116 research outputs found
Specific Gaseous Conditions Significantly Improve Lactobacillus casei and Escherichia coli Survival to Freeze Drying and Rehydration
 Background and objective: Presence of oxygen during production and rehydration of freeze-dried starters and probiotics can decrease viability of the bacteria. Indeed, removal of water from cells during freeze-drying can promote dysfunction in anti-oxidative mechanisms, resulting in oxidative stress by accumulation of reactive oxygen species. The aim of this study was to show how atmospheric or less oxidative gaseous conditions affect bacterial survival to freeze-drying and rehydration of two strains, including Lactobacillus casei, a widely used bacteria in biotechnology, and Escherichia coli, a laboratory model bacteria.Material and methods: Lactobacillus casei ATCC 334 and Escherichia coli K12 were freeze dried for 24h in 5% sucrose (m v-1). Two gaseous conditions (an oxygen-free gas and atmospheric air) were used during various steps of the process, including bacterial cultivation, mixing of the bacteria with the protectant and rehydration. Oxygen-free gas condition was obtained with an oxygen-free gas, composed of nitrogen, hydrogen and carbon dioxide (N2H2CO2)and an anaerobic chamber.Results and conclusion: Gaseous conditions included significant effects on bacterial survival rates (P<0.001 for Lactobacillus casei and Escherichia coli). Interestingly, for both bacteria, the optimal combination was atmospheric air during mixing of the bacteria with the lyoprotectant (P<0.001 for Lactobacillus casei and Escherichia coli) and N2H2CO2 during rehydration (P<0.001 for Lactobacillus casei and P<0.05 for Escherichia coli). Management of gaseous conditions during a freeze-drying process and rehydration (atmospheric air during mixing of the bacteria with lyoprotectant and oxygen-free gas during rehydration) enhances survival of the bacteria by preserving them from oxidative stress.Conflict of interest: The authors declare no conflict of interest
Study and optimization of freeze-drying cycles of a model probiotic strain
[EN] This work is based on the experimental study of the freeze-drying process to understand the impact of numerous factors on the survival rates of a model probiotic strain of Lactobacillus casei type. With the aim to find out if cell density in the matrix and survival rates are linked, we have studied the location of the cells after freeze drying inside a porous matrix composed of a lactose basis with a polymer, the polyvinylpyrrolidone (PVP) in various amounts. The best survival rate were obtained at slow freezing rate for a formulation containing 5% (m/V) of lactose and 5% (m/V) of PVP.Verlhac, P.; Vessot-Crastes, S.; Degobert, G.; Cogné, C.; Andrieu, J.; Beney, L.; Gervais, P. (2018). Study and optimization of freeze-drying cycles of a model probiotic strain. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat PolitÚcnica de ValÚncia. 635-642. https://doi.org/10.4995/IDS2018.2018.7400OCS63564
The Yin-Yang of the Green Fluorescent Protein:Impact on Saccharomyces cerevisiae stress resistance
International audienceAlthough fluorescent proteins are widely used as biomarkers (Yin), no study focuses on their influence on the microbial stress response. Here, the Green Fluorescent Protein (GFP) was fused to two proteins of interest in Saccharomyces cerevisiae. Pab1p and Sur7p, respectively involved in stress granules structure and in Can1 membrane domains. These were chosen since questions remain regarding the understanding of the behavior of S. cerevisiae facing different heat kinetics or oxidative stresses. The main results showed that Pab1p-GFP fluorescent mutant displayed a higher resistance than that of the wild type under a heat shock. Moreover, fluorescent mutants exposed to oxidative stresses displayed changes in the cultivability compared to the wild type strain. In silico approaches showed that the presence of the GFP did not influence the structure and so the functionality of the tagged proteins meaning that changes in yeast resistance were certainly related to GFP ROS-scavenging ability (Yang)
