Browsing by Author "Silva, Aurora"
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- Antibacterial Use of Macroalgae Compounds against Foodborne PathogensPublication . Silva, Aurora; Silva, Sofia A.; Lourenço-Lopes, C.; Jimenez-Lopez, C.; Carpena, M.; Gullón, P.; Fraga-Corral, M.; Domingues, Valentina; Barroso, M. Fátima; Simal-Gandara, J.; Prieto, M. A.The search for food resources is a constant in human history. Nowadays, the search for natural and safe food supplies is of foremost importance. Accordingly, there is a renewed interest in eco-friendly and natural products for substitution of synthetic additives. In addition, microbial contamination of food products during their obtaining and distribution processes is still a sanitary issue, and an important target for the food industry is to avoid food contamination and its related foodborne illnesses. These diseases are fundamentally caused by certain microorganisms listed in this review and classified according to their Gram negative or positive character. Algae have proven to possess high nutritional value and a wide variety of biological properties due to their content in active compounds. Among these capabilities, macroalgae are recognized for having antimicrobial properties. Thus, the present paper revises the actual knowledge of microbial contaminants in the food industry and proposes antimicrobial algal compounds against those pathogenic bacteria responsible for food contamination as valuable molecules for its growth inhibition. The capacity of algae extracts to inhibit some major food pathogen growth was assessed. Moreover, the main applications of these compounds in the food industry were discussed while considering their favorable effects in terms of food safety and quality control
- Ecotoxicity tests using the green algae chlorella vulgaris — a useful tool in hazardous effluents managementPublication . Silva, Aurora; Figueiredo, Sónia Adriana; Sales, M. Goreti F.; Delerue-Matos, CristinaThe treatment efficiency of laboratory wastewaters was evaluated and ecotoxicity tests with Chlorella vulgaris were performed on them to assess the safety of their environmental discharge. For chemical oxygen demand wastewaters, chromium (VI), mercury (II) and silver were efficiently removedby chemical treatments.Areduction of ecotoxicitywas achieved; nevertheless, an EC50 (effective concentration that causes a 50% inhibition in the algae growth) of 1.5% (v/v) indicated still high level of ecotoxicity. For chloride determination wastewaters, an efficient reduction of chromium and silver was achieved after treatment. Regarding the reduction of ecotoxicity observed, EC50 increased from 0.059% to 0.5%, only a 0.02% concentration in the aquatic environment would guarantee no effects. Wastewaters containing phenanthroline/iron (II) complex were treated by chemical oxidation. Treatmentwas satisfactory concerning chemical parameters, although an increase in ecotoxicitywas observed (EC50 reduced from 0.31% to 0.21%). The wastes from the kinetic study of persulphate and iodide reaction were treated with sodium bisulphite until colour was removed. Although they did not reveal significant ecotoxicity, only over 1% of the untreated waste produced observable effects over algae. Therefore, ecotoxicity tests could be considered a useful tool not only in laboratory effluents treatment, as shown, but also in hazardous wastewaters management.
- Enhancing the detection of Dinophysis spp. using electrochemical genosensorsPublication . Pereira, Eduarda; Silva, Aurora; Morais, Stephanie L.; Costa-Rama, Estefanía; Moreira, Patrícia R.; Fraga-Corral, M.; Torrado, Ana M.; Rodríguez, Francisco; Barros, Piedade; Cruz, Agostinho; Delerue-Matos, Cristina; Prieto, M. A.; Simal-Gandara, J.; Silva, Nádia F. D.; Santos, Marlene; Barroso, M. FátimaHarmful algal blooms (HABs) pose a significant threat to the environment and public health. These blooms are defined by an accumulation of microscopic algae in water, and they can occur inlakes, rivers, estuaries, orcoastal areas. Factors like the unregulated runoff of agricultural and industrial wastes into the aquatic environment are believed to have transformed these ecosystems into favorable habitats for algae growth and proliferation. As a result, the frequency of these blooms is rising worldwide. Although these blooms are mostly harmless, certain species, namely dinoflagellates from the genus Dinophysis, produce toxins that pose a risk for human health. Therefore, the need for technological developments towards fast and precise detection of these toxin-producing microalgae is critical to prevent socio economical damages, as well as to assess the ecological status of marine ecosystems. In this work, an analytical approach based on an electrochemical genosensor device was developed to create a low-cost platform able to detect two dinoflagellate species from the genus Dinophysis: D.acuminataand D.acuta. The design of the DNA-based sensor involved three key steps: i) Sensing phase: consisted by a mixed self-assembled monolayer composed by a linear DNA capture probe and mercaptohexanol on to the disposable screen-printed gold electrodessurface; ii) Hybridization of complementary DNA sequence by using a sandwich format assay with enzymatic labels and iii) Electrochemical detection by chronoamperometry using an enzymatic scheme to amplify the electrochemical signal. The best analytical conditions used to study the relationship between electrochemical signal and DNA target concentration, to produce the best electrochemical genosensor device. Molecular biology tools, namely Polymerase Chain Reaction (PCR), will be used for further validation of the electrochemical genosensor to confirm its reliability. These advancements in analytical technologies contribute to the on going efforts in environmental management and public health protection by providing effective means for detectingand mitigating the risks associated with HABs. Further research and widespread implementation of these methods are required to ensure the safety and sustainability of aquatic ecosystems, safeguard public health, and facilitate proactive environmental management practices.
