Immobilization involves attaching enzymes to a support matrix. This allows the enzyme to be reused by retaining it within a bioreactor. Common immobilization methods include adsorption, covalent bonding, entrapment, and encapsulation. The technique used depends on factors like strength of attachment and effect on enzyme activity. Immobilized enzymes have various applications in industries like pharmaceuticals, food production, and waste water treatment due to advantages like enhanced stability and easier product separation.