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Coronaviruses such as SARS CoV-2 are spherical infectious agents covered with out-pointing protein spicules. These spicules are coated with the host's glycans that display immunoevasion epitopes in the circulating medium of the infected body. The post-transcriptional construction of this external camouflaging glycan envelope provides the virus with an elusive protection from the immune system. The poly-mannose glycans are synthesized in the infected cells' endoplasmic reticulum and transferred onto the S-protein N-glycosylation sites of the spicules at the end of the virus reproduction cycle. The core structure of these glycans is composed of branched mannoses on an asparagine N-glycosylated chitobiose root. Deoxy-D-mannoses and derivatives such as fluoro-or chloro-substituted analogues possess the structural features to be potentially recognised and used by cytoplasm or endoplasmic reticulum oligo-mannose synthase enzymes during the construction of the dolichol-phosphate glycan biosynthesis. If incorporated onto the growing chitobiose rooted disaccharide, these residues would inhibit further growth of the terminal poly-mannose structure by introducing-OH glycosylation site deficiencies at key branching or elongating positions. These deficiencies would then prevent full growth of the oligo-mannose terminal glycan. The presence of shorter and incomplete glycan epitopes on the released virus spicules would leave a larger surface of the S-protein uncovered. Consequently, the virus antigenic sites would be more exposed (accessible) to the circulating antibodies of the host's immune system.

The purpose of the research presented here was to explore different possibilities in synthesizing polymeric hydrogel structures of defined sizes from nano-sized natural polymer molecules such as polysaccharides (PS) and hybrid mineral-organic silica nanoparticles. Water soluble linear or branched PS are nano-sized molecules that can be cross-linked to create larger hydrogel scaffolds at any desired micro or macro-size. Firstly 20-100 nm nanoparticles with an amorphous silica core and a reactive organic shell were synthesized and crosslinked by classical sol-gel processes. The inter-crosslinking of silica nanoparticles with polysaccharides was carried out in three different ways: by trapping the polysaccharides in a dense network of crosslinked silica nanoparticle; by co-crosslinking the chemically modified PS with the reacting nanoparticles and by using the modified polysaccharide as the cross-linker. These processes resulted in bio-hybrid mineral/organic hydrogels. Using similar chemistry multi-layered nano-particles were synthesized. These nanoparticles were made of a central amorphous mineral silica core covered by a hydrophobic organic layer. This organic layer contained reactive epoxy groups onto which a hydrophilic oligosaccharidic surface was grafted. In order to react the oligosaccharidic moiety onto the nanoparticle diethylamine was added by reductive amination onto the reducing hemiacetal function of a reducing oligosaccharide. The remaining amino group of the resulting modified sugar derivative was then attached on the nano-particles by reacting with the pending epoxy groups at the nanoparticle surface. On these multilayered nanoparticles some epoxy groups remained buried underneath the bulky oligosaccharidic external layer. Those were reacted with amine bearing molecules such as methylene blue. Purification of the obtained multilayered nanoparticles was easily performed by ultrafiltration. These three examples show the numerous possibilities of creating specific hydrogel polymeric structures at various sizes with specific functionalities by using different chemistry.

This article concerns the elaboration and the characterization of a novel biobased potato starch-beet pulp composite for packaging applications as cushion foams. A twin-screw extruder was used to elaborate composite foams. SEM observations of these materials were conducted, and thermomechanical properties were studied in terms of thermal transitions (TGA, DSC) and viscoelastic properties (DMA). The effect of relative humidity content on viscoelastic properties was analyzed as a function of frequency. The different test results show that the composite structures are homogeneously mixed. The sponge-like structure of the beet-pulp disappears indicating a good compatibility between the two mixed constituents. The DSC curve of starch-beet pulp foam shows a single thermal transition at 153.6 &deg, C, indicating the thermal homogeneity of the obtained composite material. The density value of starch-beet pulp foam is higher than conventional foams, but this can be optimized by adjusting the technological parameters of the extruder. The viscoelastic properties of the developed materials depend on the relative humidity.

