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International audience; Over the last 15 years, research efforts have been dedicated to identifying the factors that influence lignocellulosic biomass (LB) enzymatic deconstruction to develop alternatives to fossil carbon resources [1]. Accessibility of LB is an important parameter influencing the biomass deconstruction and is guided by many factors contributing to recalcitrance which can be separated between factors related to the composition of the LB (hemicelluloses, lignin or hydroxycinnamic acids content) and structural factors (the chemical structure and interaction of cell wall polymers, cell wall porosity …) [2].. This study focused on the hot water pretreatment (HWP) of maize internodes during 20 or 40 minutes, which induces disruptions within the tight inter-polymers association mainly through the breakdown of inter- and intra-polymer bonds and a reorganization of the network.The chemical characterization showed that HWP modified the cell wall composition with a loss of hemicelluloses (up to 45% for HWP 40 min) and of ferulic acid cross-linking, associated with a lignin enrichment.Impact of HWP on cellulose supramolecular organization was highlighted with the 13C CPMAS sequence [3], showing an increase of cellulose crystallinity concomitant with an increase of.agregate dimension. This acquisition also shown that the lignin structure is altered, related through a decrease of β-O-4 bonds.The study of the kinetics of polarization transfer made it possible, by using a model using two proton reservoirs [4], to characterize, on the one hand, the increase in the molecular order (T1ρH), and on the other hand, the presence of a greater density of water molecules in the macromolecular assembly (THH).Low-field T2 measurement at two different hydration levels spotlights a modulation of the domains and promotes the creation of new domains where the water is more constrained and which can be associated with pore sizes between 5 and 15 nm. This increase of the porosity, seen by NMR and Simons’ staining, should favour the mobility of enzymes and thus facilitate their catalytic activity.The results obtained by the combined use of these different NMR modalities, associated with the results obtained using chemical analyzes, were synthesized in a diagram illustrating the evolution of interactions within the macromolecular assembly.This study highlights that the loss of hemicelluloses and changes in polymers structural features induced by HWP leads to a reorganization of the cell walls. These modifications induce an increase in the specific surface area and a water redistribution allowing an increase in the accessibility of cellulases and an enhancement of the hydrolysis yield [5].

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International audience; Cereal grain cell walls are studied for their nutritional benefits (dietary fibre), their adverse effects on the digestive health of livestock such as poultry and pigs, and their effects on grain usage (bread making, pasta, brewing...). In wheat grain, the two major cell wall polysaccharides, arabinoxylans and β-glucans, have been extensively studied. By contrast, mannan was poorly documented. Nevertheless, this hemicellulosic polysaccharide might have a determinant role in wheat grain development since, in Arabidopsis thaliana, mutants with a reduced amount of mannan show an altered seed development. Our project aimed at deciphering the biochemical structure and the biological function of mannan. To study the biological function of mannan, we have studied its occurrence during wheat grain development. The detection of mannan using monoclonal antibodies showed that mannan is mainly located in the grain endosperm and that its deposition starts at an intermediate step of endosperm cellularization. We have purified mannan from wheat endosperm to determine its fine structure. Former studies have speculated that the class of mannan present in wheat was glucomannan. Our data suggest that this class of hemicelluloses is only represented by short unsubstituted chains of 1,4 linked D-mannose residues that are weakly acetylated [1]. We identified candidate mannan biosynthetic genes expressed in the endosperm. After unsuccessful attempts to generate wheat lines depleted in mannan, the heterologous expression of our best candidate genes was carried out in Pichia pastoris and Arabidopsis triple mutant depleted in glucomannan. Introducing TaCslA12 gene in yeast and Arabidopsis led to the production of wheat-like linear mannan lacking glucose residues and with moderate acetylation [2]. Therefore, this gene encodes a mannan synthase and is responsible for the synthesis or wheat endosperm mannan.

