Production of Prebiotic Galacto-Oligosaccharides from Acid Whey Catalyzed by a Novel β-Galactosidase from Thermothielavioides terrestris and Commercial Lactases: A Comparative Study
Athanasios Limnaios, Maria Tsevdou, Elena Tsika, Nausika Korialou, Anastasia Zerva, Evangelos Topakas, Petros Taoukis
Abstract
The steadily increasing global popularity of Greek strained yoghurt has necessitated alternative valorization approaches for acid whey, the major straining process effluent. In this context, prebiotic galacto-oligosaccharides can be enzymatically synthesized from acid whey lactose, via either commercial or novel β-galactosidases. A comparative study of galacto-oligosaccharide production from acid whey was carried out, employing two commercial β-galactosidases (from Kluyveromyces lactis and Aspergillus oryzae) and one novel, in-house produced (from Thermothielavioides terrestris), as a function of the initial lactose content and enzyme load. Selected reaction conditions for β-galactosidases from K. lactis, A. oryzae, and T. terrestris were 35 °C at pH 7.2, 45 °C at pH 4.5, and 50 °C at pH 4.0, respectively. Maximum galacto-oligosaccharide yields equal to 23.7, 23.4, and 25.7% were achieved with, respectively, 0.13 U/mL of K. lactis β-galactosidase in non-concentrated acid whey, 4 U/mL of A. oryzae β-galactosidase, and 8 U/mL of T. terrestris β-galactosidase in acid whey concentrated to 20% w/v initial lactose content. The increased galacto-oligosaccharide productivity of the thermophilic β-galactosidase from T. terrestris can be a determining asset in a combined concentration and oligomerization industrial process. This will allow for high galacto-oligosaccharide yields for efficient, cost-effective production of valuable prebiotics from acid whey.