Commercial β-galactosidase preparations from Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae were evaluated as catalysts for the synthesis of lactulose. Among them, the enzyme from A. oryzae was selected for further studies. The effect of reaction conditions was then studied on product composition during the kinetically controlled synthesis of lactulose by transgalactosylation with A. oryzae β-galactosidase. Product composition was ...