Résumé:
This work focuses on the isolation of the genus Bacillus from the soil. The main objective is to
identify more efficient aéro-anaerobic thermophilic bacilli for the production of alpha amylases. The
results of the morphological characterization reveal that colonies are circular beige, Gram-positive
and sporulated cells. However, all the biochemical and physiological tests are positive; the
respiratory type of the isolate is optional aéro-anaéroobic. This confirms the identification of the
strain of genus Bacillus sp. The inoculum of the strain was used in a liquid medium for the
production of alpha-amylases. The protein assay of the enzyme extract was quantified by the Biuret
method. The use of the enzyme extract in a reaction medium based on starch makes it possible to
determine the kinetic parameters Km, Vmax and Vi of the extract. This kinetics was followed by the
assay of the released product as a function of time; the enzymatic kinetics is estimated by the
colorimetric method with the Fehling liquor reagent. The Bacillus sp strain has a good affinity with
the starch substrate, the Km value is 0.006 mol l-1 and the initial enzymatic velocity Vi = 0.011 mol
1-1 min-1. The results obtained require other methods of study for identification.
