ISEP - Departamento de Engenharia Química
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- Antioxidant properties of hydroxycinnamic acids: a review of structure- activity relationshipsPublication . Razzaghi-Asl, N.; Garrido, Jorge; Khazraei, H.; Borges, Fernanda; Firuzi, O.Hydroxycinnamic acids (HCAs) are important phytochemicals possessing significant biological properties. Several investigators have studied in vitro antioxidant activity of HCAs in detail. In this review, we have gathered the studies focused on the structure-activity relationships (SARs) of these compounds that have used medicinal chemistry to generate more potent antioxidant molecules. Most of the reports indicated that the presence of an unsaturated bond on the side chain of HCAs is vital to their activity. The structural features that were reported to be of importance to the antioxidant activity were categorized as follows: modifications of the aromatic ring, which include alterations in the number and position of hydroxy groups and insertion of electron donating or withdrawing moieties as well as modifications of the carboxylic function that include esterification and amidation process. Furthermore, reports that have addressed the influence of physicochemical properties including redox potential, lipid solubility and dissociation constant on the antioxidant activity were also summarized. Finally, the pro-oxidant effect of HCAs in some test systems was addressed. Most of the investigations concluded that the presence of ortho-dihydroxy phenyl group (catechol moiety) is of significant importance to the antioxidant activity, while, the presence of three hydroxy groups does not necessarily improve the activity. Optimization of the structure of molecular leads is an important task of modern medicinal chemistry and its accomplishment relies on the careful assessment of SARs. SAR studies on HCAs can identify the most successful antioxidants that could be useful for management of oxidative stress-related diseases.
- Application of domestic greywater for irrigating agricultural products: A brief studyPublication . Gorgich, M.; Mata, T.M.; Martins, A; Caetano, Nídia; Formigo, N.The decline in annual rainfall, coupled with the growing demand for water in agricultural fields, triggered a new crisis in today’s world. Thus, the focus is on finding solutions to new water resources. Taking a look at the normal daily life, most of the households’ effluents can be ranked into a less-polluted category, called greywater. Excluding human dejects, greywater comprises the outflow from washing machines, dishwashers and bathtubs. It is considered an effluent with a more economic treatment, because it contains less microbial pollution. Hence, this work revises the effects of greywater irrigation on the quality of crops, and provides a comprehensive study of the effects of greywater on the quality of soil. Furthermore, a comprehensive discussion is carried out to evaluate the energy consumption of facilities for both greywater and wastewater treatment to provide water used in irrigation. It also addresses current methodologies for treating greywater and evaluates the effects of crops irrigation with treated and untreated greywater, indicating the type of treatment chosen depending on the type of crop to be irrigated.
- Barbecue Grill Workers Occupational Exposure to Particulate-Bound Polycyclic Aromatic HydrocarbonsPublication . Oliveira, Marta; Capelas, Sílvia; Delerue-Matos, Cristina; Pereira, Isabel; Morais, SimoneDuring a regular working day, grill workers are exposed to the emissions of charcoal-fired cooking activities, which include polycyclic aromatic hydrocarbons (PAHs) that are among the most health relevant compounds. Thus, in this work, the particulate matter at the breathing air zone of grill workers from a barbecue restaurant was sampled and the concentration of eighteen particulate-bound PAHs was determined by liquid chromatography with fluorescence and diode array detection. Median level of total PAHs (ΣPAHs) during 5 consecutive hours of exposure to barbecue fumes was 77.2 ng/m3 (maximum values of 261 ng/m3). Benzo(g,h,i)perylene, phenanthrene, and acenaphthylene were the most abundant compounds (82.7% of ΣPAHs). Levels of benzo(a)pyrene and total carcinogenic PAHs (naphthalene, benz(a)anthracene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, chrysene, and indeno(1,2,3-cd)pyrene) varied between 0.03–0.79 ng/m3 and 2.10–36.7 ng/m3, respectively. Grill worker’s exposure to PAHs was well below the existent PAHs occupational threshold limit value of 200 µg/m3 proposed by the American Conference of Governmental Industrial Hygienists for an 8-h of exposure to coal tar pitch volatiles. Some preventive measures such as adequate maintenance of barbecue ventilation system, regular wash of workers exposed skin and the use of clean working clothes can contribute to reduce grill worker’s occupational exposure to PAHs.
