β-galactosidase from Kluyveromyces lactis immobilized on to thiolsulfinate/thiolsulfonate supports for lactose hydrolysis in milk and dairy by-products.

After reversible immobilization of neutral beta-galactosidase from Kluyveromyces lactis on to thiolsulfinate/thiolsulfonate supports, more than 80 % of the activity was retained. Blocking the remaining reactive groups with glutathione increased the thermal stability of the derivatives almost two-fold. These derivatives achieved a high degree of conversion (85-90 %) of lactose (50g/l) in saline solution, whey, whey permeates, and skimmed milk, either batchwise or in packed beds. They remained fully active upon storage for 10 months in activity buffer at 4 degrees C, and when treated with sanitizing agents.