Production and properties of α-amylase from thermophilic Bacillus sp.

Abstract

α-amylase (1,4-α-D-glucan glucanohydrolase, EC 3.2.1.1) production by thermophilic Bacillus sp strain SMIA-2 cultivated in liquid media containing soluble starch reached a maximum at 48h, with levels of 57U/ mL. Studies on the α-amylase characterization revealed that the optimum temperature for activity was 70°C. The enzyme was stable for 2h at 50°C, while at 60°C, 70°C and 90°C, 4%, 13% and 38% of the original activities were lost, respectively. The optimum pH of the enzyme was 7.5. After incubation of crude enzyme solution for 24h at pH 7.5, a decrease of about 5% of its original activity was observed. The enzyme was strongly inhibited by Co2+, Cu2+ and Ba2+, but less affected by Ca2+, Mg2+, Ni2+, Sr2+ and Mn 2+. The enzyme in 1M and 5M NaCl solutions the enzyme retained 70% and 47% of the original activity after 24h of incubation at 4°C, respectively.