International audience; The reaction of esterification of plasticized Kraft lignin (KL) with succinic and maleic anhydrides using reactive extrusion (REX) was studied in detail. DMSO, glycol and glycerol were found to be efficient plasticizers for lignin. The chemical structure of these new lignin esters was determined using Solid-state 13C CP-MAS NMR and FT-IR analysis. 31P NMR analysis of phosphitylated lignins showed that the aliphatic OH groups of lignin had superior reactivity under the reactive extrusion reaction conditions. The formation of monoesters was confirmed by HSQC NMR spectroscopy. Molecular weight changes after extrusion process were studied using GPC/SEC chromatography. Thermal properties of these polymers were assessed by TGA analysis. The results were compared to lignin esters modified in classical batch conditions. These results show that REX can be used as a new fast, solvent free, and continuous process for lignin valorization.

International audience; The formulation of self-compacting concretes (SCC) and the study of their properties at the laboratory level were currently well mastered. The aim of this work is to characterize SCC under hot climatic conditions and their effects on the properties of fresh and hardened SCC. Particularly, the effect of the initial wet curing time on the mechanical behavior such as the compressive strength and the durability of the SCCs (acid and sulfate attack) as well as the microstructure of SCCs mixtures. In this study, we used two types of cement, Portland cement and slag cement, three water/binder (W/B) ratio (0.32, 0.38 and 0.44) and five curing modes. The obtained results shows that the compressive strength is strongly influenced by the curing methods, 7-days of curing in the water and then followed by a maturing in a hot climate was the optimal duration for the development of a better compressive strength, regardless of the type of binder and the W/B ratio.

This article deals with the elaboration and the characterization of an innovative 100% plant-based green composite made solely of beet pulp (BP) and potato starch (S). Using this type of material in insulation applications seems a good solution to reduce the CO₂ gas emissions in building. The influence of the starch amount on composite characteristics was studied. Four mixtures were considered with different S/BP mass ratios (0.1, 0.2, 0.3 and 0.4). The physical properties of these materials were studied in terms of porosity, apparent and absolute densities, thermal conductivity, and hygric properties. The influence of humidity content on acoustical properties was studied as a function of frequency. Test results show a real impact of both starch and humidity contents on the hygrothermal and acoustical properties of the studied material due to the porosity. The composite with the lowest amount of starch (S/BP = 0.1) seems to be the optimal composition in terms of the hygrothermal and acoustical behaviors.

International audience; Natural polymers possess physicochemical properties in their native state, which limit their use in many industrial sectors. Even limited chemical modifications radically change the properties of these macromolecular entities. Chemical modifications commonly performed at industriallevelproduction in solution or in batches [1] are often laborious and difficult to monitor. In addition, these processes suffer from energy cost and environmental issues caused by unreacted components and co-products. Reactive extrusion offers a simple process, using no solvents, shorter reaction time and improved efficacy [2-4]. In the present work we describe a method of chemical modification using reactive extrusion process (REX). In this project three families of biopolymers: starch, cellulose and lignin are studied. In the following example carboxymethyl starches (CMS) with various degrees of substitution (DS) were synthesized in one step and with high levels of reaction efficiency (RE). The results on the distribution of the carboxymethyl functions on the three different positions of the glucose monomer as well as the kinetics of the reaction are analyzed and discussed.

National audience; Sugar beet (Beta vulgaris var. saccharifera), is a biennial plant, cultivated for the production of sugar (sucrose). Following the process of extracting sugar from beets, fresh pulps are obtained which are used to feed livestock. My project describes a potential way to improve the value of sugar beet pulp in the manufacture of ecological lignocellulosic insulating concrete panels; La betterave sucrière (Beta vulgaris var. saccharifera), est une plante bisannuelle, cultivée pour la production de sucre (saccharose). Suite au processus de l’extraction de sucre de la betterave, on obtient des pulpes fraiches qui sont destinées à l’alimentation du bétail. Mon projet décrit une voie potentielle pour améliorer la valeur de la pulpe de betterave sucrière dans la fabrication de panneaux de béton isolants lignocellulosiques écologiques

International audience; Microencapsulation using the transacylation reaction in a W/O emulsion is based on the creation of amide bonds between free amine functions of a protein and polysaccharide ester groups in the aqueous phase after alkalization. Several proteins have been implicated in this process, whereas commercial propylene glycol alginate (PGA) has been the only modified polysaccharide used up to now (1,2). The intrinsic properties of PGA such as viscosity, molecular mass, ester type and substitution degree limit its use in microparticle preparation hence the need to study other potential polysaccharide esters.

