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Dupont S.,CNRS Food Processing and Microbiology Laboratory | Beney L.,CNRS Food Processing and Microbiology Laboratory | Ferreira T.,University of Poitiers | Gervais P.,CNRS Food Processing and Microbiology Laboratory
Biochimica et Biophysica Acta - Biomembranes

The plasma membrane (PM) is a main site of injury during osmotic perturbation. Sterols, major lipids of the PM structure in eukaryotes, are thought to play a role in ensuring the stability of the lipid bilayer during physicochemical perturbations. Here, we investigated the relationship between the nature of PM sterols and resistance of the yeast Saccharomyces cerevisiae to hyperosmotic treatment. We compared the responses to osmotic dehydration (viability, sterol quantification, ultrastructure, cell volume, and membrane permeability) in the wild-type (WT) strain and the ergosterol mutant erg6Δ strain. Our main results suggest that the nature of membrane sterols governs the mechanical behavior of the PM during hyperosmotic perturbation. The mutant strain, which accumulates ergosterol precursors, was more sensitive to osmotic fluctuations than the WT, which accumulates ergosterol. The hypersensitivity of erg6Δ was linked to modifications of the membrane properties, such as stretching resistance and deformation, which led to PM permeabilization during the volume variation during the dehydration-rehydration cycles. Anaerobic growth of erg6Δ strain with ergosterol supplementation restored resistance to osmotic treatment. These results suggest a relationship between hydric stress resistance and the nature of PM sterols. We discuss this relationship in the context of the evolution of the ergosterol biosynthetic pathway. © 2010 Elsevier B.V. All rights reserved. Source

Ebel B.,CNRS Food Processing and Microbiology Laboratory | Lemetais G.,CNRS Food Processing and Microbiology Laboratory | Beney L.,CNRS Food Processing and Microbiology Laboratory | Cachon R.,CNRS Food Processing and Microbiology Laboratory | And 4 more authors.
Critical Reviews in Food Science and Nutrition

Probiotic microorganisms have historically been used to rebalance disturbed intestinal microbiota and to diminish gastrointestinal disorders, such as diarrhea or inflammatory bowel diseases (e.g., Crohn's disease and ulcerative colitis). Recent studies explore the potential for expanded uses of probiotics on medical disorders that increase the risk of developing cardiovascular diseases and diabetes, such as obesity, hypercholesterolemia, arterial hypertension, and metabolic disturbances such as hyperhomocysteinemia and oxidative stress. This review aims at summarizing the proposed molecular and cellular mechanisms involved in probiotic-host interactions and to identify the nature of the resulting beneficial effects. Specific probiotic strains can act by modulating immune response, by producing particular molecules or releasing biopeptides, and by modulating nervous system activity. To date, the majority of studies have been conducted in animal models. New investigations on the related mechanisms in humans need to be carried out to better enable targeted and effective use of the broad variety of probiotic strains. © 2014 Copyright Taylor and Francis Group, LLC. Source

Cao-Hoang L.,CNRS Food Processing and Microbiology Laboratory | Cao-Hoang L.,Hanoi University of Science and Technology | Fougere R.,CNRS Food Processing and Microbiology Laboratory | Wache Y.,CNRS Food Processing and Microbiology Laboratory
Food Chemistry

β-Carotene (BC) exhibits controversial antioxidant properties as it may act also as a prooxidant. Its stability toward oxidation depends on its dispersion form and can be increased through encapsulation. In this study, oxidation of BC from synthetic and natural origins was investigated after dispersion in Tween micelles or poly lactic acid (PLA) particles. Two oxidation systems were used: autooxidation and oxidation by xanthine oxidase-generated-reactive oxygen species. Results showed that synthetic BC formed nanometric negatively-charged particles in both Tween micelle and PLA systems, whereas the natural BC sample used was shown to be already pre-oxidised, forming micrometric-uncharged aggregates in Tween micelles and nanosize PLA particles. Samples also displayed different type of supramolecular aggregation (H or J), as shown in their UV-vis spectra, which were related to their particle size and their origin. Natural BC-loaded Tween micelles displayed high absorption in the range 350-450. nm (absorption of oxidation products) and rapid autodegradation rate which could reflect a high prooxidant activity. Interestingly, these properties were both significantly reduced with PLA encapsulation. Furthermore, the degradation rate and the oxidation product apparition of the two BC forms could be related to the supramolecular structure adopted by BC during dispersion. © 2010 Elsevier Ltd. Source

Nanguy S.P.-M.,CNRS Food Processing and Microbiology Laboratory | Perrier-Cornet J.-M.,CNRS Food Processing and Microbiology Laboratory | Bensoussan M.,University of Burgundy | Dantigny P.,CNRS Food Processing and Microbiology Laboratory
International Journal of Food Microbiology

The effects of water activity (aw) of diverse media i/ culture medium for sporogenesis, aw sp ii/ liquid spore suspension medium, aw su and iii/ medium for germination, aw ge, on the germination time tG of Aspergillus carbonarius, Aspergillus flavus, Penicillium chrysogenum and Penicillium expansum were assessed according to a screening matrix at 0.95 and 0.99 aw. It was shown that i/ reduced tGs were obtained at 0.95 aw sp except for P. expansum ii/ a significant effect of aw su on tG was demonstrated for A. carbonarius, P. chrysogenum and P. expansum iii/ the most important factor for controlling the germination time was the medium for germination except for A. carbonarius (aw su). In accordance with the fact that fungal spores can swell as soon as they are suspended in an aqueous solution it is recommended to re-suspend fungal spores in a solution at the same water activity as that of subsequent germination studies. © 2010 Elsevier B.V. Source

Dupont S.,CNRS Food Processing and Microbiology Laboratory | Beney L.,CNRS Food Processing and Microbiology Laboratory | Ritt J.-F.,Laval University | Lherminier J.,University of Burgundy | Gervais P.,CNRS Food Processing and Microbiology Laboratory
Biochimica et Biophysica Acta - Biomembranes

In this study, we investigated the kinetic and the magnitude of dehydrations on yeast plasma membrane (PM) modifications because this parameter is crucial to cell survival. Functional (permeability) and structural (morphology, ultrastructure, and distribution of the protein Sur7-GFP contained in sterol-rich membrane microdomains) PM modifications were investigated by confocal and electron microscopy after progressive (non-lethal) and rapid (lethal) hyperosmotic perturbations. Rapid cell dehydration induced the formation of many PM invaginations followed by membrane internalization of low sterol content PM regions with time. Permeabilization of the plasma membrane occurred during the rehydration stage because of inadequacies in the membrane surface and led to cell death. Progressive dehydration conducted to the formation of some big PM pleats without membrane internalization. It also led to the modification of the distribution of the Sur7-GFP microdomains, suggesting that a lateral rearrangement of membrane components occurred. This event is a function of time and is involved in the particular deformations of the PM during a progressive perturbation. The maintenance of the repartition of the microdomains during rapid perturbations consolidates this assumption. These findings highlight that the perturbation kinetic influences the evolution of the PM organization and indicate the crucial role of PM lateral reorganization in cell survival to hydric perturbations. © 2010 Elsevier B.V. All rights reserved. Source

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