ESA - Dissertações de Mestrado Alunos
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- A cultura do arroz em Moçambique: uma perspetiva da investigação em curso no Instituto de Investigação Agrária de MoçambiquePublication . Mucasse, Nelma Marieta Custódio Tivane; Arrobas, Margarida; Joshua, CelestinaO arroz (Oryza sativa L.) é uma das culturas alimentares mais importantes em Moçambique, representando cerca de 20% da energia e 15% da proteína per capita na dieta da população. Apesar do seu papel estratégico na segurança alimentar, a produção nacional ainda é insuficiente para suprir a procura interna. Em 2024, Moçambique importou aproximadamente 700 000 toneladas de arroz, com um custo superior a 340 milhões de euros, evidenciando a necessidade urgente de fortalecer a produção interna para garantir a segurança alimentar e reduzir a dependência do mercado externo. Neste contexto, o Instituto de Investigação Agrária de Moçambique (IIAM) tem desenvolvido esforços significativos para aumentar a produtividade do arroz, por meio da introdução de variedades melhoradas, da realização de ensaios de adaptabilidade e praticas agronómicas inovadoras. Com objetivo de contribuir para o desenvolvimento de soluções técnicas que melhorem o rendimento, esta dissertação concentrou-se na análise de quatro ensaios experimentais conduzidos entre 2019-2024 no IIAM com os seguintes objetivos: i) Avaliação de variedades aromáticas e híbridas. As variedades estudadas demostraram estabilidade produtiva. ii) Estudo do efeito da altura de corte na cultura principal na capacidade regenerativa da planta (rebrote). Este ensaio mostrou que o corte a 45 cm de altura contribui para o aumento significativo do rendimento da cultura. iii) Pesquisas de linhas tolerantes à salinidade em 136 genótipos. Foram identificados genótipos com diferentes níveis de resistência e sensibilidade, revelando diversidade genética promissora. As principais conclusões indicam que o uso de variedades melhoradas, o maneio adequado e a adoção de práticas como o rebrote podem aumentar significativamente a produtividade do arroz em Moçambique. O trabalho reforça a importância da investigação agrária como ferramenta para garantir a segurança alimentar.
- Avaliação do impacto da radiofrequência na qualidade da castanhaPublication . Ribeiro, Caroline Silva; Fernandes, Ângela; Pires, Tânia C.S.P.
- The bioactive potential of Echinacea purpurea (L.) Moench extracts for dermatological applicationsPublication . Azevedo, Renato Emanuel Carvalho; Vieira, Sara; Barros, Lillian
- Valorização de Subprodutos de Maçã: Da Caracterização Nutricional e Bioativa ao Desenvolvimento de um Produto de Panificação EnriquecidoPublication . Lopes, André Filipe Gomes; Mandim, Filipa; Barros, Lillian
- The impact of insects larvae frass on soil fertility and plant productionPublication . Foughar, Meroua; Arrobas, Margarida; Rodrigues, Manuel ÂngeloThere is a need for alternatives or complements to synthetic fertilizers to enhance agricultural sustainability. Applying organic amendments can play a significant role in this. Insect droppings show high potential, though studies evaluating their agronomic value have only recently begun to emerge. This study compared black soldier fly (Hermetia illucens L.) and mealworm (Tenebrio molitor L.) larvae frass with another organic amendment (Nutrimais) derived from composting forestry, agro-industrial, and domestic waste. The experiment also included ammonium nitrate at two rates: the same as the organic amendments, 50 kg ha⁻¹ nitrogen (N), and half that rate and an unfertilized control. The study spanned two growth cycles of lettuce (Lactuca sativa L.) grown in pots, followed by unfertilized oats (Avena sativa L.) to assess the residual effects of the fertilizing treatments. Mealworm larvae frass mineralized rapidly, with an apparent N recovery of 37.4% over the two lettuce growth cycles, indicating its high availability to soil heterotrophic microorganisms. The average dry matter yield (DMY) of lettuce was the highest among all treatments (12.8 and 9.8 g plant⁻¹ in the first and second lettuce cycles), even compared to the FullR treatment (12.2 and 7.8 g plant⁻¹), though without significant differences. Although mealworm larvae frass exhibited a high mineralization rate, the DMY cannot be attributed solely to N supply, as plants in the FullR treatment showed better N nutritional status. Mealworm larvae frass provided strong evidence of a plant biostimulant effect, not explained by the variables measured in this study. Black soldier fly larvae frass exhibited typical behavior of a moderately reactive organic amendment, while Nutrimais showed low reactivity, with a near-neutral mineralization/immobilization balance. The results suggest mealworm larvae frass is recommended for early-maturing vegetable crops, whereas Nutrimais appears more suitable for perennial crops with low short-term nutrient requirements.
