Cyclodextrins are likely to induce cyclodextrin glycosyltransferase production inBacillus macerans

Abstract

Cyclodextrin glycosyltransferase (CGTase) activity was monitored inBacillus macerans culture fluids up to 56 h incubation time using glucose (G1), maltose (G2), maltotriose (G3), maltoheptaose (G7), α-,β-,γ-cyclodextrins (CDs) and soluble starch as carbon sources. Highest maximum specific growth rates (µmax) were observed with glucose, γ-CD and soluble starch (µmax values were 0.86, 0.74 and 0.69/h, respectively) while the maximum viable cell numbers were always within the range of 2.3–7.1×1011 CFU/mL independently of the carbon source used. Highest CGTase production was found in the presence of soluble starch and G7 (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 malto-oligosaccharides the CGTase activities were about twice higher (19.6–20.6 nkat/mL) than those obtained with the linear G2 and G3 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.