Academic literature on the topic 'Polysaccharide'

L'établissement de relations structure-propriétés peut conduire à l'amélioration des propriétés des réseaux et des gels et à l'élaboration de systèmes plus performants en vue d'une application définie. Aussi, au cours de ce travail, nous nous somme proposes de mettre en évidence la structure qui intervient pour les mélanges kappa carraghenane-caroube et agarose-caroube. Différentes techniques expérimentales d'étude nous ont permis d'aborder la gélification ainsi que les réseaux et les gels à l'état final : la résonance magnétique nucléaire du carbone 13 (RMN 13C); la diffusion aux petits angles des rayons X (DPAX); la rhéologie; la modélisation moléculaire. Les études par RMN 13C et DPAX. Nous ont permis de couvrir les domaines moléculaire et macromoléculaire. La rhéologie nous a amené à une investigation du domaine supramoléculaire. Enfin, la modélisation moléculaire a constitué une approche théorique du phénomène. Nous avons essaye d'établir des corrélations entre les informations fournies par les différentes méthodes de façon à aboutir à un modèle pour ces gels à deux composants macromoléculaires

Polysaccharides are one of the most abundant and diverse families of natural polymers, and have an incredibly wide range of natural functions including structural reinforcement, energy storage, aqueous rheology modification, and communication and identity. Application of native polysaccharides like cellulose as sustainable materials is limited by some inherent drawbacks such as insolubility in common solvents including water, and poor dimensional stability. To increase their functionality and utility, researchers have sought to tailor the chemical and physical properties of cellulose and other polysaccharides using a variety of chemical modification techniques, resulting in a number of important, useful commercial derivatives. Because of their greater biocompatibility and biodegradability, and low immunogenicity, naturally derived cationic polymers including cationic polysaccharide derivatives are very attractive candidates for biomedical applications, due to the fact that they are capable of binding with anionic biomolecules, such as nucleic acids and certain proteins, via electrostatic interactions. However, there are relatively few practical synthetic methods reported for their preparation. We demonstrated a useful and efficient strategy for cationic polysaccharide salt preparation by reaction of 6-bromo-6-deoxypolysaccharides such as 6-bromo-6-deoxycellulose esters with pyridine or 1-methylimidazole exclusively at the C-6 position, resulting in high degrees of substitution (DSs). These permanently cationic polysaccharide derivatives have been demonstrated to dissolve readily in water, and bind strongly with a hydrophilic and anionic surface. Availability of these cationic polysaccharides will facilitate structure-property relationship studies for biomedical uses including drug delivery and bioelectronics applications. We also extended the chemistry, reacting 6-imidazolo-6-deoxycellulose with propane sultone, leading to a new synthetic pathway to zwitterionic cellulose derivatives. In addition to cationic and zwitterionic derivatives, we found a simple, efficient route to carboxyl-containing polysaccharide derivatives from curdlan esters via regioselective ring-opening reactions catalyzed by triphenylphosphine (Ph3P) under mild conditions. Curdlan, a polysaccharide used by the food industry and in biomedical applications, was employed as starting material for preparing these carboxyl-containing derivatives by a reaction sequence of bromination, azide displacement and ring-opening reaction with cyclic anhydrides, affording high conversions. These modification techniques have been demonstrated to display essentially complete regio- and chemo-selectivity at C-6. These novel polysaccharide-based materials starting from abundant and inexpensive curdlan are promising for some applications such as amorphous solid dispersion (ASD) oral drug delivery.<br>Ph. D.

