CNRS Food Processing and Microbiology Laboratory

Dijon, France

CNRS Food Processing and Microbiology Laboratory

Dijon, France
SEARCH FILTERS
Time filter
Source Type

Martin-Dejardin F.,CNRS Food Processing and Microbiology Laboratory | Ebel B.,CNRS Food Processing and Microbiology Laboratory | Lemetais G.,CNRS Food Processing and Microbiology Laboratory | Nguyen Thi Minh H.,CNRS Food Processing and Microbiology Laboratory | And 3 more authors.
European Journal of Pharmaceutical Sciences | Year: 2013

The aim of this work was to apply flow cytometry in order to assess and compare the viability of freeze-dried entrapped bacteria with an usual technique by quantification by plate count techniques. It also aimed at studying the effect of various cryoprotectants on the viability of an entrapped Bifidobacterium bifidum subjected to freeze-drying to check their ability to be delivered all along the gastro-intestinal tract. The alginate-pectinate beads were chosen as the encapsulation matrix added with different protectants. The beads were characterized by scanning electron microscopy and the viability was checked by both methods. The best combination to improve viability of entrapped bacteria subjected to freeze-drying is made of glycerol 20% (one cryoprotectant) and sodium ascorbate 10% (one anti-oxidative compound). This study also demonstrates that flow cytometry allows assessment of entrapped bacteria viability. Indeed we showed that viability evaluated by plate method is correlated to that obtained by flow cytometry. So, flow cytometry is a rapid method to determine cell viability after encapsulation and freeze-drying. Finally, these beads seem to be a promising probiotic delivery system to target the colon. © 2013 Elsevier B.V. All rights reserved.


Dantigny P.,CNRS Food Processing and Microbiology Laboratory | Nanguy S.P.M.,CNRS Food Processing and Microbiology Laboratory | Judet-Correia D.,University of Burgundy | Bensoussan M.,University of Burgundy
International Journal of Food Microbiology | Year: 2011

The objective of this study was to design a germination model dedicated to fungi. The percentage of germinated spores, P(%), depended on the maximum percentage of germination Pmax (%), the germination time, τ (h) and a design parameter, d (-) according to. The model was capable to fit satisfactorily either apparent symmetric and asymmetric shapes of germination curves. The accuracy of τ determined by using the logistic or the present model was at least twice that obtained by the Gompertz equation. In contrast to the logistic model, the new model is by essence asymmetric. Therefore, its use is consistent with skewed distributions of the individual germination times that were observed experimentally in many cases. © 2011 Elsevier B.V.


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 | Year: 2010

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.


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 | Year: 2010

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.


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 | Year: 2011

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.


Kalai S.,CNRS Food Processing and Microbiology Laboratory | Bensoussan M.,CNRS Food Processing and Microbiology Laboratory | Dantigny P.,CNRS Food Processing and Microbiology Laboratory
Food Microbiology | Year: 2014

In the environment, fungal conidia are subject to transient conditions. In particular, temperature is varying according to day/night periods. All predictive models for germination assume that fungal spores can adapt instantaneously to changes of temperature. The only study that supports this assumption (Gougouli and Koutsoumanis, 2012, Modelling germination of fungal spores at constant and fluctuating temperature conditions. International Journal of Food Microbiology, 152: 153-161) was carried out on Penicillium expansum and Aspergillus niger conidia that, in most cases, already produced germ tubes. In contrast, the present study focuses on temperature shifts applied during the first stages of germination (i.e., before the apparition of the germ tubes). Firstly, germination times were determined in steady state conditions at 10, 15, 20 and 25°C. Secondly, temperature shifts (e.g., up-shifts and down-shifts) were applied at 1/4, 1/2, and 3/4 of germination times, with 5, 10 and 15°C magnitudes.Experiments were carried out in triplicate on Penicillium chrysogenum conidia on Potato Dextrose Agar medium according to a full factorial design. Statistical analysis of the results clearly demonstrated that the assumption of instantaneous adaptation of the conidia should be rejected. Temperature shifts during germination led to an induced lag time or an extended germination time as compared to the experiments conducted ay steady state. The induced lag time was maximized when the amplitude of the shift was equal to 10°C. Interaction between the instant and the direction of the shift was highlighted. A negative lag time was observed for a 15°C down-shift applied at 1/4 of the germination time. This result suggested that at optimal temperature the rate of germination decreased with time, and that the variation of this rate with time depended on temperature. © 2014 Elsevier Ltd.


