Magnetically agitated continuous-flow tube reactors with aspartate ammonia-lyase immobilized on magnetic nanoparticles

Imarah, Ali O. and Silva, Fausto M. W. G. and Bataa, Naran and Decsi, Balázs and Balogh Weiser, Diána and Poppe, László (2023) Magnetically agitated continuous-flow tube reactors with aspartate ammonia-lyase immobilized on magnetic nanoparticles. REACTION CHEMISTRY & ENGINEERING, 8. pp. 1250-1259. ISSN 2058-9883

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Abstract

Two magnetically agitated continuous-flow tube reactors (AFRs)—applying external permanent magnets to move magnetic nanoparticles coated with a biocatalyst within a stream of the reaction medium—were developed and studied with aspartate ammonia-lyase (AAL) from Pseudomonas fluorescens immobilized onto epoxy-functionalized magnetic nanoparticles (MNPs) by covalent binding. The biotransformation of L-aspartate to fumarate by the AAL-MNPs (5 mg, D = 420 nm, 6 μg g−1 AAL) took place in the reaction tube (PTFE, ID 2.15 mm) of both AFRs in a space containing the AAL-MNPs agitated within the flow of the reaction medium (0.5 mM L-aspartate solution, 4.7–14 μL min−1, 25 °C) by two permanent ring magnets (N48 neodymium, 10 × 5 × 5 mm) positioned at a fixed distance in attraction mode. In the first version (AFRXM), the two magnets positioned at opposite sides of the reaction tube (distance: 20 mm) performed axial movement (amplitude: 8 mm, frequency: 40–140 mpm) along the Y-axis, being perpendicular to the X-axis of the tube. In the second version (AFRRM), the two magnets (distance: 10 mm from each other, 5 mm from the X-axis) performed rotation movement (frequency: 40–140 rpm) around the X-axis. Whereas in the AFRXM the AAL-MNPs formed a cloud moving back and forth, they created a ring-shaped cloud rotating within the tube in the AFRRM. The efficient internal mixing in the AFRRM at the best frequency (80 rpm) resulted in the highest apparent specific activity (Ub = 354–469 U g−1, at residence times of 2.5–7.5 min) of the AAL-MNPs in the reactors studied. In the other continuous-flow systems, significantly lower Ub values were achieved (135–290 U g−1 at 120 mpm in AFRXM; or 142–273 U g−1 and 64–129 U g−1 in tubular reactors anchoring MNPs in static mode with double or single magnets, respectively), whereas more than a magnitude of order lower values could be realised in the batch mode reactors (11.4–14.9 U g−1 with rotational magnetic agitation at 120 rpm; 5.0–5.8 U g−1 with axial magnetic agitation at 160 mpm; or 4.6–5.2 U g−1 in an orbital shaker at 600 rpm) at comparable reaction times (2.5–7.5 min).

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