Isolement et purification de quelques souches d’Actinomycètes productrices des amylases, et l’évaluation de leurs cinétiques enzymatiques

Abstract

Amylases of microbial origin are the main enzymes involved in the biodegradation of starch. These enzymes have various industrial applications. In this study, a forestfloor in the region of HassiMameche (Mostaganem) wasisolated and purifiedfromactinomycetes. After the selection of the strains by biochemical and physiological tests, a fermentation in a liquid medium rich in starch was carried out for a production of amylases. Finally, the amylase extractsobtainedwerequantified by the colorimetricmethod of Biuret. In order to determine the kineticparameters km, Vmax and Vi of the enzymatic extracts, under controlled operating conditions (pH, temperature) a starch-based reaction medium was used. The Fehling Liquor Reagent method was used to assay the products (glucose) releasedafterhydrolysis of the substrate (starch) by spectrophotometryat λ = 540 nm. The results reveal macro and microscopicthatstrains of actenobacteria are part of the genusStreptomycessp. The colonies obtained are of different sizes and shapes, possessing a vegetative mycelium surmounted by an aerial mycelium of different colors, yellow, white, beige, etc. The isolates are Gram positive. All biochemical and physiological tests are positive and some are negative. The lowest Km kinetic values werenoted for twoisolatesStreptomycessp. A6 and A4 (Km = 1.3 × 10-6) with initial velocity values of 14 × 10-3 and 13 × 10-3. Finally, it is desirable to purify the amylase enzyme and characterize it by techniques such as electrophoresis and HPLC.