International audience; Apple processing for juice production suffers from yield variability due to varietal, physiological and postharvest handling factors. In order to identify markers to be used by the profession to class fruit lots and adapt process, a study was engaged on the contribution of apple cell wall on the viscoelastic mechanical properties of desert and cider varieties.

By mimicking the cutin natural polyester networks of plant cuticles, we produced hydrophobic elastomers by a sustainable process, i.e., using a catalyst- and solvent-free polycondensation of glycerol and hydroxy fatty acids, two by-products of the agro-food industry. The hydroxy-fatty acid fraction was obtained by alkaline hydrolysis in ethanol of peels from industrial tomato pomaces. This industrial-like fatty acid fraction contained more than 90% wt. of 9(10)-16 dihydroxyhexadecanoic acid (diOHC16). The co46 polyesters were designed by increasing the ratio of esterified glycerol/diOHC16 in a range observed in plant cutins (up to 6% wt.). Their structure and functional properties (thermal, mechanical, gas permeability, interaction with bacterial cells) were characterized. Increasing the glycerol contents induced a significant decrease in the reticulation degree of the polyesters and the formation of crystalline domains with an hexagonal organization. These structural modifications were related to a marked increase of elastomeric extensibility (up to 217%). While water vapor permeability was not impacted, the increase of glycerol content induced a significant decrease of oxygen permeability. None of the polyesters displayed biocide activity, but an increase of glycerol content significantly reduced the adhesion of bacterial cells, potentially giving rise to antifouling applications. Finally, the increasing content of free hydroxyl groups of the co-polyesters offer opportunities of grafting and covalent substitution for tailored functionalization; Bioinspired co-polyesters of hydroxy-fatty acids extracted from tomato peel agro-wastes and glycerol with tunable mechanical, thermal and barrier properties

International audience; The aim of the present study is to improve the understanding of the evolution of flax fibre(Linum usitatissimum L.) ultrastructure and properties caused by the retting process at the cellwall scale. The dew retting is a natural bioprocess, where the various microorganisms presentin the soil colonize the flax stems. The enzymes they secrete make it easier to extract the bastfibre bundles during the scutching stage.In this study, six different stages of retting were investigated. Differences between rettingstage 1 (R1, earlier) and the retting stage 6 (R6, over retted) are +17% and +23% with AFMPF-QNM and nanoindentation measurements, respectively.An over retting results in the loss of the cellulose that makes up the fibres (Placet et al. 2017),arguably due to secretion of cellulase. To obtain information on the supramolecular structureof cellulose fibrils in the plant cell walls, the model of Larsson and Wickholm (Larsson et al.,1997) could be used for deconvoluate the C4 region between 77 and 92 ppm. In addition, themechanical properties of flax cell walls during could be investigated by AFM Peak ForceQuantitative Nano-Mechanical property mapping (AFM PF-QNM) (Goudenhooft et al. 2018).Two complementary structural investigating technic will be presented, namely using X-RayDiffraction (XRD) and solid state Nuclear Magnetic Resonance (NMR). An estimation of thecellulose crystallinity index by XRD measurements, confirmed by NMR, shows an increaseof 8% in crystallinity with retting, mainly due to the disappearance of amorphous polymer. Inaddition, NMR investigations show a compaction of inaccessible cell wall polymers,combined with an increase in the relaxation times of the C4 carbon.One highlight of the work is that NMR results show a significant evolution in the cell wallultrastructure of flax during the retting stages. The improvement observed in the mechanicalperformance of flax cell walls can be explained by the compaction of inaccessible zones.Based on the NMR results, a schematic representation of the flax cellulose elementarymicrofibrils structure of R1 and R6 was hypothesised. In this flax cellulose evolution modelduring retting, we have considered in particular the lateral fibril dimension (LFD) and the thelateral fibril aggregate dimension (LFAD). As illustration, the LFD of samples R1 and R6 are4.1 and 4.5 nm, respectively, while the LFAD slightly decreases during retting from 17.1 nmfor R1 to 16.3 nm for R6.

