Synthesis of malto-oligosaccharides via the acceptor reaction catalyzed by cyclodextrin glycosyltransferases

The disproportionation activity (intermolecular transglycosylation) of cyclomaltodextrin glycosyltransferases (CGTases) from Thermoanaerobacter sp. and Bacillus circulans strain 251 was studied. Using soluble starch as donor, the CGTase from Thermoanaerobacter sp. showed the highest transglycosylation activity with all the malto-oligosaccharides tested as accepters. At ratios of starch:D-glucose from 2:1 to 1:2 (w/w), the formation of cyclodextrins was completely inhibited, and a homologous series of malto-oligosaccharides (G(n)) was produced. The conversion of starch into acceptor products was in the range of 63-79% in 48 h. The degree of polymerisation of malto-oligosaccharides formed could be modulated by the ratio of starch:D-glucose provided; at a ratio of 1:2 (w/w), the reaction was quite selective for the formation of G2-G3.