Abstract

This study was aimed at immobilizing Streptomyces roseiscleroticus glucose isomerase by adsorption on chitosan beads obtained from shells of water snail and investigating the properties of the adsorbed enzyme with respect to pH, temperature and reusability. The major challenge in the utilization of soluble enzymes relates to their cost of production, recovery and possible reutilization which can be solved by enzyme immobilization. Several methods of enzyme immobilization are abounding. They include, adsorption, entrapment, cross linking and covalent binding to an insoluble solid support. One major advantage of enzyme immobilization by adsorption is the little or no damage to the enzyme and the reversibility of the reaction process. Chitosan was produced by the deactivation of chitin obtained from shells of water snail. The extracted chitosan was subjected to Fourier transform infrared spectroscopy (FTIR) analysis. The FTIR spectrum of the extracted chitosan showed characteristic absorption peaks within 3641 and 3028 cm-1. The extracted chitosan was used as an immobilization support in the form of chitosan beads. Adsorption of the crude and purified glucose isomerase on chitosan beads was achieved at pH 6.0 after 120 min with an immobilization efficiency of 72.68% and 75.31% respectively. The purified adsorbed glucose isomerase had an optimum pH and temperature of 8.5 and 70°C, respectively. Studies on the reusability or storage stability of the purified adsorbed glucose isomerase on chitosan beads showed that, 66%, 52% and 30% of the adsorbed enzyme activity were retained after 24, 48 and 72 hrs. Respectively. Immobilized glucose isomerase is of huge importance in the food processing industries because of its usefulness in the production of sugar syrups and other sugar substitutes.