Optimisation of Lactose Hydrolysis by Combining Solids and ß-Galactosidase Concentrations in Whey Permeates

A detailed study of lactose hydrolysis was conducted using 50, 250 and 500 units of ß-galactosidase (Kluyveromyces lactis and Bacillus licheniformis origin) in acid and sweet whey permeates at different solid concentrations 20%, 30% and 40% (w·v⁻¹). The amount of lactose, glucose and galactose was measured by HPLC – RID. Hydrolysis was carried out at optimal enzyme temperature 42.5 °C for 4 h. Medium pH before hydrolysis was adjusted using 10% KOH. The experimental results were compared taking into account the sugar profiles and experimental conditions. The highest lactose hydrolysis occurred at solid concentration 20% (w·v⁻¹) and at enzyme amounts of 250 and 500 units for both permeates. Using 50 units of enzymes, in many cases the amounts of glucose and galactose were more or less equal in range of 6.5–43 g·l⁻¹ and the hydrolysis percentage was quite low in the range of 2.7–62%. Comparing both whey permeates, a higher hydrolysis percentage (99%) was obtained using acid whey and 500 enzyme units.