Contribution à l’étude cinétique des extraits enzymatiques de quelques souches de Streptomyces sp isolées du sol de la région de Mostaganem

Abstract

amylase in the biodegradation of starch. The main objective of this study is to demonstrate the enzymatic activity of the amylase extracts of these strains. In this work, three strains of acténobacteries belonging to the genus Streptomyces sp were isolated from soil of de Mostaganem region .Morphologically, these isolates are identified and characterized by macro and microscopic observations, followed by physiological and biochemical tests. Submerged fermentation of the isolates in liquid medium rich-starch was performed to produce the amylases after nearly the extraction of soluble enzyme fractions , the protein quantification and kinetic parameters (Km,Vmax,Vi ) of these extracts were determined by colorimetric methods Buiret and Fehling reagent at λ =554nm and λ=600nm . The results of the physiological and biochemical tests are positive with the exception of the nitrate test for the strain S3, which is negative. Macro and microscopic characterizations confirm that the three isolates of actinobacteria belong to the genus Streptomyces sp .the enzymes crude extracts of the strains have concentrations of 0,033; 0,0026 and 0,0025 μmol/l Respectively for the three isolates (S3, S2, S1).the dosage of the products released during the different hydrolysis reactions of the substrate (starch) respectively have higher values of S3and S2 μmole glucose /l for the isolate S1. However , the Km values are very low , obtained with the extracts of the strains of Streptomyces sp . 0,10×10-3, 0,12×10-3 et 0,20×10-3respectively for S3 ,S2and S1. The initial velocities (Vi) of the reactions are 0,06;0,125;0,24 mol. l-1.min-1 respectively for the three isolates (S1, S2 ,S3). The experimental results open up positive prospects for good industrial operations strains and enzymes.