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A thermostable α-amylase from a newly isolated Bacillus licheniformis NH1 was purified, characterized and the gene was isolated, sequenced and expressed in Escherichia coli BL21. The enzyme (BLA.NH1) was purified to homogeneity by 40–60% ammonium sulphate precipitation, Sephadex G-100 gel filtration and Sepharose mono Q anion exchange chromatography, with a 3.08-fold increase in specific activity and 15.9% recovery. The molecular weight of the BLA.NH1 was estimated to be 58kDa by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) and gel filtration. The enzyme was highly active over a wide range of pH from 5.0 to 10.0. The relative activities at pH 5.0, 9.0 and 10.0 were about 89, 96.6 and 90%, of that at pH 6.5, respectively. The optimum temperature of the purified enzyme was 90°C. BLA.NH1 belonged to the EDTA-sensitive α-amylase, but its activity was not …