β-Amylases fromBacillus polymyxaNo. 72

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Abstract
β-Amylase producing microorganisms were effectively isolated by using an amylase inhibitor (S–AI). Among fortytwo strains isolated, strain No. 72 was found to be the most potent β-amylase producing microorganism, and was identified as Bacillus polymyxa. This strain produced 45 units of β-amylase per ml in the medium consisting of 4% soluble starch, 1% meat extract, 1% peptone and 0.3% NaCl (pH 7.0) at 30°C. Two kinds of β-amylase, that is, 7.3 mg of β-amylase I and 3.9 mg of β-amylase II, were obtained from one liter of culture broth as electrophoretically homogeneous forms. β-Amylases I and II were very similar to each other in their enzymatic properties except the small difference in isoelectric point (I; pH 8.35, II; pH 8.59). β-Amylases I and II were most active at pH 7.5 at 45°C, and stable between pH 4 and 9 for 15 hr at 37°C. Both enzymes were strongly inhibited by PCMB, and reactivated by cysteine. The molecular weights of β-amylase I and II were estimated to be about 44,000. The amino acid compositions were also studied.