Immobilization of invertase on silica monoliths with hierarchical pore structure to obtain continuous flow enzymatic microreactors of high performance

Monolithic silica rods of 4 mm diameter and 2–5 cm length, exhibiting very open and uniform 3D hierarchical pore structure of 35 μm flow-through macropores and ca. 20 nm mesopores were synthesized using the sol–gel processing combined with pore templating and phase separation. These monoliths were successfully converted into miniaturized multichannel continuous-flow reactors which (for a single rod) could operate at flow rates up to about 20 mL/min at backpressure not exceeding 2.5 bar. After covalent attachment of invertase, considered as a model enzyme, their potentials were tested in reaction of sucrose hydrolysis and the results were compared, using Michaelis–Menten kinetics, with the performance of mesoporous cellular foam (MCF)-bound invertase immobilized in the same way. The hydrolysis of sucrose appeared to proceed with maximum velocity over 1000 times faster in the monolithic bioreactor than in MCF-based slurry system, and invertase embedded in the mesopores of silica monoliths showed notably larger affinity (lower KM) to substrate than the native enzyme. The reactors stored at 4 °C retained initial activity for at least 6 week and no change in the microreactor performance was seen for at least 2 week of continuous operation.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Silica monoliths with very open and uniform bi-modal pore structure were prepared. ► Monoliths were successfully converted into continuous micro-bioreactors. ► A single rod microreactor could operate at flow rates up to 20 mL/min at <2.5 bar. ► Invertase embedded in silica matrix was exceptionally active in sucrose hydrolysis. ► Micro-bioreactors properties remained stable for at least two weeks of operation.