Sterilization of Exopolysaccharides Produced by Deep-Sea Bacteria: Impact on Their Stability and Degradation

Polysaccharides are highly heat-sensitive macromolecules, so high temperature treatments are greatly destructive and cause considerable damage, such as a great decrease in both viscosity and molecular weight of the polymer. The technical feasibility of the production of exopolysaccharides by deep-sea bacteria Vibrio diabolicus and Alteromonas infernus was previously demonstrated using a bioproduct manufacturing process. The objective of this study was to determine which sterilization method, other than heat sterilization, was the most appropriate for these marine exopolysaccharides and was in accordance with bioprocess engineering requirements. Chemical sterilization using low-temperature ethylene oxide and a mixture of ionized gases (plasmas) was compared to the sterilization methods using gamma and beta radiations. The changes to both the physical and chemical properties of the sterilized exopolysaccharides were analyzed. The use of ethylene oxide can be recommended for the sterilization of polysaccharides as a weak effect on both rheological and structural properties was observed. This low-temperature gas sterilizing process is very efficient, giving a good Sterility Assurance Level (SAL), and is also well suited to large-scale compound manufacturing in the pharmaceutical industry

Polysaccharide structures and interactions in a lithium chloride/urea/water solvent

The molten salt hydrate, lithium chloride (LiCl)/urea/water has previously been shown to swell cellulose, but there has so far been no work done to explore its effect on other polysaccharides. In this paper we have investigated the solvent effects of LiCl/urea/water on four natural polysaccharides. Fenugreek gum and xyloglucan, which are both highly branched, were found to increase in viscosity in LiCl/urea/water relative to water, possibly due to the breakage of all intra-molecular associations whereas the viscosity of konjac glucomannan which is predominantly unbranched did not change. Locust bean gum (LBG) had a lower viscosity in LiCl/urea/water compared to water due to the disruption of aggregates. Confocal microscopy showed that fenugreek gum and LBG are able to bind to cellulose in water, however, the conformational change of fenugreek gum in these solvent conditions inhibited it from binding to cellulose in LiCl/urea/water whereas conformational change allowed xyloglucan to bind to cellulose in LiCl/urea/water whilst it was unable to bind in water. Konjac glucomannan did not bind to cellulose in either solvent system. These results provide new insights into the impact of polysaccharide fine structure on conformational change in different solvent environments

Hyperfine coupling constants on inner‐sphere water molecules of GdIII‐based MRI contrast agents

[Abstract] Herein we present a theoretical investigation of the hyperfine coupling constants (HFCCs) on the inner‐sphere water molecules of [Gd(H2O)8]3+ and different GdIII‐based magnetic resonance imaging contrast agents such as [Gd(DOTA)(H2O)]−, [Gd(DTPA)(H2O)]2−, [Gd(DTPA‐BMA)(H2O)] and [Gd(HP‐DO3A)(H2O)]. DFT calculations performed on the [Gd(H2O)8]3+ model system show that both hybrid‐GGA functionals (BH&HLYP, B3PW91 and PBE1PBE) and the hybrid meta‐GGA functional TPSSh provide 17O HFCCs in close agreement with the experimental data. The use of all‐electron relativistic approaches based on the DKH2 approximation and the use of relativistic effective core potentials (RECP) provide results of essentially the same quality. The accurate calculation of HFCCs on the [Gd(DOTA)(H2O)]−, [Gd(DTPA)(H2O)]2−, [Gd(DTPA‐BMA)(H2O)] and [Gd(HP‐DO3A)(H2O)] complexes requires an adequate description of solvent effects. This was achieved by using a mixed cluster/continuum approach that includes explicitly two second‐sphere water molecules. The calculated isotropic 17O HFCCs (Aiso) fall within the range 0.40–0.56 MHz, and show deviations from the corresponding experimental values typically lower than 0.05 MHz. The Aiso values are significantly affected by the distance between the oxygen atom of the coordinated water molecule and the GdIII ion, as well as by the orientation of the water molecule plane with respect to the Gd‐O vector. 1H HFCCs of coordinated water molecules and 17O HFCCs of second‐sphere water molecules take values close to zero.Ministerio de Educación y Ciencia; CTQ2009‐10721Xunta de Galicia; IN845B‐2010/06

