Whole proteome analyses on Ruminiclostridium cellulolyticum show a modulation of the cellulolysis machinery in response to cellulosic materials with subtle differences in chemical and structural properties

Lignocellulosic materials from municipal solid waste emerge as attractive resources for anaerobic digestion biorefinery. To increase the knowledge required for establishing efficient bioprocesses, dynamics of batch fermentation by the cellulolytic bacterium Ruminiclostridium cellulolyticum were compared using three cellulosic materials, paper handkerchief, cotton discs and Whatman filter paper. Fermentation of paper handkerchief occurred the fastest and resulted in a specific metabolic profile: it resulted in the lowest acetate-to-lactate and acetate-to-ethanol ratios. By shotgun proteomic analyses of paper handkerchief and Whatman paper incubations, 151 proteins with significantly different levels were detected, including 20 of the 65 cellulosomal components, 8 non-cellulosomal CAZymes and 44 distinct extracytoplasmic proteins. Consistent with the specific metabolic profile observed, many enzymes from the central carbon catabolic pathways had higher levels in paper handkerchief incubations. Among the quantified CAZymes and cellulosomal components, 10 endoglucanases mainly from the GH9 families and 7 other cellulosomal subunits had lower levels in paper handkerchief incubations. An in-depth characterization of the materials used showed that the lower levels of endoglucanases in paper handkerchief incubations could hypothetically result from its lower crystallinity index (50%) and degree of polymerization (970). By contrast, the higher hemicellulose rate in paper handkerchief (13.87%) did not result in the enhanced expression of enzyme with xylanase as primary activity, including enzymes from the xyl-doc cluster. It suggests the absence, in this material, of molecular structures that specifically lead to xylanase induction. The integrated approach developed in this work shows that subtle differences among cellulosic materials regarding chemical and structural characteristics have significant effects on expressed bacterial functions, in particular the cellulolysis machinery, resulting in different metabolic patterns and degradation dynamics.This work was supported by a grant [R2DS 2010-08] from Conseil Regional d'Ile-de-France through DIM R2DS programs (http://www.r2ds-ile-de-france.com/). Irstea (www.irstea.fr/) contributed to the funding of a PhD grant for the first author. The funders provided support in the form of salaries for author [NB], funding for consumables and laboratory equipment, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Omics Services provided support in the form of salaries for authors [VS, MD], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors [NB, VS, MD] are articulated in the 'author contributions' section.info:eu-repo/semantics/publishedVersio

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Analysis of the hemp fiber mechanical properties and their scattering (Fedora 17)

International audienceUnderstanding the mechanical behavior of plant fibers is a key to their development in composite reinforcement. The aim of this work is to better understand the low and scattered mechanical properties of hemp fibers (Fedora 17 variety) by highlighting innovating elements about the relationship between the cell wall components and the fiber mechanical performances. In first time, the morphology of hemp fibers within the stem is studied. Significant differences of lumen or fiber size is noted according to their location. Then, the biochemical analysis, despite a cellulose rate similar to flax varieties, highlights important differences for the nonstructural and matrix pectins distribution and quantity compared with flax. For the first time for hemp, nanoindentation investigations carried out in-situ on stems show that, no matter the location in the stem, the mechanical properties of the S2 layer were similar, proving a good reproducibility of the cell walls structure. Despite moderate differences between the crystallinity indexes, the X-ray diffraction patterns highlight the presence of a significant amorphous matrix polymer rate in the case of hemp

Control of complex inclusions during metallurgical treatments on liquid and solid steels

Adequate physical and mechanical properties, for numerous steel grades, can be obtained only with a precise control of the composition, morphology and plasticity of oxide and sulphide inclusions that remain in the product. In liquid metal, the composition of complex inclusions can be monitored by appropriate deoxidation practice, calcium treatment and/or slag-metal reaction. Further transformation may occur during solidification or heat treatments prior to hotrolling: reaction between oxides and sulphides, as well as recrystallisation of oxides. An analysis of these factors and of tools (thermodynamic models and laboratory experiments) which have been developed to comprehend and control them is presented

Internal stress effect induced by drying in starch-based composite films

Starch films containing eicosane droplets with diameters of 3-5 mu m homogeneously distributed over the thickness were prepared using the casting method. The films also contain a quantity of water (4-22%) depending on the relative humidity during conditioning (from 7% to 90%, respectively). The calorimetric behavior of dispersed eicosane droplets, studied by Differential Scanning Calorimetry, shows a shift in the melting temperature (T-m) of about 12 degrees C above the T-m of pure eicosane, which is 35.8 degrees C. This shift depends on the relative humidity during the conditioning of glassy starch films. The shift is also revealed by dynamic mechanical analysis and temperature-controlled X-ray analysis. The diffractogram did not show crystal structure changes associated with temperature shift. Based on the Pressure-Temperature phase diagram of eicosane, the temperature shift can be attributed to an internal pressure of up to 50 MPa on eicosane droplets, applied during starch drying

Shape memory starch–clay bionanocomposites

International audience1-10% starch/clay bionanocomposites with shape memory properties were obtained by melt processing. X-ray diffraction (XRD) and TEM evidenced the presence of a major fraction of clay tactoids, consisting of 4-5 stacked crystalline layers, with a thickness of 6.8 nm. A significant orientation of the nanopartides induced by extrusion was also observed. Tensile tests performed above the glass transition of the materials showed that the presence of clay nanoparticles leads to higher elastic modulus and maximum stress, without significant loss in elongation at break which typically reached 100%. Samples submitted to a 50% elongation and cooled below the glass transition showed shape memory behavior. Like unreinforced starch, the bionanocomposites showed complete shape recovery in unconstrained conditions. In mechanically constrained conditions, the maximum recovered stress was significantly improved for the bionanocomposites compared to unreinforced starch, opening promising perspectives for the design of sensors and actuators. (C) 2013 Elsevier Ltd. All rights reserved

The use of choline chloride for salt reduction and texture enhancement in bread

International audienceCereal products, and in particular bread, are the main source of salt in human diets. However, salt is a critical ingredient in breadmaking, and its reduction can have a negative impact on bread quality. In order to respond to the World Health Organization (WHO)’s recommendation to reduce dietary salt intake, this research aims to develop a bread recipe "reduced" in salt (sodium chloride or SC) by -50 % and partly substituted by choline chloride (CC). The effect of CC on the properties of bread was studied during baking, cooling and storage of bread. It was observed that partially substituting SC with CC led to an improvement in bread texture. Indeed, CC bread was technologically similar to the control bread. In aqueous solution, CC behaves like an ionic liquid and causes a reorganization of the internal structure of the starch grain. As a result, the staling study highlighted the positive effect of CC on bread texture and on the starch retrogradation. CC limited amylopectin recrystallization by reducing water availability in the medium, consequently slowing down the staling of the bread

Influence of the Presence of Choline Chloride on the Classical Mechanism of “Gelatinization” of Starch

International audienceThe aim of this research is to contribute to a better understanding the destructuration of three native starches and a wheat flour in mixtures of water and choline chloride. Model systems have thus been defined to allow a better approach to hydrothermic transformations related to the interactions between choline chloride and starch. We have observed that choline chloride has an impact on the gelatinization of starch which corresponds to the stabilizing salts phenomenon. The depolymerization and dissolution of the starch have also been demonstrated and can there dominate the gelatinization. However, the results obtained in X-ray diffraction by heating cell have shown that the exotherm which appeared was not only related to the depolymerization of the starch, but that a stage of crystalline rearrangement of the starch coexisted with this phenomenon

Where do the scatter and low mechanical properties of hemp fiber come from ?

International audienc