International audience; ABSTRACTThe aim of the present study is to improve the understanding of the evolution of fibreproperties and ultrastructure caused by the retting process at the plant cell wall scale. Twocomplementary structural investigating technic are presented here, namely using X-RayDiffraction (XRD) and solid state Nuclear Magnetic Resonance (NMR). An estimation of thecellulose crystallinity index by XRD measurements, confirmed by NMR, shows an increaseof 8% in crystallinity with retting mainly due to the disappearance of amorphous polymer. Inaddition, NMR investigations show a compaction of inaccessible cell wall polymers,combined with an increase in the relaxation times of the C4 carbon. This densificationprovides a structural explanation for the observed improvement in mechanical performance ofthe secondary wall of flax fibres during the field retting process.INTRODUCTIONDuring retting, the various microorganisms present in the soil colonize the flax stems. Theenzymes they secrete, and particularly polygalacturonases, gradually degrade the pecticcompounds located mainly in the middle lamellae of the fibre bundles. This damage to theplant tissues structure makes it easier to extract the fibre bundles during the scutching stage.An over retting results in the loss of the cellulose that makes up the fibres (Placet et al. 2017),arguably due to secretion of cellulase. To obtain information on the supramolecular structureof cellulose fibrils in the plant cell walls, the model of Larsson and Wickholm (Larsson et al.,1997) could be used for deconvoluate the C4 region between 77 and 92 ppm. In addition, themechanical properties of flax cell walls during could be investigated by AFM Peak ForceQuantitative Nano-Mechanical property mapping (AFM PF-QNM) (Goudenhooft et al. 2018).Here we explore the evolution of the flax cell wall behaviour during a controlled dew rettingphase. Structural and mechanical investigations were conducted at the cell wall scale using XRayDiffraction (XRD) and solid-state Nuclear Magnetic Resonance (NMR), whilenanomechanical measurements were performed by nanoindentation and AFM PF-QNM).RESULTS AND CONCLUSIONSThe macroscopic illustration of the flax lots is displayed in Fig 1. NMR results show asignificant evolution in the cell wall ultrastructure of flax during the retting stages. Theimprovement in the mechanical performance of plant cell walls can be explained by thecompaction of inaccessible zones (Fig 2).

International audience; In wheat endosperm, mannan, is poorly documented. Nevertheless, this hemicellulosic polysaccharide might have a determinant role in wheat grain development since, in Arabidopsis thaliana, mutants with a reduced amount of mannan show an altered seed development. In order to gain knowledge about mannan in wheat, we have determined its biochemical structure in wheat endosperm where mannose content is about 0.2% (dry weight basis). We developed a method of enzymatic fingerprinting and isolated mannan-enriched fractions to decipher its fine structure. Although it is widely accepted that the class of mannan present in grass cell walls is glucomannan, our data indicate that, in wheat endosperm, this hemicellulose is only represented by short unsubstituted chains of 1,4 linked D-mannose residues and is slightly acetylated. Our study provides information regarding the interactions of mannan with other cell wall components and help to progress towards the understanding of monocot cell wall architecture and the mannan synthesis in wheat endosperm.

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Sound field reproduction using Wave Field Synthesis has been so far limited to the positioning of virtual sources and listeners in the horizontal plane only although the underlying formulation (Kirchhoff-Helmholtz) describes the reproduction of 3 dimensional sound fields in a 3 dimensional subspace. However, a strict use of this formulation would require a surface loudspeaker array with an impractical number of loudspeakers. The authors propose here an optimized formulation of Wave Field Synthesis in 3 dimensions that account both for the limitation of localization accuracy of elevated sources and the target listening area size. In contrast to other 3 dimensional sound reproduction techniques such as Higher Order Ambisonics, the proposed approach allows for irregular and incomplete loudspeaker layouts for targeting specific areas for virtual positioning and accounting for practical limitations in loudspeaker positioning. The paper also proposes a subjective evaluation of the proposed approach in an extended listening area. The experiment relies on elevated physical sources (loudspeakers) to be matched in localization with virtual sources reproduced with the proposed approach with a 24 channels loudspeaker array that covers the frontal quarter of the upper half of a rectangular room.

