Screening of Cyanobacterial Strains for alpha-Amylase Enzyme under formal and Salt Stress Conditions

摘要

Three cyanobacterial strains-Anabaena variabilis NCCU 9, Anabaena ambigua and Anabaena variabilis NCCU 441 were screened for alpha-amylase activity in the extracellular medium. These strains were cultured on BG 11 media at pH 7.2 and 30°C temperaturewith 1500-1600 lux light intensity. Of all the three. A. variabilis NCCU 9 strain showed maximum enzyme activity. Standard protocol for a-amylase activity was optimised for cyanobacterial strains by taking different temperature and pH ranges and the highest enzyme activity was obtained at 35°C temperature and 6.5 pH. Cyanobacteria secrete a-amylase in the late log phase of their life cycle and the amount of enzyme produced was found to reach the maximum at 16th day after inoculation. It was also observed that an increase in salt concentration led to enhanced enzyme production reaching the maximum at 1M NaCl concentration in case of A. variabilis NCCU 9 strain. The a-amylase enzyme remained stable for one month at 4°C.