ABSTRACT
In recent years, enzyme immobilization has gained importance for design of artificial organs, drug delivery systems, and several biosensors. Polysaccharide based natural biopolymers used in enzyme or cell immobilization represent a major class of biomaterials which includes agarose, alginate, dextran, and chitosan. Especially, alginates are commercially available as water-soluble sodium alginates and they have been used for more than 65 years in the food and pharmaceutical industries as thickening, emulsifying, and film forming agent. Entrapment within insoluble calcium alginate gel is recognized as a rapid, nontoxic, inexpensive, and versatile method for immobilization of enzymes as well as cells. The formulation conditions of the alginate beads entrapment immobilized with the enzyme have been optimized and effect of some selected conditions on the kinetic parameter, Km, have been presented. The β-galactosidase enzymes entrapped into alginate beads are used in the study of the effect of both substrate diffusion limitation and the misorientation of the enzyme on its activity, the orientation of an immobilized protein is important for its function. Physico-chemical characteristics and kinetic parameters, the protection of the activity site using galactose as protecting agent has been presented as a solution for the misorientation problem. This technique has been successful in reduction, and orientation-controlled immobilization of enzyme. Other technique has been presented to reduce the effect of substrate diffusion limitation through covalent immobilization of the enzyme onto the surface of alginate beads after activation of its OH-groups.