- Beyond compost: Using urban biowaste derived compost to produce new fertilizing productsPublication . Machado, Telmo; Santos, Carolina Ascenso; Raimundo, Délio; Chaves, BeneditaThe agro-food sector is a contributor to CO2 emissions and polluter due to its difficulty to deal with waste generation. Using the farm to fork concept we can observe that waste is produced in every link of the food value chain. Nevertheless, efforts are being made worldwide to reduce its environmental impact - from producing food with precision agriculture to sustainable food packaging systems – hoping to influence the way each country manages its biowaste. In this work we present the first results of an experiment, conducted under the project “BIOMA – Bioeconomy integrated solutions for the mobilization of the Agro-food market”, to produce a Urban waste compost based plant biostimulant.
- Biodiesel Production Systems: Operation, Process Control and TroubleshootingPublication . Caetano, Nídia; Ribeiro, Vera; Ribeiro, Leonardo; Baptista, Andresa; Monteiro, JoaquimBiodiesel is a renewable fuel, produced from waste cooking oils, animal fats, vegetable and algae oils. Its use is intended to replace diesel in conventional diesel engines, causing lower polluting emissions. To produce biodiesel, certain details must be carefully considered, namely feedstock composition, reaction parameters, process conditions, process equipment, purification processes, analysis of biodiesel properties, troubleshooting and storage. In what concerns feedstock composition, parameters such as acidity, insolubles, moisture, phospholipids, sulphur, polymerized triglycerides, impurities, etc., must be determined to decide about the pretreatment steps (washing, degumming, filtration, bleaching, deodorization, among others) to be implemented, and the need for esterification prior to transesterification. In what concerns the selection of process equipment some questions arise, namely the materials, heating methods and thermal insulation to use, alternatives to enhance the reaction, need for neutralization and process control system. The purification process includes biodiesel purification, methanol recovery and glycerine valorisation. The excess methanol must be recovered from biodiesel and glycerine by distillation and reused in the process while glycerine can be further purified and sold for application from the chemical to the pharmaceutical industry. The quality of biodiesel must be certified by the analyses performed according to the standards (e.g. EN 14214, ASTM D6751). Troubleshooting is needed in biodiesel production during start-up and under steady production of a facility; problems may arise regarding quality and appearance of biodiesel, reaction conditions, methanol removal, stirring in reactors, glycerine and biodiesel separation, as well as excess of water and other feedstock impurities. Biodiesel can be stored for up to 6 months; its storage poses challenges concerning degradation by contact with air and light, which cause oxidation. Some additives could extend the lifespan of biodiesel by increasing oxidation stability; other technique is the fractionation to remove the undesired fatty acid methyl ester (FAME).
- Bioethanol from Brewers’ Spent Grain: Pentose FermentationPublication . Mata, Teresa M.; Tavares, Tomás F.; Meireles, Sónia; Caetano, Nídia SáThis work aims to perform a preliminary optimization of the fermentation of brewers’ spent grain (BSG) sugars to bioethanol, focusing on the pentose sugars. Firstly, it was conducted the acid pre-treatment and enzymatic hydrolysis for studying different reaction times and amounts of enzymes in order to convert cellulose and hemicelluloses into simple sugars. The greatest amount of total sugars achieved experimentally is 5.56 g/ 25g of dry BSG, corresponding to a sugars maximum conversion of 22.24 % from a BSG sample with about 6 % cellulose and about 40 % hemicelluloses. This was obtained by sequentially adding the acids HCl and HNO3 with 1 wt% of concentration to BSG to perform the pre-treatment, simultaneously with 1.0657 g of Glucanex 100g and 2.0 mL of Ultraflo L for the hydrolysis. Secondly, it was studied the fermentation step, using both synthetic medium and BSG hydrolyzate, and the yeasts Pichia stipitis NCYC 1541 (P. stipitis) and Kluyveromyces marxianus NYCY 2791 (K. marxianus). Results show that the fermentation efficiency of all sugars in the synthetic media is higher than 80_% for both yeasts, but in the BSG hydrolyzate it is just 45.10 %for P. stipitis and 36.58 % for K. marxianus for a 72 h fermentation time at a 30 °C temperature. The theoretical ethanol yield from BSG hydrolyzates is 0.27 and 0.19 g ethanol/ g of sugars for respectively, P. stipitis and K. marxianus, but the actual ethanol yield obtained in this work is 0.0856 and 0.0308 g ethanol/ g of sugars, respectively that is three times smaller than the theoretical yield for P. stipitis and six times smaller for K. marxianus, which can be attributed to the presence of inhibitors resulting from the previous steps.
