Comparative study in kinetics and thermodynamic characteristics of immobilized caseinase on novel support from basalt by physical adsorption and covalent binding
2019
Abstract Aspergillus niger WA 2017 caseinase was immobilized on a novel support prepared from raw material (basalt) by physical adsorption (PA) and covalent binding (CB). A physicochemical characterization of the more appropriate (glass-ceramic with particle size ≥ 1.0 mm) was performed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). One-factor-at-a-time (OFAT) experiments and the response surface methodology (RSM) were used to optimize the immobilization conditions for the maximum immobilization yield (IY %) and to understand the importance and interaction of the affected factors. Under optimized conditions the IY was increased by 2.4 and 1.6-fold, respectively for PA and CB caseinase. Compared to PA caseinase, CB caseinase showed the higher activation energy ( Ea ), half life time ( t 1/2 ), decimal reduction time ( D -value), activation energy for denaturation ( Ed ) and Michaelis constant ( Km ). The thermodynamic parameters for irreversible inactivation indicated that enthalpy (ΔH ◦ ), Gibbs free energy (ΔG ◦ ) and entropy (ΔS ◦ ) were higher for CB caseinase than that for PA caseinase within 50–70 °C. Caseinase supported on GC particles by PA and CB retained 21.3 and 57.5%, respectively of its initial activity after 7 consecutive cycles.
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