Mixing and enzyme reactions in a microchannel packed with glass beads

Mixing behavior in a microchannel was investigated by means of a spectrophotometer equipped with optical fiber probes. Microreactors with a Y-shaped channel were fabricated on poly(methyl methacrylate) substrates. Glass beads were packed in the intersection and the downstream regions to improve mixing performance. An NaOH solution and a BTB solution as a pH indicator were fed to the microchannel with a syringe pump. As the mixing progressed, the color of the mixed solution changed to blue. The degree of mixing was evaluated by the change in absorbance at 623 nm of the mixing solution. The packed glass beads strongly enhanced the mixing performance in the microchannels, especially in the case of packing in the intersection. The effect of mixing in the microchannel on an enzyme reaction was also investigated. The hydrolysis of o-nitrophenyl--D-galactopyranoside by -galactosidase was used as a model reaction. The results showed that the enzyme reaction was enhanced in the microreactor with glass beads compared with a batch reactor. The microreactor packed with glass beads gave the highest reaction rate.