Cyclodextrins are likely to induce cyclodextrin glycosyltransferase production in Bacillus macerans

Cyclodextrin glycosyltransferase (CGTase) activity was monitored in Bacillus macerans culture fluids up to 56 h incubation time using glucose (G(1)), maltose (G(2)), maltotriose (G(3)), maltoheptaose (G(7)), alpha-, beta-, gamma-cyclodextrins (CDs) and soluble starch as carbon sources. Highest maximum specific growth rates (mu(max)) were observed with glucose, gamma-CD and soluble starch (mu(max) values were 0.86, 0.74 and 0.69/h, respectively) while the maximum viable cell numbers were always within the range of 2.3-7.1 x 10(11) CFU/mL independently of the carbon source used. Highest CGTase production was found in the presence of soluble starch and G(7) (55.0 and 35.4 nkat/mL, respectively), these saccharides being easily transformed to CDs by CGTase. Moreover, when culture media were supplemented with cyclic maltooligosaccharides the CGTase activities were about twice higher (19.6-20.6 nkat/mL) than those obtained with the linear G(2) and G(3) saccharides (8.9 and 11.3 nkat/mL, respectively) which give rise only to negligible quantities of CDs. CDs, which are the major end products of the action of CGTase, are regarded thus as the likely physiological inducers of the enzyme.