A β-cyclodextrin glycosyltransferase from a newly isolated Paenibacillus pabuli US132 strain: Purification, properties and potential use in bread-making

A bacterial strain designed US132, isolated from a Tunisian soil was selected for its production of a potent cyclodextrin glycosyltransferase (CGTase) activity. This strain was identified as Paenibacillus pabuli by sequencing of the 16S rDNA and the 16S-23S internal transcribed spacer (ITS). The US132 CGTase, purified to homogeneity by hydrophobic interaction chromatography and starch adsorption, is a monomer of approximately 70 kDa. This enzyme exhibited a maximal activity at 65 °C, in presence of 10 mM calcium, and was most active at pH range 5.5–9 with an optimum at 6.5. Using 10% (w/v) of potato starch, this CGTase produced a high level of cyclodextrins reaching 42 g/l with a β-cyclodextrin ratio of 63%. Furthermore, this enzyme can be used in the bread-baking process since its addition in the dough mix improved significantly the loaf volume and decreased the firmness of bread during storage.