Characterization of a Thermostable α‐Amylase from <i>Bacillus licheniformis</i> NCIB 6346

Abstract

With one exception (NCIB 9668), the extracellular amylases from 10 strains of Bacillus licheniformis were thermostable and retained more than 98% of their original activity after incubation at 85°C for 60 min. The enzyme from B. licheniformis NCIB 6346 was purified 30‐fold by ion‐exchange chromatography and was characterized. It had an endo‐action on starch yielding maltopentaose as the major product, and was identified as an α‐amylase. The purified enzyme had a molecular weight of 62 650, was stable between pH 7 and 10 and was maximally active at 70‐90°C at pH 7.0. It closely resembled commercial thermostable α‐amylases in its general properties and it is concluded that B. licheniformis provides a good source of these enzymes.