Browsing by Author "Carvalho, Isabel Saraiva de"
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- A realistic scenario on microalgae based biodiesel production: third generation biofuelPublication . Ananthi, V.; Raja, Rathinam; Carvalho, Isabel Saraiva de; Brindhadevi, Kathirvel; Pugazhendhi, Arivalagan; Arun, A.Microalgae are the widely employed sources of third generation biofuels, which attracted huge attention by the researchers of the present decade because of their great productivity with lipid content. But to date, the utilization of microalgae for renewable biofuel production is not considered economically viable. The various growth modes employed for microalgal cultivation, such as phototrophic, heterotrophic, mixotrophic, photo-heterotrophic has been compared and conferred in the current investigation. A wide variety of microalgal harvesting techniques that balance energy and economic sustainability is being carried out nowadays. Based on the culture employed, mode and conditions of microalgal cultivation, the choice of bioreactor differs like an open system or closed system bioreactor. This review discusses the basis, key challenges and the future perspective of present-day microalgal cultivation conditions regarding biomass and lipid production. Concurrently the impacts of cultivation mode, bioreactor used for lipid productivity to improve profitable microalgal biodiesel have also been summarized.
- Accumulation of fatty acids in purslane grown in hydroponic salt stress conditionsPublication . Anastácio, Ana; Carvalho, Isabel Saraiva dePurslane (Portulaca oleracea L.) is the eighth most common plant distributed throughout the world being a heat- and drought-tolerant plant. In this study, we evaluated the effect of salinity on total amounts of fatty acids (FAs) and ω3/ω6 ratio in leaves of purslane. Plants exposed to four levels of chloride salinity in the root zone (60, 90, 120 and 240 mM NaCl) for 40 days showed no signs of toxicity or death. The main FAs detected were C16:0>C18:3>C18:2. The ratio of ω6 to ω3 was not changed with salt stress. Hierarchic cluster analysis brought together 60 and 90 mM NaCl in control plants, based on their FA content. The results of this study confirm the purslane as a plant rich in FAs whose consumption may contribute to dietary intake of ω3 polyunsaturated fatty acid, with obvious benefits to human health.
- An Indian scenario on renewable and sustainable energy sources with emphasis on algaePublication . Hemaiswarya, Shanmugam; Raja, R.; Carvalho, Isabel Saraiva de; Ravikumar, R.; Zambare, Vasudeo; Barh, DebmalyaIndia is the fifth largest primary energy consumer and fourth largest petroleum consumer after USA, China, and Japan. Despite the global economic crisis, India’s economy is expected to grow at 6 to 8 %/year. There is an extreme dependence on petroleum products with considerable risks and environmental issues. Petroleum-derived transport fuels are of limited availability and contribute to global warming, making renewable biofuel as the best alternative. The focus on biogas and biomass-based energy, such as bioethanol and biohydrogen, will enhance costeffectiveness and provide an opportunity for the rural community. Among all energy sources, microalgae have received, so far, more attention due to their facile adaptability to grow in the photobioreactors or open ponds, high yields, and multiple applications. Microalgae can produce a substantial amount of triacylglycerols as a storage lipid under photooxidative stress or other adverse environmental conditions. In addition to renewable biofuels, they can provide different types of highvalue bioproducts added to their advantages, such as higher photosynthetic efficiency, higher biomass production, and faster growth compared to any other energy crops. The viability of first-generation biofuels production is, however, questionable because of the conflict with food supply. In the future, biofuels should ideally create the environmental, economic, and social benefits to the communities and reflect energy efficiency so as to plan a road map for the industry to produce third-generation biofuels.
- Antioxidant activities, distribution of phenolics and free amino acids of Erica australis L. leaves and flowers collected in Algarve, PortugalPublication . Nunes, Ricardo; Carvalho, Isabel Saraiva deLeaves and flowers from Erica plant possess nutritional and medicinal properties. We determined the antioxidant activity, phenolic, flavonoid and amino acid profiles of the leaves and flowers of this plant. Total amino acid content varied from 28 to 49 and essential amino acids from 8 to 20mg/g for flowers and leaves, respectively, with different distributions within the plant. From 16 phenolic compounds identified, delphinidin-3-glucoside, caffeic acid and cyanidin-3,5-glucoside in leaves and pelargonidin-3,5-glucoside in flowers were the compounds in highest amount, all with over 500g/g. Although flowers had higher contents of phenolic compounds (4000g/g) than leaves (3400g/g), they showed lower antioxidant activity, indicating that the antioxidant activity depends not only on the content of phenolics, but also on their type. This study shows that this plant has the potential to be used as an extra dietary source of amino acids and phenolic compounds and its consumption may provide health benefits.
