Characterization of thermostable α-amylase from thermophilic andAlkaliphilic bacillus sp. isolate DM-15

Official URL: http://dx.doi.org/10.3923/rjbsci.2010.118.124

Bacillus sp. DM-15 was isolated from Çiftehan Thermal Spring, Turkey produced thermostable α-amylase at 55°C at pH 9. Analysis of the enzyme for molecular mass and amylolytic activity carried out by SDS-Starch-PAGE electrophoresis revealed a single band with high molecular mass 126 kDa. After extraction, the enzyme remained stable in a range of temperature and pH between 40-100°C and 4.5-10, respectively. The optimum enzyme activity was displayed at 60°C and pH 5.5-6.0. α-amylase production by thermophilic Bacillus sp. strain cultivated in liquid media reached a maximum at 12 h with levels of 27.5 μmol mg-1 protein min-1. The enzyme was stable for 15 min at 60°C while 24% of the original activity was lost at 100°C. Enzyme activity was increased in the presence of 5 mM CaCl2, Na2SO3 and KCl (105%) and inhibited in the presence of 5 mM EDTA, CuSO4, FeSO4, SDS (1%), Urea (8 M), Co up to 98, 79, 57, 36, 33 and 10%, respectively. The DM-15 α-amylase may be suitable for in liquefaction of starch in detergent and textile industries and in other industrial applications.