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International audience; Cell-to-cell adhesion is essential for establishment of multicellularity. In plants, such adhesion is mediated through a middle lamella composed primarily of pectic polysaccharides. The molecular interactions that influence cell-to-cell adhesion are not fully understood. We have used Arabidopsis (Arabidopsis thaliana) seed coat mucilage as a model system to investigate interactions between cell wall carbohydrates. Using a forward-genetic approach, we have discovered a gene, RUBY PARTICLES IN MUCILAGE (RUBY), encoding a protein that is annotated as a member of the Auxiliary Activity 5 (AA5) family of Carbohydrate-Active Enzymes (Gal/glyoxal oxidases) and is secreted to the apoplast late in the differentiation of seed coat epidermal cells. We show that RUBY is required for the Gal oxidase activity of intact seeds; the oxidation of Gal in side-chains of rhamnogalacturonan-I (RG-I) present in mucilage-modified2 (mum2) mucilage, but not in wild-type mucilage; the retention of branched RG-I in the seed following extrusion; and the enhancement of cell-to-cell adhesion in the seed coat epidermis. These data support the hypothesis that RUBY is a Gal oxidase that strengthens pectin cohesion within the middle lamella, and possibly the mucilage of wild-type seed coat epidermal cells, through oxidation of RG-I Gal side-chains.

The major nutrients available to human colonic Bacteroides species are glycans, exemplified by pectins, a network of covalently linked plant cell wall polysaccharides containing galacturonic acid (GalA). Metabolism of complex carbohydrates by the Bacteroides genus is orchestrated by polysaccharide utilization loci (PULs). In Bacteroides thetaiotaomicron, a human colonic bacterium, the PULs activated by different pectin domains have been identified; however, the mechanism by which these loci contribute to the degradation of these GalA-containing polysaccharides is poorly understood. Here we show that each PUL orchestrates the metabolism of specific pectin molecules, recruiting enzymes from two previously unknown glycoside hydrolase families. The apparatus that depolymerizes the backbone of rhamnogalacturonan-I is particularly complex. This system contains several glycoside hydrolases that trim the remnants of other pectin domains attached to rhamnogalacturonan-I, and nine enzymes that contribute to the degradation of the backbone that makes up a rhamnose-GalA repeating unit. The catalytic properties of the pectin-degrading enzymes are optimized to protect the glycan cues that activate the specific PULs ensuring a continuous supply of inducing molecules throughout growth. The contribution of Bacteroides spp. to metabolism of the pectic network is illustrated by cross-feeding between organisms., This work was supported in part by an Advanced Grant from the European Research Council (Grant No. 322820) awarded to H.J.G. and B.H. supporting A.S.L., D.N., A.C. and N.T., a Wellcome Trust Senior Investigator Award to H.J.G. (grant No. WT097907MA) that supported J.B. and E.C.L. a European Union Seventh Framework Initial Training Network Programme entitled the “WallTraC project” (Grant Agreement number 263916) awarded to M-C.R. and H.J.G, which supported X.Z. and J.S. The Biotechnology and Biological Research Council project ‘Ricefuel’ (grant numbers BB/K020358/1) awarded to H.J.G. supported A.L.

International audience; Rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II) domains were isolated from ginseng pectin by alkali saponification and endo-polygalacturonase hydrolysis, then purified by anion-exchange and size-exclusion chromatography. Monoclonal antibody detection indicated that ginseng RG-I contained -> 4)-alpha-GalpA-(1 -> 2)-alpha-Rhap-(1 -> repeating units as backbone, with arabinan, galactan and type II arabinogalactan (AG-II) as side chains. The use of galactose- and arabinose-releasing enzymes, mass spectrometry analysis of the oligosaccharides generated by rhamnogalacturonan hydrolase, and glycosidic linkage analyses provided evidence that ginseng RG-I contains both single galactose-branched subunits and highly branched subunits with arabinan and AG-II side chains. RG-II was analyzed by sequential acid hydrolysis followed by mass spectrometry. Ginseng RG-II contains 9 galacturonic acid units as backbone. Side chain A is an octasaccharide with 0 similar to 1 methyl ether group. Side chain B is a nonasaccharide with 0 similar to 1 acetyl group. These results provide useful information for further investigation of structure-activity relationship of ginseng pectin.

Pectin methylesterases (PMEs) catalyze the demethylesterification of homogalacturonan domains of pectin in plant cell walls and are regulated by endogenous pectin methylesterase inhibitors (PMEIs). In Arabidopsis dark-grown hypocotyls, one PME (AtPME3) and one PMEI (AtPMEI7) were identified as potential interacting proteins. Using RT-quantitative PCR analysis and gene promoter::GUS fusions, we first showed that AtPME3 and AtPMEI7 genes had overlapping patterns of expression in etiolated hypocotyls. The two proteins were identified in hypocotyl cell wall extracts by proteomics. To investigate the potential interaction between AtPME3 and AtPMEI7, both proteins were expressed in a heterologous system and purified by affinity chromatography. The activity of recombinant AtPME3 was characterized on homogalacturonans (HGs) with distinct degrees/patterns of methylesterification. AtPME3 showed the highest activity at pH 7.5 on HG substrates with a degree of methylesterification between 60 and 80% and a random distribution of methyl esters. On the best HG substrate, AtPME3 generates long non-methylesterified stretches and leaves short highly methylesterified zones, indicating that it acts as a processive enzyme. The recombinant AtPMEI7 and AtPME3 interaction reduces the level of demethylesterification of the HG substrate but does not inhibit the processivity of the enzyme. These data suggest that the AtPME3·AtPMEI7 complex is not covalently linked and could, depending on the pH, be alternately formed and dissociated. Docking analysis indicated that the inhibition of AtPME3 could occur via the interaction of AtPMEI7 with a PME ligand-binding cleft structure. All of these data indicate that AtPME3 and AtPMEI7 could be partners involved in the fine tuning of HG methylesterification during plant development.

International audience; Pectins are complex branched polysaccharides present in primary cell walls. As a distinctive feature, they contain high amount of partly methyl-esterified galacturonic acid and low amount of rhamnose and carry arabinose and galactose as major neutral sugars. Due to their structural complexity, they are modifiable by many different enzymes, including hydrolases, lyases, and esterases. Their peculiar structure is the origin of their physicochemical properties. Among others, their remarkable gelling properties make them a key additive for food industries. Pectin-degrading enzymes and -modifying enzymes may be used in a wide variety of applications to modulate pectin properties or produce pectin derivatives and oligosaccharides with functional as well as nutritional interests. This paper reviews the scientific information available on pectin structure, pectin-modifying enzymes, and the use of enzymes to produce pectin with controlled structure or pectin-derived oligosaccharides, with functional or nutritional interesting properties.