RĂŽle de la membrane plasmique dans la survie des microorganismes Ă la dĂ©shydratation : Contribution Ă lâoptimisation de procĂ©dĂ©s de conservation des microorganismes
Cette synthĂšse est consacrĂ©e au rĂŽle de la membrane plasmique des microorganismes, Ă travers ses Ă©volutions structurales et fonctionnelles, dans la survie Ă la dĂ©shydratation. Elle comprend une premiĂšre partie dans laquelle sont regroupĂ©s les principaux rĂ©sultats portant sur lâinfluence de la dĂ©shydratation sur la survie microbienne, sur le comportement membranaire in situ et sur les mĂ©canismes physiques de la dĂ©stabilisation membranaire. La deuxiĂšme partie est consacrĂ©e Ă la transposition de cette comprĂ©hension aux applications de dĂ©shydratation industrielle des microorganismes. Elle porte sur le dĂ©veloppement dâun procĂ©dĂ© de dĂ©shydratation des microorganismes et sur la mise au point dâoutils prĂ©dictifs pour le sĂ©chage des microorganismes
Louis Pasteur au cĆur de la rĂ©volution alimentaire
Louis Pasteur devoted much of his early work to wine, its fermentation and diseases. Surrounded by his colleagues, he set up a field laboratory in Arbois and analysed each diseased wine, creating a microbial landscape by observing it under the microscope. Pasteur deduced that unusual ferments were responsible for the wine's deviations from alcoholic fermentation. He realised that successful fermentations had to be carried out by human intervention, combining the principles of restraint and hygiene to stop the development of disease-causing microbes. Pasteur then sought a method to kill or inhibit the bad ferments without hindering the development and activities of the good ferments. The history of pasteurisation is thus that of a compromise between destroying undesirable microbes and preserving the treated foodstuff, its colour, taste and smell. His work paved the way for the rationalisation of preservation processes, and his method was to have a universal impact, inspiring scientific and technological developments that continue to benefit the quality of food and drink to this day.Louis Pasteur a consacrĂ© une grande partie de ses premiers travaux au vin, Ă sa fermentation et Ă ses maladies. EntourĂ© de ses collaborateurs, il installe un laboratoire de campagne Ă Arbois et analyse chaque vin malade, crĂ©ant un paysage microbien en l'observant au microscope. Pasteur en dĂ©duit que des ferments inhabituels sont responsables des dĂ©viations du vin par rapport Ă la fermentation alcoolique. Il se rend compte que les fermentations rĂ©ussies doivent ĂȘtre rĂ©alisĂ©es par l'homme, en combinant les principes de modĂ©ration et d'hygiĂšne pour stopper le dĂ©veloppement des microbes pathogĂšnes. Pasteur cherche alors une mĂ©thode pour tuer ou inhiber les mauvais ferments sans entraver le dĂ©veloppement et l'activitĂ© des bons ferments. L'histoire de la pasteurisation est donc celle d'un compromis entre la destruction des microbes indĂ©sirables et la conservation de la denrĂ©e traitĂ©e, de sa couleur, de son goĂ»t et de son odeur. Ses travaux ont ouvert la voie Ă la rationalisation des procĂ©dĂ©s de conservation et sa mĂ©thode a eu un impact universel, inspirant des dĂ©veloppements scientifiques et technologiques qui continuent Ă bĂ©nĂ©ficier Ă la qualitĂ© des aliments et des boissons jusqu'Ă aujourd'hui
Influence of the fluidity of the membrane on the response of microorganisms to environmental stresses
