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)

Root growth of different oak provenances in two soils under drought stress and air warming conditions

Background and aims: Oaks are considered to be drought- and thermo-tolerant tree species. Nevertheless, species and provenances may differ in their ecological requirements. We hypothesised that (i) provenances from xeric sites are better adapted to drought than those from more humid sites, (ii) oaks direct root growth towards resource-rich layers, and (iii) air-warming promotes root growth. Methods: To test different provenances of Quercus robur, Q. petraea and Q. pubescens, we conducted a model ecosystem experiment with young trees, grown on acidic and calcareous soil, subjected to drought, air warming, the combination of warming and drought, and a control. Results: The results were only in partial agreement with the first hypothesis. As expected the provenances originating from drier sites produced more biomass than those from more humid sites under drought conditions. Surprisingly, however, they reacted more sensitive to water limiting conditions, as they produced also substantially more biomass under well-watered conditions. The drought treatment reduced root mass substantially in the upper soil. In agreement with the second hypothesis this led to a shift in the centre of root mass to lower depth, where water was still more available than closer to the soil surface. In contrast to the third hypothesis, the air-warming treatment, which was very mild however compared to climate change scenarios, had no significant effects on root growth. Conclusions: Given that the provenances from drier sites showed more biomass loss at water limiting conditions than provenances from more humid sites, it remains questionable whether provenances from drier sites are better suited for a future climate. © 2012 Springer Science+Business Media Dordrecht

A conceptual model for the development of Phytophthora disease in Quercus robur

Here, a conceptual model is presented for the development of Phytophthora disease in pedunculate oak. The model is presented using the causal loop diagram tool and gives an overview of how various abiotic and biotic factors, such as soil moisture, nutrient availability and mycorrhizal colonization, may affect the reproduction and the infective capacity of soil-borne Phytophthora species, the susceptibility of the host and subsequent disease development. It is suggested that the link between the root damage caused by Phytophthora species and overall tree vitality is in the assimilation and allocation of carbon within the plants. The potential impact of environmental factors on these processes is discussed. The model is presented with reference to scenarios related to variation in soil moisture and nutrient availability. The need for species-specific validation of the model and the implications of the model are discussed