- Flavoured versus natural waters: macromineral (Ca, Mg, K, Na) and micromineral (Fe, Cu, Zn) contentsPublication . Barroso, M. Fátima; Silva, Aurora; Ramos, Sandra; Oliva-Teles, Maria Teresa; Delerue-Matos, Cristina; Sales, M. Goreti F.; Oliveira, M. Beatriz P. P.Macro (Ca, Mg, K, Na) and micromineral (Fe, Zn, Cu) composition of 39 waters was analysed. Determinations were made by atomic flame spectrophotometry for macrominerals and electrothermic atomisation in graphite furnace for microminerals. Mineral contents of still or sparkling natural waters (without flavours) changed from brand to brand. Mann–Whitney test was used to search for significant differences between flavoured and natural waters. For that, the concentration of each mineral was compared to the presence of flavours, preservatives, acidifying agents, fruit juice and/or sweeteners, according to the labelled composition. The statistical study demonstrated that flavoured waters generally have increased contents of K, Na, Fe and Cu. The added preservatives also led to significant differences in the mineral composition. Acidifying agents and fruit juice can also be correlated to the increase of Mg, K, Na, Fe and Cu. Sweeteners do not provide any significant difference in Ca, Mg, Fe and Zn contents.
- Fucoxanthin’s Optimization from Undaria pinnatifida Using Conventional Heat Extraction, Bioactivity Assays and In Silico StudiesPublication . Lourenço-Lopes, Catarina; Fraga-Corral, Maria; Soria-Lopez, Anton; Nuñes-Estevez, Bernabe; Barral-Martinez, Marta; Silva, Aurora; Li, Ningyang; Liu, Chao; Simal-Gandara, Jesus; Prieto, Miguel A.Brown macroalgae are a potential source of natural pigments. Among them, Undaria pinnatifida is recognized for its high concentration of fucoxanthin (Fx), which is a pigment with a wide range of bioactivities. In this study, three independent parameters were optimized for conventional heat extraction (CHE) to maximize the recovery of Fx from Undaria pinnatifida. Optimal conditions (temperature = 45 °C, solvent = 70%, and time = 61 min) extracted 5.1 mg Fx/g dw. Later, the bioactivities of the Fx-rich extracts (antioxidant, antimicrobial, and neuroprotective) were assessed using in vitro and in silico approaches. In vitro assays indicated that Fx has a strong antioxidant capacity and even stronger antimicrobial activity against gram-positive bacteria. This data was supported in silico where Fx established a high binding affinity to DR, a Staphylococcus aureus protein, through aa ALA-8, LEU-21, and other alkane interactions. Finally, the in vitro enzymatic inhibition of AChE using Fx, was further supported using docking models that displayed Fx as having a high affinity for aa TYR72 and THR 75; therefore, the Fx extraction behavior explored in this work may reduce the costs associated with energy and solvent consumption. Moreover, this paper demonstrates the efficiency of CHE when recovering high amounts of Fx from Undaria pinnatifida. Furthermore, these findings can be applied in different industries.
- Heterogeneous kinetics of the reduction of chromium (VI) by elemental ironPublication . Fiúza, António; Silva, Aurora; Carvalho, Goreti; Fuente, António V. de la; Delerue-Matos, CristinaZero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III) in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily modelled using a pseudo-first-order kinetics which is inappropriate for a heterogeneous reaction. We assumed a shrinking particle type model where the kinetic rate is proportional to the available iron surface area, to the initial volume of solution and to the chromium concentration raised to a power ˛ which is the order of the chemical reaction occurring at surface. We assumed α= 2/3 based on the likeness to the shrinking particle models with spherical symmetry. Kinetics studies were performed in order to evaluate the suitability of this approach. The influence of the following parameters was experimentally studied: initial available surface area, chromium concentration, temperature and pH. The assumed order for the reaction was confirmed. In addition, the rate constant was calculated from data obtained in different operating conditions. Digital pictures of iron balls were periodically taken and the image treatment allowed for establishing the time evolution of their size distribution.