The plant cell wall is held together by the interactions between four major components: cellulose, pectin, hemicellulose, and proteins. Mucilage is a powerful model system to study the interactions between these components as it is formed of polysaccharides that are deposited in the apoplast of seed coat epidermal cells during seed development. When seeds are hydrated, these polysaccharides expand rapidly out of the apoplastic pocket, and form an adherent halo of mucilage around the seed. In Arabidopsis, mutations in multiple genes have similar loss of mucilage adherence phenotypes including CELLULOSE SYNTHASE 5 (CESA5)/MUCILAGE-MODIFIED 3 (MUM3), MUM5/MUCI21, SALT-OVERLY SENSITIVE 5 (SOS5), and FEI2. Here, we examine the interactions between these factors to better understand how they participate to control mucilage adherence. Double mutant phenotypes indicated that MUM5 and CESA5 function in a common mechanism that adheres pectin to the seed through the biosynthesis of cellulose and xylan, whereas SOS5 and FEI2, encoding a fasciclin-like arabinogalactan protein or a receptor-like kinase, respectively, function through an independent pathway. Cytological analyses of mucilage indicates that heteromannans are associated with cellulose, and not in the pathway involving SOS5 or FEI2. A SOS5 fluorescent protein fusion (SOS5-mCITRINE) was localized throughout the mucilage pocket, consistent with a structural role in pectin adhesion. The relationship between SOS5 and FEI2 mediated mucilage adherence was examined in more detail and while sos5 and fei2 mutants show similar phenotypes, key differences in the macromolecular characteristics and amounts of mucilage polymers were observed. FEI2 thus appears to have additional, as well as overlapping functions, with SOS5. Given that FEI2 is required for SOS5 function, we propose that FEI2 serves to localize SOS5 at the plasma membrane where it establishes interactions with mucilage polysaccharides, notably pectins, required for mucilage adherence prior to SOS5 being released into the apoplast.

International audience; Arabidopsis (Arabidopsis thaliana) seed coat epidermal cells produce large amounts of mucilage that is released upon imbibition. This mucilage is structured into two domains: an outer diffuse layer that can be easily removed by agitation and an inner layer that remains attached to the outer seed coat. Both layers are composed primarily of pectic rhamnogalacturonan I (RG-I), the inner layer also containing rays of cellulose that extend from the top of each columella. Perturbation in cellulosic ray formation has systematically been associated with a redistribution of pectic mucilage from the inner to the outer layer, in agreement with cellulose-pectin interactions, the nature of which remained unknown. Here, by analyzing the outer layer composition of a series of mutant alleles, a tight proportionality of xylose, galacturonic acid, and rhamnose was evidenced, except for mucilage modified5-1 (mum5-1; a mutant showing a redistribution of mucilage pectin from the inner adherent layer to the outer soluble one), for which the rhamnose-xylose ratio was increased drastically. Biochemical and in vitro binding assay data demonstrated that xylan chains are attached to RG-I chains and mediate the adsorption of mucilage to cellulose microfibrils. mum5-1 mucilage exhibited very weak adsorption to cellulose. MUM5 was identified as a putative xylosyl transferase recently characterized as MUCI21. Together, these findings suggest that the binding affinity of xylose ramifications on RG-I to a cellulose scaffold is one of the factors involved in the formation of the adherent mucilage layer.

Plant cell walls are the earth's most abundant source of terrestrial biomass. When potatoes are processed for starch production, a low-value, cell wall-rich byproduct known as potato pulp is produced. The huge amounts of pulp available have motivated the reemergence of research devoted to potato cell wall polysaccharide extraction and use.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Assemblies of pectin, xyloglucan and cellulose were studied in vitro using two ternary systems. In the first one, xyloglucan concentration varied, while pectin amount was kept constant. In the second one, pectin concentration varied, whereas xyloglucan amount was fixed. The use of ternary systems allowed to put forward the hypothesis that pectin/cellulose and xyloglucan/cellulose associations may exist together or separately, depending on the proportion of non-cellulosic polysaccharides in cell walls. It can be hypothesized that pectin plays a double role within primary cell walls: (i) pectin loosely bound to cellulose, in xyloglucan-rich cell walls, (ii) pectin associated with cellulose, in xyloglucan-poor cell walls.

International audience; Binding modelling of tamarind and pea xyloglucans, sugar beet and potato pectins, and pectic side chains (branched arabinan, debranclied arabinan, galactan) onto microcrystalline Avicel cellulose and primary cell wall (PCW) cellulose was performed. The most commonly used binding models, namely the Langmuir, the Freundlich and the Scatchard models, were applied to the data. It appeared that the Freundlich model was more appropriate to describe the binding of all the polysaccharides used in this study. The heterogeneity index calculated from the slope of Freundlich isotherms highlights an important heterogeneity of Avicel and PCW cellulose surfaces, in agreement with the Scatchard representation.

International audience; Pectins are anionic polysaccharides that are sensitive to cations, a property that is widely used in food science. The interactions of a cationic lipid film (dimethyldioctadecylammonium bromide, DODAB) with a set of pectins bearing the same charge, which was either distributed randomly or pseudorandomly or blockwise, are investigated. The combination of Brewster angle microscopy BAM and infrared reflection-absorption spectroscopy IRRAS at the air-water interface reveals that pectin strongly binds to the cationic lipid film in forming a stacked layer underneath the lipid film. The detailed vibrational study of this stable mixed film indicates furthermore that pectin induces a disorder in the internal structure of the cationic film. The strong binding induces a splitting of the carboxylate stretching mode of pectin that is pressure and charge distribution dependent. The occurrence of an intermediate plateau below the collapse of the mixed film originates probably from a change in conformation of the pectin structure underneath the film.