- Antioxidant and free radical scavenging activities of different plant parts from two Erica speciesPublication . Nunes, Ricardo; Anastácio, Ana; Carvalho, Isabel Saraiva deAqueous extractions from two species of Erica consumed as infusions in several countries to heal ailments were investigated for their phenolic and flavonoid contents, along with antioxidant capacity and radical scavenging capacity using total antioxidant activity, ferric-reducing antioxidant power, reducing power, 1,1-diphenyl-2-picrylhydrazyl and 2-2'-azino-bis(3 ethylbenzothiazoline-6-sulfonic acid) radicals, respectively. Antioxidant properties and total phenolic content differed significantly among these plants. Aqueous extracts of leaves possessed, on average, the highest antioxidant capacity and phenolic content (34.09 ± 10.81 mg ascorbic acid equivalent/g dry weight and 30.59 ± 10.19 mg gallic acid equivalent/g dry weight, respectively) of all three plant parts. A significant correlation (r2 = 0.952) between antioxidant capacity and total phenolic content was found, indicating that phenolic compounds are the major contributors to the antioxidant properties of these plants. Upon application of hierarchical cluster analysis to the results obtained, leaves with flowers were grouped in one cluster, whereas branches remained in another cluster, showing little interference from the collection site or species factors.
- Chemical and microbial changes during the natural fermentation of strawberry tree (Arbutus unedo L.) fruitsPublication . Cavaco, Teresa; Longuinho, Carla; Quintas, Célia; Carvalho, Isabel Saraiva deAguardente de medronho is the name given in Portugal to a spirit made from the fermented fruit of Arbutus unedo (strawberry tree), a plant grown in the Mediterranean region. In order to gain a better understanding of the fermentation process, as it is performed in the farms, a natural fermentation with wild microbiota was carried out during 36 days, and some physicochemical and microbiological parameters were studied. The microbial parameters analyzed were total viable, lactic and acetic acids bacteria, and yeast counts. The physicochemical parameters monitored were sugars, minerals, ethanol, organic acids and pH. Yeasts were the main responsible for the fermentation of the fruits, as the lactic and acetic acids bacteria are absent. As the fermentation progressed, the sugars increased during the first 2 days and gradually decreased along the fermentation period. Maintaining the good quality of the product could contribute to the preservation and valorization of traditional resources that are of great importance to prevent their disappearance.
- Effect of Betula pendula leaf extract on alpha-glucosidase and glutathione level in glucose-induced oxidative stressPublication . Bljajic, Kristina; Sostaric, Nina; Petlevski, Roberta; Vujic, Lovorka; Brajkovic, Andrea; Fumic, Barbara; Carvalho, Isabel Saraiva de; Koncic, Marijana ZovkoB. pendula leaf is a common ingredient in traditional herbal combinations for treatment of diabetes in southeastern Europe. Present study investigated B. pendula ethanolic and aqueous extract as inhibitors of carbohydrate hydrolyzing enzymes, as well as their ability to restore glutathione concentration in Hep G2 cells subjected to glucose-induced oxidative stress. Phytochemical analysis revealed presence of rutin and other quercetin derivatives, as well as chlorogenic acid. In general, ethanolic extract was richer in phenolic substances than the aqueous extract. Furthermore, a comprehensive analysis of antioxidant activity of two extracts (determined by DPPH and ABTS radical scavenging activity, total antioxidant activity, and chelating activity as well as ferric-reducing antioxidant power) has shown that ethanolic extract was better radical scavenger and metal ion reductant. In addition, ethanolic extract effectively increased cellular glutathione levels caused by hyperglycemia and inhibited alpha-glucosidase with the activity comparable to that of acarbose. Therefore, in vitro research using B. pendula plant extracts has confirmed their antidiabetic properties.