Lemetais G.,CNRS Food Processing and Microbiology Laboratory | Dupont S.,CNRS Food Processing and Microbiology Laboratory | Beney L.,CNRS Food Processing and Microbiology Laboratory | Gervais P.,CNRS Food Processing and Microbiology Laboratory
Applied Microbiology and Biotechnology | Year: 2012

The plasma membrane (PM) is a key structure for the survival of cells during dehydration. In this study, we focused on the concomitant changes in survival and in the lateral organization of the PM in yeast strains during desiccation, a natural or technological environmental perturbation that involves transition from a liquid to a solid medium. To evaluate the role of the PM in survival during air-drying, a wild-type yeast strain and an osmotically fragile mutant (erg6?) were used. The lateral organization of the PM (microdomain distribution) was observed using a fluorescent marker related to a specific green fluorescent proteinlabeled membrane protein (Sur7-GFP) after progressive or rapid desiccation. We also evaluated yeast behavior during a model dehydration experiment performed in liquid medium (osmotic stress). For both strains, we observed similar behavior after osmotic and desiccation stresses. In particular, the same lethal magnitude of dehydration and the same lethal kinetic effect were found for both dehydration methods. Thus, yeast survival after progressive air-drying was related to PM reorganization, suggesting the positive contribution of passive lateral rearrangements of the membrane components. This study also showed that the use of glycerol solutions is an efficient means to simulate air-drying desiccation. © Springer-Verlag 2012.


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 | Year: 2011

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.


Dao T.,CNRS Food Processing and Microbiology Laboratory | Dantigny P.,CNRS Food Processing and Microbiology Laboratory
Food Control | Year: 2011

This review discusses the effects of ethanol on the inhibition of growth and germination of fungi and on the inactivation of fungal spores. After a brief survey on the impact of spoilage fungi on the economy and food quality, the major applications of ethanol in controlling fruit decay and extending the shelf-life of food products are reviewed. Many parameters including minimum inhibitory concentration (MIC) and D-values for various moulds are included. The thermodynamic relationship between the liquid phase and the headspace and the mode of action of ethanol on fungi are explained. Due to their promising use as a fumigant, special attention is paid to ethanol vapours. © 2010 Elsevier Ltd.


Nguyen Thi Minh H.,CNRS Food Processing and Microbiology Laboratory | Durand A.,CNRS Food Processing and Microbiology Laboratory | Loison P.,CNRS Food Processing and Microbiology Laboratory | Perrier-Cornet J.-M.,CNRS Food Processing and Microbiology Laboratory | Gervais P.,CNRS Food Processing and Microbiology Laboratory
Applied Microbiology and Biotechnology | Year: 2011

Bacillus subtilis(B. subtilis) cells were placed in various environmental conditions to study the effects of aeration, water activity of the medium, temperature, pH, and calcium content on spore formation and the resulting properties. Modification of the sporulation conditions lengthened the growth period of B. subtilis and its sporulation. In some cases, it reduced the final spore concentration. The sporulation conditions significantly affected the spore properties, including germination capacity and resistance to heat treatment in water (30 min at 97°C) or to high pressure (60 min at 350 MPa and 40°C). The relationship between the modifications of these spore properties and the change in the spore structure induced by different sporulation conditions is also considered. According to this study, sporulation conditions must be carefully taken into account during settling sterilization processes applied in the food industry. © 2011 Springer-Verlag.

Loading CNRS Food Processing and Microbiology Laboratory collaborators
Loading CNRS Food Processing and Microbiology Laboratory collaborators