International audience; Pectins of different structures were extracted from citrus peels with water, oxalate, hot dilute hydrochloric acid and cold dilute sodium hydroxide. Homogalacturonans (HGs) were isolated from the four pectins by mild acid hydrolysis after deesterification. The study of their macromolecular properties revealed that they have similar number- and weight-average degrees of polymerisation, in the range of 81–117 galacturonic acid units, irrespective of the initial pectin. It was inferred that citrus peel pectins consist of HG strectches of similar lengths whatever the mode of extraction. Rhamnogalacturonan I (RG I) and rhamnogalacturonan II (RG II) were isolated from the oxalate- and the acid-extracted pectins using an endo-1,4-α-polygalacturonase followed by anion-exchange and size-exclusion chromatographies. RG I was composed mainly of arabinose, galactose, galacturonic acid and rhamnose, suggesting the presence of arabinan and/or (arabino)galactan side chains. Debranched RG I (dRG I) was obtained by treating the RG I arising from acid-extracted pectin with endo-1,5-α-l-arabinanase, endo-1,4-β-d-galactanase, α-l-arabinofuranosidase and β-d-galactosidase in admixture. The molar ratios of galacturonic acid to rhamnose of RGs I and dRG I were very close to 1/1, indicating a strict repeating [GalA–Rha]n pattern in the backbone. It is concluded that citrus pectins consist predominantly of HG, with a few RG I and a minor RG II fraction.

Main conclusion The derivation of two sensitive monoclonal antibodies directed to heteroxylan cell wall polysaccharide preparations has allowed the identification of potential inter-linkages between xylan and pectin in potato tuber cell walls and also between xylan and arabinogalactan-proteins in oat grain cell walls. Plant cell walls are complex composites of structurally distinct glycans that are poorly understood in terms of both in muro inter-linkages and developmental functions. Monoclonal antibodies (MAbs) are versatile tools that can detect cell wall glycans with high sensitivity through the specific recognition of oligosaccharide structures. The isolation of two novel MAbs, LM27 and LM28, directed to heteroxylan, subsequent to immunisation with a potato cell wall fraction enriched in rhamnogalacturonan-I (RG-I) oligosaccharides, is described. LM27 binds strongly to heteroxylan preparations from grass cell walls and LM28 binds to a glucuronosyl-containing epitope widely present in heteroxylans. Evidence is presented suggesting that in potato tuber cell walls, some glucuronoxylan may be linked to pectic macromolecules. Evidence is also presented that suggests in oat spelt xylan both the LM27 and LM28 epitopes are linked to arabinogalactan-proteins as tracked by the LM2 arabinogalactan-protein epitope. This work extends knowledge of the potential occurrence of inter-glycan links within plant cell walls and describes molecular tools for the further analysis of such links. Electronic supplementary material The online version of this article (doi:10.1007/s00425-015-2375-4) contains supplementary material, which is available to authorised users.

This work was supported by a grant from the Conseil Regional de Picardie, France and the European Regional Development Fund (PECTINHIB project) through a studentship awarded to ML' and from the Agence National de la Recherche (GALAPAGOS project, ANR-12-BSV5-0001; International audience; Pectin methylesterases (PMEs) play a central role in pectin remodeling during plant development. They are also present in phytopathogens such as bacteria and fungi. We investigated the substrate specificity and pH dependence of plant and fungi PMEs using tailor-made pectic substrates. For this purpose, we used two plant PMEs (from orange peel: Citrus sinensis and from Arabidopsis thaliana) and one fungal PME (from Botrytis cinerea). We showed that plant and fungi PMEs differed in their substrate specificity and pH dependence, and that there were some differences between plant PMEs. We further investigated the inhibition of these enzyme activities using characterized polyphenols such as catechins and tannic acid. We showed that PMEs differed in their sensitivity to chemical compounds. In particular, fungal PME was not sensitive to inhibition. Finally, we screened for novel chemical inhibitors of PMEs using a chemical library of similar to 3600 compounds. We identified a hundred new inhibitors of plant PMEs, but none had an effect on the fungal enzyme. This study sheds new light on the specificity of pectin methylesterases and provides new tools to modulate their activity. (C) 2015 Elsevier B.V. All rights reserved.

Sugar beet pectin was extracted from fresh sugar beet pulp and further deesterified by base, plant or fungal pectin esterase or esterified in acid methanol. The modified sugar beet pectins were characterised by chemical analyses, macromolecular and rheological properties, capillary electrophoresis and enzymatic fingerprinting. The majority of the modified sugar beet pectins had the same molar mass and neutral sugar content except for loss of arabinose by prolonged acid hydrolysis. The ferulic acid content was almost stable at about 0.8%. It was found that the enzymatically modified sugar beet pectins were more inhomogeneous due to the presence of acetyl groups hindering the attack by pectin esterases.

Five series of pectins with different levels and patterns of methyl esterification and/or different levels of acetyl esterification were produced by chemical or enzymatic treatment of an acid-extracted sugar beet pectin. The relationship between pKa and the degree of dissociation and the free fractions of monovalent and calcium counterions were determined on dilute pectin salt-free solutions. Calcium sensitivity was determined in more concentrated solutions. The presence of acetyl groups hindered the formation of calcium-pectinate precipitates in different manners according to the demethoxylation mode and the pectin concentration. The base-deesterified pectins appeared to have the most homogeneous methyl ester distribution. Pectins demethoxylated by fungus-PME exhibited a peculiar distribution of free galacturonic acid residues. Blocks of contiguous free galacturonic acid were generated by treatment of sugar beet pectin with a plant-PME. Those blocks were not long enough to induce abnormal polyelectrolyte behaviour or to promote dimerisation of pectic molecules in dilute solution but allow the formation of calcium-pectinate precipitates in concentrated medium for high DM. © 2003 Elsevier Science B.V. All rights reserved.

An experimental design was used to study the influence of different parameters (pH, temperature, time, and type of acid) on extraction of pectins from fresh sugar beet. The extraction conditions have important effects on the features of extracted pectins. Their composition (neutral and acidic sugars, degrees of esterification, amounts of ferulic and diferulic acids) and some physicochemical properties (molar mass, intrinsic viscosity) were determined. The type of acid used (HCl or HNO3) had no effect on the characteristics of extracted pectins. Different kinds of pectins can be obtained with good yields at pH 1. Galacturonic acid amounts of the extracted pectins were nearly constant whatever the extraction conditions, whereas the degrees of methylation and acetylation showed large variations. At pH 1, the extracts were particularly rich in rhamnogalacturonan regions, the nature and the quantity of side chains differing according to extraction conditions. The molar masses of extracted pectins were higher than those obtained from sugar beet pulp; beside the sole impact of raw material, possible cross-linking of pectic molecules through diferulic bridges is discussed.

