Bacillus thuringiensis: a specific gamma-cyclodextrin producer strain

Abstract

An anaerobic microbial isolate Bacillus species, designated B. thuringiensis GU-2, was isolated from soil as a specific gamma-cyclodextrin (CD) producer strain in alkaline medium under anaerobic conditions. The optimum pH and temperature for bacterial growth and gamma-CD production were estimated to be pH 8.5 and 37 degrees C in the presence of 1.0% starch substrate, respectively. A high purity yield > 95% of gamma-CD from the total CD yield in the reaction mixture was obtained from starch that was supposed to be converted by gamma-cyclodextrin glycotransferase, tentatively named as gamma-CGTase. The maximum gamma-CGTase activity was estimated at 2.45 U/mL under optimized condition. This is the first report demonstrating the generation of a specific c-cyclodextrin (CD) producer strain by the action of a gamma-CGTase under anaerobic conditions. (C) 2014 Elsevier Ltd. All rights reserved.