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Olive pomace (OP) is the agro-industrial residue of olive oil extraction composed of residual pulp and stone. This work aims at exploring the possibility of using dry fractionation (combination of grinding and sorting processes) to produce pulp-rich and stone-rich fractions with the highest purity and yield. The physical-chemical characteristics (composition, thermal stability, color, surface free energy) of the obtained powders were discussed in relation to the applied processes. It was shown that dry fractionation could be successfully used to convert OP into valuable fractions using processes avoiding the consumption of water and the generation of effluents or co-products. Results revealed that the separation of the pulp from the stone using friction solicitations in a ball mill operating in mild conditions (2 min at a frequency of 15 Hz) was as efficient as wet fractionation in terms of powder characteristics, achieving a total yield of 99.4% against only 82.1% in the case of wet fractionation and without using water while a water:biomass ratio of 5:1 was required for wet fractionation. Produced powders exhibited contrasted biochemical composition (either rich in lignin or cellulose) and surface free energy, and were thermally stable up to at least 210 °C. It was concluded that they could be interestingly used as raw resources for the production of fillers that will be further incorporated in polymer matrices to produce a range of biocomposites.

Rapeseed (RSM) and sunflower (SFM) meals are highly abundant and protein-rich by-products from the oilseed industry. Besides their basic use as animal feed, they are seen nowadays as interesting raw materials for the production of high value added products such as protein isolates, peptides, emulsifiers and biomaterials. In other respects, they contain significant amounts of phenolic compounds exhibiting antioxidant or antimicrobial properties but widely untapped so far. Therefore, any process allowing the single-step separation of both the protein and phenolic parts of meals would be beneficial to the whole oilseed sector. To achieve this double objective this study attempted to separate the RSM and the SFM into their major constituents by using dry fractionation technologies. In a first step, ultrafine milling was applied to the meals. As a function of raw material type, the grid size turned out to be decisive on the particle size distribution and its modality. Then two separation technologies based either on particle charge (electrostatic sorting – ES) or density (turbo-separation – TS) were applied to the previously obtained fractions. Regardless the separation technique, the best results were obtained from fractions of an average particle diameter by mass (D50) of 23.7 ± 1.0 μm and 105.5 ± 8.3 μm, for RSM and SFM respectively. Electrostatic sorting allowed increasing simultaneously the protein and phenolic contents by 50–55% and 80–100% for RSM and SFM respectively, while a lower increase was observed for turbo-separation (23–29% and 58–64% for RSM and SFM respectively). Finally, depending on the process and meal types, the overall recovery yield of the most enriched fractions was in the range of 30–40%.

The possible use of specific biochemical compounds identified in wheat grains was evaluated for monitoring barley grain tissues during fractionation. First barley grain anatomy was studied through microscopic observation and quantification of the relative proportion of each anatomical part in four distinct barley samples from both hulled and hulless genotypes. As expected from cereal phylogeny and irrespective of the possible presence of hull, common features were observed between barley and wheat grains, but the aleurone layer predominated in the outer layers. The specific location of the coumpounds identified in wheat was established. Phytic acid was specifically localized in the aleurone layer and alkylresorcinols in the composite layer containing the testa, even if their concentration differed from that observed in wheat grain tissues. Thus, these two markers identified in wheat can be used to monitor the corresponding barley tissues, independent of the presence of hulls. Conversely, phenolic compounds, either ferulic acid trimer or p-coumaric acid, cannot be used to monitor respectively the outer pericarp or the aleurone cell walls in barley grains. p-coumaric acid was identified as an efficient marker of the hull and could be used to distinguish hulled or hulless barley grains and to help monitor the dehulling process.