Two series of pectins with different levels and patterns of methyl esterification were produced by treatment of a very highly methylated lime pectin with a fungus- or plant-pectin methylesterase. The interchain distribution of free carboxyl groups was investigated by size exclusion and ion exchange chromatography. "Homogeneous" populations with respect to molar mass or charge density were thereby obtained, and their composition, molar mass, and calcium binding properties were investigated. The composition varies from one size exclusion chromatography fraction to another, the highest molar mass fraction being richer in rhamnogalacturonic sequences and exhibiting a slightly higher degree of methylation (DM). Separation of pectins by ion exchange chromatography revealed a narrow charge density distribution for pectins deesterified by fungus-pectin methylesterase, in agreement with a multichain mechanism. Conversely, pectins deesterified by plant-pectin methylesterase exhibited a very large charge density distribution suggesting a processive mechanism. The interchain polydispersity with regard to DM was however shown to have no impact on calcium binding properties of the different fractions. The progressive dimerization through calcium ions with decreasing DM of pectins deesterified by plant-pectin methylesterase seems to be the result of a peculiar intrachain pattern of methyl esterification that can be attributed to a multiple attack mechanism.

In certain plant species, including Arabidopsis, seed coat epidermal cells accumulate a large quantity of polysaccharides that are released as mucilage upon imbibition. Once released, Arabidopsis seed coat mucilage appears as two distinct layers, the outer non-adherent composed of unsubstitutedrhamnogalacturonan I (RG-I), and the inner adherent one mainly made of RG-I and cellulose. CELLULOSE SYNTHASE5 and MUCILAGE-MODIFIED (MUM)5 have both been shown to be required for anchoring the mucilage pectin to the seed coat surface [1-5]. The identity and molecular role of MUM5 remained to be determined. A comparison of sequentially extracted seed mucilage components from cesa5 and mum5 mutants was carried out. Both mutants showed a redistribution of mucilage pectin from the inner adherent layer to the outer soluble one. cesa5 further showed a clear reduction in cellulose content, whereas mum5 had a wild-type cellulose content, but had reduced Xyl contents in the outer mucilage layer. Accordingly, MUM5 was identified as a putative xylosyltransferase. Biochemical and in vitro binding assay data demonstrated that xylan chains are attached to RG-I chains and mediate the adsorption of mucilage to cellulose microfibrils. The importance of having both a correctly synthesized cellulose scaffold and pectin structure will be discussed with regard to mucilage partitioning into non-adherent and adherent layers.

Background [br/] The epidermal cells of the seed coat of certain species accumulate polysaccharides during seed development for cell wall reinforcement or release on imbibition to form mucilage. Seed-coat epidermal cells show natural variation in their structure and mucilage production, which could explain the diverse ecophysiological roles proposed for the latter. Arabidopsis mucilage mutants have proved to be an important tool for the identification of genes involved in the production of seed-coat polysaccharides. [br/] Scope [br/] This review documents genes that have been characterized as playing a role in the differentiation of the epidermal cells of the arabidopsis seed coat, the natural variability in polysaccharide features of these cells and the physiological roles attributed to seed mucilage. [br/] Conclusions [br/] Seed-coat epidermal cells are an excellent model for the study of polysaccharide metabolism and properties. Intra-and interspecies natural variation in the differentiation of these epidermal cells is an under-exploited resource for such studies and promises to play an important part in improving our knowledge of polysaccharide production and ecophysiological function.

Arabidopsis seeds rapidly release hydrophilic polysaccharides from the seed coat on imbibition. These form a heavy mucilage layer around the seed that makes it sink in water. Fourteen natural Arabidopsis variants from central Asia and Scandinavia were identified with seeds that have modified mucilage release and float. Four of these have a novel mucilage phenotype with almost none of the released mucilage adhering to the seed and the absence of cellulose microfibrils. Mucilage release was modified in the variants by ten independent causal mutations in four different loci. Seven distinct mutations affected one locus, coding the MUM2 β-D-galactosidase, and represent a striking example of allelic heterogeneity. The modification of mucilage release has thus evolved a number of times independently in two restricted geographical zones. All the natural mutants identified still accumulated mucilage polysaccharides in seed coat epidermal cells. Using nuclear magnetic resonance (NMR) relaxometry their production and retention was shown to reduce water mobility into internal seed tissues during imbibition, which would help to maintain seed buoyancy. Surprisingly, despite released mucilage being an excellent hydrogel it did not increase the rate of water uptake by internal seed tissues and is more likely to play a role in retaining water around the seed., Author Summary Seeds of the model plant Arabidopsis release sticky mucilage on imbibition that is constituted of complex polysaccharides. In this study, we have identified and characterised natural Arabidopsis variants that do not release mucilage and found that their seeds float. The accumulation of unreleased polysaccharides in the seed coat reduced water uptake rates on imbibition and would maintain buoyancy. We subsequently identified additional floating natural variants where mucilage is released, but is not attached to the seed, apparently due to defective cellulose production. The different variants arise from at least ten independent unique mutations and were collected from two discrete geographical areas. Arabidopsis seed flotation has thus evolved several times due to modifications in mucilage release. Released mucilage was found to retain water, but did not improve imbibition of internal seed tissues, indicating a role in maintaining seeds hydrated. These findings highlight the physical and potential physiological effects of mucilage production by the seed coat.

International audience; Background and Aims Pectin is a complex macromolecule, the fine structure of which is influenced by many factors. It is used as a gelling, thickening and emulsifying agent in a wide range of applications, from food to pharmaceutical products. Current industrial pectin extraction processes are based on fruit peel, a waste product from the juicing industry, in which thousands of tons of citrus are processed worldwide every year. This study examines how pectin components vary in relation to the plant source (orange, lemon, lime, grapefruit) and considers the influence of extraction conditions on the chemical and macromolecular characteristics of pectin samples. Methods Citrus peel (orange, lemon, lime and grapefruit) from a commercial supplier was used as raw material. Pectin samples were obtained on a bulk plant scale (kilograms; harsh nitric acid, mild nitric acid and harsh oxalic acid extraction) and on a laboratory scale (grams; mild oxalic acid extraction). Pectin composition (acidic and neutral sugars) and physicochemical properties (molar mass and intrinsic viscosity) were determined. Key Results Oxalic acid extraction allowed the recovery of pectin samples of high molecular weight. Mild oxalic acid-extracted pectins were rich in long homogalacturonan stretches and contained rhamnogalacturonan I stretches with conserved side chains. Nitric acid-extracted pectins exhibited lower molecular weights and contained rhamnogalacturonan I stretches encompassing few and/or short side chains. Grapefruit pectin was found to have short side chains compared with orange, lime and lemon. Orange and grapefruit pectin samples were both particularly rich in rhamnogalacturonan I backbones. Conclusions Structural, and hence macromolecular, variations within the different citrus pectin samples were mainly related to their rhamnogalacturonan I contents and integrity, and, to a lesser extent, to the length of their homogalacturonan domains.

