High Field NMR Spectroscopy Analysis of Beta-limit Dextrins From Starch-like Polysaccharides: an Approach to the Understanding of Amylopectine Crystallinity

International audienceAmongst all branched alpha-1,4 glucans, amylopectine is outstanding. Its specific, well-ordered alpha-1,6 branching pattern, originating from a complex enzymatic control, permits a very efficient packing of short linear chains within the currently accepted cluster model and allows amylopectine to grow into exceptionally large macromolecules. These characteristics lead to unique physicochemical properties such a s gelling properties, reversible swelling, crystallinity of high water content, complexes with linear and apolar molecules as well as several others. It is essential to uncover this intimate branching organisation in order to understand the unique architecture of amylopectine and its relations to some of starch's macroscopic properties

Extrusion réactive des polymères naturels. Intensification des réactions de modification des Lignines et amidons

International audienceReactive extrusion technology is presented as an alternative to intensifying chemical modification reactions of synthetic polymers as well as polymers of natural origin. The principle of the technology as well as the materials on the laboratory scale and on the industrial scale is explained, then examples of polysaccharides and lignins chemical modifications are developed.La technologie d'extrusion réactive est présentée comme un alternative d'intensification des réactions de modification chimiques des polymères de synthèse ainsi que les polymères d'origine naturelle. Le principe de la technologie ainsi que les matériels à l'échelle laboratoire et à l'échelle industrielle est expliqué puis les exemples de réalisation sur des modifications chimiques de polysaccharides et de lignines sont développés

NEO-AMYLOPECTINYL MODELS SYNTHESIS OF COMPLEX BETA-BRANCHED MALTO-OLIGOSACCHARIDES IN SOLUBLE AND SOLID PHASE

International audienceStarch is the ubiquitous glucidic reserve compound in nature. Synthesized by most plants from solar energy it is easily produced in very large scale cultures (cereals, tubers, legumes…). Besides its irreplaceable position in the food chain Starch is also a widely used commodity for its non-alimentary properties (paper, textile industry, adhesive, gels…) in almost all human activities. Though the polysaccharidic nature and the basic structure : poly-alpha(1,4) glucopyrannose of its minor constituent Amylose, and alpha-1,6) branched alpha-1,4-polyglucopyrannose of the major amylopectin has long been known, to date, the fine primary structure of the former still remains to be described ! The branching pattern found in amylopectin can reach extreme complexity. The determination of amylopectins' primary structures from various botanical origins families can be a real challenge. Moreover, though the enzymes involved in starch synthesis have been well-described, no satisfactory in-vitro synthesis has been achieved to date, one of the reasons invoked being the lack of proper primer substrate. In this paper we present an investigation of such structural diversity by rebuilding well-defined branched malto-oligosaccharidic model structures through chemical hemisynthesis, in order to obtain such substrates. Several isoamylase resistant, beta-branched neo-amylopectinyl oligosaccharides having degrees of polymerisation (DP) 4 to 8, with well-defined structures, were obtained. The construction of these models was performed using chemically modified malto-oligosaccharides in solution. All structures were confirmed by long distance heteronuclear NMR spectroscopy. Using activated Wang resin, solid-phase supported oligosaccharides were synthesised and the structures analysed by HR-MAS NMR

NEO-AMYLOPECTINYL MODELS SYNTHESIS OF COMPLEX BETA-BRANCHED MALTO-OLIGOSACCHARIDES IN SOLUBLE AND SOLID PHASE

International audienceStarch is the ubiquitous glucidic reserve compound in nature. Synthesized by most plants from solar energy it is easily produced in very large scale cultures (cereals, tubers, legumes…). Besides its irreplaceable position in the food chain Starch is also a widely used commodity for its non-alimentary properties (paper, textile industry, adhesive, gels…) in almost all human activities. Though the polysaccharidic nature and the basic structure : poly-alpha(1,4) glucopyrannose of its minor constituent Amylose, and alpha-1,6) branched alpha-1,4-polyglucopyrannose of the major amylopectin has long been known, to date, the fine primary structure of the former still remains to be described ! The branching pattern found in amylopectin can reach extreme complexity. The determination of amylopectins' primary structures from various botanical origins families can be a real challenge. Moreover, though the enzymes involved in starch synthesis have been well-described, no satisfactory in-vitro synthesis has been achieved to date, one of the reasons invoked being the lack of proper primer substrate. In this paper we present an investigation of such structural diversity by rebuilding well-defined branched malto-oligosaccharidic model structures through chemical hemisynthesis, in order to obtain such substrates. Several isoamylase resistant, beta-branched neo-amylopectinyl oligosaccharides having degrees of polymerisation (DP) 4 to 8, with well-defined structures, were obtained. The construction of these models was performed using chemically modified malto-oligosaccharides in solution. All structures were confirmed by long distance heteronuclear NMR spectroscopy. Using activated Wang resin, solid-phase supported oligosaccharides were synthesised and the structures analysed by HR-MAS NMR

