Preparation of Cross-Linked Glucoamylase Aggregates Immobilization by Using Dextrin and Xanthan Gum as Protecting Agents

In this paper glucoamylase from Aspergillus niger was immobilized by using a modified version of cross-linked enzyme aggregates (CLEA). The co-aggregates were cross-linked with glutaraldehyde; meanwhile dextrin and xanthan gum as protecting agents were added, which provides high affinity with the enzyme molecules. The immobilized glucoamylase was stable over a broad range of pH (3.0-8.0) and temperature (55-75 degrees C); dependence shows more catalytic activity than a free enzyme. The thermostability, kinetic behavior, and first-order inactivation rate constant (k(i)) were investigated. The two types of protector made the immobilized glucoamylase more robust than the free form. Both of the immobilized enzymes have excellent recyclability, retaining over 45% of the relative activity after 24 runs. In addition, immobilized enzymes reduced only 40% of the initial activity after three months by the storability measure, indicating high activity.