BETA-AMYLASES FROM BACILLUS, POLYMYXA NO-72

.beta.-Amylase [EC 3.2.1.2] producing microorganisms were effectively isolated by using an amylase inhibitor(S-AI). Among 42 strains isolated, strain No. 72 was the most potent .beta.-amylase producing microorganism, and was identified as B. polymyxa. This strain produced 45 units of .beta.-amylase/ml in the medium consisting of 4% soluble starch, 1% meat extract, 1% peptone and 0.3% NaCl (pH 7.0) at 30.degree. C. Two kinds of .beta.-amylase, that is 7.3 mg of .beta.-amylase I and 3.9 mg of .beta.-amylase II, were obtained from 1 l of culture broth as electrophoretically homogeneous forms. .beta.-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). .beta.-Amylases I and II were most active at pH 7.5 at 45.degree. C, and stable between pH 4 and 9 for 15 h at 37.degree. C. Both enzymes were strongly inhibited by PCMB [p-chloromercuri-benzoate], and reactivated by cysteine. The MW of .beta.-amylase I and II were estimated to be about 44,000. The amino acid compositions were also studied.