Influence of reaction conditions on the selectivity of the synthesis of lactulose with microbial β-galactosidases

Cecilia Guerrero, Carlos Vera, Francisco Plou, Andrés Illanes

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81 Scopus citations


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 not affected by pH, temperature, total initial concentration of sugar (lactose plus fructose) and enzyme to substrate ratio within the ranges studied. However, lactose to fructose ratio strongly influenced product composition being then possible to control the lactulose to galacto-oligosaccharide ratio within ample margins. Maximum lactulose yield (0.282 g of lactulose per g initial lactose) was obtained using 1/8 lactose to fructose molar ratio, 50% (w/w) total initial sugars, 40 °C, pH 4.5 and enzyme to initial lactose ratio equivalent to 200 IU/g.

Original languageEnglish
Pages (from-to)206-212
Number of pages7
JournalJournal of Molecular Catalysis B: Enzymatic
Issue number3-4
StatePublished - Nov 2011
Externally publishedYes


  • Galacto-oligosaccharides
  • Lactulose
  • Prebiotic
  • Transgalactosylation
  • β-Galactosidase


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