Characterization and cultural conditions of a novel cyclodextrin glucanotransferase-producing Bacillus stearothermophilus strain

A cyclodextrin glucanotransferase (CGTase)-producing thermophilic bacterium (strain 2/2) was isolated from Bulgarian hyperthermal springs with a tempe rature of 102 degrees C and a pH value of 8.0-8.8. The strain was aerobic, Gram-positive, and endospore forming with a temperature optimum of about 60 degrees C and a pH optimum of about 9.0. According to morphological, cultu ral and biochemical characteristics, and molecular properties, the isolate was identified as an alkalotolerant member of the species Bacillus stearoth ermaphilus. The effect of various carbon sources on CGTase production was studied and g lucose (0.5%) was found to be the most suitable substrate for CGTase biosyn thesis (10 U/ml). The addition of glutamic acid (0.1%) to the medium increa sed the CGTase yield 1.7-fold and the specific enzyme activity 1.5-fold.