Astragalus gombo Bunge (Fabaceae) est une plante bien représentée dans le Sahara Septentrional Est Algérien (région de Ouargla, Algérie) et couramment utilisée comme fourrage pour les animaux ou en médecine traditionnelle. Malgré de nombreuses publications sur la richesse en polysaccharides d’autres espèces appartenant au genre Astragalus et la description de leurs propriétés biologiques putatives ou avérées, aucune étude ne s’est intéressée à l’espèce gombo. L’objectif de ce travail de thèse a donc été de réaliser des investigations sur plusieurs parties de cette plante en vue d’extraire, identifier et caractériser son contenu en polysaccharides. Dans un second temps les propriétés biologiques et rhéologiques de ces polymères ont été étudiées afin d’identifier d’éventuelles voies de valorisation. Les résultats obtenus ont permis de détecter la présence de composés pectiques et hémicellulosiques dans la tige d’Astragalus gombo et celle d’un galactomannane dans les graines. Le galactomannane est de haute masse moléculaire (1,1x106 Da) et est constitué d’une chaine principale de β-(1→4)-D-mannane ramifiée en α-(1→6) par des résidus Dgalactopyranoses avec un rapport M/G de 1,7. La caractérisation de ses propriétés rhéologiques a révélé un comportement typique rhéofluidifiant et des propriétés viscoélastiques. L’étude des activités biologiques associées à ce biopolymère a révélé son potentiel comme prébiotique et antioxydant<br>Astragalus gombo Bunge (Fabaceae) is a terrestrial plant occuring in the East Septentrional Sahara (Ouargla, Algeria). It is commonly used as fodder or in traditional medicine by local populations. Despite numerous publications focusing on polysaccharidic contents of Astragalus species and the designation of their putative or proved biological activities, no study has examined those of A. gombo. The objective of this thesis was firstly to investigate several organs of this plant for their polysaccharide contents. In a second step, the biological and rheological properties of these biopolymers have been studied to identify ways of adding value. Results led to the identification of pectic compounds and hemicelluloses in the rods of Astragalus gombo whereas a galactomannan was detected in its seeds. This galactomannan was a high molecular weight macromolecule composed of a β-(1→4)-D-mannan skeleton ramified by residues of D-galactopyranoses. The M/G ratio was of 1.7. The characterization of its rheological behavior was typic of that of a rheofluidifiant fluid with viscoelastic properties. The study of its biological properties showed its potential as prebiotic and antioxidant agent

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Food Technology in the Faculty of Applied Sciences at the Cape Peninsula University of Technology<br>The aim of this study was to evaluate bambara groundnut [BGN] non-starch polysaccharides [NSP] subject to the incorporation into model and food systems with a view to establish their functional and physicochemical properties. BGN insoluble dietary fibre [BGNIF] and soluble dietary fibre [BGNSF] were successfully extracted from four varieties (black-eye: BLE, red: RED, brown: BRN and brown-eye: BRE). Physicochemical properties evaluated revealed the high bulk density of all BGNIF and BGNSF varieties, which could contribute to cost-effective packaging. The microstructures of BGNIFs were irregular in shape with different sizes. The colour parameters (lightness, redness, yellowness, chroma and hue angle) differed significantly [p ≤ 0.05] across all BGNIF and BGNSF varieties; and indicated a yellowish-red colour for BGNIFs and a light yellow colour for BGNSFs. Negligible amounts of condensed tannins [CT] were found in BGNIFs (0.014 – 0.160 mg.g-1). Higher amounts polyphenols [PP] were present in BGNSFs (45.42 – 55.90 mg.g-1 gallic acid equivalents [GAE]) compared to the amount PP in BGNIFs (6.14 – 15.56 mg.g-1 GAE). Major sugars identified were arabinose/galactose, xylose and mannose in BGNIFs, and xylose and mannose in BGNSFs. The functional properties evaluated revealed high swelling capacity of BGNIFs (6.37 – 7.72 ml.g-1) and no significant [p > 0.05] difference in water retention capacity. Fat absorption capacity ranged from 1.38 – 1.52 g oil.g-1 dry weight for BGNIFs and 4.04 – 4.55 g oil.g-1 dry weight for BGNSFs. Variability in BGNIF (91.2%) and BGNSF (79.4%) physicochemical and functional properties could both be explained by two principal components (BGNIF component 1: PP, redness, yield; and component 2: xylose, yellowness and chroma; BGNSF component 1: yellowness, chroma, mannose content; and component 2: redness, fat absorption and fructose content). Following an IV optimal mixture design, an optimum white bread formulation was obtained using 59.5% water, 4.3% yeast and 8.5% BGNIF. Bread