pH stability of the β-galactosidases from <i>B. breve</i> β-gal I (•) and β-gal II (○) incubated at 37°C in Britton-Robinson buffer over a pH range of pH 5.0–9.0 for 4 h (solid lines) and 10 h (dashed lines).

<p>The residual activity was measured after 4(B) and <i>o</i>NPG was used as substrate for the enzyme assay. Values are the mean of two independent experiments and the standard deviation was always less than 5%.</p>