A thermostable glucoamylase from a thermophilic Bacillus sp.: characterization and thermostability.

A thermostable glucoamylase (GA) showed optimum activity at 70 degrees C and pH 5.0. It was highly stable at pH 7.0. The half-life of the enzyme at pH 7.0 was 13, 8, and 3 h 40 min at 60, 65, and 70 degrees C respectively. The residual activity of the enzyme sample incubated at 5 psi (110 degrees C) for 30 min was about 32% of the control set (incubated at 4 degrees C), while no activity was observed at 10 and 15 psi. The thermostability of the enzyme was enhanced twofold in the presence of 0.5% (w/v) starch at 5 psi. Thin-layer chromatography indicated that this enzyme is a GA.