This work evaluated the effects of processing faba bean flour on textural, structural and sensory properties of gluten-free pasta. Pasta was prepared using faba bean flour, starch-rich fraction of faba bean flour or faba bean flour fermented with lactic acid bacteria. The impact of cross-linking enzyme transglutaminase (TG) on the quality of faba pasta was also studied. The structure, cooking quality, starch digestibility, textural and sensory characteristics of faba pasta samples were evaluated and compared to semolina pasta. Pasta prepared with faba bean and fermented faba bean flours had higher cooking loss (10.8–11.5%) and lower water absorption (130–160%) than semolina pasta (6 and 193%), but pasta prepared from fractionated faba flour had similar water absorption to semolina pasta. The texture of pasta made with faba bean flour was comparable to that of semolina pasta. Fermentation adversely affected the texture by increasing hardness, chewiness, sourness and flavour intensity. Starch hydrolysis index of pasta prepared with the three faba bean flours was similar to semolina pasta (46–50). TG reduced the in vitro starch hydrolysis index and increased some textural parameters of pasta made with faba bean flour, but no influence was observed on pasta made with fractionated or fermented faba.

Lignocellulose fractionation to chemicals and biofuels often requires severe conditions and consume high energy. Although some of these pretreatment processes are nowadays developed at pilot scale, they are not always cost effective, and they are responsible for environmental impacts. Recently, mechanocatalysis pretreatment emerged as a promising technology for the activation and deconstruction of lignocellulosic biomass. In particular, these dry processes have the potential to limit the use of solvent and the production of liquid effluents. In this study, we propose an innovative one-pot eco-friendly approach based on the combination of dry chemical and vibro-ball-milling (VBM) for biomass activation, coupled to enzymatic conversion without an external source of heating, and without the assistance of any organic solvent. NaOH activation coupling to VBM fractionation for 10, 30, and 60 min was compared to H3PO4, H2O2, betaine, and betaine-Cl activation. NaOH-VBM-10 min appears more effective in sugar production compared to other chemical-mechanical activation. NaOH-VBM in 10 min consumed less energy, resulting in higher energy efficiency compared to that of other chemical-mechanical activation. Therefore, NaOH-VBM-10 min appears the most suitable and interesting pretreatment for the production of sugars and biofuels from corn stover biomass.

A simulation of a SBR using Benchmark procedure was done prior to field operation in order to optimize the cycle and phases lengths. The accurate identification of ASM1 variables is a prerequisite to achieve a good prediction. A fractionation procedure was applied to samples, corresponding to dry and rainy weather conditions, for taking into account the ASM1 state variable characteristics of specific wastewater (mixture of domestic and industrial wastewater), which differ largely from the default ones used in ASM1. The choice of the ASM1 state variables identification methodology is very important as it influences the results. Two methods were carried out: a batch test in closed reactors, and a coagulation/flocculation procedure. An optimal 12‑hour cycle length was determined, in terms of discharged water quality and reactor productivity. The described methodology led to valuable results in terms of carbon and nitrogen removal: respectively more than 90% of COD removal and more than 80% on total nitrogen removal., Une méthodologie d’optimisation des durées du cycle et des phases d’un procédé SBR avant une mise en oeuvre réelle a été développée grâce à l’utilisation de la modélisation mathématique (utilisation du modèle ASM1). Les valeurs par défaut du modèle ASM1 ne permettent pas toujours de tenir compte de la variabilité de la qualité des eaux usées, notamment dans le cas d’eaux usées particulières (cas d’un mélange d’eaux usées industrielles et domestiques). Afin de tenir de tenir compte de cette variabilité et dans le but de déterminer plus précisément les valeurs des variables du modèle ASM1, une procédure de fractionnement a été appliquée à des échantillons d’eaux usées urbaines, par temps de pluie et par temps sec. Le choix de la méthode d’identification des variables du modèle ASM1 est très important car il conditionne en partie le résultat. Deux méthodes ont été mises en oeuvre : des tests de biodégradation en réacteurs fermés, et des tests de coagulation floculation. L’utilisation des variables définies notamment par les tests de biodégradation a permis de définir un cycle de 12 heures permettant d’allier une bonne qualité de l’eau de sortie à une productivité optimale. La méthodologie décrite permet d’obtenir de très bons taux d’abattement du carbone et de l’azote pour une eau usée urbaine, respectivement supérieurs à 90 % et 80 %.

