Glutaraldehyde-copper gelled chitosan beads: Characterization and utilization as covalent immobilizers

Abstract

The robust chitosan (CHS)–Cu2+ interactions were utilized to prepare CHS beads. Glutaraldehyde (GA) was also added to the gelling medium to provide the functional entities needed for β-d-galactosidase (βG) covalent immobilization. The preparation of the GA-Cu-CHS beads was honed with respect to the concentrations of the utilized CuSO4, CHS, and GA solutions. A CHS concentration of 2% was favored. The optimal gelling medium comprised 0.2% CuSO4-1.12% GA. The beads were characterized via SEM and EDX. The beads enhanced mechanical traits were verified. The GA-Cu-CHS beads immobilized βG, and the immobilization efficiency reached 47.67% when 2.56 Ug−1 βG loading activity was adopted. The immobilized βG (iβG) experienced an acidic shift in its optimal pH range from 4.4 to 5.5 to 3.6–4.4. Moreover, its optimal temperature was slightly shifted following immobilization from 55-60 °C–60 °C. The Km and Vmax values of βG were reduced from 84.4 mM to 19.0 μmol/min mg enzyme to 64.9 mM and 5.6 μmol/min mg enzyme following immobilization. The operational stability of iβG was also studied while performing the 15 min lactose hydrolytic reaction at 37 °C, and 81.79% activity was obtained throughout the 15th hydrolytic cycle. Moreover, the iβG provided 97.30% activity after 77 days of storage in distilled water in the fridge. Finally, the iβG was utilized to degrade lactose in cheese whey and also in buffered lactose solution (BLS) at 45 °C and at pH 4.4. Each degradation cycle lasted 24 h and 78.52% of the inceptive released glucose was released during the BLS 5th degradation cycle.