enriched with the four BGNIF varieties (BLE, RED, BRN and BRE) were tested for several physicochemical properties. Significant [p ≤ 0.05] differences existed between the control and BGNIF enriched loaves for crumb grain characteristics (including pore area distribution, feret angle, circularity, roundness and aspect ratio). Specific loaf volume of BGNIF enriched loaves ranged from 3.33 – 3.85 ml.g-1 and were significantly [p ≤ 0.05] lower compared to the control bread (4.16 ml.g-1). Favourable texture characteristics obtained with the BGNIF enriched breads were lower hardness, chewiness and gumminess compared to the control loaf. Crust and crumb colour parameters (lightness, redness, yellowness, chroma and hue angle) were significantly [p ≤ 0.05] different across all loaves. BRE BGNIF bread (3.43 ± 0.20) had the significantly [p ≤ 0.05] lowest crumb colour difference compared to the control bread; whilst BRN (1.72 ± 0.42) and BRE (2.44 ± 0.78) loaves had the lowest significant [p ≤ 0.05] crust colour difference compared to the control. Favourable chemical properties were the high total dietary fibre [TDF] (7.14 – 8.33%) content of all BGNIF enriched loaves compared to the control loaf (4.96%). Significant [p ≤ 0.05] differences were also observed for some loaves for moisture content, condensed tannins and polyphenol content. Variability in bread physicochemical properties was differentiated by three components (component 1: bread textural properties; component 2: specific loaf volume and bread lightness; component 3: crumb colour parameters) which accounted for a cumulative variation of 92.8%. All bread loaves were also sensorially acceptable as rated moderately like to like very much (>3 rating on a 5-point hedonic scale) by consumers for all parameters (appearance, crust and crumb colour, aroma, taste, texture and overall acceptability) evaluated. Furthermore, brown BGNSF was tested for stabilising effects in an orange beverage emulsion. BGNSF and orange oil were varied at two levels each based on a 22 augmented factorial design and the effects determined on the equilibrium backscattering [BS] flux as emulsion stability indicator. The BS profiles which resulted from the Turbiscan stability analysis revealed flocculation at low rates as the major destabilisation mechanism. The optimal formulation producing a stable emulsion was identified as low oil (6%) and high BGNSF (30%) concentrations. The objective of this study was therefore achieved and showed that positive physicochemical and functional properties are associated with BGNIF and BGNSF from black-eye, red, brown and brown-eye varieties. Furthermore, the incorporation of BGN fibres in white bread and a beverage emulsion was shown to contribute positive technological properties in these systems.

Thesis (Doctor of Philosophy)--Case Western Reserve University, 2010<br>Department of Chemical Engineering Title from PDF (viewed on 2010-05-25) Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center

The role of hydrophobic substituents on the gelation mechanism of highly esterified pectin and the cellulose derivatives methylcellulose and hydroxypropylmethylcellulose (HPMC) has been explored by monitoring the behaviour of the amphiphilic polysaccharides in varying combinations of an ethylene glycoVwater solvent. The gelling ability (mechanical spectroscopy, visual observation) of very highly esterified (- 100%) pectin in high concentrations of ethylene glycol (>60%) is greatly reduced, however, the polymer still undergoes conformational ordering (CD, OR). A model for gel formation involving a two stage process has been proposed, comprising adoption of the ordered structure stabilised by hydrogen bonding between OH groups of contiguous polysaccharide chains, followed by (or coincident with) aggregation of the ordered sequences by 'hydrophobic' clustering of the fundamental structural subunits to form the three dimensional gel network. It has been found that ethylene glycol promotes the fIrst stage (ordering) but is antagonistic to the second (aggregation). The reversibility (mechanical spectroscopy) of the thermo-gelling cellulose derivatives can be largely abolished in the presence of ethylene glycol (40% for methylcellulose, 10% for HPMC), attributed to solubilisation of the proposed ordered 'bundle' structure at low temperatures removing the enthalpic advantage (DSC) of gel melting. The increased sensitivity of HPMC to modification of the solvent environment is due to the presence of the polar hydroxypropyl substituent causing an inceptive destabilisation of the 'bundle' structure. It is suggested that gelation is driven by the entropic advantage of melting-out 'cages' of structured water surrounding the hydrophobic groups giving rise to intermolecular 'hydrophobic' aggregation.