International audience; A surface response experimental design was used to quantify the effects of the final cooling temperature and the residence time at this temperature on the filtration characteristics of the crystal suspension and the quality of the fractions during chicken fat dry fractionation. The crystal morphology was monitored to gain insight into the observed effects. Temperature affected crystallization and the characteristics of the olein and stearin fractions. The crystals became fragmented as the residence time increased, thus leading to a decrease in the filterability of the crystal suspension and an increase in the proportion of the entrained liquid phase. The residence time only affected the quality of the stearin fraction. This time effect was noted at high cooling temperatures in the investigated experimental domain. At low temperatures, increasing the residence time enhanced crystal growth and increased the extent of unsaturation of both fractions without modifying the filtration features. (Résumé d'auteur)

The impacts of the cooling program on crystal morphology, crystal suspension filtration properties and the characteristics of fractions resulting from chicken fat dry fractionation were assessed. The quality of the fractions was found to depend on the nature of the crystallized material and was also closely related to the filtration properties of the crystal suspension, which in turn were controlled by the cooling conditions. A slow cooling rate during the nucleation step was necessary to enhance process selectivity, and this rate could be accelerated once the first crystals had formed. These findings enhanced our understanding of the mechanisms involved during dry fractionation and highlighted the efficacy of a three-phase cooling program, including (1) cooling from 70 to 26°C, (2) slowdown in the cooling rate, and (3) a second rapid cooling down to the final temperature at which the fat is held for a specified time. (Resume d'auteur)

Organic matter characterization is the starting point to describe organic waste treatments mechanisms and to propose their modelling. Two relevant characterization methodologies were frequently used in the literature based on chemical extractions and fluorescence spectroscopy. However, they could not be generalised to all the type of wastes because of the different molecules targeted. Consequently, a new fractionation methodology was proposed to unify the characterization of a wide range of organic wastes. This new method was built by merging the two previously mentioned protocols to simulate bioaccessibility combined with 3D fluorescence spectroscopy to highlight the complexity of the extracted organic fractions. Sixty samples including representative samples used to validate the method were characterised according to their bioaccessibility and their complexity. Thanks to a principal component analysis, organic wastes were classified according to their nature, their complexity and accessibility. The applicability of this method in statistical or dynamic models is very promising.

