WorldCat Identities

École doctorale Végétal-Environnement-Nutrition-Agro-Alimentaire-Mer (Angers)

Overview
Works: 172 works in 244 publications in 2 languages and 260 library holdings
Roles: Other, Degree grantor
Publication Timeline
.
Most widely held works by École doctorale Végétal-Environnement-Nutrition-Agro-Alimentaire-Mer (Angers)
Les produits solaires : des pistes pour améliorer leur efficacité : mise au point de méthodes in vitro d'évaluation - criblage de molécules d'intérêt by Clotilde Cheignon( )

2 editions published in 2012 in French and held by 4 WorldCat member libraries worldwide

After bibliographic reminders on skin physiology and the active ingredients used in sunscreen products, we focused on developing methods for evaluating the water resistance. We wanted to demonstrate that it is possible to use another type of equipment that usually recommended for such studies. To assist the formulator in the different steps of the development of sunscreens, tedious job, we have developed a quick process to qualify the product in terms of water resistance. in vitro method for water resistance is indeed quite long, at least 40 minutes of immersion are required, with two successive baths separated by drying stages. Our job was to shorten the duration of this manipulation. It was found that a non water resistant product is rapidly losing its effectiveness (from 5 minutes of immersion) which is very telling. Finally, we evaluated a number of molecules of interest to increase the water resistance of sunscreens, but also to increase their activity in terms of filtration in the UVB and / or UVA. To do this, we used the plant world
Métabolites bioactifs d'Ascomycètes marins : déréplication, isolement, identification et étude de production by Isabelle Kerzaon( Book )

2 editions published in 2009 in French and held by 3 WorldCat member libraries worldwide

In the search for novel bioactive substances, marine-derived micromycetes are a promising source of novel compounds. Previous woks on fungi of regional shellfish farming areas have shown a wide diversity of fungal strains with more than 30 percent producing toxins or bioactive compounds. The present work presents the study of some of these Ascomycetes in order to search novel fungal bioactive substances and to estimate their ability to produce mycotoxins in marine conditions. The 42 extracts from cultures of 11 marine-derived Penicillium sp. strains have been subjected to a screening for biological activities and dereplication by LC-UV/DAD and LC-MS/MS. This led to the selection of 10 neuroactive or cytotoxic extracts and to the identification of 38 metabolites. Bioguided fractionation of an extract of a P. expansum strain led to the isolation and structural identification by NMR of communesin B as the neuroactive compound. Thorough analyses by LC-HRMS/MS led to identification of 14 other communesins including 10 new derivatives. Their structures were determined after development of a predictive model of fragmentation. Meanwhile, 15 marine and terrestrial strains of Aspergillus fumigatus were studied for their production of gliotoxin in the marine environment. The development of a bioassay for the detection and quantification of this mycotoxin has shown the influence of salinity on its excretion
Bridging the gap between social and digital works : system modeling and trust evaluation) by Nagham Alhadad( Book )

3 editions published in 2014 in English and French and held by 3 WorldCat member libraries worldwide

Nowadays, digital systems are connected through complex architectures. Participants to these systems perform activities like chatting or sharing data. Persons, physical and digital resources are involved in these activities, such that a system can be considered as a representation of two worlds, the social world and the digital world and their relations. Evaluating these systems is generally limited to technical aspects. Today, trust becomes an important key in the evaluation process. In this context, we raise two questions: how to formalize the entities that compose a system and their relations for a particular activity? and how to evaluate trust in a system for this activity? Our contributions are divided into two parts. The first part proposes a formal metamodel named SocioPath, to model a system with all entities of social and digital worlds and their relations. The second part evaluates the users' trust in the systems they use for a given activity. We propose an approach named, SocioTrust, to compute the user's trust in a system using probability theory. Then we propose a second approach named, SubjectiveTrust that takes into account the uncertainty in the trust values. This approach is based on subjective logic
La gestion des ressources et des territoires : application à la mise en œuvre de projets de valorisation de sous-produits de poisson by Anaïs Penven( Book )

