Isolement de quelques souches des actinomycètes productrices des amylases et évaluation de leurs paramètres cinétiques

Abstract

Enzymes of bacterial origin represent an important source in industrial applications,such as amylases which are the main enzymes involved in the biodegradation of starch. In this study, three strains of actinomycetes were isolated from the soil of the region of Ouilis (Mostaganem). These isolates are identified and characterized by macro and microscopic observations, followed by physiological and biochemical tests. Submerged fermentation of the isolates in amylase-rich liquid medium was performed to produce the amylases. After the extraction of the soluble enzyme fractions, quantification and kinetics of the enzymatic extracts were carried out at wavelengths λ = 540 nm by Buiret and Fehling colorimetric methods assays. The results of the macro, microscopic characterizations and the physiological and biochemical tests confirm that the three isolates of actinomycetes belong to the genus Streptomyces sp. The crude enzymatic extracts of the strains have concentrations of 0.1265; 0.1098 and 0.0967 mg / ml respectively for the three isolates (A1, A2 and A6). The dosage of the products released during the different hydrolysis reactions of the substrates respectively have higher values of 0.0226 and 0.0246 mol glucose / l for the isolates A1 and A2. However, the Km values are the lowest for Streptomyces sp. A1 and A2 (6 × 10-3 and 1,2 × 10-3) compared to isolate A6 (8,9 × 10-3). The initial velocities (Vi) of the reactions are 5.62 ; 21.9 and 7.5 mol.l-1.min-1 respectively for the three isolates A1 ; A2 and A6. The results obtained deserve further study, from which it is desirable to purify the amylase enzyme and open up positive prospects for good industrial exploitation of the strains and their enzymes.