A series of pectins with different levels and patterns of methyl esterification was produced by treatment of a very highly methylated pectin with acid, alkali, plant pectin methyl esterase and fungus pectin methyl esterase. The intrinsic pK values, as well as the free fractions of monovalent and calcium counterions, were determined on pectin salt-free solutions. The variations of pK(a) versus the ionisation degree were found to depend on the de-esterification process but a unique value of 2.90+/-0.15 was estimated for the intrinsic pK value. Calcium binding properties of chemically and enzymatically de-esterified pectins were investigated and experimental results were compared to Manning's theoretical values. A progressive dimerisation process for pectins with a blockwise distribution of carboxyl groups in the presence of calcium ions is hypothesised.

The foaming properties of undenaturated potato raw proteins and of isolated patatin and 16–25 kDa fraction are investigated over a pH range of 4–8 with and without added NaCl. The patatin fraction was shown to be a very promising foaming agent with a foamability and foam stability equivalent or even superior to that of egg-white powder.

The inter-molecular distribution of free carboxyl groups of two highly methoxylated pectins enzymatically deesterified by plant and fungus pectin methyl-esterases were investigated by size-exclusion (SEC) and ion-exchange chromatography (IEC). “Homogeneous” populations with respect to molar mass or charge density were thereby obtained and their chemical composition and physico-chemical properties (transport parameter for monovalent cations and calcium, calcium activity coefficient) were studied. Chemical analysis showed that the composition varies from one SEC fraction to another, the highest molar mass fraction being richer in rhamnose and galactose and exhibiting a slightly higher degree of methylation. Separation of pectins by IEC revealed a quite homogeneous charge density distribution for F58 contrary to P60 which exhibited a large distribution of methoxyl groups. The free carboxyl groups distributions and calcium binding behaviours of SEC and IEC fractions were shown to differ widely for highly methoxylated pectins deesterified by plant and fungus pectin methyl-esterases.

Water-soluble potato proteins were extracted and an acidic and a basic fraction were isolated by ion-exchange chromatography. The acidic fraction contained mainly patatin (67%), the major soluble protein of potato tubers. The basic fraction contained the 20–25-kDa proteins family (64%) and a 16-kDa polypeptide (22%), probably corresponding to the protease inhibitor potato II. Functionality as pH–solubility curves, thermocoagulation sensitivity, kinetics of creaming and resistance to coalescence were determined. The patatin fraction showed a sharp solubility minimum at pH 4 and a marked sensitivity to thermocoagulation at pH 4 or in the presence of NaCl at both pH 4 and 7. The 16–25-kDa fraction was highly soluble whatever the pH and could be readily thermocoagulated only at 80°C at pH 7 or in the presence of NaCl at both pH 4 and 7. Both fractions could not be thermocoagulated at 1 mg/mL at pH values far from pI (pH 7 for the patatin fraction and pH 4 for the 16–25-kDa fraction) and without NaCl. The 16–25-kDa fraction led to stable emulsions towards creaming and coalescence whatever the pH and ionic strength. The patatin fraction exhibited poorer emulsification properties and the stability of the emulsions obtained was more pH- and ionic strength-dependent with the better results obtained near pI in the absence of NaCl. A thermal treatment (80°C, 30 min) of the emulsions had a marked positive effect on the resistance to coalescence of the patatin emulsions whatever the pH and the ionic strength, while it had a deleterious effect on the resistance to coalescence of emulsions from the 16–25-kDa fraction.

National audience; Pectin methylesterase (PME) catalyses the de-methylesterification of pectin in plant cell walls during cell elongation. While it is generally assumed that fungal PMEs have a random mode of action, plant PMEs are thought to act in a processive manner to generate long stretches of non-methylesterified residues. However, it is unlikely that all plant PMEs have a strictly similar mode of action. One A. thalianaPME gene (PME3) has been over-expressed in an heterologous system and its protein product purified by affinity chromatography. Homogalacturonans (HGs) from citrus pectin with varied degrees of methyl esterification (DM) have been generated and characterized. Kinetic properties of PME3 have been determined. PME activity from the purified PME3 was performed on the characterized HG substrates with respect to pH. PME3 shows a highest activity at a basic pH but displays different affinities towards specific methyl esterification patterns on the pectin substrates. Demethylesterified blocks assessed by measuring the degree of blockiness and absolute degree of blockiness will be presented. PME activities are also regulated by endogenous pectin methylesterase inhibitors (PMEIs), which control the DM of HG. PMEI7 inhibits PME3 enzyme activity. Docking analysis indicates that the inhibition of PME3 occurs via the PMEI7 interaction with a PME ligand-binding cleft structure.

Activity of an esterase from Pseudomonas fluorescens subsp. cellulosa (XYLD) on an insoluble feruloylated hemicellulose substrate (de-starched wheat bran) was dependent on the source of added endo-xylanase. The esterase exhibited high selectivity for the nature, position of linkage and size of the feruloylated oligosaccharides generated by hydrolysis of the hemicellulose. Increased affinity of XYLD with increasing size of the oligosaccharide substrate suggests that optimal activity is observed on substrates with at least 4 sugars.

International audience; Partially degraded sugar beet (Beta vulgaris) pectins were characterised in terms of galacturonic acid, neutral sugar and ferulic acids contents. It was shown that the total neutral sugar content is correlated with the ferulic acid content. One pectin (C) was further characterised by size exclusion chromatography coupled to refractive index and UV detectors (SEC-RI-UV). This gave the opportunity to estimate how the ferulic acid and neutral sugar contents changed with hydrodynamic radius. Pectin C was found to be heterogeneous in composition with neutral sugar-rich fractions of both high and low hydrodynamic radii. A neutral sugar-poor fraction was found at intermediate hydrodynamic radii.

