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Hidalgo-Cantabrana C.,Dairy Research Institute IPLA CSIC | Sanchez B.,Dairy Research Institute IPLA CSIC | Sanchez B.,University of Vigo | Alvarez-Martin P.,Nestle | And 15 more authors.
Applied and Environmental Microbiology | Year: 2015

Exopolysaccharides (EPS) are extracellular carbohydrate polymers synthesized by a large variety of bacteria. Their physiological functions have been extensively studied, but many of their roles have not yet been elucidated. We have sequenced the genomes of two isogenic strains of Bifidobacterium animalis subsp. lactis that differ in their EPS-producing phenotype. The original strain displays a nonmucoid appearance, and the mutant derived thereof has acquired a mucoid phenotype. The sequence analysis of their genomes revealed a nonsynonymous mutation in the gene Balat_1410, putatively involved in the elongation of the EPS chain. By comparing a strain from which this gene had been deleted with strains containing the wild-type and mutated genes, we were able to show that each strain displays different cell surface characteristics. The mucoid EPS synthesized by the strain harboring the mutation in Balat_1410 provided higher resistance to gastrointestinal conditions and increased the capability for adhesion to human enterocytes. In addition, the cytokine profiles of human peripheral blood mononuclear cells and ex vivo colon tissues suggest that the mucoid strain could have higher anti-inflammatory activity. Our findings provide relevant data on the function of Balat_1410 and reveal that the mucoid phenotype is able to alter some of the most relevant functional properties of the cells. © 2015, American Society for Microbiology.

Alvarez-Sieiro P.,Dairy Research Institute IPLA CSIC | Redruello B.,Dairy Research Institute IPLA CSIC | Ladero V.,Dairy Research Institute IPLA CSIC | Marti M.C.,Dairy Research Institute IPLA CSIC | And 2 more authors.
Canadian Journal of Microbiology | Year: 2016

A selective culture medium containing acid-hydrolyzed gliadins as the sole nitrogen source was used in the search for sourdough-indigenous lactic acid bacteria (LAB) with gliadin-metabolizing activity. Twenty gliadindegrading LAB strains were isolated from 10 sourdoughs made in different ways and from different geographical regions. Fifteen of the 20 isolated strains were identified as Lactobacillus casei, a species usually reported as subdominant in sourdough populations. The other 5 gliadin-degrading strains belonged to the more commonly encountered sourdough species Leuconostoc mesenteroides and Lactobacillus plantarum. All these strains were shown to be safe in terms of their resistance to antimicrobial agents. When individually incubated with the _2-gliadinderived immunotoxic 33-mer peptide (97.5 ppm), half of the L. casei strains metabolized at least 50% of it within 24 h. One strain metabolized 82% of the 33-mer peptide within 8 h and made it fully disappear within 12 h. These results reveal for the first time the presence in sourdough of proteolytic L. casei strains with the capacity to individually metabolize the coeliac-disease-related 33-mer peptide. © 2016, National Research Council of Canada. All rights reserved.

Alvarez-Sieiro P.,Dairy Research Institute IPLA CSIC | Redruello B.,Dairy Research Institute IPLA CSIC | Ladero V.,Dairy Research Institute IPLA CSIC | Canedo E.,Dairy Research Institute IPLA CSIC | And 3 more authors.
Food Chemistry | Year: 2015

For patients with celiac disease, gliadin detoxification via the use of gliadinases may provide an alternative to a gluten-free diet. A culture medium, in which gliadins were the sole source of nitrogen, was developed for screening for microorganisms with gliadinase activity. The problem of gliadin insolubility was solved by mild acid treatment, which renders an acid-hydrolysed gliadin/peptide mixture (AHG). This medium provided a sensitive and reliable means of detecting proteases, compared to the classical spectrophotometric method involving azocasein. When a sample of fermented wheat (a source of bacteria) was plated on an AHG-based culture medium, strains with gliadinase activity were isolated. These strains' gliadinase profiles were determined using an AHG-based substrate in zymographic analyses. © 2014 Elsevier Ltd. All rights reserved.

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