- Biofixation of CO2 emissions from natural gas combined cycle power plantPublication . Oliveira, Gisela M.; Caetano, Nídia; Mata, Teresa M.; Martins, António A.The growing impacts of climate change mainly due to the increasing emissions of GHG, especially carbon dioxide, has led to the development and implementation of specific strategies and policies to reduce them. Carbon capture and utilization (CCU) is currently seen as a good option, as it contributes to reduce the net carbon emissions and fulfil the goals of the Paris Agreement. This work analyses the economic potential of CO2 biofixation by microalgae from the exhaust gas of a Portuguese Natural Gas Combined Cycle (NGCC) power plant. Literature and real operational data are used, collected from reports of Portuguese power generation companies. A preliminary design and economic analysis of the carbon biofixation system was done. Results show that, although requiring a very large investment, the process is economically viable. In further studies a more in depth approach and detailed project combined with a sensitivity analysis, and a comparison with the chemical based CO2 fixation will be done.
- Biotechnological potential of Phaeodactylum tricornutum for biorefinery processesPublication . Branco-Vieira, Monique; San Martin, Sergio; Agurto, Cristian; Freitas, Marcos A.V.; Martins, António A.; Mata, Teresa M.; Caetano, NídiaMicroalgae are a rich source of proteins, carbohydrates and lipids, among other components, and thus, are considered to be the next generation biomass. However, in order to enhance the economic viability of its industrial production, all biomass components need to be valorized, requiring a multi-product biorefinery. Thus, this work proposes and conceptually analyses biorefinery processes for valorizing Phaeodactylum tricornutum for biofuels and high-value compounds, based on real data from a pilot-scale process. The algal biomass was biochemically characterized and the production was scaled-up to an industrial approach to analyze three biorefinery configurations, based on a 18 ton·year−1 of microalga biomass. The biomass revealed a composition of 7.85 wt% carbohydrates, 38.40 wt% proteins, 9.08 wt% lipids, 0.86 wt% fucoxanthin and 5.19 wt% biosilica. The biorefinery process addressed for biofuels production has an estimated annual production of 1.72, 0.35 and 1361 m3·year−1 of respectively biodiesel, bioethanol and biomethane. The biorefinery addressed for high-value compounds yields 0.18, 0.93 and 6.95 ton·year−1 of respectively fucoxanthin, biosilica and protein. The biorefinery designed for valorizing full microalgae biomass, showed to be more beneficial for promoting a circular economy. Biorefinery approach is useful for making sound and profitable decisions regarding microalgae bioproducts.
- Carbon nanotube β-cyclodextrin-modified electrode for quantification of cocaine in seized street samplesPublication . Garrido, Jorge; Borges, F.; Brett, C. M. A.; Garrido, E. ManuelaDetection and quantification of cocaine is a key tool in fields such as police apprehensions and the fight against drug trafficking. Thus, a simple, fast and inexpensive electroanalytical methodology for the determination of cocaine in seized street samples has been developed, employing linear sweep voltammetry. The method is based on the use of a glassy carbon (GC) electrode modified by a combination of multi-walled carbon nanotubes (MWCNT) with β- cyclodextrin (β-CD) incorporated in a polyaniline film. The proposed method shows high reproducibility, repeatability and specificity. Under optimal conditions, the β-CD/ MWCNT-modified GC electrode gives a detection limit of 1.02 μM cocaine. The results obtained are in good agreement with those obtained by the high-performance liquid chromatography reference method. The new methodology proposed has excellent potential as the basis of a portable analytical sensor for on-site screening of cocaine in seized street samples.
- Catalytic bi-reforming of methane for carbon dioxide ennoblementPublication . Cunha, Adelino F.; Mata, T.M.; Caetano, Nídia; Martins, A.A.; Loureiro, J.M.New processes that may reduce the net carbon emissions and contribute to a more circular economy are needed. Bi-reforming of methane (BRM) is a promising method for syngas production, with a hydrogen-to-carbon monoxide ratio of two in the reaction products, relevant for example when the purpose is methanol synthesis. In this work, reaction studies were carried out over a nickel-based catalyst varying the temperature (798–1123 K). Three main temperature zones have been identified; a low temperature zone where the conversion of carbon dioxide is almost null, a middle temperature range where steam reforming of methane (SRM) is dominant while the conversion of carbon dioxide via dry reforming of methane (DRM) is low, and finally a high temperature range where DRM becomes more significant. The results show that syngas can be successfully produced using this process. For the range of operating conditions studied, the carbon dioxide and methane conversions increase with temperature, reaching 40% and 100%, respectively at the largest temperature studied. However, the production of syngas in a molar ratio of 1:2 for CO-to-H requires the use of high temperatures. Most probably the nickel agglomerates on top of the -alumina support are responsible for the poor catalyst performance.