Purification and properties of a new, commercial, thermostableBacillus stearothermophilusα‐amylase

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Abstract
A rapid purification has been developed for Bacillus stearothermophilus α‐amylase starting with the commercial enzyme product. The two‐step procedure, using hydrophobic interaction chromatography and ion exchange, results in a 6.8‐fold increase in specific activity with an 86% recovery of starting activity. The molecular weight of the enzyme was 58,000 when measured by SDS‐PAGE The enzyme preparation consisted of three isozymes with pl values of 8.1, 8.0, and 7.8–7.7. The enzyme mixture had a broad pH optimum of pH 4.0–7.0 at 40° C and a narrower optimum of pH 5.2–6.5 at 90° C. The temperature optimum was 80° C when measured by the starch‐iodine assay; hydrolysis of maltodextrin indicated a constant, maximum rate between 70° C and 100° C. Calcium was shown to increase the half life of the enzyme at 90° C approximately 10‐fold; addition of 10% maltodextrin and calcium increased the half life of the enzyme 80‐fold.