title: Cloning, expression and characterization of a β-D-xylosidase from Lactobacillus rossiae DSM 15814(T).
abstract: BACKGROUND
  Among the oligosaccharides that may positively affect the gut microbiota, xylo-oligosaccharides (XOS) and arabinoxylan oligosaccharides (AXOS) possess promising functional properties. Ingestion of XOS has been reported to contribute to anti-oxidant, anti-bacterial, immune-modulatory and anti-diabetic activities. Because of the structural complexity and chemical heterogeneity, complete degradation of xylan-containing plant polymers requires the synergistic activity of several enzymes. Endo-xylanases and β-D-xylosidases, collectively termed xylanases, represent the two key enzymes responsible for the sequential hydrolysis of xylan. Xylanase cocktails are used on an industrial scale for biotechnological purposes. Lactobacillus rossiae DSM 15814(T) can utilize an extensive set of carbon sources, an ability that is likely to contribute to its adaptive ability. In this study, the capacity of this strain to utilize XOS, xylan, D-xylose and L-arabinose was investigated.
  
  
  RESULTS
  Genomic and transcriptomic analyses revealed the presence of two gene clusters, designated xyl and ara, encoding proteins predicted to be responsible for XOS uptake and hydrolysis and D-xylose utilization, and L-arabinose metabolism, respectively. The deduced amino acid sequence of one of the genes of the xyl gene cluster, LROS_1108 (designated here as xylA), shows high similarity to (predicted) β-D-xylosidases encoded by various lactic acid bacteria, and belongs to glycosyl hydrolase family 43. Heterologously expressed XylA was shown to completely hydrolyse XOS to xylose and showed optimal activity at pH 6.0 and 40 °C. Furthermore, β-D-xylosidase activity of L. rossiae DSM 15814(T) was also measured under sourdough conditions.
  
  
  CONCLUSIONS
  This study highlights the ability of L. rossiae DSM 15814(T) to utilize XOS, which is a very useful trait when selecting starters with specific metabolic performances for sourdough fermentation or as probiotics.
authors.affiliation: Department of Soil, Plant and Food Science, University of Bari Aldo Moro, Via G. Amendola 165/A, 70126, Bari, Italy.
authors.forename: Erica
authors.initials: E
authors.lastname: Pontonio
authors.affiliation: School of Microbiology, University College Cork, Cork, Ireland.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mahony
authors.affiliation: Department of Soil, Plant and Food Science, University of Bari Aldo Moro, Via G. Amendola 165/A, 70126, Bari, Italy. raffaella.dicagno@uniba.it.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Di Cagno
authors.affiliation: School of Microbiology, University College Cork, Cork, Ireland.|Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.
authors.forename: Mary
authors.initials: M
authors.lastname: O'Connell Motherway
authors.affiliation: Laboratory of Probiogenomics, Department of Life Sciences, University of Parma, Parma, Italy.
authors.forename: Gabriele Andrea
authors.initials: GA
authors.lastname: Lugli
authors.affiliation: School of Microbiology, University College Cork, Cork, Ireland.|Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.
authors.forename: Amy
authors.initials: A
authors.lastname: O'Callaghan
authors.affiliation: Department of Soil, Plant and Food Science, University of Bari Aldo Moro, Via G. Amendola 165/A, 70126, Bari, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: De Angelis
authors.affiliation: Laboratory of Probiogenomics, Department of Life Sciences, University of Parma, Parma, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Ventura
authors.affiliation: Department of Soil, Plant and Food Science, University of Bari Aldo Moro, Via G. Amendola 165/A, 70126, Bari, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Gobbetti
authors.affiliation: School of Microbiology, University College Cork, Cork, Ireland.|Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.
authors.forename: Douwe
authors.initials: D
authors.lastname: van Sinderen
mesh_terms: D001089:Arabinose / Q000378:metabolism; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007778:Lactobacillus / Q000145:classification / Q000201:enzymology* / Q000235:genetics*; D005810:Multigene Family; D009844:Oligosaccharides / Q000378:metabolism; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D013696:Temperature; D014994:Xylose / Q000378:metabolism; D014995:Xylosidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D009844:Oligosaccharides; D011994:Recombinant Proteins; D014994:Xylose; D001089:Arabinose; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase
keywords: Functional foods; Gut microbiota; Prebiotic; Probiotic; Sourdough; Xylo-oligosaccharides