Thermally Responsive Amphiphilic Conetworks and Gels Based on Poly(N‑isopropylacrylamide) and Polyisobutylene

Novel amphiphilic conetworks (APCN) consisting of thermoresponsive poly(N-isoproplyacrylamide) (PNiPAAm) cross-linked by hydrophobic methacrylate-telechelic polyisobutylene (MA-PIB-MA) were successfully synthesized in a broad composition range. The resulting PNiPAAm-l-PIB conetworks (“l” stands for “linked by”) were obtained by radical copolymerization of NiPAAm with MA-PIB-MA in tetrahydrofuran, a cosolvent for all the components. Low amounts of extractables substantiated efficient network formation. The composition dependent two glass transition temperatures (Tg) by DSC analysis indicate microphase separation of the cross-linked components without mixed phases. It was found that the PNiPAAm-l-PIB conetworks are uniformly swellable in both water and n-hexane; i.e., these new materials behave either as hydrogels or as hydrophobic gels in aqueous or nonpolar media, respectively. The uniform swelling in both polar and nonpolar solutes indicates cocontinuous (bicontinuous) phase morphology. The equilibrium swelling degrees (R) depend on composition, that is, the higher the PIB content, the lower the R in water and the higher in n-hexane. The PNiPAAm phase keeps its thermoresponsive behavior in the conetworks as shown by significant decrease of the swelling degree in water between 20 and 35 °C. The lower critical solubility temperature (LCST) values determined by DSC are found to decrease from 34.1 °C (for the pure PNiPAAm homopolymer) to the range of 25–28 °C in the conetworks, and the extent of the LCST decrease is proportional with the PIB content. Deswelling-swelling, i.e., heating–cooling, cycle indicates insignificant hysteresis in these new thermoresponsive materials. This indicates that PNiPAAm-l-PIB conetworks with predetermined and thermoresponsive swelling behavior can be designed and utilized in several advanced applications on the basis of results obtained in the course of this study

Between-speaker variation in English Learners' Realisation of Dental Fricatives

Anecdotally, it has been observed that Swiss Germans speaking English use a plethora of sounds for the dental fricatives /θ/ and /ð/. It is unsurprising that L2 speakers tend to substitute a sound not present in their native phoneme inventory with a sound that is present; however, there is wide intra- and inter-speaker variation in the sounds chosen to replace the dental fricatives. The present study is an initial examination of how speakers of Swiss German differ in their choice of sound substitution when speaking English. We recorded read speech from 45 high school students. Data was coded auditorily and acoustically. Findings confirm substantial variation between the learners, with the most common replacement being [d] for the voiced dental fricative and [f] for the unvoiced counterpart. We discuss potential reasons for the reported between-speaker variation

Réalisation d'un répertoire informatisé des imprimeurs/libraires genevois du XVIIème siècle

Ces dernières années, les livres anciens suscitent de plus en plus l’intérêt des uns et des autres. En effet, les nouvelles technologies et les règles de catalogage plus détaillées facilitent l’accès aux notices de ces ouvrages. Il manque encore toutefois aux catalogueurs de livres anciens un instrument - couvrant le XVIème, le XVIIème et le XVIIIème siècle - pour les aider à rédiger les points d’accès aux imprimeurs/libraires suisses. Certes, quelques outils disparates existent déjà, mais aucun ne répond entièrement aux besoins des professionnels. C’est dans cet esprit que ce travail de diplôme sur les imprimeurs/libraires genevois du XVIIème siècle a vu le jour. Le mandat comprenait deux parties. Nous avons d’abord choisi le support informatique : une copie de la base de données « Fleuron » - mise au point à la Bibliothèque cantonale et universitaire de Lausanne – tournant sur Access, Version 7.0 sous Windows 95. Puis nous avons collecté diverses informations sur les imprimeurs/libraires genevois du XVIIème siècle, ainsi que des marques typographiques, provenant de différentes sources. Par la suite, le personnel de la bibliothèque s’occupant des livres anciens pourra introduire de nouvelles notices dans cette base de données. Les imprimeurs/libraires genevois des XVIème et XVIIIème siècles ne devraient d’ailleurs pas tarder à faire leur entrée dans « Fleuron ». En outre, un accès Internet devrait très bientôt voir le jour. Ainsi, les chercheurs, les bibliophiles et les curieux pourront également accéder à ces renseignements