Les lixiviats de décharge constituent une source de nuisance qui vient s'ajouter aux nombreux problèmes de contamination du milieu environnant s'ils ne sont pas traités avant leur rejet. La matière organique, principale composante de ces effluents, doit retenir une grande attention dans la mesure où il est difficile d'éviter la propagation et la diffusion de cette pollution dans les sols et vers les nappes phréatiques. Cette étude vise à fractionner et à caractériser la matière organique présente dans des lixiviats de décharges d'ordures ménagères afin de prévoir et d'orienter le choix des traitements les plus adaptés compte tenu de leur biodégradabilité.La méthode de fractionnement utilisée comprend une adsorption spécifique sur résines macroporeuses Amberlite XAD (combinaison de XAD-7 et XAD-4) pour séparer les composés hydrophobes et hydrophiles qui sont ensuite extraits à la soude (composés acides) et au dichlorométhane (composés neutres). Le fractionnement de la matière organique par filtration sur résines XAD-7 et XAD-4, après une première étape de précipitation en milieu acide (pH=1), a permis de répartir l'ensemble des composés organiques du lixiviat dans six fractions de spécificités différentes fonction de la taille et/ou du caractère hydrophile ou hydrophobe des molécules. Les résultats montrent que ce protocole expérimental permet d'extraire au moins 98 % de la matière organique totale (pourcentage relatif aux teneurs de la demande chimique en oxygène ou DCO), dont la plus grande proportion est constituée des substances humiques (76 % à 90 % en DCO). Diverses méthodes analytiques ont été proposées en vue de caractériser les fractions isolées telles que l'analyse élémentaire, la spectrophotométrie infrarouge, la résonanoe magnétique nucléaire C13 (RMN Cl3) et la chromatographie CG/FID et CG/SM., Landfill leachates represent an obvious source of pollution for the environment and many studies have attempted to analyze organic pollutants found in leachates. A number of methods have been described in the literature for the isolation and concentration of dissolved organic matter from landfill leachate samples. Membrane ultrafiltration, gel permeation and high performance liquid chromatography are commonly used because these techniques can be easily adapted to separate soluble organic substances from large volumes of leachate. The objective of this study was to fractionate and characterize dissolved organic matter found in leachates collected from sanitary landfills.The discharges are defined with regard to the geological context from which they are situated and the nature of the waste. The discharges are classified in three categories, based upon the value of the permeability coefficient K, the substratum and its continuity.- class 1; impermeable site (K < 10-[sup]9 ms-¹ minimal thickness of 5 m). - class 2; semi permeable site (10-[sup]9 ms-¹ < K < 10-[sup]6 ms-¹). - class 3; permeable site ( K > 10-[sup]6 ms-¹). The studied leachates come from landfill of class 2:- Crézin (Haute-Vienne) of compacted type: it was used for household rubbish and assimilated ordinary wastes. - Foussais-Payre (Vendée): leachate coming from the fermentation area of a composting plant and from the compost refuse. Fractionation of dissolved organic matter was applied on three leachates samples. The first sample was the raw leachate collected from the Crézin landfill and the two others came from Foussais-Payre (a raw sample and a sample treated in an aerated lagoon for 52 days). Because of the wide variety of organic compounds that can be found in such leachates, we classified and isolated the different groups of organic constituents using an XAD resin adsorption procedure. The experimental method consisted of acidifying samples to pH 1 to isolate the first fraction (fig. 1) and then treating the remaining supernatant with XAD-7 and XAD-4 resins. The adsorption on XAD resins allowed the isolation of the other organic fractions (figs. 2 to 6). Various analytical techniques were applied to characterize the isolated fractions such as elementary analysis infrared spectroscopy, ¹3C nuclear magnetic resonance (¹3C CP/MAS NMR), gas chromatography (GC/FID), and gas chromatography coupled to mass spectrometry (GC/MS). Results showed that more then 90% of the total organic carbon (TOC) in leachates can he recovered by the isolation procedure. Most of the isolated compounds corresponded to humic substances (76% to 90% of the chemical oxygen demand). Hydrophobic and hydrophilic neutral compounds were found only in small concentrations.

Chicken fat was processed by dry fractionation to obtain a solid fraction at ambient temperature. Crystallisation and separation were performed using industrial-type procedures. Crystal formation and changes were monitored, while determining the composition, physical characteristics and thermal behaviour of the initial fat and resulting fractions. Dry fractionation, under the described conditions, produced stearin that resembled other animal fats such as lard and tallow and with better physical features than the initial fat stock. The results of this study also highlighted the mechanisms involved during the dry fractionation process.

International audience; The isotopic exchange kinetic (IEK) method allows assessing the rate of orthophosphate ions (Pi) exchange between the solid phase and the solution of the soil with time. However, two challenges have to be tackled when using this technique in soils with a very low water extractable Pi concentration (C-P) and with a high sorbing capacity for Pi. The first is that current colorimetric methods do not allow quantifying Pi concentrations lower than 10 mu g P L-1. While the second challenge is that a significant fractionation between P isotopes may occur in the soil solution system in the presence of soils with high Pi sorption capacity. We assessed here: i) whether concentrating the blue phosphomolybdate complex (BPMC) in hexanol prior to its measurement would allow to lower the detection and quantification limits of Pi, ii) whether a significant isotopic fractionation between (32)Pi and (33)Pi could occur during IEK experiments conducted in the presence of high Pi sorbing substrates (e.g., pure goethite or Malagasy soils) and iii) whether the IEK method when used in conjunction with the hexanol concentration of the BPMC to measure C-P would detect changes in Pi isotopic exchangeability in a ferralsol cropped with upland rice following the input of manure or water soluble fertilizer. The detection and quantification limits of the BPMC concentrated by hexanol were 0.3 and 0.8 mu g P L-1, respectively, using a cell of 10 cm length for the colorimetric measurement. The IEK conducted on Pi amended goethite and on Malagasy soils with (32)Pi and (33)Pi did not show any systematic isotopic fractionation between both isotopes, suggesting that in these soils (31)Pi and (32)Pi or (33)Pi have a similar behavior during isotopic exchange. The analysis of the soils sampled in the field experiment showed a significant increase in the amount of Pi isotopically exchangeable after 1 min only after the application of water soluble P. This increase was paralleled by increases in rice yield and P export by grains demonstrating an increased P availability in this treatment. In conclusion, the IEK method can be used in low P and high Pi sorbing soils as the hexanol concentration method allows measuring very low C-P and as the different P isotopes have a similar behavior in the soil/solution system. The IEK experiments conducted in the presence of goethite, however, point out to the necessity of taking into account the dispersion of particles for a proper interpretation of the isotopic data.