Thesis (MSc)--Stellenbosch University, 2015.<br>ENGLISH ABSTRACT: Lignocellulosic material is composed of three major macromolecule components i.e., cellulose, hemicelluloses and lignin. These components are chemically associated and directly linked to each other through covalent bonding which is scientifically denoted as lignin-carbohydrate complexes (LCCs) and their interaction is fundamentally important as to understand wood formation and reactivity during chemical and biological processing e.g. pulping and enzymatic hydrolysis. The association of lignin with polysaccharides (covalent linkages) has been surrounded by contradictions and controversy in several wood chemistry studies. These linkages exist in lignocellulosic materials from wood to herbaceous plants. In woody plants, they consist of ester and ether linkages through sugar hydroxyl to α-carbonyl of phenyl-propane unit on lignin. However, in herbaceous plants ferulic and p-coumaric acids are esterified to hemicelluloses and lignin respectively. In recent studies, the existence of the bonds has been shown by applying indirect analysis strategies which resulted to low yields and contaminations. The general aim of the current study was to isolate and fractionate LCCs from raw lignocellulosic materials (E. grandis and sugarcane bagasse) and corresponding processed materials (chemical pulps and water-insoluble residues (WIS)) in order to determine the chemical structure of the residual lignin associated with polysaccharides and how they affected industrial processing. The objective of the study is to compile a document that when the development of pulping and bio-ethanol bio-refinery will greatly depends on the detailed wood chemistry on how the components interact with each before and after hemicelluloses pre-extraction prior to pulping and steam explosion pre-treatment prior to enzymatic hydrolysis. The current study was focusing on understanding the effect LCCs isolated from two different industrial processing methods, i.e. pulping and enzymatic hydrolysis (EH). There were two lignocelluloses feedstocks used for pulping, i.e. Eucalyptus grandis and sugarcane bagasse whereas sugarcane bagasse was the only feedstock used for enzymatic hydrolysis. Hemicelluloses pre-extracted (mild alkali or dilute acid and autohydrolysis for sugarcane bagasse) pulps of Kraft or soda AQ from E. grandis and sugarcane bagasse were used to understand the effect of xylan pre-extraction prior to pulping on lignin-carbohydrate complexes has not been reported to the best knowledge of the primary author. Also prior to EH the material was subjected to two different treatment methods, i.e. steam explosion and ionic liquid fractionation in varying conditions. The study illustrated the types of extracted and fractionated LCCs from hemicelluloses pre-extracted pulps and WIS in comparison to the non-extracted pulps and reports from the literature. Lignin-carbohydrate complexes (LCCs) were isolated and fractionated by an inorganic method which yielded reasonable quantification quantities and no contamination and low yields for the hardwood compared to reports of using an enzymatic method. To the best knowledge of the authors, no work has been done on WIS material. The lignocelluloses were subjected to ball milling which was followed by a sequence of inorganic solvents swelling and dissolution into 2 fractions i.e. glucan-lignin and xylan-lignin-glucan. Characterisation of the isolated LCCs was made using a variety of analytical tools such as FTIR-PCA, HPLC, GPC and GC-MS. LCCs were evident when FTIR and HPLC studies were conducted. Residual lignin isolated from the lignocelluloses was assumed to be chemically bonded to carbohydrates and mostly to xylan. Approximately 60% and 30% of the lignin was linked to xylan while for the second and first fractions respectively. It is reported that lignin associated with xylan is more resistant and reduce the delignification process than when linked to glucan that is easily hydrolysable. With the FTIR and GPC analyses of LCC fractions, it was evident that the ester bonds of LCCs were destroyed through pre-extraction and pre-treatment, where this resulted to more cellulose being more accessible to alkaline pulping and enzymatic hydrolysis respectively. The linkages were either partially broken down or