Halophilic characterization of starch-binding domain from Kocuria varians α-amylase

The tandem starch-binding domains (KvSBD) located at carboxy-terminal region of halophilic α-amylase from moderate halophile, Kocuria varians, were expressed in E. coli with amino-terminal hexa-His-tag and purified to homogeneity. The recombinant KvSBD showed binding activity to raw starch granules at low to high salt concentrations. The binding activity of KvSBD to starch was fully reversible after heat-treatment at 85 °C. Circular dichroism and thermal scanning experiments indicated that KvSBD showed fully reversible refolding upon cooling after complete melting at 70 °C in the presence of 0.2-2.0 M NaCl. The refolding rate was enhanced with higher salt concentration.