- A HPLC‐DAD method for identifying and estimating the content of fucoxanthin, β‐carotene and chlorophyll a in brown algal extractsPublication . Lourenço-Lopes, C.; Fraga-Corral, M.; Garcia-Perez, P.; Carreira-Casais, A.; Silva, Aurora; Simal-Gandara, J.; Prieto, M.A.Seaweeds are photosynthetic organisms that have high contents of pigments. The coloration of each alga is defined by the content and combination of pigments synthesized, which varies among species and environmental conditions. The most abundant pigments in algae are chlorophylls and carotenoids, lipophilic molecules that can be used as natural colorants and have high acceptance by consumers. In this work, a simple and short hands-on time HPLC-DAD method for identifying and estimating the pigment content of algal extracts, specifically fucoxanthin, β-carotene and chlorophyll a was carried out. Using this optimized method, a pigment screening was performed on the ethanolic extracts obtained by ultrasound-assisted extraction from nine brown algal from the Atlantic coastline: Ascophyllum nodosum, Bifurcaria bifurcata, Fucus spiralis, Himanthalia elongata, Laminaria saccharina, Laminaria ochroleuca, Pelvetia canaliculata, Sargassum muticum and Undaria pinnatifida. HPLC results permitted to highlight L. saccharina and U. pinnatifida as promising sources of these three target pigments containing a total amount of 10.5 – 11.5 mg per gram of dry weight. Among them, the most abundant one was fucoxanthin, an added-value compound with a high potential to be commercially exploited by different industries, such as the food, cosmetic, and pharmaceutical sectors.
- Impact of excipients in the chronic toxicity of fluoxetine on the alga Chlorella vulgarisPublication . Silva, Aurora; Santos, Lúcia; Delerue-Matos, Cristina; Figueiredo, Sónia AdrianaFluoxetine is a selective serotonin reuptake inhibitor (SSRI) widely used in the treatment of major depression. It has been detected in surface and wastewaters, being able to negatively affect aquatic organisms. Most of the ecotoxicity studies focused only in pharmaceuticals, though excipients can also pose a risk to non-target organisms. In this work the ecotoxicity of five medicines (three generic formulations and two brand labels) containing the same active substance (fluoxetine hydrochloride) was tested on the alga Chlorella vulgaris, in order to evaluate if excipients can influence their ecotoxicity. Effective concentrations that cause 50% of inhibition (EC50) ranging from 0.25 to 15 mg L−1 were obtained in the growth inhibition test performed for the different medicines. The corresponding values for fluoxetine concentration are 10 times lower. Higher EC50 values had been published for the same alga considering only the toxicity of fluoxetine. Therefore, this increase in toxicity may be attributed to the presence of excipients. Thus more studies on ecotoxicological effects of excipients are required in order to assess the environmental risk they may pose to aquatic organisms.
- Is it possible to prevent Harmful Algal Blooms? An electrochemical genosensor that detects dinoflagellates could be the answerPublication . Pereira, Eduarda; Silva, Aurora; Morais, Stephanie L.; Costa-Rama, Estefanía; Moreira, Patrícia R.; Fraga-Corral, M.; Torrado, Ana M.; Rodríguez, Francisco; Barros, Piedade; Cruz, Agostinho; Delerue-Matos, Cristina; Prieto, M. A.; Simal-Gandara, J.; Silva, Nádia F. D.; Santos, Marlene; Barroso, M. FátimaHarmful Algal Blooms (HABs) are a very common phenomenon in the last few years that results from the accumulation of microalgae, such as dinoflagellates of the Dinophysis genus. Hence, the development of analytical technologies capable of detecting these microorganisms and thereby avoiding environmental and public health crisis, has become a major priority. Biosensors have been gaining recognition lately given their notable assets: they are fast, sensitive and allow in situ analysis.
- Macroalgae as a Source of Valuable Antimicrobial Compounds: Extraction and ApplicationsPublication . Silva, Aurora; Silva, Sofia A.; Carpena, M.; Garcia-Oliveira, P.; Gullón, P.; Barroso, M. Fátima; Prieto, M.A.; Simal-Gandara, J.n the last few decades, attention on new natural antimicrobial compounds has arisen due to a change in consumer preferences and the increase in the number of resistant microorganisms. Macroalgae play a special role in the pursuit of new active molecules as they have been traditionally consumed and are known for their chemical and nutritional composition and their biological properties, including antimicrobial activity. Among the bioactive molecules of algae, proteins and peptides, polysaccharides, polyphenols, polyunsaturated fatty acids and pigments can be highlighted. However, for the complete obtaining and incorporation of these molecules, it is essential to achieve easy, profitable and sustainable recovery of these compounds. For this purpose, novel liquid–liquid and solid–liquid extraction techniques have been studied, such as supercritical, ultrasound, microwave, enzymatic, high pressure, accelerated solvent and intensity pulsed electric fields extraction techniques. Moreover, different applications have been proposed for these compounds, such as preservatives in the food or cosmetic industries, as antibiotics in the pharmaceutical industry, as antibiofilm, antifouling, coating in active packaging, prebiotics or in nanoparticles. This review presents the main antimicrobial potential of macroalgae, their specific bioactive compounds and novel green extraction technologies to efficiently extract them, with emphasis on the antibacterial and antifungal data and their applications.