International audience; The benefits of using organic waste as fertilizer and soil amendment should be assessed together with the environmental impacts due to the possible presence of heavy metals (HMs). This study involved analysing major element and HM contents in raw and size-fractionated organic wastes (17 sewage sludges and composts) from developed and developing countries. The overall HM concentration pattern showed an asymmetric distribution due to the presence of some wastes with extremely high concentrations. HM concentrations were correlated with the size of cities or farms where the wastes had been produced, and HM were differentiated with respect to their origins (geogenic: Cr-Ni; anthropogenic agricultural and urban: Cu-Zn; anthropogenic urban: Cd-Pb). Size fractionation highlighted Cd, Cu, Zn and Pb accumulation in fine size fractions, while Cr and Ni were accumulated in the coarsest. HM associations with major elements revealed inorganic (Al. Fe, etc.) bearing phases for Cr and Ni, and sulfur or phosphorus species for Cd, Cu Pb and Zn. (c) 2012 Elsevier Ltd. All rights reserved.

Ultrafiltration can be envisaged as an alternative to chromatography for the fractionation of proteins (and especially metalloproteins) provided the in-depth understanding of mechanisms involved during the process is completed. In the past, optimization of filtration processes was mainly envisaged by minimizing fouling issues and enhancing both membrane selectivity and final purity of produced fractions. But little attention was paid to the evolution of protein structure and functionality even if metalloproteins are highly attractive due to their numerous biological potentialities: catalytic activity for enzymes, passive or active transport of a substrate, etc. For metalloproteins, such a biological activity is related to the presence of at least one metallic ion (called cofactor), linked to lateral chains of amino acid residues (α-lactalbumin, lactoferrin) or coordinated into a prosthetic group (hemoglobin, cytochrome, peroxidase). But surprisingly, even composition analyses and/or the role of protein conformation (apo-form without cofactor vs. holo-form with cofactor) were rarely mentioned in filtration studies although the presence of ionic cofactors is highly decisive in preserving metalloprotein structure, bioactivity and stability. To our knowledge, only one recent study focused on both composition and properties of metalloprotein fractions during UF, showing the predominant role of cofactors to explain performances of the process (Portugal et al., 2006). In this work, a progressive depletion in Fe3+ and Ca2+ was evidenced after dead-end permeation of horseradish peroxidase through a UF membrane and this depletion was explained by the affinity of the membrane material towards ionic species. Unfortunately in this work, relevant information is only given concerning the impact of UF on the native form of the metalloprotein and no comparison is done with the apo-form even if it could have confirmed the mechanism involved.The aim of our work is to help understanding mechanisms that control process performances during UF of metalloproteins both in holo and apo conformations. Two crucial questions are then addressed. i) Do apo- and holo-forms have the same behaviour during UF? ii) Does the behaviour of a mixture between both conformations reflect the composition of the filtered solution? And if not, what are the mechanisms involved? For this study, dead-end ultrafiltration was performed with polyethersulfone membranes (10, 30 and 100 kg.mol-1) and α-lactalbumin (α-LA, 14 kg.mol-1) was used as a model protein. This milk protein has a high-added value (nutritional, biological and functional properties) and is considered as a metalloprotein due to its capacity to bind specifically one calcium ionic entity per protein molecule. Holo-α-LA (calcium-binding form) is the native form of the protein and in solution, it always coexists with apo-α-LA. The cofactor Ca2+ guarantees structure, bioactivity and stability of the protein α-LA. In this work, we have evidenced for the first time that protein conformation impacts UF performances of a metalloprotein: a higher transmission of apo-α-LA (calcium-depleted form) compared to holo-α-LA (native form) was observed during UF with pure solutions using a 30 kg.mol-1 membrane. Such a phenomenon was not controlled by electrostatic repulsions but was supposed to be linked to a distinct flexibility and/or hydrophobicity of the two conformations. Besides, we have shown that the behavior of the mixture of both conformations of α-LA did not reflect the behavior of individual conformations. When filtering a protein mixture, membrane selectivity was responsible for a displacement of the equilibrium between apo-α-LA and holo-α-LA. The higher transfer of apo-α-LA was suspected to be responsible for the displacement of the equilibrium between the ionic cofactor (Ca2+) and the protein (Figure, displacement (b)) resulting in preferential permeation of free calcium, and then in an increased Ca2+/α-LA molar ratio in the permeated fraction. The ratio of the permeate was closed to the ratio of a holo-α-LA solution, and this phenomenon was favoured for membranes with a low cut-off compared to the molecular weight of α-LA. The validity of the displacement of the equilibrium between apo-α-LA and holo-α-LA during UF was reinforced by structural and functional analyses of proteins before and after permeation (intrinsic fluorescence, circular dichroism, solubility). As apo- and holo-α-LA conformations are known to have distinct structure and functionality, it was important to test whether protein properties observed after UF reflect changes in composition described above. Results showed that after permeation α-LA properties evolved towards the one of holo-α-LA. In this study, we have clearly evidenced the importance of composition analyses for the understanding of UF performances when considering metalloproteins. We have shown that the equilibrium between the two forms of a metalloprotein (holo-apo) infleunces the performances of ultrafiltration. Such information is highly decisive for the control of protein properties after membrane permeation and the production of pure protein fractions having a targeted functionality.

