(507g) Microreactors Driven By Electric Field for Enzyme Catalysis in ATPS

Aqueous two phase systems (ATPS) are widely used for the separation and purification of proteins. They consist of one or two organic polymers (polyethylene glycol - PEG, dextran), water and inorganic salts. Both aqueous phases typically provide mild conditions for enzyme reactions. Particular composition of ATPS strongly affects partitioning of proteins and low molecular reactants/products. Ideally, enzyme reaction can be carried out in one phase and reaction products can by selectively transported into the other phase. The system then works as an integrated reactor-separator.

Recently we have found that small droplets of salty phases dispersed in PEG phase (PEG-water-salt ATPS) can be efficiently addressed to a particular place of microfluidic chips by dc electric field [1]. Even if both phases are electrically conductive, certain amount of electric charge is fixed on the liquid-liquid interface. High apparent electrophoretic mobility of salty droplets enables fast addressing under relatively low electric field.

We suggested a microfluidic reactor-separator in which small droplets of salty phase are generated in an array of orifices. Reaction components are transferred through the interface into PEG phase. To simply separate both phases, two microelectrode compartments are placed parallel to microfluidic channel. When electric field is switched on, droplets are attracted to the negatively charged electrode. The droplets then quickly coalesce and parallel flow of the separated phases is observed. Moreover, electric field affects the partitioning of ionic reactants/products. Here we are looking for a regime, in which electrophoretic transport of salty droplets and particular chemical components will work in synergy to obtain high yield of pure products.

Two enzyme reactions were chosen to test the developed microfluidic platform: (i) hydrolysis of penicillin G by penicillin acylase to produce 6-aminopenicillanic acid, and (ii) synthesis of cephalexin form 7-aminodesacetoxycephalosporanic acid again catalyzed by penicillin acylase. Our findings and possible benefits or disadvantages of the microfluidic system will be discussed.

[1] Vobecka, L., Khafizova, E., Stragier, T., Slouka, Z., Pribyl, M., Electric field driven addressing of ATPS droplets in microfluidic chips (2017) Microfluidics and Nanofluidics, 21 (3), art. no. 51.