A beta-cyclodextrin glycosyltransferase from a newly isolated Paenibacillus pabuli US 132 strain: Purification,properties and potential use in bread-making

摘要

A bacterial strain designed US 132,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 US 132 CGTase,purified to homogeneity by hydrophobic interaction chromatography and starch adsorption,is a monomer of approximately 70kDa.This enzyme exhibited a maximal activity at 65 deg 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/1 with a beta-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.