Chitosan-glutaraldehyde activated carrageenan-alginate beads for β-D-galactosidase covalent immobilisation

Abstract

Chitosan (CS) and glutaraldehyde (GA) were exploited to activate carrageenan-alginate (Car-Alg) beads and enable their utilisation as covalent immobilisation matrices. The GA/CS activated Car-Alg beads were utilised to immobilise the Aspergillus oryzae β-D-galactosidase (β-gal). Initially, the beads gelling solution was optimised, and it was shown that the upmost amount of immobilised β-gal (iβ-gal) was acquired upon utilising a 1% CaCl2–2% KCl gelling solution. Afterwards, the GA/CS activation protocol was honed via the Box Behnken design (BBD). The BBD revealed that soaking the Car-Alg beads with a 1.62% CS solution of pH 6 followed by a 3% GA solution was the optimum activation protocol that would provide 13.94 U/g beads iβ-gal. Noteworthy, a 72.64% immobilisation yield was accomplished via the optimally activated Car-Alg beads. The free and the iβ-gals were compared with respect to their Km and V max values, their temperature profiles, and their pH profiles. The reusability of the iβ-gal was also assessed, and 79.74% of its first round activity was retained throughout the 10th reusability round.