The replacement of batch processes with continuous ones, as well as the replacement of large chemical reactors with microreactors, are gaining more and more importance and enable the intensification of processes, while the inclusion of biological catalysts in processes contributes to improving the sustainable aspect of production. The small dimensions enable short diffusion paths and a high surface-to-volume ratio, which improves mass and heat transfer. By creating different flow regimes in a multiphase system, we can influence the formation of a larger interphase surface.
In the thesis, we discussed the laccase-catalyzed dimerization of tyrosol acetate to 1,1′-dityrosol-8,8′-diacetate in a microflow reactor. First, we performed the reaction in a glass microreactor with three inlets and observed the current regime with an optical microscope. Ethyl acetate with dissolved tyrosol acetate was pumped on the sides of the microreactor, and acetate buffer with dissolved laccase was pumped in the middle. The liquids flowed parallel and created two phase boundaries between them. The reaction takes place only at the phase boundary, where the laccase and substrate move by diffusion. At lower flow rates, the two aqueous phases merged and only one phase boundary remained, greatly reducing the surface area and conversion potential. The microreactor did not allow us long enough retention times for the reaction to take place completely, so we repeated it in a longer tube. In this case, a segmented flow was formed where the buffer with laccase represented the continuous phase. The phase surface was larger and the retention time was longer, so the reaction could proceed. The reaction was then repeated by pumping a third phase ̶ air into the system. Again, a segmented flow was formed in which the ethyl acetate trapped the air bubble and thus prevented the diffusion of oxygen to the enzyme dissolved in the continuous phase of the acetate buffer. Nevertheless, the highest conversion of tyrosol acetate to 1,1′-dityrosol-8,8′-diacetate was achieved in this system, which was 3,7 %.
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