International audienceThe aim of this mini-review is to relate membrane physical properties to the adaptation and resistance of microorganisms to environmental stresses. In the first part, the effects of various stresses on the structure and dynamic properties of phospholipid and biological membranes are presented. The compensation of these effects, i.e., change in membrane fluidity, phase transitions, by the active cellular control of the membrane chemical composition, is then described. In this natural process, the change in membrane fluidity is viewed as the detecting "input" signal that initiates the regulation, activating proteic effectors that in turn may influence the chemical composition of the membrane (feedback). This adaptation system allows the maintenance of the physical characteristics of membranes and, thereby, of their functionality. When environmental stresses are extreme and occur abruptly, the regulation process may not compensate for the changes in the membrane physical characteristics. In such cases, important variations in the membrane fluidity and structure may induce cellular damages and cell death. However, the lethal consequences are not systematically observed because protective effects of changes in the membrane physical state on the resistance to stresses are also reported
Sélection et intégration d'une souche probiotique fonctionnelle dans une matrice sÚche
Les probiotiques sont des micro-organismes vivants, capables d interagir avec le microbiote et les cellules de l organisme hĂŽte. Par leurs prĂ©sences ou leurs mĂ©tabolismes, ils contribuent notamment Ă la rĂ©gulation du systĂšme immunitaire. D un point de vue technologique, le dĂ©veloppement d un complĂ©ment alimentaire contenant des probiotiques nĂ©cessite la maitrise des Ă©tapes de sĂ©lection et de production d une bactĂ©rie fonctionnelle sous forme sĂšche et revivifiable. Au cours de ce travail, nous avons dĂ©veloppĂ© des tests de criblage en cytomĂ©trie en flux, permettant de dĂ©terminer l aptitude d une bactĂ©rie Ă ĂȘtre sĂ©chĂ©e et l origine de sa sensibilitĂ©. Pour mettre en place ces tests, nous nous sommes intĂ©ressĂ©s aux mĂ©canismes mis en jeu lors du procĂ©dĂ© de sĂ©chage. Ainsi, lors de la dĂ©shydratation, les micro-organismes vont subir simultanĂ©ment un stress osmotique et un stress oxydant. Les rĂ©sultats montrent un fort impact du sĂ©chage sur la viabilitĂ© et le potentiel immuno-modulateur avec une diminution de la composante pro-inflammatoire (IL-12). Pour protĂ©ger les bactĂ©ries, trois stratĂ©gies d optimisation ont Ă©tĂ© dĂ©veloppĂ©es : le sĂ©chage par formation de mousse, l encapsulation dans une matrice alginate-protĂ©ines de pois, et le co-sĂ©chage d une bactĂ©rie fragile avec une bactĂ©rie rĂ©sistante. Les connaissances acquises au cours de cette Ă©tude ont permis d optimiser la production industrielle de la souche finale du projet. Afin de rĂ©pondre au nouveau cadre rĂ©glementaire europĂ©en, une Ă©tude clinique en double aveugle contre placĂ©bo est actuellement en cours (2011-2013)Probiotics are live microorganisms that can act on the immune system at specific sites in the gastro-intestinal tract. From a technological point of view, the development of a dietary supplement containing viable and functional probiotics requires the control of the selection and production steps. In a first time, we have developed specific and sensitive screening tests to determine the ability of bacteria to be dried and the origin of its sensitivity. To develop these tests, we investigated the mechanisms involved during drying process. Thus, microorganisms simultaneously undergo osmotic stress and oxidative stress. Results show a strong impact of drying on the survival rate and immunomodulatory potential with a decrease of proinflammatory cytokines (IL-12). To protect probiotic bacteria, three optimization strategies have been developed: drying by foam formation, encapsulation of probiotic bacteria using a pea-protein alginate matrix and drying of a sensitive probiotic strain with a resistant bacterium. Knowledge obtained during this study was used to optimize the industrial process of the final strain of the project. A randomized double blinded (RDB) trial is in progress (2011-2013) to test the bacteria in humansDIJON-BU Doc.Ă©lectronique (212319901) / SudocSudocFranceF
Conservation Ă long terme de systĂšmes biologiques viables et fonctionnels
