Stable, inducible thermoacidophilic alpha-amylase from Bacillus acidocaldarius

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Abstract
B. acidocaldarius Agnano 101 produces an inducible thermoacidophilic .alpha.-amylase. The enzyme production occurs during the stationary phase of growth in the presence of compounds with .alpha.-1,4-glucosidic linkages. The enzymatic activity is present in the culture medium and associated with the cells; the enzymes purified from both sources show identical molecular and catalytic properties. The purified amylase has a single polypeptide chain of MW 68,000 and behaves like an .alpha.-amylase with affinity constants for starch and related substances of 0.8 to 0.9 mg/ml. The pH and temperature optima for activity are 3.5 and 75.degree. C, respectively. The amylase is stable at acidic pH (below 4.5). Its thermal stability is strictly dependent upon protein concentration; the half-life at 60.degree. C of the amylase in a 70-.mu.g/ml solution is .apprx. 5 days.