Bound Enzymes in Continuous-Flow Systems

MEMBRANE BOUND ENZYMES IN CONTINUOUS-FLOW SYSTEMS 

In recent years a large number of techniques have been suggested in the literature for immobilizing enzymes on insoluble carriers in particular, immobilization on polymeric solid supports or glass beads. A stable attachment can result from ionic binding, cross-linking and covalent linking to a water-insoluble matrix. A full description of chemical and/or physical procedures required to make enzymes insoluble is beyond the scope of this chapter and is extensively dealt with elsewhere.112 113 

Enzymes are covalently immobilized primarily onto the surface of the membrane exposed to the feed solution, known as the active side of the asymmetric membrane. In general, it is not clear whether reaction between enzymes and polymeric membranes via coupling agents simply results in enzyme attachment to the membrane, or if it leads to an enzyme-carrier network inside the polymer matrix. For the sake of simplicity let us assume that asymmetric membranes are used, that suitable active groups are available on the polymeric surface and that the membrane molecular weight cut-off is such that the active layer is enzyme-impermeable. In this way, even though their activity is often drastically reduced, surface bound enzymes are in close proximity to the substrate solution-thus reducing the mass transfer resistance to that associated with the boundary layer. When enzymes are covalently immobilized in the 

As far as membrane electrodes are concerned, readers are referred to the literature.3 113 115-116 

When the substrate has a molecular weight lower than the membrane cutoff, enzymes can be covalently bound either to the active side of the membrane or within the sponge-like substructure of the membrane. 

---