Calcium pectinate-agar beads as improved carriers for β-d-galactosidase and their thermodynamics investigation

Polyethyleneimine (PEI) glutaraldehyde-refined calcium pectinate (CaP)-agar beads were presented as improved covalent immobilization matrices. The CaP-agar beads exhibited incremented mechanical stability which facilitated their handling. The beads' concoction and activation processes were honed using the Box-Behnken design which recommended utilizing 5.4% agar, and a 2.95% PEI solution of pH 8.67. The honed CaP-agar beads established a more efficient ionic interaction with PEI which enabled the immobilization of more enzyme while utilizing less PEI than that required to activate the neat CaP beads. Furthermore, the activated CaP-agar beads granted superior operational stability to the immobilized enzyme, beta -d-galactosidase (beta gal), where it preserved 86.84 +/- 0.37% of its precursive activity during its thirteenth reusability round. The CaP-agar immobilized beta gal (i beta gal) also showed incremented storage stability where it preserved 85.05 +/- 3.32% of its precursive activity after 38 days of storage. The thermal stability of the i beta gal was shown to be superior to that of the free enzyme as the i beta gal exhibited incremented thermodynamic parameters, such as the t(1/2) values, the D values, the thermal denaturation activation energy, the enthalpies, and the Gibb's free energies. The beta gal's immobilization onto the activated CaP-agar beads also shifted the enzyme's optimal pH from 4.6-5.1 to 3.3-4.9, whereas its optimal temperature was retained at 55 degrees C. The procured biocatalyst was exploited to efficiently hydrolyze the lactose in whey permeate.