CYCLODEXTRIN GLYCOSYLTRANSFERASE MAY BE THE ONLY STARCH-DEGRADING ENZYME IN BACILLUS-MACERANS

Cyclodextrin glycosyltransferase (CGTase) was released into the cultur e fluid by Bacillus macerans predominantly in the late stationary phas e of growth and during autolysis in the presence of either glucose or starch as a carbon source. in both cases significant soluble intracell ular enzyme activity could be observed in the early stationary phase, and a low non-soluble intracellular CGTase activity could be demonstra ted also in the exponential growth phase in the presence of starch. At the end of the exponential phase the non-soluble specific intracellul ar enzyme activity was found to be constant with a value of 0.63 +/- 0 .06 nkat/10(9) viable cells. Since amylase activity could not be detec ted in any intracellular or extracellular sample taken at any culture time, we conclude that cell-bound CGTase is the only starch-digesting enzyme in growing B. macerans and, hence, may be fully responsible for the degradation of starch in the culture fluid.