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Microfluidics, as the technology for continuous flow processing in microscale, is being increasingly elaborated on in enzyme biotechnology and biocatalysis. Enzymatic microreactors are a precious tool for the investigation of catalytic properties and optimization of reaction parameters in a thriving and high-yielding way. The utilization of magnetic forces in the overall microfluidic system has reinforced enzymatic processes, paving the way for novel applications in a variety of research fields. In this review, we hold a discussion on how different magnetic particles combined with the appropriate biocatalyst under the proper system configuration may constitute a powerful microsystem and provide a highly explorable scope.

In the present study, we developed novel β-glucosidase-based nano-biocatalysts for the bioconversion of oleuropein to hydroxytyrosol. Using non-covalent or covalent immobilization approaches, β-glucosidases from almonds and Thermotoga maritima were attached for the first time on oxidized and non-oxidized porous carbon cuboids (PCC). Various methods were used for the characterization of the bio-nanoconjugates, such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and fluorescence spectroscopy. The oxidation state of the nanο-support and the immobilization procedure play a key role for the immobilization efficiency or the catalytic activity of the immobilized β-glucosidases. The nano-biocatalysts were successfully used for the hydrolysis of oleuropein, which leads to the formation of its bioactive derivative, hydroxytyrosol (up to 2.4 g L−1), which is a phenolic compound with numerous health benefits. The bio-nanoconjugates exhibited high thermal and operational stability (up to 240 hours of repeated use), which indicated that they are efficient tools for various bio-transformations.

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Microreactor technology is being increasingly utilized in the field of biocatalysis, offering cost-effectiveness and environmental sustainability. On the other hand, enzyme immobilization on nanomaterials can provide biocatalytic systems with the operational stability demands of an intensified bioprocess. Combining the methodology for ZnO nanowire growth on glass surfaces with enzyme immobilization techniques, we developed a novel continuous-flow microbioreactor system, with β-glucosidase activity. Morphological, spectroscopic, and biocatalytic characterization of the developed enzyme microreactor is presented. The immobilized enzyme exhibited almost 100% remaining hydrolytic activity after 1000 cycles of continuous use and more than 70% residual activity after 24 h of exposure to different organic solvents. The system productivity was enhanced up to 10 times compared to the free enzyme form and 30 times compared to the batch immobilized system. Compared to previous studies in batch reactor systems, the enzyme microbioreactor exhibited a productivity enhancement of 315 and 12 times, respectively, for the continuous glycosylation of the natural compounds perillyl alcohol and tyrosol toward the synthesis of their bioactive glycosylated derivatives. The entire arrangement seems to provide a proper microenvironment for enzyme stabilization, under the scope to broaden the biocatalyst’s potentiality.