μMORE: A microfluidic magnetic oscillation reactor for accelerated parameter optimization in biocatalysis

• Construction of a microfluidic device for biotransformations.
• Parallelized parameter optimization for biocatalytic processes at μscale.
• Magnetic bead-based enzyme immobilization, retention, and microfluidic mixing.
• His-tag immobilized thiamin diphosphate-dependent enzyme.
• Benzoylformate decarboxylase catalyzed formation of (R)-2-hydroxy-1-phenylpropan-1-one.

Enzymatic parameter determination is an essential step in biocatalytic process development. Therefore higher throughput in miniaturized devices is urgently needed. An ideal microfluidic device should combine easy immobilization and retention of a minimal amount of biocatalyst with a well-mixed reaction volume. Together, all criteria are hardly met by current tools. Here we describe a microfluidic reactor (μMORE) which employs magnetic particles for both enzyme immobilization and efficient mixing using two permanent magnets placed in rotating cylinders next to the a glass chip reactor. The chip geometry and agitation speed was optimized by investigation of the mixing and retention characteristics using simulation and dye distribution analysis. Subsequently, the μMORE was successfully applied to determine critical biocatalytic process parameters in a parallelized manner for the carboligation of benzaldehyde and acetaldehyde to (S)-2-hydroxy-1-phenylpropan-1-one with less than 5 μg of benzoylformate decarboxylase from Pseudomonas putida immobilized on magnetic beads. Here, one run of the device in six parallelized glass reactors took only 2–3 h for an immobilized enzyme with very low activity (∼2 U/mg). The optimized parameter set was finally tested in a 10 mL enzyme membrane reactor, demonstrating that the μMORE provides a solid data base for biocatalytic process optimization.