Mechanically stable egg white protein based immobilization carrier for β-D-galactosidase: Thermodynamics and application in whey lactose hydrolysis

Abstract

β-D-Galactosidase (β-gal), a crucial enzyme in food industries, was immobilized onto egg white protein (EWP) based covalent immobilization carriers of escalated mechanical stability. This escalated mechanical stability was acquired after incorporating the mechanically stable calcium gelled gellan gum (GG) beads. The EWP established a coating layer around the gellan gum (GG) beads, and the EWP-GG beads were then processed with glutaraldehyde (GA). The preparation process of the GA-EWP-GG beads was optimized, and it was disclosed that the optimum EWP pH, EWP concentration, and GA concentration were 2–4, 7% (w/w), and 20–25% (v/v), respectively. β-Gal was immobilized onto the GA-EWP-GG beads with a 50.28% immobilization efficiency. The immobilized β-gal (iβ-gal) acquired an escalated thermal stability as compared to its free analogue, and this was proven from the escalations recorded in the iβ-gal half-lives, D-values, activation energy of thermal denaturation, enthalpies, and Gibbs free energies. The proposed biocatalyst exhibited superior operational stability where 89.47 ± 1.34% of the iβ-gal preliminary activity was retained throughout its 24th reusability cycle. The storage stability of the GA-EWP-GG iβ-gal was also superior and 87.64 ± 1.86% of the inceptive iβ-gal activity was retained after 63 days of storage. The biocatalyst efficiently hydrolyzed the whey permeate lactose for five consecutive cycles.