Approaches in biotechnological applications of natural polymers

Natural polymers, such as gums and mucilage, are biocompatible, cheap, easily available and non-toxic materials of native origin. These polymers are increasingly preferred over synthetic materials for industrial applications due to their intrinsic properties, as well as they are considered alternative sources of raw materials since they present characteristics of sustainability, biodegradability and biosafety. As definition, gums and mucilages are polysaccharides or complex carbohydrates consisting of one or more monosaccharides or their derivatives linked in bewildering variety of linkages and structures. Natural gums are considered polysaccharides naturally occurring in varieties of plant seeds and exudates, tree or shrub exudates, seaweed extracts, fungi, bacteria, and animal sources. Water-soluble gums, also known as hydrocolloids, are considered exudates and are pathological products; therefore, they do not form a part of cell wall. On the other hand, mucilages are part of cell and physiological products. It is important to highlight that gums represent the largest amounts of polymer materials derived from plants. Gums have enormously large and broad applications in both food and non-food industries, being commonly used as thickening, binding, emulsifying, suspending, stabilizing agents and matrices for drug release in pharmaceutical and cosmetic industries. In the food industry, their gelling properties and the ability to mold edible films and coatings are extensively studied. The use of gums depends on the intrinsic properties that they provide, often at costs below those of synthetic polymers. For upgrading the value of gums, they are being processed into various forms, including the most recent nanomaterials, for various biotechnological applications. Thus, the main natural polymers including galactomannans, cellulose, chitin, agar, carrageenan, alginate, cashew gum, pectin and starch, in addition to the current researches about them are reviewed in this article.. }To the Conselho Nacional de Desenvolvimento Cientfíico e Tecnológico (CNPq) for fellowships (LCBBC and MGCC) and the Coordenação de Aperfeiçoamento de Pessoal de Nvíel Superior (CAPES) (PBSA). This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and COMPETE 2020 (POCI-01-0145-FEDER-006684) (JAT)

Amphiphilic properties of synthetic glycolipids based on amide linkages, 4a) - 13C NMR spectroscopy studies on the gelation of N-octyl-D-gluconamide in aqueous solution

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Infrared spectra of cerium and thorium pentacarbonate complexes

Infrared spectra of Na6[M(CO3)5].12 H2O and (CN3H6)[M(CO3)5]\ub74 H2O complexes (M = Ce,Th) are presented. The spectra are discussed on the basis of the bicoordination of the CO32- groups. The determining effect of the polarizing power of the central ion on the splitting of the V3, (E) vibration of the free carbonate group is evidenced, as well as the role of hydrogen bondings and external cations. \ua9 1982

Infrared determination of the coordination state of CO2-3 ions in cerium and thorium tetracarbonato complexes

Infrared spectra and thermal decomposition curves of Na4(M(CO3)4] \ub7 7H2O and Gm4[M(CO3)4] \ub7 6H2O (Gm = guanidinium cation; M = Ce, Th) are reported. The coordination state of carbonate groups in the complex ions is described on the basis of criteria discussed in the introductory part as derived by theoretical and experimental results. \ua9 1983

Influence of high spressures on CH4, CO2 and H2S solubility in polyethylene: Experimental and molecular simulation approaches for pure gas and gas mixtures. Modelling of the sorption isotherms

International audienceThe sorption of methane, carbon dioxide and hydrogen sulphide in polyethylene (PE) was investigated. Data were obtained in a large range of pressures from both experiments and molecular simulation. Monte Carlo (MC) simulations in the osmotic ensemble were used to predict gas concentrations in the amorphous polymer phase. An ad hoc constraint in the osmotic simulations was used to mimic the effect of the crystalline phase. The results obtained from MC simulation compared favourably to experimental results and data from literature. Different sorption mechanisms were evidenced in the low to middle gas pressure range as a function of the gas nature. However, the decrease of gas solubility was evidenced at high pressure. It was assigned to a hydrostatic effect and the bulk modulus of the PE amorphous phase was determined. A simple model allowing the accurate description of gas solubility from low to high gas pressure range was proposed. It was shown to accurately describe the different sorption isotherm shapes obtained for PE and the characteristic parameters of the model were determined for each gas

A thin layer cell adapted for corrosion studies in confined aqueous environments

International audienceIn order to investigate the influence of the confinement on the corrosion behaviour of metallic materials, an innovative thin layer electrochemical cell was developed. The cell includes a device which allows a continuous gas supply within the electrolyte film covering the metallic specimen under study. A procedure based on high frequency impedance measurements is also proposed to control and precisely adjust the setting of the electrolyte film geometry.The experimental set-up was validated by performing measurements of the stationary limiting cathodic current on a steel disk immersed in a K2SO4 aerated solution for various electrolyte layer thicknesses. The results obtained demonstrate the reliability of the experimental method

A Kinetic Model for CO2 Corrosion of Steel in Confined Aqueous Environments

International audienceA kinetic model of the physicochemical processes occurring during the corrosion of steel covered by a thin water film exposed to a Formula atmosphere is proposed. This model explains theoretically the unusual physicochemical behaviors generally observed in such confined corrosive media: Formula supersaturations, low corrosion rates, high pH values, and their respective dependence on the electrolyte film thickness. More quantitatively, the model predictions agree well with pH and corrosion rate measurements performed in environments similar to the annulus space of flexible pipelines