Preparation of proteolytic microreactors by freeze-drying immobilization

highlights
• Protease (enzyme) was immobilized in a freeze-dried micromonolith directly prepared in a microreactor.
• The reactors demonstrated continuous proteolytic activity for 9 days with considerable reaction yields.
• The proteolytic product varied depending on the flow rates and the microchannel patterns.
• The proteolytic performance was significantly influenced by the microchannel patterns.
• The proteolytic performance was closely linked to the pressure drops in the reactors.

Protease from Bacillus licheniformis was immobilized in a freeze-dried poly(vinyl alcohol) (PVA) micromonolith directly prepared in the microchannels of a microreactor. The prepared PVA micromonoliths had porous microstructures of ~10–30 μm in size. Five microreactors were prepared, with microchannels consisting of interconnected straight and elbow segments or a plain straight segment. The system performance was characterized in terms of proteolytic reaction activities. The reactors demonstrated continuous proteolytic activity for 9 d with considerable reaction yields. The proteolytic performance was significantly influenced by the microchannel patterning, and was closely linked to the pressure drops in the reactors. The product distributions varied depending on the flow rates of the substrate solutions and the microchannel patterns. Fractions obtained from different reactors gave different product compositions even when operating under similar conditions and producing comparable yields.