Random clivage of branched polymers composed of two different (a) and (b) linking types lead to complex oligomeric mixtures of various polymeric degree (DP). Each family of given DP consists in a mixture of molecules containing all possible combinations of (a) and/or (b) sub-structure. For example, the industrial hydrolysis of starches composed of polymers [alpha (1-4)] and [alpha (1-6) produce syrups mixtures with a low DP (typically from 1 to 20). The number of potential oligosaccharidic structures accessible by random hydrolysis of these branched polymers grow exponentially with the DP. The number of isomeric structures for each given DP (n) is a Catalan number, noted C(n), with C(n) = (1 / ( n + 1)) (2nn) = (2n)! / (n! (n + 1)!). The calculation gives 2 isomers (maltose and isomaltose) for a disaccharide (DP2), 16796 deca-saccharides potential isomers (DP10) and more than 6 million potential eicosasaccharide isomers (DP20)., Le clivage aléatoire de polymères branchés par deux types de liaisons différentes (a ou b) conduit à des mélanges complexes d'oligomères de degré de polymérisation (DP) différents. Chaque famille de DP donné est composé de mélanges de molécules de structure contenant toutes les combinaisons possibles des 2 sous-structures (a) et/ou (b). Par exemple l’hydrolyse industrielle d’amidons composé de polymères [alpha (1-4)] et [alpha (1-6] permet de produire des mélanges sous forme de sirops de faibles DP (typiquement de 1 à 20). Le nombre de structures oligosaccharidiques potentielle accessibles par hydrolyse aléatoire de ces polymères ramifiés croît de façon exponentielle avec le DP. Le nombre de structures isomères pour un DP donné (n) est un nombre de Catalan noté C(n) avec C(n)= (1/(n+1)) (2nn)= (2n)!/(n!(n+1)!). Le calcul montre que l'on accède à 2 isomères (maltose et isomaltose) pour le disaccharide (DP2), 16796 isomères déca-saccharides (DP10) et plus de 6 millions d’isomères eicosasaccharide (DP20) potentiels différents.

International audience; In this poster we present the synthesis of new hybrid materials constituted of a dual siloxane-polysaccharidic based materials by inter intertwining/cross-linking two polymeric epoxy-silane/polysaccharide based networks in aqueous solution ; using the carbohydrate framework as the building template for the siloxane polymerization. The advantage of cross-linkable sol-gel matrices over traditional sol-gel chemistry methods are primarily the use of low temperature processing to prepare the material, the opportunity to incorporate useful organic functionality into the final matrix, modified mechanical properties and partial and adjustable biodegradability. Depending on the starting silanes and polysaccharides these gels are cross-linked in a number of ways, to produce materials with unique, innovative and potentially valuable properties.

International audience

National audience; L'amidon est un composé de réserve glucidique abondant et peu coûteux synthétisé par les végétaux (céréales, légumineuses, tubercules…) à partir de l'énergie solaire. L'amidon est utilisé dans l'industrie alimentaire (agents de texture, gélifiants…) et non-alimentaire (papeterie, textile, adhésifs…). Bien que la nature polysaccharidique des constituants de l'amidon ait été déterminée depuis longtemps, à ce jour la structure fine du constituant principal, l'amylopectine reste encore mal décrite. Notre projet consiste donc à étudier cette structure afin de mieux comprendre les différences de propriétés physico-chimiques (rhéologiques, mécaniques…) qui existent entre des amidons d'origines botaniques différentes.