3 editions published in 2014 in French and held by 3 WorldCat member libraries worldwide

Beyond the technical and technological advances in the conversion of marine by-products into useful products, the territorial, economic, social, political and environmental parameters, which govern all forms of approaches for fish by-products upgrading, must be taken in account. This is essential to understand why and how bioconversion technologies are applicable. The fishery sector is facing several issues such as fish stocks weakening, recourse to imports, aquaculture rising or consumers behaviors which complicate the approach of fish by-products upgrading as it is linked to the raw material processing. Thanks to some projects addressed this thematic in recent years, several quantitative and qualitative data about by-products deposits are available. Then, the aim is to study the feasibility of an upgrading project application on different territories. Firstly based on a study of the French different scenarios, a comparison with the situation in Galicia (Spain) has been made. The comparison of these cases allows to identify factors of success or sticking points such as volumes treated, number and proximity of fish processors, qualitative parameters or management regarding to all kind of up-grading fields. An optimal up-gradation of fish by-products depends of many of these factors it is so essential to identify and to study them. Such demonstration will help developing an efficient decision support instrument (DSI) for future projects. For territories which cannot reach the specifications developed in this work, an alternative solution has been studied which consists in mixing several types of organic by-products from agrofood industries and supermarkets, on a reduced scale. This schematic will permit to bypass the ottlenecks identified in particular by increasing the sources of raw materials, but will induce other issues that should be highlighted
Fondements de la gestion de la pêche à pied sur les vasières du Gois (Côte atlantique française by Inna Boldina( Book )

2 editions published in 2013 in French and held by 3 WorldCat member libraries worldwide

The objective of this thesis is to establish the foundations for understanding the potential impact of clam fishing on the intertidal mudflat ecosystem as well as its economical importance, using an ecosystem approach. This thesis has three parts: the legal component including the synthesis of national and regional clam fishing legal framework, ecological and economical parts. The ecosystem where the recreational clam fishing has been practiced for several decades was studied to evaluate the eventual impact of this activity. Three major biotic components were analyzed : bivalves targeted by the clam fishing (Cerastoderma edule and Venerupis philippinarum), the non-targeted macrofauna and meiofauna. Geostatistical methods were used to assess the impact of the clam fishing on the spatial distribution of organisms belonging to different taxonomic groups. "Non-traditional" methodological approaches have been used to detect the presence of spatial and temporal indicators of regime shift in this ecosystem. The economic surplus generated by recreational clam fishing on Gois site was calculated with the travel cost method. The results of this study provide a basis for sustainable management of the clam fishing at Gois site, and allow a better understanding of the environmental and economical issues of this exceptional site
Caractérisation de la microstructure spatiale de la pomme en lien avec ses propriétés mécaniques par des méthodes quantitatives d'IRM by Guillaume Winisdorffer( Book )

3 editions published in 2014 in French and held by 3 WorldCat member libraries worldwide

Mechanical properties of the pericarp of apple fruit are defined by multiple factors. Dry matter, as an insoluble fraction (cell wall) and a soluble fraction, water status and distribution within cell and tissues, the fraction of air between the cells and their size and organization influence the mechanical behavior of the tissue. Quantitative MRI is an interesting tool as it can non-destructively measure water status and distribution, which have seldom been studied.An original approach was applied by measuring the MRI multi-exponential relaxation signal of the fruit to extract the signal of different water pools. Studying the variations in amplitude and relaxation times of these fractions in fruit of different calibers allowed characterizing the heterogeneity of the fruit and the influence of cell size on MRI signal. A multi-instrumental approach applied to the parenchyma during cold storage then allowed comparing its viscoelastic properties (dynamic mechanical analysis) to its water distribution and its porosity (MRI) and the size, shape (macro-vision) and chemical composition (dosage of soluble sugars, cell wall hemicellulose and pectin) of its cells. Finally, the MRI signal of the tissues of whole fruit was studied at 1 and 6 month's storage.This study demonstrated the interest of MRI approach for characterizing the heterogeneity of the tissue according to water status and distribution and porosity. A better undestanding of some mechanisms implied in the NMR relaxation and of the relative influence of the structural and composition parameters on mechanical properties of the tissues was achieved
Ovatoxines : purification à partir d'Ostropsis cf.Ovata en culture et niveaux d'acccumulation dans les produits de la mer by Charline Brissard( Book )

