Abstract
The calcium pectinate (CP) gel beads were treated with polyethyleneimine (PEI) and glutaraldehyde (GA). This treatment greatly enhanced the beads’ mechanical strength. Moreover, it enabled the CP beads to covalently immobilize enzymes, such as β-d-galactosidase (β-gal). The central composite design (CCD) was applied to optimize the PEI/GA treatment while employing the observed activity of the immobilized β-gal as a response. The CCD predicted that treating the CP beads with a 3.49% PEI solution of pH 10.55, followed by a 5.66% GA solution in 0.1M phosphate buffer pH 7.02 would allow for the immobilization of 6.25U/g gel of the β-gal. The verification experiment run at these optimum conditions offered 6.285±0.22U/g gel immobilized β-gal which was in close agreement with the predicted value. The reusability study revealed that the β-gal immobilized onto the treated CP beads retained 79.34% of its initial activity after being used for fourteen times.
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