Enzymatic Reaction in a Capillary Microreactor with Surface-Immobilized Enzyme

Enzymatic processes coupled with continuous microfluidic techniques have significant application prospects in pharmaceuticals and fine chemicals. It is important to stably load enzymes in microreactors. This study reported a sol–gel method for preparing wall-coated immobilized enzyme microreactors (W-IMERs) by entrapment of Candida antarctica lipase B (CALB). The W-IMERs were simply constructed in one step by a flow coating process in a capillary. Compared with the free enzyme, the tolerance of immobilized enzyme to ethanol and temperature is significantly improved, and the yield of immobilized enzyme activity is 76.12% in the batch reactor. In W-IMERs, the yield of immobilized enzyme activity increased to 82.95%. The W-IMERs maintained stable activity in 10 cycles for up to 30 days. A CFD model was also established to explore the relationship between the internal reaction and the mass transfer in W-IMERs. The relationship between the internal and external diffusion limits of W-IMERs and the overall reaction rate was analyzed by dimensionless numbers. The results indicated that sol–gel flow coating is a simple and effective method for the preparation of enzymatic microreactors. An in-depth understanding of the relationship between diffusion limitation and reaction rate will have a significant impact on the overall performance of enzyme-catalyzed microreactors.