Development and modification of PVA-alginate as a suitable immobilization matrix

This study reports the immobilization of invertase in the PVA-alginate matrix via a modified method. The PVA-alginate modified method involved the treatment of immobilized beads in sodium sulfate solution. In this study, the steps involved in the preparation of matrix were analyzed. The influence of the sodium sulfate concentration on the bead formation was investigated and its mechanism of immobilization was further elucidated by means of FTIR and EDX. In addition, the stability of invertase in sodium sulfate and boric acid solution was also studied. EDX results revealed that borates were completely replaced by sulfates as the cross-linking agent. Through the mechanism of nucleophilic substitution, it was revealed that sulfate attacked the carbon atom bearing borate on the opposite side to the side bonded to borate due to steric hindrance. Carbon therefore underwent backside attack by sulfate and inverted its original configuration through a phenomenon known as Walden Inversion. The presence of sulfate was also supported by FTIR spectra. The best sodium sulfate concentration was found to be 0.5 M. (C) 2011 Elsevier Ltd. All rights reserved.