National audienceLa congélation et la déshydratation permettent la conservation de systÚmes biologiques sur de longues périodes par le ralentissement des réactions de dégradation cellulaire. Ces opérations impliquent des transferts de chaleur et de masse pouvant conduire à l'altération des structures cellulaires. La maßtrise de la cinétique de ces transferts, associée à l'utilisation de différents protectants cellulaires, permet la mise en place de protocoles de congélation et de déshydratation spécifiques en fonction du systÚme biologique à conserver
Implication de la membrane plasmique dans la survie de Saccharomyces cerevisiae lors de perturbations hydriques (rÎle clé de l'ergostérol)
La conservation de microorganismes d intĂ©rĂȘt (ferments, probiotiques) sous forme sĂšche et revivifiable est trĂšs rĂ©pandue dans l industrie. Cependant, les procĂ©dĂ©s de dĂ©shydratation conduisent Ă des taux de survie variables en fonction du groupe, de l espĂšce et de la souche de microorganismes considĂ©rĂ©e ainsi que du type de procĂ©dĂ© utilisĂ© (sĂ©chage, lyophilisation, congĂ©lation). La membrane plasmique (MP), de par sa position entre l environnement intra et extracellulaire, est une cible privilĂ©giĂ©e des perturbations hydriques. Les modifications de cette structure lors de stress hydriques sont dĂ©crites pour ĂȘtre directement impliquĂ©es dans la mort des microorganismes. La comprĂ©hension des rĂ©ponses membranaires se produisant pendant un cycle de dĂ©shydratation/rĂ©hydratation est essentielle afin d optimiser la survie des microorganismes lors des procĂ©dĂ©s de dĂ©shydratation. Les manipulations rĂ©alisĂ©es lors de cette Ă©tude ont visĂ© Ă caractĂ©riser les modifications fonctionnelles (intĂ©gritĂ©) et structurales (dĂ©formations, rĂ©partition latĂ©rale de microdomaines riches en stĂ©rols) de la MP de Saccharomyces cerevisiae lors de diffĂ©rents types de perturbations hydriques (dĂ©shydratations osmotiques de diffĂ©rentes amplitudes et cinĂ©tiques, sĂ©chage dans diffĂ©rentes ambiances gazeuses). L impact de la composition de la MP sur la survie des levures a Ă©galement Ă©tĂ© Ă©tudiĂ© par l utilisation de mutants accumulant diffĂ©rents types de stĂ©rols au niveau membranaire. Ce travail a confirmĂ© la forte implication de la MP dans la mort des cellules lors de perturbations hydriques. L Ă©tude des modifications membranaires a permis d Ă©lucider le lien entre la cinĂ©tique de dĂ©shydratation et la survie des levures. Il a Ă©galement Ă©tĂ© montrĂ© que l ergostĂ©rol est une molĂ©cule clĂ© dans la survie des levures aux perturbations hydriques.Preservation of microorganisms of interest (ferments, probiotics) in dry form is widespread in the industry. However, the dehydration processes lead to variable survival rates according to the group, species and strain of microorganism considered, but also according to the type of process used (drying, freeze drying, freezing). The plasma membrane (PM), by its position between the intra-and extracellular environment, is a target of hydric perturbations. Changes in this structure during hydric stresses are described to be directly involved in microorganism death. Understanding of membrane responses occurring during a dehydration/rehydration cycle is essential to maximize the survival of microorganisms in the process of dehydration.Manipulations performed in this study aimed to characterize functional (integrity) and structural (deformations, lateral distribution of sterol-rich microdomains) changes of the PM of Saccharomyces cerevisiae during different types of hydric perturbations (osmotic dehydration of different magnitudes and kinetics, drying in different gas atmospheres). The impact of the composition of PM on yeast survival was also studied by using mutants accumulating different types of sterols in membranes. This work confirmed the strong involvement of the PM in cell death during hydric perturbations. The study of membrane changes helped to elucidate the relationship between the kinetics of dehydration and survival of yeasts. It has also been shown that ergosterol is a key molecule for the survival of yeasts during hydric perturbations.DIJON-BU Doc.Ă©lectronique (212319901) / SudocSudocFranceF
- âŠ