The carrier should expose the active sites of the catalyst for easy attachment of substrate molecules and to reduce diffusional limitations of the substrates and products. This is particularly important in the case of covalent immobilization. ![]() Additionally, there should be affinity between the functional groups of the two materials to allow the formation of these enzyme–matrix interactions and effective binding of the enzyme to the support. However, there are some limitations in this area, because the matrix must not have a negative effect on the structure of the enzyme and should not disturb the enzyme more than is required to create stable enzyme–matrix interactions. Moreover, use of a suitable material, for example hydrophobic carriers in lipase immobilization, may additionally increase the activity of the biocatalyst. The support should protect the enzyme structure against harsh reaction conditions and thus help the immobilized enzyme to retain high catalytic activity. These materials may, in general, be divided into organic, inorganic and hybrid or composite. However, it should be emphasized that the selection of the support materials is the most crucial challenge due to the major impact the support material may have on the properties of the biocatalytic system.Ī very broad variety of materials of various origins can be used as supports for enzyme immobilization. Selection of the most appropriate immobilization method and support material depends strongly on the type and conditions of the catalytic process as well as the type of the enzyme. These differ in the type and character of the interactions formed and in the form and type of the support materials used. ![]() Various immobilization techniques have been developed, including adsorption, covalent binding, entrapment, encapsulation and cross-linking. Moreover, after binding the enzyme molecules, the catalysts change from a homogeneous to a heterogeneous form, which facilitates simple separation of the biocatalytic system from the reaction mixture and results in products of higher purity. ![]() The greatest advantage of immobilization is that it significantly improves the stability of the biomolecules under various reaction conditions and enhances the reusability of biomolecules over successive catalytic cycles. One of the most important and widely used techniques is enzyme immobilization in which catalysts are attached to a solid support that is insoluble in the reaction mixture. The use of enzymes in multiple catalytic processes has resulted in studies leading to significant improvement of the enzyme properties. For these reasons enzymes have become extremely important catalysts which exhibit great potential in many practical applications in industries ranging from food to pharmaceuticals. Additionally, enzymes may reduce the number of reaction steps and quantities of hazardous solvents needed and thus make a process more inexpensive and environmentally friendly. Enzymes are well-known as highly effective and efficient catalysts of a wide variety of processes characterized by high selectivity and activity.
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