Cheese and Yogurt By-Products as Valuable Ingredients for the Production of Prebiotic Oligosaccharides

The growing global market of dairy products has led to the need for alternative approaches regarding whey valorization, which is the primary by-product of cheese and strained yogurt production. In this context, prebiotic galactooligosaccharides can be produced enzymatically from whey using commercially available beta-galactosidases. A comparative study was conducted to assess the production of galactooligosaccharides from sweet and acid whey, thereby employing two commercial beta-galactosidases from Aspergillus oryzae and Kluyveromyces lactis. The study considered the initial lactose content and enzyme load as variables. The maximum yields of galactooligosaccharides in concentrated sweet whey (15% w/v initial lactose) and raw acid whey (3.1% w/v initial lactose) reached 34.4 and 14.7% with lactase from Kluyveromyces lactis (0.13 U/mL), respectively. The corresponding galactooligosaccharide yields for lactase from Aspergillus oryzae were equal to 27.4 and 24.8% in the most concentrated sweet and acid whey, respectively, using enzyme loads of 2 U/mL in sweet whey and 1 U/mL in acid whey. Concerning the profile of the produced galactooligosaccharides, the Kluyveromyces lactis lactase hydrolyzed lactose more rapidly and resulted in higher levels of allolactose and lower levels of 6-galactosyl-lactose, compared to the lactase from Aspergillus oryzae, and achieved in both cases a polymerization degree of up to six.