Product inhibition in packed-bed immobilized enzyme reactors for complex processes: Modelling of two-substrate processes

Dual enzyme multi-layer bioreactors: analytical modeling and experimental studies

Enzymic reactors are developed for a variety of biomedical-biotechnological applications, including blood detoxification. For the latter, an appropriate approach is to use enzymes of the Mercapturic Acid Pathway. The first two enzymes of this pathway are Glutathione-S-Transferase (GST) and gamma-Glutamyl Transpeptidase (gamma GT). Earlier, the performance of an immobilized GST reactor was investigated experimentally and theoretically. Here, the analytical model was extended to describe a dual-enzyme continuous packed-bed reactor (DCP), in which the two enzymes (E1 and E2) are arranged in alternating layers. The performance of DCP reactors was first studied by numerical simulations, considering the effects of reactor configuration (i.e. number of enzyme layers), kinetic characteristics (K(m), Vmax, Kiq) and operational parameters (flow rate, substrates concentration). Results were obtained in terms of substrate and products concentration profiles along the reactor. The theoretical calculation were supplemented by experimental studies. In the latter GST (i.e. E1) and gamma GT (i.e. E2), were used when immobilized on porous beads, and the reactor was set up and operated in various configurations. It was found that the factors which mostly affect the performance of DCP systems are reactor configuration and extent of inhibition of E1 by its reaction product.