International audience; A partially degraded sugar beet pectin (C) was found to be heterogeneous in composition with neutral sugar-rich fractions of both high and low hydrodynamic radii. A neutral sugar-poor fraction was found at intermediate hydrodynamic radii. In this paper we demonstrate using both conformation zoning and the global analysis method that fractions of sugar beet pectin rich in neutral sugar side chains (RG-I regions) are less flexible than those rich in galacturonic acid (HG regions). (C) 2012 Elsevier Ltd. All rights reserved.

Cell wall composition, pectin, and hemicellulose fine structure variation were assessed in peach and related genotypes with contrasted texture and fruit shape. Cell walls were prepared from four commercial peaches, eight genotypes from the Jalousia × Fantasia peach cross, and six genotypes from the Earlygold peach × Texas almond cross. Sugar composition was determined chemically while fine structure of homogalacturonan pectin and xyloglucan hemicellulose were assessed by coupling pectin lyase and glucanase degradation, respectively, with MALDI-TOF MS analysis of the degradation products. The results indicate clear compositional and structural differences between the parents and their related genotypes on the basis of pectin versus cellulose/hemicellulose content and on the fine structure of homogalacturonan and xyloglucan. A relation between methyl- and acetyl-esterification of pectin with fruit shape is revealed in the Fantasia × Jalousia peach genotypes., This work has been supported in part by funds from the program EU FP6 ISAFRUIT (Contract No. FP6-FOOD 016279-2).

The amount of water-soluble pectins was largely increased after extrusion-cooking of lemon fibres. These pectins showed the ability to form a gel in the presence of sucrose and at acidic pH. The gels obtained with the water-extracted pectins after extrusion-cooking and with pectins acid-extracted on a laboratory scale were softer than those prepared with commercial citrus pectins. The water-extracted pectins after extrusion-cooking and the pectins acid-extracted on a laboratory scale contained long neutral side-chains and required a higher sucrose concentration to gel than the commercial citrus pectins. The extruded lemon fibres showed the ability to form gels in the presence of sucrose and at acidic pH. The gels obtained with the extruded fibres containing some water-solube pectins of high molecular weight were stronger than those obtained with the extruded fibres containing higher amounts of more depolymerised water-soluble pectins. The extruded fibres containing 12.5–14.9% of water-soluble pectins of high molecular weight (intrinsic viscosity: 413–504 mL/g) were those showing the better gelation properties.

Enzymatically and chemically de-esterified lime pectins : physico-chemical characterisation, polyelectrolyte behaviour and calcium binding properties

International audience; Fruit development is a highly complex process, which involves major changes in plant metabolism leading to cell growth and differentiation. Changes in cell wall composition and structure play a major role in modulating cell growth. We investigated the changes in cell wall composition and the activities of associated enzymes during the dry fruit development of the model plant Arabidopsis thaliana. Silique development is characterized by several specific phases leading to fruit dehiscence and seed dispersal. We showed that early phases of silique growth were characterized by specific changes in non-cellulosic sugar content (rhamnose, arabinose, xylose, galactose and galacturonic acid). Xyloglucan oligosaccharide mass profiling further showed a strong increase in O-acetylated xyloglucans over the course of silique development, which could suggest a decreased capacity of xyloglucans to be associated with each other or to cellulose. The degree of methylesterification, mediated by the activity of pectin methylesterases (PMEs), decreased over the course of silique growth and dehiscence. The major changes in cell wall composition revealed by our analysis suggest that it could be major determinants in modulating cell wall rheology leading to growth or growth arrest.

The effects of extrusion-cooking on pea hulls were investigated. Two batches of pea hulls of different average particle size (80 μm and 500 μm) were extruded under various conditions with a twin screw extruder (Clextral BC 45). In all cases, the water-solubility of the product increased (3·6–15·3%) with the severity of the treatment, monitored by the specific mechanical energy (115–363 kWh/t). A redistribution from insoluble dietary fibre to soluble dietary fibre, indicating a partial solubilisation of fibre without extensive degradation of the polymeric structure, was observed. The solubilised material was composed of pectic substances and hemicelluloses. The hydration properties of pea hulls differed much within the particle size distribution of the products and were not markedly modified by extrusion-cooking treatment.

International audience; With the aim of mimicking the plant cell wall, a layer by layer approach was used to build a thin film consisting of successive adsorption of pectin and extensin. Elaboration of the thin film was monitored by surface plasmon resonance, quartz crystal microbalance, and ellipsometry. All data indicate that formation of the film was successful and that growth occurred according to a nonuniform growth. It is likely that diffusion of the polymers occurred within the multilayer structure and that the final structure is not constituted by layered individual pectin and extensin films. Polymer rearrangements were also supported by the atomic force microscopy images that show a smoother surface after extensin adsorption than after pectin deposition

International audience; Acid extracted sugar beet (Beta vutgaris) pectin was subjected to enzymatic hydrolysis using fungal pectin methyl esterase (f-PME) and two endopolygalacturonanases (PGs land II). From the hydrolysate, the RG-I fraction was separated and purified by chromatographic techniques. This RG-I fraction was shown to be of high weight average molar mass (188,000 g/mol), but low intrinsic viscosity (36 ml/g), which is consistent with a random coil conformation(L(p) = 1.4 nm). The HG fraction was prepared by mild acid hydrolysis of acid extracted pectin. The HG fraction was found to have a relatively low weight average molar mass (20,000 g/mol), but a rather high intrinsic viscosity (77 ml/g), which is consistent with the HG fraction being rigid in solution (L(p) = 9.8 nm). Lower molar mass pectins are richer in HG regions and pectins of higher molar mass are richer in RG-I regions. We conclude that the degradation of the HG region has an important impact on intrinsic viscosity, but less on molar mass and the inverse is true for the degradation of RG-I region. This has important consequences in terms of the functionality of sugar beet pectin molecules. (C) 2010 Elsevier Ltd. All rights reserved.

