Purification and characterisation of cyclodextrin glycosyltransferase from Paenibacillus sp. F8

Cyclodextrin glycosyltransferases (E.C. 2.4.1.19) (CGTases) are industrially important enzymes for the production of cyclodextrins (CD) from starch. While cyclomaltohexaose (α-CD), cyclomaltoheptaose (β-CD), and cyclomaltooctaose (γ-CD) are the most commonly reported products, the production of cyclomaltononaose (δ-CD) by CGTases has not been studied previously. A CGTase from Paenibacillus sp. F8 was purified and characterised. The molecular weight was estimated to be 72 kDa by SDS-PAGE. The pH optima of the enzyme were 7.5 for the cyclisation activity and 8.0 for the hydrolysis activity. The temperature optima for the cyclisation and hydrolysis activities were 50 and 60 °C, respectively. Ca++ had a stabilising effect on the enzyme activity. The initial production ratio of α-CD, β-CD, γ-CD, and δ-CD from soluble starch was 0.09:1:0.25:0.14. Prolonged incubation times resulted in a decreased ratio of δ-CD and, to a lesser extent, of γ-CD and a increased ratio of α- and β-CD compared to the other CD. Coupling experiments showed that δ-CD was more easily degraded by Paenibacillus sp. F8 CGTase compared to α-, β-, and γ-CD.