Formation of oligosaccharides from whey UF-permeate by enzymatic hydrolysis — analysis of factors

Two-level fractional factorial experiments were designed to study effects of enzyme (0.05 and 0.1%) and initial lactose concentrations (Lo: 14 and 23%), pH (5.0 and 7.0) and temperature (35 and 45 °C) on enzymatic formation of oligosaccharides (OS) from whey UF-permeate in a batch reactor. β-d-galactosidase from Aspergillus oryzae (A), Kluyveromyces lactis (B) and K. fragilis (C) were compared. Hydrolysis with B and C gave comparable yields which were higher than that from A at identical conditions. Lo did not influence reaction time, but concentration of OS significantly increased by increasing Lo for all enzymes. Increasing Lo reduced the yield after hydrolysis with A and B, but improved the yield for C. Lo had negligible effect on degree of hydrolysis (DH) for A and C. However, increasing Lo significantly lowered DH for B. Increasing enzyme concentration significantly reduced reaction time for A, but it had no effect on that for B and C. DH significantly decreased after increasing concentration of A. Consequently, OS and yield were reduced. Applying B and C at higher concentration improved DH, OS and yield. Increasing temperature or pH reduced DH, OS and yield for A, but increased the responses for B and C.