Low molecular weight alkaline thermostable α-amylase from Geobacillus sp. nov.

摘要

Industrial demands for enzymes that are stable in a broad range of conditions are increasing. Such enzymes, one of which is α-amylase, could be produced by extremophiles. This study reports a thermostable α-amylase produced by a newly isolated Geobacillus sp. nov. from a geothermal area. The phylogenetic analysis of the 16S rRNA gene showed that the isolate formed a separate branch with 95% homology to Geobacillus sp. After precipitation using ammonium sulphate followed by ion-exchange chromatography, the enzyme produced a specific activity of 25.1 (U/mg) with a purity of 6.5-fold of the crude extract. The molecular weight of the enzyme was approximately 12.2 kDa. The optimum activity was observed at 75 °C and pH 8. The activity increased in the presence of Ba²⁺ and Fe²⁺ but decreased in the presence of K⁺ and Mg²⁺. Ca²⁺ and Mn²⁺ increased the activity slightly. The activity completely diminished with the addition of Cu²⁺. EDTA and PMSF also sharply reduced enzyme activity. Although the stability was moderate, the low molecular weight could be an important feature for its future applications.