3 editions published between 2014 and 2016 in French and held by 3 WorldCat member libraries worldwide

Les dinoflagellés du genre Ostreopsis sont connus dans les zones tropicales pour être à l'origine d'intoxications alimentaires, suite à l'accumulation de palytoxine dans les produits de la mer. Probablement en lien avec le changement climatique, Ostreopsis sp. est de plus en plus présent depuis 2006 en Méditerranée française. Dans le cadre de la thèse, les études terrain effectuées durant les étés 2011 et 2012, ont montré que : i) les souches d'Ostreopsis cf. ovata présentent un profil toxinique complexe composé de la palytoxine et surtout 90 % d'ovatoxines (OVTX-a, -b, -c, -d, -e). Un nouvel analogue (OVTX-h) a également été détecté ; ii) les concentrations cellulaires et toxiniques d'O. ovata diminuent avec la profondeur ; iii) différents produits de la mer accumulent les toxines, pouvant présenter un risque réel pour les baigneurs et les consommateurs. Comme il n'existe pas d'étalon d'OVTXs, un des objectifs de la thèse a porté sur le développement d'une procédure de leur purification à partir des extraits d'O. ovata. Pour cela, des conditions optimales de culture ont été recherchées permettant une production maximale d'OVTXs (300 pg/cellule). Les différentes étapes d'extraction et de concentration développées ont permis d'obtenir une fraction très riche en toxines. La purification finale a été menée par chromatographie liquide/ spectrométrie de masse/détection UV en utilisant une colonne Uptisphere C18-TF. Les travaux de thèse ont permis d'acquérir des données qui vont contribuer à l'analyse de l'impact sanitaire puisque actuellement, au niveau international, il existe très peu de données permettant d'établir des seuils d'alerte d'Ostreopsis sp. et de sécurité sanitaire
Optimisation des conditions hydrobiologiques pour la conservation de l'huître creuse Crassostrea gigas en système re-circulé by Florence Buzin( Book )

3 editions published in 2011 in French and held by 3 WorldCat member libraries worldwide

The maintenance of bivalve commercialisation during periods when sales are prohibited represents a major economic issue for shellfish-farming. To ensure their survival and to preserve the oyster Crassostrea gigas quality, their storage in land-based systems has been studied i) out of water in a cold room at 3°C with controlled humidity, enabling the bivalve sensory quality to be retained for 15 days, and ii) in recirculating systems in immersed conditions for 30 days. For the latter, the oysters were stored at 167 kg.m-3 density in a tank equipped with an air-lift system, with water treated with UV and thermoregulated. A minimum of food was supplied to avoid mass tissue loss. A temperature of 16°C was defined as optimal to limit mortality and to avoid spawning risks. The thermal stress linked to the transfer of oysters into this environment induced disruptions of the ecophysiological responses for around 30 hours. The speed of the water current within the system, which is essential to transport food and oxygen, presented a significant negative effect on bivalve clearance rate. The oyster nitrogen excretion was quantified according to the temperature and food supply. The ammonia excreted by bivalves is nitrified by a bacterial population which is mainly located on the oyster shells. This process keeps NH4+ and NO3- concentrations below the toxic level for the bivalve. The modelling of nitrogen and organic matter fluxes in the recirculating system enabled the optimal conditions of storage to maintain oyster dry weight and survival to be simulated
Etude de l'effet d'un mélange d'oligosaccharides prébiotiques sur le système immunitaire, la barrière intestinale et la prévention d'une allergie, au moyen d'un modèle souris d'allergie au blé by Pascal Gourbeyre( Book )

