title: Human milk and mucosal lacto- and galacto-N-biose synthesis by transgalactosylation and their prebiotic potential in Lactobacillus species.
abstract: Lacto-N-biose (LNB) and galacto-N-biose (GNB) are major building blocks of free oligosaccharides and glycan moieties of glyco-complexes present in human milk and gastrointestinal mucosa. We have previously characterized the phospho-β-galactosidase GnbG from Lactobacillus casei BL23 that is involved in the metabolism of LNB and GNB. GnbG has been used here in transglycosylation reactions, and it showed the production of LNB and GNB with N-acetylglucosamine and N-acetylgalactosamine as acceptors, respectively. The reaction kinetics demonstrated that GnbG can convert 69 ± 4 and 71 ± 1 % of o-nitrophenyl-β-D-galactopyranoside into LNB and GNB, respectively. Those reactions were performed in a semi-preparative scale, and the synthesized disaccharides were purified. The maximum yield obtained for LNB was 10.7 ± 0.2 g/l and for GNB was 10.8 ± 0.3 g/l. NMR spectroscopy confirmed the molecular structures of both carbohydrates and the absence of reaction byproducts, which also supports that GnbG is specific for β1,3-glycosidic linkages. The purified sugars were subsequently tested for their potential prebiotic properties using Lactobacillus species. The results showed that LNB and GNB were fermented by the tested strains of L. casei, Lactobacillus rhamnosus (except L. rhamnosus strain ATCC 53103), Lactobacillus zeae, Lactobacillus gasseri, and Lactobacillus johnsonii. DNA hybridization experiments suggested that the metabolism of those disaccharides in 9 out of 10 L. casei strains, all L. rhamnosus strains and all L. zeae strains tested relies upon a phospho-β-galactosidase homologous to GnbG. The results presented here support the putative role of human milk oligosaccharides for selective enrichment of beneficial intestinal microbiota in breast-fed infants.
authors.affiliation: Laboratorio de Bacterias Lácticas y Probióticos, Departamento de Biotecnología de Alimentos, IATA-CSIC, Valencia, Spain.
authors.forename: Gonzalo N
authors.initials: GN
authors.lastname: Bidart
authors.affiliation: Departamento de Microbiología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Rodríguez-Díaz
authors.affiliation: Structural Biochemistry Laboratory, Centro de Investigación Príncipe Felipe, Eduardo Primo Yúfera 3, E-46012, Valencia, Spain.
authors.forename: Martina
authors.initials: M
authors.lastname: Palomino-Schätzlein
authors.affiliation: Laboratorio de Bacterias Lácticas y Probióticos, Departamento de Biotecnología de Alimentos, IATA-CSIC, Valencia, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Monedero
authors.affiliation: Laboratorio de Bacterias Lácticas y Probióticos, Departamento de Biotecnología de Alimentos, IATA-CSIC, Valencia, Spain. yebra@iata.csic.es.
authors.forename: María J
authors.initials: MJ
authors.lastname: Yebra
mesh_terms: D000116:Acetylgalactosamine / Q000378:metabolism; D000117:Acetylglucosamine / Q000378:metabolism; D004187:Disaccharides / Q000737:chemistry / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006031:Glycosylation; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D007778:Lactobacillus / Q000201:enzymology / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008895:Milk, Human / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D056692:Prebiotics
chemical_list: D004187:Disaccharides; D056692:Prebiotics; C056853:6-O-galactopyranosylgalactose; C040456:lacto-N-biose II; D006026:Glycoside Hydrolases; C022361:6-phospho-beta-galactosidase; D000116:Acetylgalactosamine; D000117:Acetylglucosamine
keywords: Galacto-N-biose; Human milk oligosaccharides; Lacto-N-biose; Lactobacillus; Prebiotic; Transglycosylation