International audience; Monoclonal antibodies were raised against rhamnogalacturonan I backbone, a pectin domain, using Arabidopsis thaliana seed mucilage-derived rhamnogalacturonan I oligosaccharides-BSA conjugates. Two monoclonal antibodies, designated INRA-RU1 and INRA-RU2, selected for further characterization, were specific for the backbone of rhamnogalacturonan I, displaying no binding activity against the other pectin domains i.e. homogalacturonans, galactans or arabinans. A range of oligosaccharides was prepared by enzymatic digestion of rhamnogalacturonan I isolated from Arabidopsis thaliana seed mucilage and from sugar beet pectin, purified by low-pressure chromatography and characterized by high-performance anion-exchange chromatography and mass spectrometry. These rhamnogalacturonan I oligomers were used to characterize the binding site of the two monoclonal antibodies by competitive inhibition. Both INRA-RU1 and INRA-RU2 showed maximal binding to the [-> 2)-alpha-l-rhamnosep-(1 -> 4)-alpha-d-galacturonic acid p-(1 ->](7) structural motif but differed in their minimum binding requirement. INRA-RU2 required at least two disaccharide (rhamnose-galacturonic acid) repeats for the antibody to bind, while INRA-RU1 required a minimum of six disaccharide repeats. Furthermore, the binding capacity of INRA-RU1 decreased steeply as the number of disaccharide repeats go beyond seven. Each of these antibodies reacted with hairy regions isolated from sugar beet pectin. Immunofluorescence microscopy indicated that both antibodies can be readily used to detect rhamnogalacturonan I epitopes in various cell wall samples

International audience; Pectins are a family of highly complex multifunctional cell wall polysaccharides. Little is known on the relation between pectin structure, hydrodynamic properties, and cellular function. In this study, we took advantage of the Arabidopsis pectin mutant quasimodo2 (qua2), which specifically lacks half of its homogalacturonan blocks, to study the relationship between the amount of homogalacturonan blocks and the hydrodynamic properties of pectins. It was first shown that, in qua2 pectins, homogalacturonans had maintained the same size as those in the wild type. The persistence lengths of isolated homogalacturonan and rhamnogalacturonan-I blocks were then measured and it was shown that homogalacturonan was over 4-fold more rigid than rhamnogalacturonan-I. WT and qua2 pectins were next compared and it appeared that the specific reduction of the number of homogalacturonan blocks leads to an increased flexibility of qua2 pectins. These results show for the first time how mutant pectins can be used to demonstrate the opposite influence of rhamnogalacturonan-I and homogalacturonan blocks on the hydrodynamic properties of pectins.

International audience; Commercial acid-extracted sugar beet pectin was extensively hydrolysed using an endo-polygalacturonase (AnPGI from Aspergillus niger or AnPGII from A. niger or FmPG from Fusarium moniliforme) in combination with Aspergillus aculeatus pectin methyl-esterase (AaPME). The homogalacturonan-derived oligogalacturonates released were quantified by high-performance anion-exchange chromatography and their structure determined by mass spectrometry. The different endo-polygalacturonases exhibited variable tolerance towards acetyl groups. AnPGI was the most active and FmPG the less. A hypothetical homogalacturonan was constructed using the AnPGI-recovered oligogalacturonates as building blocks and the validity of the model was checked taking into account FmPG observed requirements and hydrolysis products. A blockwise repartition of the acetyl groups onto sugar beet pectin homogalacturonan is proposed.

International audience; The extraction of pectins from mango peels can offer a way to upgrade byproducts arising from the processing of these tropical fruits. In this work, several extraction conditions (HCl, or deionised water, or ammonium oxalate) were tested in order to isolate pectins from the peels of two mango varieties (Amelioree and Mango) harvested in Cameroon. After determining uronic acid and neutral sugar contents of mango peels and their alcohol insoluble residues (AIR), extracted pectins were analysed for their uronic acid and neutral sugar contents, their degree of methylation and acetylation, and their average molar mass and intrinsic viscosity. The extraction method was shown to significantly act upon yield (9-32% dry AIR), uronic acid (262-709 mg/g dry weight) and neutral sugar (160-480 mg/g) contents of pectin, their degree of methylation (52-86%) and acetylation (1-8%), their molar mass (245,000-432,000 g/mol), and their intrinsic viscosity (320-1346 mL/g). The physicochemical behaviour of pectins could be influenced thereof. With a good recovery yield, a high average molar mass and intrinsic viscosity and a high degree of methylation, ammonium oxalate-extracted mango pectins present good characteristics to be exploited industrially for their gelling properties.

Publisher Summary Fruit and vegetable processing (preservation or production of juice, wine, sugar, starch, oil, etc.) generates huge amounts of wastes. Vegetable wastes are also often spread on land or composted. These wastes have high water content and are consequently perishable and microbiologically instable. It can result in environmental issues such as noxious odors or microbiological hazards. Wastes arising from fruit and vegetable processing industries are rich in cell wall materials. Such plant-derived wastes are generally heterogeneous as they may contain entire vegetable, leaves, stems, roots, tubers, seeds, stones, etc., which makes their upgrading rather difficult. Therefore, this chapter discusses the upgrading of plant-derived food processing by-products, mainly vegetable trimmings and residues from extraction. After an inventory of the main origins of the by-products, the upgrading of these plant wastes as a whole, of the constituting polymers, and of the monomeric components, will be addressed. The major solid waste is obtained by pressing of fruits or vegetables and solid–liquid separation. This pomace can contain pulp, peels, seeds, and stones. The further utilization of pomace depends on the fruit or vegetable type. Pomace is generally used for the extraction of valuable compounds and for the production of foodstuffs.

International audience; Rhamnogalacturonan I (RGI) is a pectic polysaccharide composed of a backbone of alternating rhamnose and galacturonic acid residues with side chains containing galactose and/or arabinose residues. The structure of these side chains and the degree of substitution of rhamnose residues are extremely variable and depend on species, organs, cell types and developmental stages. Deciphering RGI function requires extending the current set of monoclonal antibodies (mAbs) directed to this polymer. Here, we describe the generation of a new mAb that recognizes a heterogeneous subdomain of RGI. The mAb, INRA-AGI-1, was produced by immunization of mice with RGI oligosaccharides isolated from potato tubers. These oligomers consisted of highly branched RGI backbones substituted with short side chains. INRA-AGI-1 bound specifically to RGI isolated from galactan-rich cell walls and displayed no binding to other pectic domains. In order to identify its RGI-related epitope, potato RGI oligosaccharides were fractionated by anion-exchange chromatography. Antibody recognition was assessed for each chromatographic fraction. INRA-AGI-1 recognizes a linear chain of (1 -> 4)-linked galactose and (1 -> 5)-linked arabinose residues. By combining the use of INRA-AGI-1 with LM5, LM6 and INRA-RU1 mAbs and enzymatic pre-treatments, evidence is presented of spatial differences in RGI motif distribution within individual cell walls of potato tubers and carrot roots. These observations raise questions about the biosynthesis and assembly of pectin structural domains and their integration and remodeling in cell walls.

