Culture condition for the production of glucoamylase enzyme by different isolates of Aspergillus spp.

Optimization of the growth conditions for maximum production of the glucoamylase enzyme by different isolates of Aspergillus spp. isolated from various sources were carried out in liquid culture. Screening of amylase producers was carried out on PDA agar plates supplemented with 2% soluble starch and were detected by the index of amylolytic activity. High thermostable amyloglucosidase yielding isolates designated as, Aspergillus awamori (A1and A7) A. niger (A10), A. terreus (At) and A. tamarii (Aw) used in this study. Maximum enzyme production was recorded at pH 6.0 and 2.0% rice bran as a carbon source for all isolates except Aspergillus terreus (At) which gave the highest enzyme yield at pH 4.0. The enhancement of the nitrogen supplements appear differently among the different isolates, for Aspergillus tamarii (Aw) highest production was obtained in medium supplemented with peptone, whereas A. niger (A10) with sodium nitrate, A. awamori (A1and A7) accomplished this with ammonium chloride and A. terreus (At) recorded the highest production with ammonium sulphate. These isolates are good producers of extracellular thermostable glucoamylases which could be suitable for application in starch processing and food industries.