Résumé:
Amylases are the main enzymes involved in the biodegradation of starch. These enzymes have various industrial applications. In this study, three strains of actenobacteria belonging to the genus Streptomyces sp were isolated from the soil of the region Abdelmalek Ramdan (Mostaganem), characterized morphological and physiological, biochemical tests. The abilities of starch degrading amylase by isolates were determined in a starch rich culture medium.
The selection of the amylase-producing strains is established by measuring the diameters of the hydrolysis zones formed around the cultures. Quantification and kinetics of the enzymatic extracts were carried out at wavelengths μ = 540 nm by colorimetric assays. The results of the macro-microscopic characterizations and the physiological, biochemical tests confirm that the three isolates of actinobacteria belong to the genus Streptomyces sp. The crude enzymatic extracts of the strains have concentrations of 0.112; 0.184 and 0.565 mg / ml respectively for the three isolates (S1, S2, S3). The assay of the products released during the different hydrolysis reactions of the substrates have respectively higher values of 1.38 and 1.043 μmol glucose / ml for isolates S3 and S2. However, the Km values are the lowest for Streptomyces sp. S2 and S3 (0.19 × 10-3 and 0.15 × 10-3) relative to isolate S1 (8.08 × 10-3). The initial velocities (Vi) of the reactions are 0.006; 0.10 and 0.13 mol l-1min-1 respectively for the three isolates (S1, S2, S3). The results obtained deserve further study, it is desirable to purify the amylase enzyme and monitor the growth of both actinomycetal strains on optimized medium, to determine their production mechanisms for the enzyme
