NADH Oxidation in a Microreactor with an Oscillating Magnetic Field

Abstract

In this study, magnetic nanoparticles (MNPs) of maghemite (γ-Fe 2 O 3 ) were synthesized and characterized. The method of multifactor experimental design and evolutionary operation (EVOP) was used to optimize immobilization of the alcohol dehydrogenase (ADH) enzyme on MNPs. Optimal operating conditions for the immobilization process were determined (γ ADH = 0.08 mg/mL, 2% glutaraldehyde for surface activation, t = 28 h), and in such conditions, a specific activity of S.A. = 118 ± 6 U/mg and immobilization efficiency of η = 84.97 ± 3.67% were achieved. Compared to the native enzyme, ADH immobilized on MNPs retained 66.45 ± 3.66% of the initial activity. ADH immobilized on MNPs at optimal conditions was used as a biocatalyst for model reaction -NADH oxidation. NADH oxidation was performed in two different magnetic microreactor configurations: (1) microreactor equipped with permanent square magnets and (2) microreactor equipped with an electromagnet and an oscillating magnetic field that enables magnetic particles movement in the microreactor. In the system with the oscillating magnetic field, equal conversion (X = 100%) was achieved in 2-fold shorter residence time.

Flow Bioreactors as Complementary Tools for Biocatalytic Process Intensification

“…Different arrangements for immobilized reactors are used: i) biocatalyst immobilized on beads that are packed in the reactor, allowing for high enzyme load but being prone to excessive back-pressure (Configuration 2, Figure 2) [27]; ii) biocatalyst immobilized on the inner surface of the channels (coated wall reactor) (Configuration 3, Figure 2) [28]; iii) biocatalyst immobilized on a monolith contained in the microchannel (Configuration 4, Figure 2) [15], which minimizes the limitation of configurations 2 and 3; iv) biocatalyst immobilized on a membrane (Configuration 5, Figure 2), as reviewed recently [29,30]. A number of immobilization techniques are nowadays available for either using packed immobilized biocatalysts, also including the innovative use of magnetic nanoparticles, [31,32] or for directly attaching enzymes onto the reactor surface, also exploiting tagged enzymes [33][34][35]. Immobilization within the reactor allows to localize the enzyme in a microfluidic environment and to perform multienzymatic reactions where the sequential distribution of each enzyme across the structure of the reactor may be crucial to control the cascade reactions [36].…”

Recovery of Magnetic Catalysts: Advanced Design for Process Intensification

“…For example, the micro-QMS could be exploited by Šalić et al in order to recover the MMC used for the oxidation of NADH in a microreactor with an oscillating magnetic field. 22 , 24 , 50 However, the use of microfluidic platforms in industrial processes is scarce due to the huge gap between the volumetric throughputs that are required in industry compared to the ones provided by microdevices (for example, 5 μL·min –1 in the above-mentioned study of Šalić et al). 24 , 51 , 52 Increasing the volumetric throughput in microfluidic systems by enlarging their dimensions results in the fading of their key advantages, since they stem from the reduced size of microstructures.…”

“…In these systems, the dual role of the magnetic beads is noticeable, since they are not only used as enzyme carriers but also for enhancing mixing. 19 , 21 − 23 For example, Šalić et al 22 , 24 performed the oxidation of nicotinamide adenine dinucleotide hydrate (NADH), catalyzed by the alcohol dehydrogenase enzyme supported on magnetic nanoparticles, in a microreactor equipped with an electromagnet that generated the oscillating magnetic field. Once the reaction completes, the recovery of the particles is required in order to obtain an enzyme-MMCs free stream with the target product, as well as to recycle MMCs for further uses.…”

Development of Static Mixers for Millireactors and Their Production by Vat Photopolymerization

“…Microreactors are characterized by small volumes with limited production, making them suitable for laboratory-scale optimization of flow chemistry reactions [8,9]. In contrast to microreactors, millireactors have wider channels (an order of a few millimeters), which results in a lower pressure drop and higher pipe flow rate.…”