2 editions published in 2011 in French and held by 3 WorldCat member libraries worldwide

Les allergies alimentaires sont un problème de santé publique car ces pathologies s'accroissent et demeurent incurables. Une stratégie émergente pour agir de manière préventive sur la survenue des allergies est l'utilisation de prébiotiques. Cependant, leurs effets sur le microbiote, la barrière intestinale et le système immunitaire demeurent peu documentés. Mon objectif de thèse était de voir si des prébiotiques pouvaient modifier le microbiote intestinal, agir sur la barrière intestinale, orienter le système immunitaire du nouveau-né, et exercer un effet préventif sur la survenue d'une allergie, dans un modèle de souris. Pour ce faire, j'ai déterminé dans un premier temps quelle période d'administration (périnatale ou postnatale) était la plus propice. J'ai établi un modèle de souris sensibilisé par voie intra-péritonéale avec des allergènes de blé. Les résultats obtenus lors de ce travail de thèse prouvent, pour la première fois, qu'une exposition périnatale (mères gestantes, allaitantes et souriceaux) à des prébiotiques exerce un effet santé notable sur l'organisme : barrière intestinale renforcée et terrain immunitaire inducteur de la tolérance orale. Cette stratégie s'est aussi avérée prometteuse pour prévenir d'une allergie dans la mesure où les voies immunitaires de la tolérance orale étaient préservées à l'issue d'une sensibilisation drastique avec des allergènes de blé. L'étude des mécanismes d'action des prébiotiques doit maintenant être approfondie et les tests pourraient être étendus à des cohortes de mères et d'enfants à terrain allergique
La co-limitation par l'azote et le phosphore : étude des mécanismes chez la microalgue Tisochrysis lutea by Gaël Bougaran( Book )

3 editions published in 2014 in French and held by 3 WorldCat member libraries worldwide

Interactions between nitrogen (N) and phosphorus (P) on the growth of phytoplankton are not fully elucidated. Here, we propose the hypothesis that, since phosphorus plays a central role in energy, it can control the active transport of NO3. Our model for N-P co-limitation provides an asymmetric structure which reflects the respective roles of both nutrients and the differences in the control of absorption. The model succeeds in describing the different trends observed for N and P cell content in data sets taken from the literature. We further conducted experiments in batch and chemostat under different N: P ratios. Our results highlighted that P-limited cells were characterized by a low content of ATP and a low net absorption of NO3. When PO4 was resupplied, the cells showed a dramatic increase in the net absorption of NO3. Conversely, N limitation did not interact with the absorption of PO4 and the observations were successfully described by our model. Our experiments also raised the probable role of organic N excretion in N-P co-limitation and led us to propose a variant of our initial model. Finally, the effects of N-P co-limitation did not clearly affect the storage of lipids that responds to growth rate rather than the type of limitation
Apport des dernières évolutions en spectrométrie de masse pour l'étude structurale des polysaccharides by David Ropartz( Book )

3 editions published in 2015 in French and held by 3 WorldCat member libraries worldwide

Glycosciences are dedicated to the study of the structure and function of carbohydrates as well as enzymes and proteins of biological processes involving glycan structures. Still scarcely developed, especially compared to other fields of biology, this knowledge is nevertheless essential in order to understand the functioning of living cells, as well as to allow a better use of carbohydrates in various industries. Development of glycosiences is closely linked to that of analytical methods for studying the structure and function of carbohydrates. The main objective of this thesis was thus to evaluate the contribution of recent instrumental advances in mass spectrometry and separation techniques coupled to determine the structure of complex natural polysaccharides. The work initially focused on the discovery of new enzymatic tools for the deconstruction of the polysaccharides. The second theme was to develop separation tools coupled with mass spectrometry for the structural characterization of oligosaccharides mixture and to resolve isoforms. Finally, we explored a new mode of fragmentation, called photodissociation, to characterize the fine structure of oligosaccharides. All the results and the analytical improvements which were brought by my work led to progress in the use of mass spectrometry in the complex field of the structural determination of polysaccharides. They also brought unprecedented information both on these biopolymers and on the mode of action of their depolymerizing enzymes
Compréhension des facteurs physiques et physiologiques impliqués dans les changements de propriétés mécaniques de la baie de raisin au cours de la maturation : impact de l'hétérogénéité de la matière première by Stéphanie Doumouya( Book )

