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PublicationJournal of Molecular Catalysis B: Enzymatic
Year2011
Volume72
Pages206-212
International

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

Authors:Cecilia Guerrero , Carlos Vera , Francisco José Plou Gasca, Andres Illane
Groups of research:Applied Biocatalysis
Commercial β-galactosidase preparations from Bacillus circulansKluyveromyces lactis and Aspergillus oryzae were evaluated as catalysts for the synthesis of lactulose. Among them, the enzyme from A. oryzaewas 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.
Keywords:Lactulose; Prebiotic; β-Galactosidase; Transgalactosylation; Galacto-oligosaccharides
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