Modeling of hydrogel immobilized enzyme reactors with mass-transport enhancement by electric field

Effects of electro-transport processes in enzymatic reactors with spatially continuous unstirred reaction media (e.g., gels or polymers) on enzyme reactions are studied by numerical simulations. Two model enzyme reactions are chosen for analysis: (i) with no ionic reaction components, and (ii) with only ionic components and with production of H+ ions. The electrophoretic migration and electro-osmotic flux are considered as mechanisms altering transport rates of reaction components in unstirred reaction medium. Mathematical models of reactor system with hydrophilic membrane (or slab) containing immobilised enzyme with the DC electric field applied in a direction perpendicular to the membrane are constructed. Remarkable increase of the immobilised enzyme productivity was observed when the electric current of proper intensity was applied to the system. This optimum current value depends on substrate concentration, the slab thickness and the rate of enzyme inactivation. Main factor limiting applicability of the electric current to the reaction slab is heating of the slab due to the Joule heat. The electrophoretic migration of H+ ions in the second reaction system prevents local over-acidification, i.e. the averaged reaction yield is higher compared to the system with no electric field applied. An example of experimental results obtained in a laboratory-scale electro-membrane reactor with immobilised penicillin G acylase is also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.