3 editions published in 2014 in French and held by 3 WorldCat member libraries worldwide

The wine quality is closely related to the quality of grapes. It is therefore necessary for the viticulturist to have reliable indicators for predicting the quality , allowing a choice of optimum harvest date and a choice of routes for wine . The quality assessment is based on multiple criteria indicators, including emerging mechanical properties of berries grouped under the term " texture ". This indicator allows to evaluate the relaxation and softening of grape berries during ripening. Previous work has helped to understand the textural quality of the grapes by sensory approach (Le Moigne, 2008) and instrumental approach( Zouid, 2011) by establishing a link between the resistance and elasticity of the berry skin and the diffusion of phenolic compounds during the winemaking process. Although promising, the concept of textural maturity is not yet systematically integrated as a parameter for monitoring the quality and ripening grapes. Some technical and scientific limitations remain including the fact that it was difficult for an instrumental approach to differentiate different textural maturity stages . Measurements were taken by a berry per berry approach, so it is important to know the impact of the heterogeneity of grapes on texture measurements . In this context, this thesis discusses the concept of textural maturity in connection with the development of physical and physiological parameters during ripening, in order to understand the impact of heterogeneity on the mechanical properties and adapt the sampling protocols.First, the comparison of two varieties of wine grapes white and red by five instrumental methods of texture measurement was used to validate the Cabernet Franc and the technique of double compression 20% respectively as plant material and instrumental technique of reference for our study. Secondly, changes during ripening of double compression's parameters and key physical and physiological parameters of berries has been studied according to a protocol by sampling whole grape bunches . These results have highlighted the important role of physiological parameters related to water in the evolution of the mechanical properties of the grape. Furthermore , it is shown that the impact of the position and exposure of berries on the cluster is a significant factor textural heterogeneity .The results of this work provide key information on the evolution of the texture of berries during ripening. They also demonstrated the importance of considering the heterogeneity of intra-cluster measures and propose a new texture sampling mode to plot both representative and comparable from one date to another for reliable monitoring textural maturity
Etude de la dégradation enzymatique de couches semi-réflectives à base de biopolymères by Abir Dammak( Book )

3 editions published in 2014 in French and held by 3 WorldCat member libraries worldwide

Les polysaccharides pariétaux (cellulose et les hémicelluloses) peuvent être utilisés pour la production de bioéthanol. L'amélioration de la bio-raffinerie par hydrolyse enzymatique nécessite un effort constant pour la découverte d'enzymes performantes par des outils de criblage rapides, sensibles et robustes. L'objectif a été d'utiliser des films multicouches à base de biopolymères, comme substrats modèles d'assemblages de polysaccharides pariétaux. Nous avons élaboré deux types de films incluant des nanocristaux cellulose (CNC) combinés soit avec des xylanes cationiques(CX) soit avec des xyloglucanes (XG). La particularité de ces systèmes nanométriques est de provoquer l'apparition d'une couleur structurale. L'action d'une enzyme hydrolytique sur ces films peut être détectée par un changement de couleur lié à la diminution de l'épaisseur provoquée par l'hydrolyse. La pertinence de ces systèmes en tant que détecteurs visuels d'activité enzymatique a été validée avec une sensibilité équivalente (CNC-CX) ou meilleure (CNC-XG) que celle d'une méthode colorimétrique de référence. Des films (CNC-XG) avec architectures contrôlées ont été élaborés en jouant sur la concentration des CNC. L'étude de la structure interne de ces films par réflectivité des neutrons a montré que l'augmentation de la concentration induit une densification de l'adsorption des CNC. Les profils de dégradation obtenus en QCM-D et les pourcentages de perte de matière associés ont été comparés sur les films CNC3- XG et CNC5-XG. Un pourcentage de dégradation significatif a été obtenu dans les deux cas bien qu'il soit légèrement plus élevé pour les films CNC3 reflétant une accessibilité de chaînes de XG plus aisée
Emulsions stabilisées par des nanocristaux de cellulose : élaboration et propriétés fonctionnelles by Fanch Cherhal( Book )

