title: Reaction kinetics and galactooligosaccharide product profiles of the β-galactosidases from Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae.
abstract: β-Galactosidase enzymes are used in the dairy industry to convert lactose into galactooligosaccharides (GOS) that are added to infant formula to mimic the molecular sizes and prebiotic functions of human milk oligosaccharides. Here we report a detailed analysis of the clearly different GOS profiles of the commercial β-galactosidases from Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae. Also the GOS yields of these enzymes differed, varying from 48.3% (B. circulans) to 34.9% (K. lactis), and 19.5% (A. oryzae). Their incubation with lactose plus the monosaccharides Gal or Glc resulted in altered GOS profiles. Experiments with13C6labelled Gal and Glc showed that both monosaccharides act as acceptor substrates in the transgalactosylation reactions. The data shows that the lactose isomers β-d-Galp-(1→2)-d-Glcp, β-d-Galp-(1→3)-d-Glcp and β-d-Galp-(1→6)-d-Glcp are formed from acceptor reactions with free Glc and not by rearrangement of Glc in the active site.
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands. Electronic address: h.yin@rug.nl.
authors.forename: Huifang
authors.initials: H
authors.lastname: Yin
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands. Electronic address: jelle.bultema@gmail.com.
authors.forename: Jelle B
authors.initials: JB
authors.lastname: Bultema
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands. Electronic address: l.dijkhuizen@rug.nl.
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands. Electronic address: s.s.van.leeuwen@rug.nl.
authors.forename: Sander S
authors.initials: SS
authors.lastname: van Leeuwen
mesh_terms: D001236:Aspergillus oryzae / Q000201:enzymology; D001407:Bacillus / Q000201:enzymology*; D005690:Galactose / Q000737:chemistry*; D006801:Humans; D007716:Kluyveromyces / Q000201:enzymology*; D009844:Oligosaccharides / Q000737:chemistry*; D056692:Prebiotics; D001616:beta-Galactosidase / Q000737:chemistry*
chemical_list: D009844:Oligosaccharides; D056692:Prebiotics; D001616:beta-Galactosidase; D005690:Galactose
keywords: Aspergillus oryzae; Bacillus circulans; Galactooligosaccharides; Infant nutrition; Kluyveromyces lactis; Prebiotics; β-Galactosidase