A novel alginate–CMC gel beads for efficient covalent inulinase immobilization

Abstract

Covalent immobilization of inulinase, produced by the marine-derived fungus Aspergillus terreus, on novel gel beads was made by the combination of alginate and carboxymethyl cellulose. Optimization of the loading time and loading units was done by response surface methodology. The bound enzyme displayed a change in optimum operating pH from 5.0 to 5.5 while the optimum operating temperature increased from 50 to 55 °C. K m value has been increased (from 3.6 to 7.1 mg/ml) in comparison with the free enzyme. However, the V max was lowered (from 145 to 77.5 U/g carrier) after immobilization. The immobilized inulinase showed enhancement in thermal stability against high temperature. There was an observed increase in half-lives and D values which revealed the improvement in the enzyme thermal stability. Thermodynamically, after immobilization, a remarkable increase in enthalpy and free energy was observed due to the enhancement of enzyme stability. Immobilized inulinase showed retention of 60% of its original activity after 10 successive cycles. Stability and reusability of immobilized inulinase on alginate–CMC enable the enzyme to be more convenient for industrial application.