Kinetics of galactooligosaccharide (GOS) production with two β-galactosidases combined: Mathematical model and raw material effects

Galactooligosaccharides (GOS), functional carbohydrates generally produced from different lactose sources, are relevant by-products in dairy industry. Experimental GOS production and kinetic profiles were evaluated in three raw materials with different content of lactose (pure lactose, permeate, and cheese whey). Reaction media with 40% (w/w) of initial lactose and β-galactosidase from Aspergillus oryzae, Kluyveromyces lactis or their mixture were assayed. Also, a kinetic enzymatic model was proposed, correlated, and validated. GOS production was in the range of 32–46% of total carbohydrates for all lactose sources. After evaluating their combination, polymerisation degree (DP) of GOS contained mainly DP3 species and similar concentration of DP2 and DP4, which is the desired mixture for probiotic growth. Results suggest that a combination of β-galactosidases from different sources improves GOS quality in prebiotic synthesis. Moreover, the mathematical model describes GOS kinetics for the experimental data, regardless of raw material or β-galactosidase employed.