UMR IATE Axe 4 Biotechnologie microbienne et enzymatique des lipides et des agropolymères Contacts : stephane.dubascoux@supagro.inra.fr, frederic.bonfils@cirad.fr; Abstract: This paper presents results from the first analyses of the mesostructure of natural rubber (NR) by asymmetrical flow field flow fractionation (AF4). The results are compared with those obtained by size exclusion chromatography (SEC) in terms of average molar masses, radius of gyration and insoluble part (or gel quantity). Comparable results were obtained for the sample not containing gel. Conversely, for samples with gel, significant differences were found due to the presence of microaggregates. Contrary to SEC, AF4 fractionation enables partial fractionation of polyisoprene chains and microaggregates in a single run without preliminary treatment. The results presented here also highlight the special structure (very compact spheres) of microaggregates in NR compared to chemical crosslinked microaggregates in synthetic polyisoprene. The advantages and drawbacks of both techniques for analysing NR samples are also discussed.

In addition to total organic carbon and nitrogen, potential organic carbon mineralization under controlled laboratory conditions and indicators such as the indicator of remaining organic carbon in soil (I-ROC), based on Van Soest biochemical fractionation and short-term carbon mineralization in soil, are used to predict the evolution of exogenous organic matter (EOM) after its application to soils. The purpose of this study was to develop near infrared reflectance spectroscopy (NIRS) calibration models that could predict these characteristics in a large dataset including 300 EOMs representative of the broad range of such materials applied to cultivated soils (plant materials, animal manures, composts, sludges. etc.). The NIRS predictions of total organic matter and total organic carbon were satisfactory (R(2)p = 0.80 and 0.85, ratio of performance to deviation, RPDp = 2.2 and 2.6, respectively), and prediction of the Van Soest soluble, cellulose and holocellulose fractions were acceptable (R(2)p = 0.82, 0.73 and 0.70. RPDp = 2.3, 1.9 and 1.8, respectively) with coefficients of variation close to those of the reference methods. The NIRS prediction of carbon mineralization during incubation was satisfactory and indeed better regarding the short-term results of mineralization (R(2)p = 0.78 and 0.78, and RPDp = 2.1 and 2.0 for 3 and 7 days of incubation, respectively). The I-ROC indicator was predicted with fairly good accuracy (R(2)p = 0.79, RPDp = 2.2). Variables related to the long-term C mineralization of EOM in soil were not predicted accurately, except for I-ROC which was based on analytical and well-identified characteristics, probably because of the increasing interactions and complexity of the factors governing EOM mineralization in soil as a function of incubation time. This study demonstrated the possibility of developing NIRS predictive models for EOM characteristics in heterogeneous datasets of EOMs. However. specific NIRS predictive models still remain necessary for sludges, organo-mineral fertilizers and liquid manures.