- Effect of Erica australis extract on Caco-2 cells, fibroblasts and selected pathogenic bacteria responsible for wound infectionPublication . Nunes, Ricardo; Rodrigues, Susana; Pasko, Pawel; Tyszka-Czochara, Malgorzata; Grenha, Ana; Carvalho, Isabel Saraiva dePlants from the genus Erica are used in many countries to treat several ailments. In this work we intend to evaluate the potential in vivo benefits of Erica australis L. by testing in vitro the effect induced by the plant extract when in contact with BJ fibroblasts (3 and 9 hours) and Caco-2 cells (3, 6 and 24 hours). Effects on five pathogenic microorganisms(Enterococcus faecalis, Bacillus cereus, Escherichia coli, Staphylococcus aureus and Listeria monocytogenes) were also determined. It was found that the extracts enhanced fibroblast proliferation (maximum of 484% of control at 6 hour exposure) while Caco-2 cells viability was reduced in a concentration and time dependent manner (minimum of 22.3% of control at 24 hour exposure). Antimicrobial effects were also detected, with differences registered among the plant parts and solvent used, with the lowest minimum concentration for diffusion inhibition (MCDI) of 1 mg/mL. Results obtained with the fibroblasts and bacteria strongly show that this plant has potential to be used in wound healing as a stimulant of fibroblast growth and disinfection, as well as an antibiotic. Results obtained with Caco-2 cells indicate this plant also has some potential for and application as anticancer agent.
- Effect of photoperiod on flavonoid pathway activity in sweet potato (Ipomoea batatas (L.) Lam.) leavesPublication . Carvalho, Isabel Saraiva de; Cavaco, Teresa; Carvalho, Lara M.; Duque, PaulaCompared with those of major commercial leafy vegetables, leaves of sweet potato have higher contents of flavonoids and phenolic acids, which provide significant health benefits and may be used as natural colourants. We have analysed the expression of key flavonoid biosynthesis genes using RT-PCR and the accumulation of polyphenolic compounds using high-performance liquid chromatography coupled to a photodiode-array detector, during the development of leaves of sweet potato plants growing under either long day or short day photoperiods. A massive induction of flavonoid pathway gene expression, correlating with a dramatic increase in the content of an anthocyanin, catechins, flavonols, hydroxycinnamic acids and hydroxybenzoic acids, was observed during sweet potato leaf exposure to a long day photoperiod. These results provide further support for the protective role of flavonoids and phenolic acids against enhanced light exposure in plants.
- Effects of salt stress on purslane (Portulaca oleracea) nutritionPublication . Teixeira, Monica; Carvalho, Isabel Saraiva deThe objective of this study was to determine the influence of saline stress on the chemical composition of purslane (Portulaca oleracea), in particular the mineral composition. Four salinity levels were investigated using irrigation solutions with electrical conductivity values of 0.8, 6.8, 12.8 and 24.2 dS m−1 and two planting dates (May and July) were tested. Samples of full-grown leaf and stems of purslane were harvested after 7 and 15 days of the saline treatment exposure. Chemical analysis (dry matter basis) of leaves showed significant differences among the different saline treatments for all the characteristics measured. Salinity levels, planting date and harvest time significantly influenced (P < 0.05) the levels of crude protein, total lipids, ash and carbohydrate content. Salinity treatments did not significantly (P > 0.05) affect the water content of purslane leaves. The crude protein content of purslane leaves decreased with increasing salinity levels and time of exposure to treatment. However, carbohydrates and mineral residue content increased. An unusual phenomenon was noted for intermediate salinity levels, whereby an increase in total lipid content was measured in leaves of plants exposed to salinity treatments of 6.8 and 12.8 dS m−1. The highest mineral residue content was seen in leaves of purslane exposed to the highest salinity treatment. The mineral composition was also affected by salinity levels, Na and Cl uptake, and accumulation increased with increasing salinity in irrigation solution; Mg concentration was not significantly (P > 0.05) affected by salinity levels, although a slight increase was seen, and Ca, K and Zn levels significantly (P < 0.05) decreased. Ca and Zn preferentially accumulated in the leaves, while K and Na values were higher in the stems. A significant increase (P < 0.05) in relative ratio of Na/K, Mg/K, Na/Ca and Mg/Ca was observed with increasing salinity levels. A decrease in the yield of purslane was only observed for the most severe saline treatment, where the highest ratio of Mg/Ca was seen. This study reveals that purslane is relatively tolerant to conditions of moderate salinity, thus improving its potential to become a key vegetable crop for animal and human consumption.