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)

Electroweak parameters of the Z0^0 resonance and the standard model

Media temporalities of the elderly : evolutions in stability This article shows the context of analysis and the first results of a research on media temporalities of the elderly. Several works have finely analysed the diversity of the media practices and studied meanings of media uses. I wish to continue these analyses by insisting on the evolutionary and dynamic aspect of the practices and temporalities of users having expanded, enhanced, so called "interactive" radio and especially television programming. A priori, the elderly, upon retirement, have a "full-time free time". Their media practices seem strongly influenced by their first experiments ; the appropriation of the various peripheral accessories which gradually came with the media, to the latest digital ones, seems to reinforce their habits of watching television. Their representations and relations with times and media are very far away from the image of television like omnipresent media or "devourer of time". Rather, their media practices are to be understood like a temporality of the occupation, according to the expression of Gerard Derèze, characterized by interest and utility. A particular glance at the users who do not carry out a systematic selection of the programs, accepting the unforeseen, highlights an approach of media and time that allow "useful encounter" which I would qualify in a first stage by : "chance and encounter" and "random and the following". The few points presented here make me assume that the global relation of the autonomous elderly persons to the media can evolve when confronted to their new temporal framework and the new program offer, whereas their representations and use of the media remain quite stable