Contact: ghizzi@supagro.inra.fr; Grinding plant biomass may allowthe lignocellulosic assembly to become more reactive/accessible by providing energy for polymer dissociation, increasing contact surface (particle size reduction) and reducing cellulose crystallinity. Moreover lignocellulosic composition varies considerably affecting biomass processability as resource for bio-based energies, composite materials and chemicals. The aims of this work were: (i) to analyse composition of wheat anatomic parts present into wheat straw, (ii) to characterize the behaviour of major components upon successive centrifugal grinding steps (2 mm-screen cutting milling followed by 4-step centrifugal grinding) and (iii) to relate particle size distribution and component concentrations into the finest sized product (0.12 mm-screen ground). The powders from successive centrifugal grindings were sieved and their chemical compositions were determined. Ground straw powders were heterogeneous according to different particle aspects: size, shapes and roughness. In general fractionswith lower particle size had higher ash and protein contents whereas cellulose contents are higher in the larger fractions. Wheat straw exhibited a non homogeneous reduction behaviour when finely ground. Fraction compositions were only slightly distinct suggesting that although sieving can constitute a preliminary fractionation step, it is necessary to reduce still more the particle size to reach more effective dissociation of macromolecules assembly

Separation and size measurement of protein particles are a relevant approach to monitor heat-induced changes in skim milk. Unfortunately, no method is currently available at low cost and without excessive preparation of the samples. Therefore, the present study aimed at evaluating the interest of asymmetrical flow field-flow fractionation (AFlFFF) coupled with multiangle laser light scattering (MALLS) for this purpose. Unheated and heated skim milk samples at pH 6.5 and 7.2 were prepared and comparatively analyzed using AFlFFF-MALLS, size exclusion chromatography (SEC-MALLS) and dynamic light scattering. The results showed that AFlFFF could evidence the conversion of the native whey proteins of unheated milk into heat-induced whey protein/κ-casein complexes in the serum phase of milk and possibly on the surface of the casein micelles. The pH-induced changes in the partition of the complexes between the serum and the micellar phases could also be observed. The results therefore showed the interest of AFlFFF-MALLS to monitor the heat-induced changes in particle sizes in skim milk and to separate the different protein components of unheated and heated skim milk.