completely destroyed leading to significant changes of chemical structures. The polydispersity of the LCCs assisted in determining the structure of lignin, either existing as monolignols on the surfaces of fibres or a as complex two or three-dimensional structure that is linked to carbohydrates as the Mw increased or decreased. In general, these findings may have an important implication for the overall efficiency on bio-refinery. The molecular weights (Mw) of the extracted LCCs were measured by gel permeation chromatography. From the chromatograms, it was observed that the materials that were subjected to pre-processing prior to further processing, the Mw shifted to lower Mws regions. It was found that LCCs isolated from mild alkali pre-extracted pulps had high lignin syringyl to guaiacyl lignin contents than LCCs isolated from dilute acid pre-extracted pulps. High syringyl/guaiacyl ratio (S/G ratio) was an indication of low lignin content as a result of processing which will result to high product yields after downstream processing. The 5 average S/G ratio for the pulps from E. grandis and sugarcane bagasse was ranging between 1.1 to 19.01 and 1.4 to 18.16 respectively, while for the WIS-material generated from ionic liquid fractionated and steam exploded materials ranged from 3.29 to 9.27 and 3.5 to 13.3 respectively. The S/G ratios of the LCCs extracted from E. grandis and sugarcane bagasse pulps ranged from 0.42 to 2.39 and 0.041 to 0.31 was respectively while for the LCCs extracted from water-insoluble-solids (WIS) material generated from steam exploded material was from 4.87 to 10.40. The determination of S/G ratio is recommended for the LCC extraction and characterisation study as an evaluation of residual lignin in processed materials such as pulps and WIS. The obtained saccharifications were low, possibly due to the severity of the steam explosion pre-treatment and ionic liquid fractionation conditions which resulted on high accumulation of acetic acid and increased in cellulose crystallinity respectively. From quantitative analysis of the LCCs perspective it could be concluded that free lignin was present in mild alkali pre-extracted pulps than for the dilute acid pre-extracted pulps.<br>AFRIKAANSE OPSOMMING: Cellulose materiaal is saamgestel uit drie groot makromolekule komponente naamlik, sellulose, hemisellulose en lignien. Hierdie komponente is chemies verwante en direk met mekaar verbind deur kovalente binding wat wetenskaplik aangedui as lignien-koolhidraat komplekse (LCCs) en hul interaksie is fundamenteel belangrik as hout vorming en reaktiwiteit tydens chemiese en biologiese verwerking bv om te verstaan verpulping en ensiematiese hidrolise. Die vereniging van lignien met polisakkariede (kovalente verbindings) is omring deur teenstrydighede en omstredenheid in verskeie hout chemie studies. Hierdie skakeling bestaan in cellulose materiaal uit hout te kruidagtige plante. In houtagtige plante, hulle bestaan uit ester en eter bindings deur suiker hidroksiel te α-karboniel van feniel-propaan eenheid op lignien. Maar in kruidagtige plante ferulic en p-coumaric sure veresterd te hemisellulose en lignien onderskeidelik. In onlangse studies, het die bestaan van die bande is getoon deur die toepassing van indirekte analise strategieë wat gelei tot lae opbrengste en kontaminasie. Die algemene doel van die huidige studie was om te isoleer en fraksioneer LCCs van rou cellulose materiaal (E. grandis en suikerriet bagasse) en die ooreenstemmende verwerkte materiaal (chemiese pulp en water-oplosbare residue (WIS)) ten einde die chemiese struktuur van die te bepaal oorblywende lignien wat verband hou met polisakkariede en hoe hulle geaffekteerde industriële verwerking. Die doel van die studie is 'n dokument op te stel dat wanneer die ontwikkeling van verpulping en bio-etanol bio-raffinadery sal grootliks afhang van die gedetailleerde hout chemie oor hoe om die komponente met mekaar voor en na hemisellulose pre-onttrekking voor verpulping en stoom ontploffing pre-behandeling voor ensiematiese hidrolise. Die huidige studie was die fokus op die begrip van die effek LCCs geïsoleerd van twee verskillende industriële verwerking, maw verpulping en ensiematiese hidrolise (EH). Daar was twee lignocelluloses voerstowwe gebruik vir verpulping, dws Eucalyptus grandis en