title: Synthesis of Oligosaccharides Derived from Lactulose (OsLu) Using Soluble and Immobilized Aspergillus oryzae β-Galactosidase.
abstract: β-Galactosidase from Aspergillus oryzae offers a high yield for the synthesis of oligosaccharides derived from lactulose (OsLu) by transgalactosylation. Oligosaccharides with degree of polymerization (DP) ≥ 3 have shown to possess higher in vitro bifidogenic effect than di- and tetrasaccharides. Thus, in this work, an optimization of reaction conditions affecting the specific selectivity of A. oryzae β-galactosidase for synthesis of OsLu has been carried out to enhance OsLu with DP ≥ 3 production. Assays with β-galactosidase immobilized onto a glutaraldehyde-agarose support were also carried out with the aim of making the process cost-effective and industrially viable. Optimal conditions with both soluble and immobilized enzyme for the synthesis of OsLu with DP ≥ 3 were 50 °C, pH 6.5, 450 g/L of lactulose, and 8 U/mL of enzyme, reaching yields of ca. 50% (w/v) of total OsLu and ca. 20% (w/v) of OsLu with DP 3, being 6'-galactosyl-lactulose the major one, after a short reaction time. Selective formation of disaccharides, however, was favored at 60 °C, pH 4.5, 450 g/L of lactulose and 8 U/mL of enzyme. Immobilization increased the enzymatic stability to temperature changes and allowed to reuse the enzyme. We can conclude that the use, under determined optimal conditions, of the A. oryzae β-galactosidase immobilized on a support of glutaraldehyde-agarose constitutes an efficient and cost-effective alternative to the use of soluble β-galactosidases for the synthesis of prebiotic OsLu mixtures.
authors.affiliation: Laboratorio de Higiene Inspección y Control de Alimentos, Departamento de Química Analítica, Nutrición y Bromatología, Universidade de Santiago de Compostela , Lugo , Spain.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Cardelle-Cobas
authors.affiliation: Departamento Bioactividad y Análisis de Alimentos, Instituto de Investigación en Ciencias de la Alimentación (CIAL, CSIC-UAM) , Madrid , Spain.
authors.forename: Agustin
authors.initials: A
authors.lastname: Olano
authors.affiliation: Departamento de Biociencias, Facultad de Química, Universidad de la República , Montevideo , Uruguay.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Irazoqui
authors.affiliation: Departamento de Biociencias, Facultad de Química, Universidad de la República , Montevideo , Uruguay.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Giacomini
authors.affiliation: Departamento de Biociencias, Facultad de Química, Universidad de la República , Montevideo , Uruguay.
authors.forename: Francisco
authors.initials: F
authors.lastname: Batista-Viera
authors.affiliation: Departamento Bioactividad y Análisis de Alimentos, Instituto de Investigación en Ciencias de la Alimentación (CIAL, CSIC-UAM) , Madrid , Spain.
authors.forename: Nieves
authors.initials: N
authors.lastname: Corzo
authors.affiliation: Departamento Producción y Caracterización de Nuevos Alimentos, Instituto de Investigación en Ciencias de la Alimentación (CIAL, CSIC-UAM) , Madrid , Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Corzo-Martínez
keywords: Aspergillus oryzae; glutaraldehyde–agarose; immobilization; lactulose; oligosaccharides