Evaluation of a novel oxidative stress-adaptation method on membrane integrity, intracellular oxidation states, and survival of Bifidobacterium spp. during yoghurt fermentation and storage

<div>This dataset describes the research conducted in the study, “Survival of Oxidative Stress-Adapted <em>Bifidobacterium</em> spp. in Yoghurt,” which consisted of three research phases. During phase 1, cultures of <em>B. bifidum, B. breve</em>, and <em>B. animalis</em> subsp. <em>animalis</em> were subjected to a sublethal (0.4 mM) H₂O₂ treatment followed by exposure to lethal (1 mM) H₂O₂ treatments for three successive generations. Phase 2 tested the H₂O₂-treated <em>Bifidobacterium</em> cells against previously lethal oxidative stress conditions. Finally, phase 3 evaluated the survival of the stress-adapted <em>Bifidobacterium</em> spp. during yoghurt fermentation and storage (28 days; analysis on days 0, 7, 14, 21, and 28).</div> <p><br></p> <div>The dataset files are organised by chapters: Chapters 2, 4, 5, and 6. The fluorescent histograms show the effects of the H₂O₂ treatments on the membrane integrity and intracellular oxidation states of the <em>Bifidobacterium</em> cells. SEM and TEM images indicate morphological and ultrastructural adaptations resulting from the H₂O₂ treatments. Furthermore, the fluorescent biplots illustrate both the membrane integrity and intracellular oxidation responses of the H₂O₂-treated <em>Bifidobacterium</em> cells following a lethal oxidative stress challenge. The tables display growth kinetics and maximum population density, along with the statistical analysis of the stress-adapted <em>Bifidobacterium</em> spp. under varying conditions of oxidative stress (0, 0.1, and 1 mM H₂O₂). Scanning and transmission electron microscopy (SEM and TEM) images also reflect the morphological and ultrastructural adaptations of stress-adapted <em>Bifidobacterium</em> spp. in response to lethal oxidative stress.</div> <p><br></p> <div>The analyses conducted during the yoghurt shelf-life study are presented in various figures and tables within the dataset. The figures show pH measurements (at 0, 1, 2, 3, and 3.4 hours) and <em>Bifidobacterium</em> spp. viability levels (before and after fermentation), along with the statistical analyses in the relevant tables. Physicochemical analyses, including pH, titratable acidity (TA), oxidation-reduction potential (ORP), and % syneresis, are shown during refrigerated storage on days 0, 7, 14, 21, and 28. Bacteriological analyses, such as standard plate counts and viability proportion index (VPI₂₈), are also presented, along with the respective statistical analyses for each yoghurt. Principal component analysis (PCA) was conducted on data collected during the shelf-life stage.</div> <p>The dataset also includes the determination of bacterial viability using a novel propidium monoazide quantitative polymerase chain reaction (PMAxx-qPCR) method, with measurements on days 0 and 28 of shelf-life. Relevant tables and figures show the melt curve, standard curve, simple linear regression, and Bland-Altman method of comparison (% Difference vs. Average) of the PMAxx-qPCR method compared to the standard plate count method, along with the statistical analyses of bacterial viability measured by the PMAxx-qPCR method. Finally, a summary table linking the yoghurt shelf-life study to the thesis' problem statement is shown.</p>