suikerriet bagasse terwyl suikerriet bagasse was die enigste grondstof gebruik vir ensiematiese hidrolise. Hemisellulose pre-onttrek (ligte alkali of verdunde suur en autohydrolysis vir suikerriet bagasse) pulp van Kraft of soda AQ van E. grandis en suikerriet bagasse is gebruik om die effek van Xylan pre-onttrekking te voor verstaan verpulping op lignien-koolhidraat komplekse het nie aan die berig is beste kennis van die primêre outeur. Ook voor EH die materiaal is onderworpe aan twee verskillende behandeling metodes, naamlik stoom ontploffing en ioniese vloeistof fraksionering in wisselende toestande. Die studie geïllustreer die tipes onttrek en gefractioneerd LCCs van hemisellulose pre-onttrek pulp en WIS in vergelyking met die nie-onttrek pulp en verslae van die literatuur. Lignien-koolhidraat komplekse (LCCs) is geïsoleer en gefraksioneer deur 'n anorganiese metode wat redelike kwantifisering hoeveelhede en geen besoedeling en lae opbrengste opgelewer vir die hardehout vergelyking met verslae van die gebruik van 'n ensiematiese metode. Na die beste kennis van die skrywers, het geen werk op WIS materiaal gedoen. Die lignocelluloses is onderworpe aan die bal maal wat gevolg is deur 'n reeks van anorganiese oplosmiddels swelling en ontbinding in 2 breuke dws glucan-lignien en Xylan-lignien-glucan. Karakterisering van die geïsoleerde LCCs is gemaak met behulp van 'n verskeidenheid van analitiese gereedskap soos FTIR-PCA, HPLC, GPC en GC-MS. LCCs was duidelik wanneer FTIR en HPLC studies is uitgevoer. Residuele lignien geïsoleerd van die lignocelluloses is aanvaar moet word chemies gebind aan koolhidrate en meestal te xylan. Ongeveer 60% en 30% van die lignien is gekoppel aan xylan terwyl dit vir die tweede en eerste breuke onderskeidelik. Dit is gerapporteer dat lignien wat verband hou met Xylan is meer bestand en die delignification proses as wanneer gekoppel aan glucane wat maklik hidroliseerbare verminder. Met die FTIR en GPC ontledings van LCC breuke, was dit duidelik dat die ester bande van LCCs is deur pre-ontginning en pre-behandeling, waar dit gelei tot meer sellulose om meer toeganklik te alkaliese verpulping en ensiematiese hidrolise onderskeidelik vernietig. Die skakeling is óf gedeeltelik afgebreek of heeltemal vernietig lei tot beduidende veranderinge van chemiese strukture. Die polydispersity van die LCCs bygestaan in die bepaling van die struktuur van lignien, hetsy bestaande as monolignols op die oppervlak van die vesel of 'n as komplekse twee of drie-dimensionele struktuur wat gekoppel is aan koolhidrate as die Mw vermeerder of verminder. In die algemeen, kan hierdie bevindinge het 'n belangrike implikasie vir die algehele doeltreffendheid op bio-raffinadery. Die molekulêre gewigte (Mw) die onttrek LCCs gemeet deur gelpermeasie- chromatografie. Van die chromatograms, was dit opgemerk dat die materiaal wat blootgestel is aan die pre-verwerking voor verdere verwerking, die Mw verskuif MWS streke te verlaag. Daar is gevind dat LCCs geïsoleerd van ligte alkali pre-onttrek pulp het hoë lignien syringyl lignien inhoud as LCCs geïsoleerd van verdunde suur vooraf onttrek pulp te guaiacyl. Hoë syringyl / guaiacyl verhouding (S/G-verhouding) was 'n aanduiding van 'n lae lignien inhoud as 'n resultaat van verwerking wat sal lei tot 'n hoë produk opbrengste ná stroomaf verwerking. Die gemiddelde S/G-verhouding vir die pulp van E. grandis en suikerriet bagasse was wat wissel tussen 1,1-19,01 en 1,4-18,16 onderskeidelik, terwyl dit vir die WIS-materiaal gegenereer uit ioniese vloeistof gefraksioneer en stoom ontplof materiaal het gewissel 3,29-9,27 en 3.5 13,3 onderskeidelik. Die S/G verhoudings van die LCCs onttrek uit E. grandis en suikerriet bagasse pulp gewissel 0,42-2,39 en ,041-,31 was onderskeidelik terwyl dit vir die LCCs onttrek uit water-oplosbare-vastestowwe (WIS) materiaal gegenereer uit stoom ontplof materiaal was van 4,87-10,40. Die bepaling van S/G-verhouding word aanbeveel vir die LCC ontginning en karakterisering studie as 'n evaluering van die oorblywende lignien in verwerkte materiaal soos pulp en WIS. Die verkry saccharifications was laag, moontlik as gevolg van die erns van die stoom ontploffing pre-behandeling en ioniese vloeistof fraksionering voorwaardes wat gelei op 'n hoë opeenhoping van asynsuur en vermeerder in sellulose kristalliniteit.