SCREENING OF ASPERGILLUS NIGER AND A. FLAVUS STRAINS FOR EXTRA CELLULAR ALPHA-AMYLASE ACTIVITY

Abstract

Five fungal strains of each of the two filamentous fungi viz., Aspergillus niger Van Tieghem and A. flavus Link ex Gray, indigenous to Pakistan, were screened for their alpha-amylase activity. Different selected strains were grown on two growth media viz., Potato Dextrose Agar (PDA) and Enzyme Production Medium (EPM), at three pH levels viz., 4.5, 5.5 and 6.5, in all the possible combinations. Performance of various strains was recorded in terms of hydrolyzing zone formation. Generally test strains exhibited their best performance on EPM at pH 4.5. On the basis of their best performance on solid media, strain 74 and strain 198 of A. niger and strain 209 and strain 231 of A. flavus were selected for periodic evaluation of their alpha-amylase activity in liquid medium, using shake flask technique. All the test strains exhibited their maximum alpha-amylase activity after 48 h incubation.