Résumé
One hundred and twenty five soil samples were collected from the regions of roots of corn, cassava, potato, bean, sugar cane, soya, and pumpkin. From these, 75 strains were isolated that produced a yellowish halo surrounding the colonies, due to a phenolphtalein-cyclodextrin (CD) complex, and these were selected as alkalophilic CGTase-producing bacteria. All the 75 strains were identified as Bacillus firmus by microscopy and biochemical tests. The activity of the CGTase's varied from 2² to 2(10) dilutions,when assayed by CD-trichloroethylene (TCE)-complex precipitation. Strain 31 that produced the enzyme at the higher level was selected, and its enzyme was partially purified by starch adsorption (x 17) in a yield of 51 percent. Maximum enzyme activity occurred at pH 5.5 and 8.5. At pH 5.5, the optimum temperature was 60°C. On increased from 30°C to 85°C, the thermodynamic parameter for activation energy was 8.27 kcal.mol-1. The enzyme was inhibited by Ca2+, Mg2+, Fe2+, Cu2+, Mn2+, and Zn2+