Polyelectrolyte complexes are rapidly formed when oppositely charged polyions are mixed. There are two basic principles making use of polyelectrolyte complexes for immobilization of cells and enzymes—entrapment and microen-capsulation. Because the entrapment in polyelectrolyte complexes (1 ) yields only amorphous polymeric structures complicating handling of these immobilizates, this chapter concentrates on microencapsulation within polyelectrolyte complexes. Microencapsulation is based on membrane confinement. For encapsulation, the biocatalysts are enclosed in semipermeable membranes retaining the catalyst without limiting the exchange of substrates and products.
