Protease immobilization on a novel activated carrier alginate/dextrose beads: Improved stability and catalytic activity via covalent binding

Protease from Bacillus thuringiensis strain-MA8 was successfully immobilized onto activated Alginate/dextrose (Alg/dex) beads as a new carrier with immobilization yield 77.6 %. The carrier was characterized using Scanning electron microscopy and Fourier transforms infrared spectrophotometer at every step of the immobilization process. Immobilized protease showed an increase of 10 degrees C in the optimum temperature compared to the free enzyme. However, the optimum pH for both the free and the Alg/dex/protease was found to be 8. The lower activation energy and deactivation rate constant and the higher half-life time and D-value confirm that the new Alg/dex carrier is suitable for promoting enzyme stability. The raise in thermal stability is also shown by the increased deactivation energy of the Alg/dex/protease compared to its free form by 1.47-fold. Likewise, the enzyme immobilization enhancement of Alg/dex/protease was accompanied by a marked increase in enthalpy and Gibbs free energy. The negative entropy for both free and Alg/dex/protease indicates that the enzyme is more stable in thermal deactivation. The Km and Vmax for the Alg/dex/protease were 2.05 and 1.22-times greater than the free form. Furthermore, Alg/dex/protease displayed good reusability as it retained 92.7 and 52.4 % of its activity after 8 and 12 hydrolysis cycles.