Enhancement of α-CGTase thermostability with the addition of calcium or barium ions

The poor thermostability of native cyclodextrin glycosyltransferases (CGTases), which are essential for cyclodextrin production, limits their use in industrial applications. The effects of 4 divalent metal ions (Ca2+, Ba2+, Zn2+, and Mg2+) on the thermostability of the α-CGTase from Paenibacillus macerans JFB05-01 were investigated. The addition of Ca2+ or Ba2+ to the α-CGTase solution significantly enhanced the enzyme's thermostability, while the presence of Zn2+ or Mg2+ had little effect. The greatest increase in α-CGTase thermostability was obtained with a final concentration of 1.5 mM Ba2+ or 0.5 mM Ca2+. Under these conditions, the α-CGTase solutions retained 56.1 or 29.1%, respectively, of their initial cyclization activity after 120 min at 60 °C. Mechanistic analyses showed that the addition of Ca2+ or Ba2+ significantly protected the secondary and tertiary structures of α-CGTase. This study provides a theoretical foundation and a useful strategy for improving the thermostability of enzymes.