The characteristics of B-galactosidase from Bncillus circulms, and its suitability for hydrolysis of milk lactose were compared with those of Escherichia co/i and Kluywwwn~ces In&s enzymes. Enzyme activity of P-galactosidase from B. circu/ms was not affected by major cations and proteins present in skim milk, whereas milk proteins and sodium and calcium ions decreased the activity of the enzymes from E. co/i and K. Incris. The enzyme from B. circulnns produced less oligosaccharides than E. co/i and K. /actis during hydrolysis of lactose in skim milk at different lactose concentrations. Oligosaccharides produced by the enzyme from B. circulms disappeared almost completely at the latter stage of hydrolysis, while a large amount of oligosaccharides were still detected even at 98% conversion of lactose with enzymes from E. co/i and K. Inctis.

jg-Galactosidases (EC 3.2.1.23) from Bacillus circulans were purified and separated into two different enzyme forms, using Sephadex G-150, ion-exchange, polybuffer chromatography, and preparative polyacrylamide gel electrophoresis. The molecular weights estimated for these two enzymes were 2.4x lO5 (jS-galactosidase-1) and 1.6x lO5 (/?-galactosidase-2). They showed similar isoelectric points of about 4.5 and the same optimum pH of 6.0, whereas they were considerably different in Km values, substrate specificity, and particularly oligosaccharideproducing activity./?-Galactosidase-2 produced many galacto-oligosaccharides, including di-, tri-, tetra-, and pentasaccharides, during hydrolysis of4.56% lactose. When 60% of the lactose was converted, the total amount of oligosaccharide production reached a maximum at which about 41% of the products formed were oligosaccharides. /?-Galactosidase-1 produced only 6%at its maximum.

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