NADH oxidation in a microreactor catalysed by ADH immobilised on γ-Fe₂O₃ nanoparticles

Abstract

A new concept of nicotinamide adenine dinucleotide hydrate (NADH) oxidation which combines advantages of the microreactor technology with the advantages of magnetic nanoparticles (MNPs) application is developed. Acetaldehyde was used as a substrate for the NADH regeneration process while the reaction was performed in a batch reactor and in a microreactor using alcohol dehydrogenase (ADH)-loaded MNPs. Three different microreactor systems with MNPs were studied, two with stationary MNPs trapped on the inner surface of microchannel by permanent magnetic field and one where the MNPs actively moved across the channel (movement inside microchannel allowed by an oscillating magnetic field). In a reactor system with an oscillating magnetic field and an actively moving ADH-loaded MNPs 100% NADH conversion was achieved for residence time of just 2 min.

NADH Oxidation in a Microreactor with an Oscillating Magnetic Field

“…Acetaldehyde (c i,acetaldehyde = 40 mmol/L) was used as a [20], the same reaction, using ADH-loaded MNPs, was performed in a batch reactor (V = 1.5 mL) and in a poly(tetrafluoroethylene) (PTFE) tubular minireactor (length : diameter = 330:1 mm with internal volume of 0.27 mL). The results obtained indicated that the ADH-loaded MNPs could be efficiently used in the NADH oxidation process.…”

“…When working with tubular minireactor [20] equipped with electromagnet that generates oscillating magnetic field, the particles align themselves along the lines of magnetic flux. In this way, beads cover the whole channel cross-section in an almost parallel way.…”

“…In one of our previous work [20], ADH-loaded MNPs long-term was tested for t = 7 days at a total flow rate of Φ = 5 μL/min. Obtained results indicated that biocatalyst could be used for continuous operation, but constant decrease of conversion was observed practically from the start of the experiment.…”

“…According to literature, immobilized enzymes have greater thermal and operational stability at various pH values and ionic strengths. Therefore, they are more resistant to * ** * denaturation than the soluble native form of the enzyme [20]. In order to increase enzyme stability via covalent immobilization, and using all the advantages of magnetic nanoparticles, parallel research was performed [21].…”

“…Surface Activation and Enzyme Immobilization. The surface of chemically modified maghemite nanoparticles was then subject to activation [20,22,23]. Briefly, MNPs were washed with deionized water prior to exposure to 2% glutaraldehyde aqueous solution for 2 h. After the surface activation, MNPs were washed out with deionized water and the enzyme was introduced (γ ADH = 0.08 mg/mL) to attach during the 28 h. These conditions were determined to be optimal using evolutionary operation method (EVOP) [24][25][26] (data not shown).…”