3 editions published in 2015 in French and held by 3 WorldCat member libraries worldwide

The last decade, an increasing interest in the development and characterization of emulsions stabilized by colloidal bio-based particles, the so-called Pickering emulsions, has emerged. Notably, nanocrystals of polysaccharides such as cellulose, are of particular interest since they are more respectful of the environment. This thesis concerns the understanding of the parameters responsible for the stabilization of cellulose nanocrystals (CNC) at the water/oil interface. Therefore, three CNC batches with variable surfaces charge densities were prepared and characterized. AFM, TEM and small angles neutron scattering (SANS) were used to visualize the different morphologies and determine the dimensions of isolated and aggregated CNC. A fractal aggregation process with fractal dimensions of 2.1 to 2.3 was determined. Pickering emulsions were produced with various CNC. The evolution of drop diameters of emulsions stabilized by CNC depending on the concentration and surface charge density of the CNC shows two distinct areas. One, at the low concentrations, governed by the limited coalescence process at constant drop coverage, and another, at the higher concentrations, where a densification of the interface is observed at a constant drops diameter. The structural study by SANS defined thicknesses from 6 nm to 22 nm of the cellulose layer. Adding internal phase led to high internal phase emulsions (HIPE). These emulsions were characterized by confocal laser scanning microscopy and drop diameters distribution. It is observed that by including additional oil to the starting emulsion, a second population of large diameter drop arises. Depending on the amount of CNC, a variation of the drop distribution is observed. This is explained by the variable coverage of the surface, leading to coalescence beyond a critical value of concentration. Finally, textur of the HIPE was tuned based on the concentration of CNC, the salinity and surface charge density
Rôle des agrégats de protéines dans la formation et la stabilisation de mousses by Bénédicte Rullier( Book )

2 editions published in 2009 in French and held by 2 WorldCat member libraries worldwide

The foam formation depends on the nature of the protein and on their capacity to stabilize the air/water interfaces. During food processes, proteins undergo thermomechanical treatments leading to their aggregation in self-assembled structures. However, only a given fraction of the proteins is aggregated and this part may be considerably influence the foaming properties. This thesis aims at considering the aggregation part in the foam formation and stabilization at the different foam scales (air/water interface and foam film). Protein aggregates with different sizes were obtained by heat-induced denaturation of b-lactoglobulin, major whey protein for which the aggregation is well-known. Whatever the aggregate size, solutions containing exclusively protein aggregates lead to less stable foams than that of non aggregated proteins alone, due to the low capacity of aggregates to adsorb at the air/water interfaces. With non aggregated proteins, aggregates are able to improve the foaming properties. The viscoelasticity of the interfacial adsorbed layers is reinforced and a gel-like network is formed within the foam film, rigidifying the interface and slowing down the foam drainage. In the case of the gel-like network cannot be formed, protein aggregates can locate in the Plateau borders, slowing down the flow in the foam
Relation entre tableaux de données : exploration et prédiction by Angélina El Ghaziri( )

