Enzymatic microreactors in biocatalysis: history, features, and future perspectives

Abstract

Microfluidic reaction devices are a very promising technology for chemical and biochemical processes. In microreactors, the micro dimensions, coupled with a high surface area/volume ratio, permit rapid heat exchange and mass transfer, resulting in higher reaction yields and reaction rates than in conventional reactors. Moreover, the lower energy consumption and easier separation of products permit these systems to have a lower environmental impact compared to macroscale, conventional reactors. Due to these benefits, the use of microreactors is increasing in the biocatalysis field, both by using enzymes in solution and their immobilized counterparts. Following an introduction to the most common applications of microreactors in chemical processes, a broad overview will be given of the latest applications in biocatalytic processes performed in microreactors with free or immobilized enzymes. In particular, attention is given to the nature of the materials used as a support for the enzymes and the strategies employed for their immobilization. Mathematical and engineering aspects concerning fluid dynamics in microreactors were also taken into account as fundamental factors for the optimization of these systems.

Hydroxynitrile lyases covalently immobilized in continuous flow microreactors

“…Recently, the application of immobilized enzymes in continuous flow (micro) reactors is gaining momentum. [15][16][17][18][19][20][21][22] Flow systems are advantageous compared to batch operation as no catalyst separation step is required, the catalyst can easily be reused, higher productivities can be achieved and catalyst instability problems due to high shear forces are precluded. [23][24][25] Additionally, the microreactor technology provides a handle to tune reaction conditions, facile scale-out by parallelizing multiple units and process intensification or even automation.…”

Flow Process for Ketone Reduction Using a Superabsorber-Immobilized Alcohol Dehydrogenase from Lactobacillus brevis in a Packed-Bed Reactor

“…In particular, for active pharmaceutical ingredients (APIs), this aspect is important, as the FDA along with the EPA, as the respective institutions in United States and Europe for approval of medicines, added aspects of continuous manufacturing to their guidelines [2,3], whereas for a long time the focus of flow processes was on "classic" chemical processes with, for example, hazardous and thermally labile substances and chemocatalytic reactions [4][5][6]. Recently, biocatalysis in flow processes has become an emerging field with an increasing number of examples [7][8][9]. An enzymatic reaction of particular interest for an application in flow mode due to its matured technology level is asymmetric ketone reduction, having a proven track record underlined by many successful examples demonstrated in the past for the batch mode [10][11][12][13].…”

Let the substrate flow, not the enzyme: Practical immobilization of d‐amino acid oxidase in a glass microreactor for effective biocatalytic conversions

“…There is a strong trend to shift bio‐chemical transformations from batchwise to continuous operation (Adamo et al, ; Gutmann et al, ). Microstructured flow reactors constitute an emerging class of microprocess engineering tools for continuous bioprocess development (Bolivar et al, ; Laurenti and dos Santos Vianna Jr., ; Wohlgemuth et al, ). Universal feature of these microreactors is their operation under continuous flow.…”

“…Exploiting enzymes in continuous reactions usually requires their reuse for multiple rounds of conversion (Buchholz and Kasche, 2005;Illanes and Altamirano, 2010). Achieving this in a microreactor is not an easy task (Bolivar and Nidetzky, 2013a;Laurenti and dos Santos Vianna Jr., 2016;Matosevic et al, 2011;Miyazaki et al, 2008;Wohlgemuth et al, 2015;Yesil-Celiktas, 2014). Immobilizing the enzymes on microchannel walls is a promising approach.…”

“…As shown in this study, a fusion protein approach for direct immobilization of enzymes on glass represents an attractive solution. Glass is a biocompatible and chemically resistant material widely used for fabrication of microstructured plates (Laurenti and dos Santos Vianna Jr., 2016;Lee et al, 2003;Miyazaki and Maeda, 2006;Wohlgemuth et al, 2015;Yesil-Celiktas, 2014;). Z basic2 is a three-helical mini-protein of about 7 kDa mass.…”