Catalytic properties of β-cyclodextrin glucanotransferase from alkalophilicBacillus sp. BL-12 and intermolecular transglycosylation of stevioside

Abstract

The catalytic properties of β-cyclodextrin glucanotransferase (β-CGTase) from alkalophilicBacillus sp. BL-12 specific for the intermolecular transglycosylation of stevioside were investigated. The molecular mass of purified β-CGTase by ultra-filtration and β-cyclodextrin polymer affinity chromatography was estimated to be 90 kDa, which is high compared to other known bacterial CGTases. The optimal pH and temperature were 9.0 and 50°C, respectively, and thermal stability at 40°C was elevated 10-fold in the presence of 1% maltodextrin. The kinetic parameters of the new β-CGTase from alkalophilicBacillus sp. BL-12 indicate that it is more suitable for transglycosylation than the cyclization reaction. Maltodextrin was the most suitable glycosyl donor for transglycosylation of stevioside. The transglycosylation of stevioside was carried out using 60 units of CGTase per gram of maltodextrin, 20 g/L stevioside as the glycosyl acceptor, and 50 g/L maltodextrin as the gycosyl donor at 40°C for 6 h, and a conversion yield of stevioside as high as 76% was obtained.