Statut nutritionnel et vitaminique avant et 1 an après chirurgie bariatrique (analyse retrospective comparative de 3 techniques chez 50 patients obèses)

LYON1-BU Santé (693882101) / SudocSudocFranceF

Development of thermo-responsive supports for the culture of adherent cells and their protease-free detachment

Les cellules adhérentes, dont les cellules souches, sont très prometteuses pour de nombreuses applications dans le domaine des biotechnologies. Toutefois, leur culture représente un défi puisque les méthodes enzymatiques et mécaniques, couramment utilisées pour l’étape de détachement du support de culture, présentent des inconvénients majeurs. Le but de ce travail de thèse a été de développer un support pour la culture de cellules adhérentes permettant leur détachement par modification de la température. Pour cela, nous avons produit des échantillons thermo-associatifs de xyloglucane, un polysaccharide naturel, par réaction avec une enzyme, la ß-galactosidase. Les échantillons obtenus ont été caractérisés par rhéologie, viscosimètrie, diffusion de la lumière et chromatographie par perméation de gel. Nous nous sommes aussi intéressés à l’évaluation de méthodes de stérilisation efficaces capables de préserver les propriétés du polymère. De plus, afin de rendre ce polymère bioadhésif, nous avons étudié son activation et sa fonctionnalisation par un peptide contenant le motif arginine-glycine-aspartate (RGD). Nous avons montré que des cellules modèles A375 surexprimant le récepteur pour le RGD sont capables d’adhérer et de proliférer à 37°C sur des films formés à partir de xyloglucane modifié par du RGD. Leur détachement est possible à température ambiante. L'utilisation de ce nouveau support pour la culture de cellules souches embryonnaires humaines, la production d’un système pour la libération contrôlée de facteurs de croissance ainsi que la conception de billes de taille micrométrique à base de xyloglucane font partie des perspectives de cette thèse.Adherent cells, including stem cells, hold great promise for many applications in biotechnology. However, cell detachment from standard culture surfaces remains a challenging task since both commonly used enzymatic and mechanical methods have major drawbacks. The aim of my PhD work was to develop a thermoresponsive culture surface supporting cell attachment and survival while enabling a temperature-assisted cell detachment. In order to achieve this goal, thermoresponsive xyloglucan was initially produced by partial galactose removal after reaction with the β-galactosidase enzyme. Samples were characterized by rheology, viscosimetry, light scattering analysis and size-exclusion chromatography. We were also interested in evaluating sterilization methods and their effect on the properties of the polymer. Additionally, in order to obtain a bioadhesive polymer from partially degalactosylated xyloglucan, we studied its functionalization with a peptide containing the arginine-glycine-aspartate (RGD) groupment motif. We have shown that A375 model cells overexpressing the RGD receptor were able to adhere and proliferate at 37 °C on xyloglucan-derived films grafted with RGD and their detachment at room temperature was also demonstrated. The culture of human embryonic stem cells, as well as the introduction of a controlled release system for growth factors and the development of thermoresponsive beads for cell culture comprise the perspectives of this thesis

Développement de nouveaux supports pour la culture de cellules adhérentes permettant leur détachement sans utilisation de protéases

Résumé soumis à confidentialitéAbstract not availableEVRY-Bib. électronique (912289901) / SudocSudocFranceF