International audience; The organisation of sugar beet and potato cell walls was studied using alkaline extractions following a response surface methodology, simultaneously with solid-state C-13 NMR spectroscopy. The influence of two extraction parameters: NaOH concentration (0.05, 0.275, 0.5 M) and temperature (40, 65, 90 degrees C) on the composition (neutral and acidic sugars) of the residues recovered was established. Treatments of increasing harshness progressively washed off non-cellulosic polysaccharides from the cell walls. Alkaline treatments applied to sugar beet cell wall material (SB-CWM) revealed the presence of diverse pectin populations. The existence of distinct pectin populations in potato cell wall material (P-CWM) was less outstanding. Solid-state C-13 NMR applied to SB-CWM and P-CWM and residues after treatment by 0.275 M NaOH at 65 degrees C revealed two fractions of pectic arabinan and galactan side chains. One fraction was highly mobile, whereas the other one displayed restricted mobility.

Arabinan and galactan side chains of sugar beet pectins are esterified by ferulic acid residues that can undergo in vivo oxidative reactions to form dehydrodiferulates. After acid and enzymatic degradation of sugar beet cell walls and fractionation of the solubilized products by hydrophobic interaction chromatography, three dehydrodiferulate-rich fractions were isolated. The structural identification of the different compounds present in these fractions was performed by electrospray-ion trap-mass spectrometry (before and after (18)O labeling) and high-performance anion-exchange chromatography. Several compounds contained solely Ara (terminal or alpha-1-->5-linked-dimer) and dehydrodiferulate. The location of the dehydrodiferulate was assigned in some cases to the O-2 and in others to the O-5 of non-reducing Ara residues. One compound contained Gal (beta-1-->4-linked-dimer), Ara (alpha-1-->5-linked-dimer) and dehydrodiferulate. The location of the dehydrodiferulate was unambiguously assigned to the O-2 of the non-reducing Ara residue and O-6 of the non-reducing Gal residue. These results provide direct evidence that pectic arabinans and galactans are covalently cross-linked (intra- or inter-molecularly) through dehydrodiferulates in sugar beet cell walls. Molecular modeling was used to compute and structurally characterize the low energy conformations of the isolated compounds. Interestingly, the conformations of the dehydrodiferulate-bridged arabinan and galactan fragments selected from an energetic criterion, evidenced very nice agreement with the experimental occurrence of the dehydrodiferulated pectins. The present work combines for the first time intensive mass spectrometry data and molecular modeling to give structural relevance of a molecular cohesion between rhamnogalacturonan fragments.

Side chains of sugar beet (Beta vulgaris) pectins, which are mainly composed of arabinose (Ara) and galactose (Gal) residues, are esterified by ferulic acid units. Enzymatic hydrolysis of beet cell walls yielded several feruloylated oligosaccharides, which were separated by hydrophobic interaction chromatography. Two new oligomers were isolated in the fraction eluted by 25:75 (v/v) ethanol:water. An arabinotriose and an arabinotetraose esterified by two ferulic acid residues were obtained, and their structure was elucidated by mass spectrometry. It is shown that feruloyl groups are linked to O-5 of Ara residues, in addition to the known O-2 position. This work establishes for the first time, to our knowledge, that two neighboring Ara units may be esterified by two ferulic acid units. This close proximity may have important biochemical implications.

An experimental design was constructed to study the influence of different parameters of acidic extraction on yield, chemical composition and intrinsic viscosity of pectins from fresh sugar-beet roots. pH, and, to a lower extent, time and temperature of extraction, affected greatly the yield and features of extracted pectins whereas the type of acid had no effect. Influences of extraction conditions on pectins characteristics were quantified and second order models were built.

Maize bran heteroxylan samples were extracted in various conditions of severity. Their ferulate and diferulate content was investigated by GC-MS of methyl ester-TMSi derivatives. When extracted by 0.5 M NaOH in mild conditions, the heteroxylan sample contained a low level of ferulic acid (0.032% by wt.) and the main diferulate surviving alkaline extraction was found to be the 8-8' diferulate. On peroxidase treatment, this sample nevertheless produced a firm and brittle gel without any change in the diferulate profile. Typical lignin structures, mainly comprising syringyl units interconnected through beta-O-4, beta-1 and beta-beta interunit bonds, were evidenced in the maize bran sample. More importantly, these lignin structures were found to be tightly associated with the alkali-extracted heteroxylans. Thioacidolysis revealed the occurrence of 0.1-0.5% (by wt.) lignin structures in heteroxylan fractions extracted in mild or severe conditions, before and after purification of the polysaccharides. The gelling potential of the heteroxylan fractions was not only dependent on their ferulate level, but also influenced by associated lignin structures. These results argue for the occurrence of covalent linkages between heteroxylan chains and lignin structures which could participate in the peroxidase-driven gelation of feruloylated polysaccharides. They demonstrate the role of low lignin levels in the organization of native or reconstructed polysaccharide networks.

Pea and soybean globulins were phosphorylated by a casein kinase II from Yarrowia lipolytica. Soybean 7S was the best substrate, followed by pea 7S, pea US and soybean US. Phosphate was incorporated into soybean 7S a and α’ subunits, pea 7S 47, 23 and 17 kDa polypeptides, and US acidic subunits.

Some by-products from the food industry contain high proportions of plant cell walls which can be used in human nutrition to produce “dietary fibre” or “functional fibre”, i.e. compounds which can be used for their water-holding/binding properties, oil-binding capacity,… or as a source of polysaccharides such as pectins which are suitable after extraction, as gelling or thickening agents. Extrusion-cooking of cell-wall rich products (e.g. wheat bran, apple pomace, citrus peels, sugar-beet pulp, pea hulls…) led to an important solubilisation of polysaccharides of various types without extensive degradation of the polymeric structure. The possibility of obtaining gelled systems directly with the extruded pectin-rich materials was demonstrated. This treatment has the advantage of avoiding the acid extraction of the pectins; it could be also used to obtain extruded products which could be used in various preparations traditionnally requiring high methoxyl pectins as gelling agents. The final products could be therefore enriched in dietary fibres and devoid of additives.