FIG. 1.

pH optima of cell-associated β-galactosidase and lactase activities of Bifidobacterium angulatum. Cells were harvested after 18 h of growth on 10 g of lactose liter⁻¹; lactase activity (■) was determined using lactose as the substrate (1 μmol of glucose released min⁻¹ mg of protein⁻¹), and β-galactosidase activity (●) was determined using p-nitrophenyl-β-galactoside as the substrate (in nanomoles of p-nitrophenol released minute⁻¹ milligram of protein⁻¹) at 37°C.