pH (A and B) and temperature (C and D) optimum of β-galactosidase activity for <i>B. breve</i> β-gal I (•) and β-gal II (○) using <i>o</i>NPG (A and C) and lactose (B and D) as substrate.

<p>Values are the mean of two independent experiments and the standard deviation was always less than 5%.</p>