Characterisation by SEC and High Field NMR of Limit-Dextrins from Enzymatically Degraded Cationic Starches

International audienceChemically modified starches are widely used derivatives in fields such as paper-making and textile industries. Based on the results of enzymatic degradation Kavitha and Bemiller [3] showed that a commercial hydroxy-The physicochemical macroscopic properties of these products are closely linked to their structural organisation propyl starch seemed to more modified in areas near to the branching zones. Commercial cationic at the molecular level. There is a wide range of possible modification pattern on macromolecules such as starches are synthesised either in solution or more likely by dry process, grafting ammonium groups amylopectins. Different reactions may lead to a variety of structures. In a earlier work we observed that high ether bonds [4]. In a recent work we describe an alternative synthetic route to cationic starches using Acetylated starches of the same DS, but synthesised via two different processes, had different structures as via a glycerol-water plasticised molten medium to achieve the reaction [5]. The products of the b-seen from their NMR spectra [1]. Woortman and Steeneken [2] reported that granular starch was methylated amylolytic degradation are separated by SEC and analysed by NMR Spectroscopy. The results of In a more block-wise manner whereas when reacted in solution it was modified in a random fashion. structural characterisation are presented. [1] B. Laignel, C. Bliard, G. Massiot and J.M. Nuzillard, Carbohyd. Res., 298 (1997) 251-260 [2] P.A.M Steeneken, A

Synthesis of New Hybrid Mineral / Renewable Sol-Gel Matrices by Inter-Cross-Linking Siloxane Based Polymers with Polysaccharides

International audienceSilicon based sol-gels are polymeric matrices that have a wide range of applications from high porosity to corrosionprotection coatings. Our research has specialized in the synthesis of a variety of sol gel matrices using binary orternary combinations of alkylalkoxysilanes. Depending on the starting silane, these colloids are crosslinked in anumber of ways, to produce materials with unique, innovative and potentially valuable properties. In our group atReims University we have developed several unique processes for polysaccharide modification and cross-linkingleading to hydrogels and materials possessing innovative properties, such as renewable and biodegradablematerials from amylaceous polysaccharides. In the present work we present the synthesis of hybrid materialscomposed of a dual synthetic and renewable - siloxane / polysaccharidic base by inter-crosslinking the two polymeric networks in aqueous solution. The advantage of crosslinkable sol-gel hybrid matrices over traditional sol-gel chemistry methods are primarily the ability to avoid using high temperature processing to solidify the material, the opportunity to incorporate useful organic functionality into the final matrix, improved mechanical strength andpotential partial biodegradability

Comparative Reactivity of the Three Glucosyl -OH Positions -2, -3 and -6 during esterification and saponification of starch by nmr spectroscopy of partially Deutero-acetylated material

International audienceThe individual reactivity of the three hydroxyle groups, (OH-2, OH-3, OH-6) of the glucosyl monomer residue in starch, under esterification and saponification conditions, were analyzed by 1H nmr spectroscopy. A first sample, obtained by direct acetylation, led to an intermediate DS of 1.5, leaving half of hydroxyle positions untouched. These free -OH groups were then esterified with deuterated acetic anhydride. In order to analyse the reactivity under saponification conditions, a second sample was fully acetylated, then, half of the acetate groups were removed by saponification with ethanolic KOH. These regenerated OH groups were then re-esterified with deuterated acetic anhydride as per the previous sample. The proton nmr spectra of each sample was recorded in deuterated chloroform. Integration of the (CH3) peaks in the 1 to 2 ppm region allowed the measurement of the relative (1H) acetate level on each of the three hydroxyle positions

Biosynthesis of a reserve endopolysaccharide in the hyperthermophilic archaeon Thermococcus hydrothermalis

International audienceThe hyperthermophilic archaeon Thermococcus hydrothermalis produces a reserve endopolysaccharide during its exponential growth phase. This endopolymer was purified from the crude intracellular content after a 3-hour and a 4-hour culture (corresponding to ¾ of the log phase and to the end of this phase respectively). After analysis of the endopolysaccharide it appeared that its structure changed with the physiological cellular states: A glycogen type structure (with 8% of -1,6 linkages) was purified from the 3 hours culture whereas an “amylopectin-like” structure (7,5% of -1,6 branching points and glucanic chains of 14 -1,4 linked glucose residues) was purified at the end of the log phase. These new results show that this former “amylopectin-like” is a very ephemeral structure, built prior to the polymer degradation.Moreover, the polymer biosynthesis involves one partially purified elongation activity and probably only one branching activity. The optimal pH and temperature for the elongation enzyme was observed at 80-85°C and at pH 5.5 respectively. The branching activity was optimally active between 70°C and 80°C and between pH 4 to pH 7.Together, the presence of a glycogen-like structure and the number of isoform involved in its biosynthesis suggest a relationship between Archaea and the other prokaryotic organisms

SYNTHESE D'OLIGOMALTO-ISOMALTOSIDES BRANCHES COMPLEXES MODELES DES STRUCTURES DE RAMIFICATION DES AMYLOPECTINES

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