9 research outputs found

    Image_1_Fermentation of Nocellara Etnea Table Olives by Functional Starter Cultures at Different Low Salt Concentrations.TIF

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    <p>Nocellara Etnea is one of the main Sicilian cultivars traditionally used to produce both olive oil and naturally fermented table olives. In the present study, the effect of different salt concentrations on physico-chemical, microbiological, sensorial, and volatile organic compounds (VOCs) formation was evaluated in order to obtain functional Nocellara Etnea table olives. The experimental design consisted of 8 treatments as follow: fermentations at 4, 5, 6, and 8% of salt with (E1-E4 samples) and without (C1-C4 samples) the addition of starters. All the trials were carried out at room temperature (18 ± 2°C) and monitored for an overall period of 120 d. In addition, the persistence of the potential probiotic Lactobacillus paracasei N24 at the end of the process was investigated. Microbiological data revealed the dominance of lactic acid bacteria (LAB), starting from the 7th d of fermentation, and the reduction of yeasts and enterobacteria in the final product inoculated with starters. VOCs profile highlighted a high amount of aldehydes at the beginning of fermentation, which significantly decreased through the process and a concomitant increase of alcohols, acids, esters, and phenols. In particular, esters showed an occurrence percentage higher in experimental samples rather than in control ones, contributing to more pleasant flavors. Moreover, acetic acid, ethanol, and phenols, which often generate off-flavors, were negatively correlated with mesophilic bacteria and LAB. It is interesting to note that salt content did not affect the performances of starter cultures and slightly influenced the metabolome of table olives. Sensory data demonstrated significant differences among samples registering the highest overall acceptability in the experimental sample at 5% of NaCl. The persistence of the L. paracasei N24 strain in experimental samples, at the end of the process, revealed its promising perspectives as starter culture for the production of functional table olives with reduced salt content.</p

    Mucus adhesion and SpaCBA pili gene diversity among <i>L. rhamnosus</i>.

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    <p>Panel (A) shows the genotype and phenotype of all strains. Based on our genomic analysis, pilin and sortase genes were assigned as present (green) or divergent (red). Sequences of corresponding genes were further analyzed using blastx. The sequence identity was shown by an upper triangle superposed to the SOLiD genomic data, where the colour gradient corresponds to the identity percentage to GG pili genes. We also indicated if the strains were tested by immunoblotting analysis (DB), electron microscopy (EM) or <i>in vitro</i> competitive binding assay (AB). Green is for pili positive and red for pili negative. Panel (B) shows the human mucus binding ability (%) of all <i>L. rhamnosus</i> isolates ranked from the lowest to the highest mucus binder.</p

    CRISPR spacer oligotyping and CRISPR-associated protein diversity in <i>L. rhamnosus</i> species.

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    <p>Panel (A) illustrates the genetic organization of the CRISPR system and its associated genes in <i>L. rhamnosus</i> GG. Panel (B) shows the conservation (blue), the partial conservation (grey) or the absence (yellow) of <i>L. rhamnosus</i> GG spacers. The presence (green) or the absence (red) of the <i>cas</i> genes is also indicated in Panel (C). Strains are organized according to their genetic relatedness defined in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003683#pgen-1003683-g001" target="_blank">Figure 1</a>.</p

    Analysis of genome diversity in <i>L. rhamnosus</i> by mapped SOLiD sequencing.

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    <p>The 100 <i>L. rhamnosus</i> strains were clustered using hierarchical clustering <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003683#pgen.1003683-Sturn1" target="_blank">[78]</a> based on their relative shared gene content with <i>L. rhamnosus</i> GG. Strain names were colour-coded as follows: green for dairy isolates, purple for intestinal isolates, orange for oral isolates, magenta for vaginal isolates and blue for clinical/other isolates. Four main groups or clusters were highlighted and numbered. The <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003683#pgen-1003683-g001" target="_blank">Figure 1</a> also shows the 17 variable chromosomal regions identified in GG, as further detailed in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003683#pgen-1003683-t001" target="_blank">Table 1</a>. Each row corresponds to one strain, and each column shows the genes in these variable regions, colour-coded as follows: blue for present and yellow for absent.</p

    API 50CH fermentative profile of <i>L. rhamnosus</i> strains.

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    <p>Fermentation ability is indicated in black for positive, grey for partially positive and white for negative. Strains are organized according to their genetic relatedness as defined in the hierarchical clustering and coloured according to their respective niche/origin (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003683#pgen-1003683-g001" target="_blank">Figure 1</a>). Carbohydrates of interest are marked by a red asterisk. Black arrows show fermentative profile shifts among <i>L. rhamnosus</i> strains.</p

    Pilosotype distribution in our <i>L. rhamnosus</i> collection.

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    <p>The table describes the niches or isolation sources, the number of strains per group and their pilosotype, <i>i.e.</i> the presence of an intact and functional SpaCBA pili cluster as determined in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003683#pgen-1003683-g006" target="_blank">Figure 6</a>. Probiotic strains GG, VIFIT, IDOF, AK-RO and CO-RO were classified as intestinal isolates. The group ‘Others’ contained strains of unspecified origins (clinical specimens) or from minor isolation source (<i>n</i><2), <i>i.e.</i> hip punction or pus.</p

    Anthropocentric view of the <i>L. rhamnosus</i> species.

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    <p>The interactions between <i>L. rhamnosus</i> and the human cavities are frequent and occur in various contexts, <i>i.e.</i> consumption of food products (common scenario) or development of bacteremia (rare event). For each niche or isolation source, the strains were grouped according to their geno-phenotype (radar plot). The geno-phenotype is based on the scoring of distinctive genetic and phenotypic traits measured in this study, <i>i.e.</i> gene-content, CRISPR oligotype, bile resistance, pilosotype, sugar group I (dulcitol, D-arabinose and L-fucose), sugar group II (D-saccharose, D-maltose, methyl-α-D-glucopyranoside and D-turanose) and sugar group III(L-rhamnose, L-sorbose, D-ribose and D-lactose). The distinction between the two main geno-phenotypes mostly relies on gene acquisition and loss, point mutations, genetic reorganization that possibly reflect strain adaptation to an ecological niche.</p
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