Selection of the Constitutive Mutant of Bacillus firmus var. alkalophilus and its Characteristics of Cydodextrin Glucanotransferase Production

To investigate the role of induction on CGTase production for alkalophilic Bacillus firm us var. alkalophilus H609, the constitutive mutants that form a halo around its colonies at non-inducible AG agar media containing amylose and glucose were selected. The selected constitutive mutants could produce CGTase in the range of 18.9 to 28.8 units/ml $\cdot A_{600}$ in the alkaline basal medium, and finally a constitutive mutant Bacillus firmus var. alkalophilus CM46 was selected. The constitutive nature of CM46 was also confirmed in protein level using SDS-PAGE. The effects of induction and catabolite repression for both parent strain Bacillus firmus var. alkalophilus H609 and constitutive mutant CM46 were also compared by adding soluble starch and glucose during cultivation. The selected mutant CM46 was a non-inducible but a catabolite regulated type mutant. Even though inductive regulation was released, the specific CGTase activity defined as CGTase activity per cell concentration was not increased compared with that of parent strain. The cell growth and CGTase production patterns of constitutive mutant Bacillus firmus var. alkalophilus CM46 were compared with the parent strain to identify CGTase production characteristics.