1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide

La recherche développée dans le cadre de cette thèse aborde différents aspects relevant de l'analyse statistique de données. Dans un premier temps, une analyse de trois indices d'associations entre deux tableaux de données est développée. Par la suite, des stratégies d'analyse liées à la standardisation de tableaux de données avec des applications en analyse en composantes principales (ACP) et en régression, notamment la régression PLS sont présentées. La première stratégie consiste à proposer une standardisation continuum des variables. Une standardisation plus générale est aussi abordée consistant à réduire de manière graduelle non seulement les variances des variables mais également les corrélations entre ces variables. De là, une approche continuum de régression a été élaborée regroupant l'analyse des redondances et la régression PLS. Par ailleurs, cette dernière standardisation a inspiré une démarche de régression biaisée dans le cadre de régression linéaire multiple. Les propriétés d'une telle démarche sont étudiées et les résultats sont comparés à ceux de la régression Ridge. Dans le cadre de l'analyse de plusieurs tableaux de données, une extension de la méthode ComDim pour la situation de K+1 tableaux est développée. Les propriétés de cette méthode, appelée P-ComDim, sont étudiées et comparées à celles de Multiblock PLS. Enfin, la situation où il s'agit d'évaluer l'effet de plusieurs facteurs sur des données multivariées est considérée et une nouvelle stratégie d'analyse est proposée
De l'utilisation de protéases industrielles pour la production de sances de poisson by Minh Chau Le( Book )

2 editions published in 2015 in French and held by 2 WorldCat member libraries worldwide

Fish sauces are traditionally used in most Asian countries. Whatever the process, the principle is the same i.e. a fish autolysis in saline media followed by a fermentation step. Not less than 18 months are needed to obtain a brown liquid rich in salt and amino acids. This PhD work aims to determine if an addition of proteases can speed up the process while keeping the nutritional and sensorial properties. The first chapter presents the characteristics of fish sauces and the key parameters of the processes used. In the second chapter, several industrial proteases are compared each other for their capacity to liquefy the fishes in hyper saline conditions. Kinetics of proteolysis and biochemical characteristics of the resulting hydrolysates are established allowing the ranking of the proteases. In the last chapter, a comparative study is conducted on the production of anchovy sauce with or without an addition of Protex 51FP retained as the most effective enzyme. It appears that addition of such protease increase the production yield and contributes to improve several qualitative parameters such as contents in nitrogen and amino nitrogen and leads to the recovery of smaller peptides. This study confirms that despite a hyper saline media, industrial proteases may help the liquefaction of raw material and thus considerably reduce the duration of the production of traditional fish sauces
Structure, assemblage et comportement hydrodynamique d'AtPP2-A1 et AtPP2-A2 chez Arabidopsis thaliana by Élise Douville( Book )

2 editions published in 2010 in French and held by 2 WorldCat member libraries worldwide

Dicotyledonous sieve elements typically contain saccharose transported at long distances by mass flow and protein inclusions, called P-Proteins. In Arabidopsis thaliana, P-proteins are found as filaments and immunolocalization studies had confirmed that PP2s are indeed associated to Pproteins. Two PP2 genes were shown to be expressed specifically in the phloem: AtPP2-A1 and AtPP2-A2. Based on observations in microscopy, it was hypothesized that P proteins could, in response to injury of the phloem, participate in the occlusion of sieve tubes by peculiar assembly mechanisms. In order to check this hypothesis, PP2-A1 and PP2-A2 recombinant proteins were produced in E. coli and their structure and self-assembly properties were studied under different physical chemical conditions, close to phloem sap conditions. Proteins PP2-A1 and PP2-A2 were present in solution as elongated shape oligomers whatever the pH, with a degree of oligomerization N being higher for PP2-A2 than for PP2-A1. These results obtained by small angle X-ray scattering together with observations using transmission electron microscopy suggest that the oligomers self-associate to form an arrangement of filamentous and twisted structures. Increasing ionic strength enhances the proteins self-association. By the contrary, the presence of calcium, sucrose or shear rate do not affect PP2-A1 self-association. Alltogether, these results suggest that the presence of PP2 proteins within phloem sieve tubes do not compromise mass flow
Classification de variables autour de variables latentes avec filtrage de l'information : application à des données en grande dimension by Mingkun Chen( Book )