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This paper addresses road traffic monitoring using passive acoustic sensing. Recently, the feasibility of the wheelbase length estimation of a road vehicle using one compact microphone array, laid out near the road, has been demonstrated. In essence, the directions of arrival of each incoming sound waves related to the tyre noise are discriminated during the pass-by of the vehicle thanks to a time delay estimation (TDE) technique between signals acquired by distant microphones. The tracking of each DOA is performed thanks to a sequential Monte-Carlo method, also known as particle filtering. This allows the estimation of the trajectory of each wideband moving sound sources; these lasts are identified as axles of the vehicle, the wheelbase length is then recursively estimated. As many TDE techniques are available in the literature, the study investigates their usefulness and their ability to deliver the best tyre noise detection and to feed the tracking algorithm giving kinematics of the axles of the tracked vehicle.

L'environnement industriel ou urbain peut être composé de nombreuses sources nuisibles compétitives. Les stratégies optimales pour réduire le bruit nécessitent en amont une connaissance la plus précise possible des caractéristiques acoustiques et physiques de ces sources. Ce document propose une méthode pour localiser et estimer la puissance acoustique de plusieurs sources de bruit simultanément. Par opposition aux méthodes les plus classiques impliquant des microphones directifs ou des systèmes d'antennerie dit à formation de voie pour lesquels les performances dépendent fortement de la qualité et/ou du nombre de microphones utilisés (généralement important), nous utiliserons des microphones omnidirectionnels en nombre limité. Basé sur les intercorrélations entre microphones, le traitement combinatoire proposé est illustré par des simulations et une expérience en salle anéchoïque dans lesquelles une antenne tridimensionnelle doit localiser et comparer l'énergie de haut-parleurs aléatoirement distribués dans l'espace. Dans cette étude les sources sont considérées monopolaires, large bande, immobiles, stationnaires et décorellées deux à deux.

Toute production de musique ou de parole dans un espace clos fait intervenir en amont des questionnements d’acoustique. Pour offrir à l’auditeur des conditions d’écoute optimales, l’acousticien utilise des descripteurs caractérisant le champ sonore. Les méthodes usuelles basées sur la réponse impulsionnelle ou l’échogramme, selon le principe d’acoustique géométrique, permettent de calculer des indices pour la qualification de la salle (temps de réverbération, clarté, rapport S/N, dispersion des réflexions précoces, etc.). Ces indices ne suffisent toutefois pas pour des salles à géométrie complexe, particulièrement lorsque les densités et distributions temporelles des rayons d’un échogramme sont telles que l’interprétation de ce dernier est trop difficile, voire impossible. Dans ce cas, l’expertise acoustique ne peut être menée à bien qu’à l’aide de modélisations numériques puis par comparaison directe des mesures et des simulations. Nous avons simplifié ce problème par la mesure d’échogrammes spatialement distribués : un réseau omnidirectionnel de microphones, couplé à un modèle source‐image restreint, permet de tirer profit des informations temporelles et spatiales des rayons détectés. En effet, la discrimination spatio‐temporelle ou chrono‐goniométrie des rayons détectés permet la reconstruction inverse de leur trajet acoustique. Elle délivre une information globale sur le trajet entre la source et le réseau de microphones, et locale, pour les surfaces de réflexion identifiées. Ce principe a été validé par simulation puis par traitement de cas réels : d’abord dans une salle‐test rectangulaire avec ou sans traitement absorbant de ses parois, puis dans les salles d’audition d’un Conservatoire de musique et enfin, dans un espace commercial en vue de la production d’un concert classique. Les résultats obtenus valident le procédé et mettent en évidence ses apports, mais aussi les difficultés de mise en oeuvre. Enfin, ce principe a été appliqué à la consolidation des valeurs optimales des temps de dispersion des premières réflexions.