D-Glucose/D-Galactose (solid lines) and GalGlc/GalGal (dashed lines) ratios (A); GalGlc/GalLac (solid lines) and GalGal/GalLac (dashed lines) ratios (B) during lactose conversion by B. breve β-gal I (close symbol) and β-gal II (open symbol).

The reactions were performed at 30°C at an initial lactose concentration of 200 g L−1 in sodium phosphate buffer (pH 6.5) and 1 mM MgCl2 with 1.0 ULac mL−1 β-gal I or 2.5 ULac mL−1 β-gal II.