2 editions published in 2014 in French and held by 2 WorldCat member libraries worldwide

With the development of high-throughput analysis techniques, researchers have adopted systematic approaches to describe simultaneously a large number of variables. However, one of the important challenges lies in the diffculty to summarise and interpret this enormous quantity of information. We adopt a clustering of variables approach (CLV) which allows us to highlight disjunctive structures, and therefore, reduce the dimensionality of the problem and facilitate the interpretation of the data at hand. However, in order to further improve the relevance of such approaches, two directions of investigation are proposed. The first direction involves filtering the data by setting aside atypical variables or variables associated with noise. For this purpose, a strategy to create an additional group of variables, called noise cluster, and a strategy based on the definition of sparse latent variables are proposed and compared. The second direction concerns the development of a clustering of variables procedure directed to the explanation of a response variable. The implementation of iterative algorithms provides a sequence of group latent variables with good predictive performance. These latent variables are also easy to interpret since each predictive component is associated with a subset of variables assumed to have a one-dimensional structure
Etudes des interactions entre une bactérie bioprotectrice, Lactococcus piscium CNCM I-4031, et Brochotrix thermosphacta et Listeria monocytogenes dans la crevette tropicale by Papa Abdoulaye Fall( Book )

2 editions published in 2011 in French and held by 2 WorldCat member libraries worldwide

Le potentiel bioprotecteur de Lactococcus piscium CNCM I-4031 vis à vis d'une bactérie altérante, Brochothrix thermosphacta, a été testé sur de la crevette cuite décortiquée conservée sous atmosphère protectrice. En co-culture, L. piscium permet d'inhiber la croissance de B. thermosphacta de 4 log ufc/g, tout en améliorant la qualité sensorielle du produit pendant 31 jours. L'inhibition n'est pas due à la production d'acide lactique ni à une compétition pour les acides aminés libres. La croissance de L. piscium et B. thermosphacta a été modélisée en fonction du pH, de la température et du taux de NaCl. Les valeurs optimales de croissance sont proches mais B. thermosphacta présente une tolérance au sel plus élevée et L. piscium un caractère psychrotolérant plus marqué. L'effet du niveau d'inoculation par L. piscium, en combinaison avec la température et le sel, sur l'interaction avec B. thermosphacta a été modélisé. Un inoculum fort en L. piscium (6-7 log ufc/g) est nécessaire pour maintenir le nombre de B. thermosphacta inférieur à 4 log ufc/g, cependant une amélioration sensorielle de la crevette est obtenue même avec un inoculum assez bas. L'inhibition de Listeria monocytogenes par L. piscium a ensuite été testée sur la crevette cuite, montrant une inhibition de 4 log ufc/g. Les mécanismes d'action impliqués dans cette activité ont été étudiés sur un milieu chimiquement défini (MSMA) reproduisant l'inhibition. Celle-ci n'est pas liée à la consommation du glucose, la production d'acide lactique ou la compétition pour les acides aminés, les bases ou les vitamines. En revanche le contact cellulaire entre les deux bactéries est nécessaire pour obtenir l'inhibition
 
moreShow More Titles
fewerShow Fewer Titles
Audience Level
0
Audience Level
1
  Kids General Special  
Audience level: 0.91 (from 0.85 for Optimisati ... to 0.95 for Les produi ...)

Alternative Names
École doctorale 495

École doctorale V.E.N.A.M.

École doctorale Végétal Environnement Nutrition Agroalimentaire Mer (Angers)

École doctorale VENAM

ED 495

ED495

Université de Nantes. École doctorale Végétal Environnement Nutrition Agoalimentaire Mer

Université de Nantes. Faculté des sciences et des techniques. Ecole doctorale VENAM

Languages
French (46)

English (3)