The quantification of silicon isotopic fractionation by biotic and abiotic processes contributes to the understanding of the Si continental cycle. In soils, light Si isotopes are selectively taken up by plants, and concentrate in secondary clay-sized minerals. Si can readily be retrieved from soil solution through the specific adsorption of monosilicic acid (H4SiO40) by iron oxides. Here, we report on the Si-isotopic fractionation during H4SiO40 adsorption on synthesized ferrihydrite and goethite in batch experiment series designed as function of time (0-504 h) and initial concentration (ic) of Si in solution (0.21-1.80 mM), at 20 degrees C, constant pH (5.5) and ionic strength (1 mM). At various contact times, the delta Si-29 vs. NBS28 compositions were determined in selected solutions (ic = 0.64 and 1.06 mM Si) by MC-ICP-MS in dry plasma mode with external Mg doping with an average precision of +/- 0.08 parts per thousand (+/- 2 sigma(SEM)). Per oxide mass, ferrihydrite (74-86% of initial Si loading) adsorbed more Si than goethite (37-69%) after 504 h of contact over the range of initial Si concentration 0.42-1.80 mM. Measured against its initial composition (delta Si-29 = +0.01 +/- 0.04 parts per thousand (+/- 2 sigma(SD))), the remaining solution was systematically enriched in Si-29, reaching maximum delta Si-29 values of +0.70 +/- 0.07 parts per thousand for ferrihydrite and +0.50 +/- 0.08 parts per thousand for goethite for ic 1.06 mM. The progressive 29 Si enrichment of the solution fitted better a Rayleigh distillation path than a steady state model. The fractionation factor (29)epsilon(+/- 1 sigma(SD)) was estimated at -0.54 +/- 0.03 parts per thousand for ferrihydrite and -0.81 +/- 0.12 parts per thousand for goethite. Our data imply that the sorption of H4SiO40 onto synthetic iron oxides produced a distinct Si-isotopic fractionation for the two types of oxide but in the same order than that generated by Si uptake by plants and diatoms. They further suggest that the concentration of light Si isotopes in the clay fraction of soils is partly due to H4SiO40 sorption onto secondary clay-sized iron oxides. (C) 2008 Elsevier Ltd. All rights reserved.

Forty-seven different animal wastes were characterized using chemical and organic matter fractionation methods (water extraction and Van Soest method) and 224-day incubation studies to assess their decomposition in soil. Simple correlation and multiple factor analysis were performed to establish relationships between the composition of these wastes and C and N mineralization. Carbon and N contents ranged from 101 to 469 mg C kg−1 dry matter (d.m.) and from 4 to 39 mg N kg−1 d.m. Soluble C and N represented less than 9% of organic C and 1.5% of total N at 20°C, respectively. The C fractions soluble at 100°C or in neutral detergent were larger and represented 14 and 32% of the organic C, respectively. The hemicellulose-like (HEM) and cellulose-like (CEL) fractions contained about 16.5 and 6% of the organic N, respectively. The C distribution in the lignin-like (LIG) and CEL fractions was comparable, but the former contained more N. Carbon mineralization varied from 5 to 62% of the organic C added during the 224-day incubation; 70% of the wastes induced net N mineralization at the end of incubation (from 3 to 51% of organic N). Other wastes induced net soil inorganic N immobilization, from −1 to −31% of the organic N added. Most highly significant correlations were established between the C mineralization and the C present in the water-soluble fraction at 20°C, and the HEM and LIG fractions. Relationships between N mineralization and biochemical characteristics were weak, except with the soluble Van Soest fraction, and highly significant correlations were observed between N mineralization rates calculated at 224 days of incubation and the organic N content or C/N ratio of wastes. Finally, an objective hierarchical classification based on composition criteria and C and N mineralization led to the definition of six different classes of wastes. It permitted differentiation between four composted wastes and intrinsically different wastes (i.e., cattle manures, pig manures, and poultry manures) which could not be objectively regrouped. It also placed some very different types of waste (solid phase from pig slurry separation, pig manures, and composted pig mixtures) in the same class.

International audience; This article reports detailed procedures : 1) to decrease organic contamination of samples in the laboratory; 2) to extract sewage sludge with methylene chloride; and 3) to fractionate extracts by silica-gel thin layer chromatography (TLC) into fractions enriched in alkanes, aromatic hydrocarbons, ketones, alcohols and fatty acids, eluting either hexane or methylene chloride.

Summary A tropical semi-arid soil was fractionated by successive wet sieving at 200 μ m and 50 μ m in order to separate two light fractions, two mineral fractions, and one organo-mineral fraction. Each fraction was incubated separately for N mineralization. It was observed that 60 to 80 per cent of mineral N, produced in the whole soil was due to the organo-mineral fraction. Expressed as per cent of total N in the fraction, mineralized N was higher in organo-mineral fraction than in light fractions, and was weakly correlated with C/N ratio. Mineralized N decreased with soil depth in all fractions.