A series of polyvinyl alcohol (PVA), PVA/chitosan (CS) and PVA/cyanobacterial extracellular polymeric substances (EPS) blended nanofibrous membranes were produced by electrospinning using a microfiltration poly(vinylidene fluoride) (PVDF) basal membrane, for potential applications in water filtration. Nanofibres were obtained from solutions of 20% (w/w) PVA with 1% (w/w) CS or EPS, using a weight ratio of 60/40. Blended nanofibres have shown a smooth morphology, no beads formation and diameters between 50 and 130 nm. Thermo-mechanical analysis demonstrated that there were inter and/or intramolecular hydrogen bonds between the molecules of PVA/CS and PVA/EPS in the blends. The electrospun blended PVA/EPS membrane showed better tensile mechanical properties when compared with PVA and PVA/CS, and resisted more against disintegration in the temperature range between 10 and 50 °C. Finally, the blended membranes have shown an increase in chromium binding capacity of 5%. This is the first successful report of a blended membrane of electrospinned cyanobacterial polysaccharide with PVA.

Cyanobacterial extracellular polymeric substances (EPS) are heteropolysaccharides that possess characteristics suitable for industrial applications, notably a high number of different monomers, strong anionic nature and high hydrophobicity. However, systematic studies that unveil the conditions influencing EPS synthesis and/or its characteristics are mandatory. In this work, Cyanothece sp. CCY 0110 was used as model organism. Our results revealed that this strain is among the most efficient EPS producers, and that the amount of RPS (released polysaccharides) is mainly related to the number of cells, rather than to the amount produced by each cell. Light was the key parameter, with high light intensity enhancing significantly RPS production (reaching 1.8 g L(-1)), especially in the presence of combined nitrogen. The data showed that RPS are composed by nine different monosaccharides (including two uronic acids), the presence of sulfate groups and peptides, and that the polymer is remarkably thermostable and amorphous in nature.

The aim of this study was to evaluate the effects of low air temperature during nocturnal (T N ) and diurnal (T D ) periods as well as the substrate temperature (T S ) on photosynthesis of 'Valencia' orange tree grafted on Rangpur lime rootstock. The experiment was carried out in a growth chamber with seven-month-old plants. The plants were exposed to the following temperature regimes: low substrate temperature (LT S , with: T D = 28°C, T N = 20°C, T S = 10°C); low air temperature during night (LT N , with: T D = 28°C, T N = 10°C, T S = 26°C); low temperature during nighttime and also low substrate temperature (LT SN, with: T D = 28°C, T N = 10°C, T S = 10°C); low air temperature during both diurnal and nocturnal periods (LT ND , with: T D = 17°C, T N = 10°C, T S = 26°C); and finally to low air temperature (night and day) and low substrate temperature (LT SND , with: T D = 17°C, T N = 10°C, T S = 10°C). As reference (control), plants were subjected to T D = 28°C, T N = 20°C, and T S = 26°C. Measurements of leaf gas exchange, photochemical activity and carbohydrate concentrations were performed after six days of exposure to each thermal treatment. Compared to the control, all thermal regimes caused reductions in photosynthesis due to diffusive and metabolic limitations. The photoinhibition was transient in plants exposed to night and substrate low temperatures, whereas it was severe and chronic in plants subjected to chilling during the diurnal period. However, the lowest photosynthesis was observed in plants with low substrate temperature of 10°C (in LT S , LT SND and LT SN treatments), regardless of air temperature. The occurrence of cold night and/or its combination with low substrate temperature caused accumulation of starch in leaves. When considering carbohydrate concentrations in stems and roots, it was not possible to establish a clear response pattern to chilling. In conclusion, the low substrate temperature causes a greater reduction of CO 2 assimilation in citrus plants as compared to the occurrence of low air temperature, being such response a consequence of diffusive and biochemical limitations.