternized, using various alkylhalides, in order to study the effect on surface antimicrobial properties. It was shown that antimicrobial activity not only depended highly on the charge density but also on the amphiphilicity of the surface. The fast reaction rate, high oxygen tolerance, increased antimicrobial activity, and the overall robustness and simplicity of the presented method collectively move PDMS closer to its full-scale exploitation in biomedical devices.