- Development of a DNA-based methodology for the identification of Pfaffia glomerata in herbal productsPublication . Richter, Camila Palacio; Amaral, Joana S.; Maniglia, Thiago Cintra; Rodrigues, VâniaPfaffia glomerata (Brazilian ginseng) is a medicinal plant widely recognized for its adaptogenic, anti-inflammatory, and immunomodulatory properties. Due to its growing commercial value, as well as to its common name that includes the word “ginseng”, and the morphological similarity to other ginsengs, it is increasingly prone to adulteration. This study aimed to develop and validate a species-specific real-time PCR method for the identification and quantification of P. glomerata in commercial herbal products. Primers targeting the ITS1 region were designed and evaluated both in silico and experimentally. Specificity was assessed against 51 medicinal plant samples, including other species known for their adaptogenic properties. Sensitivity assays confirmed an absolute detection limit of 0.001 ng of P. glomerata DNA. Quantitative analysis using binary mixtures with Withania somnifera and the ∆Cq normalization method reliably detected P. glomerata at levels as low as 0.1% (w/w) and allowed the accurate estimate of the percentage of P. glomerata material in the range of 50% to 0.1% (m/m). The method was applied to 25 commercial products labeled as P. glomerata, Pfaffia paniculata, Pfaffia, Brazilian ginseng, or other possibly adulterant species of Brazilian ginseng, seven samples showed inconsistencies with the label and were considered as adulterated. P. glomerata DNA was also found to be present in nine other samples, but only at trace amounts (
- Utilization of peanut by-products as a preservative for peanut-based beveragePublication . Sasahara, Mateus Malaguti; Fernandes, Filipa Alexandra; Heleno, Sandrina A.; Pena, Aline de Cassia Campos
- Endophytic community of olive tree and its importance for host plant performancePublication . Giovanella, Nathália Hister; Baptista, Paula; Silva, Sofia Teixeira daEndophytic microorganisms play key roles in plant growth and stress tolerance, yet their diversity, host specificity, and functional potential in olive trees remain poorly understood. This study evaluated the influence of host genotype (at cultivar level) on the structure and functional traits of both fungal and bacterial endophytic communities inhabiting the roots of three olive cultivars (Galega Vulgar, Madural, and Cobrançosa) with contrasting susceptibilities to biotic and abiotic stress. The microbial community was characterized through a culture-dependent approach, and the isolates were functionally evaluated based on biochemical traits associated with plant growth promotion (indole-3-acetic acid production - IAA, phosphate solubilization, nitrogen fixation) and biocontrol potential (lytic enzyme, hydrogen cyanide, and siderophore production). A total of 19 fungal and 17 bacterial perational taxonomic units (OTUs) were isolated. Fungal endophytes were dominated by Ascomycota, mainly Fusarium and Meyerozyma, whereas bacterial isolates were predominantly Proteobacteria, particularly Pseudomonas. The composition of both fungal and bacterial communities differed among cultivars, with Cobrançosa hosting distinct assemblages, Galega and Madural displaying closer profiles, Network analyses identified shared and cultivar-specific OTUs, highlighting a potential core microbiota comprising Fusarium, Penicillium, Phomopsis, Dactylonectria, and Meyerozyma for fungi, and Pseudomonas and Paenibacillus for bacteria. Functional assays showed greater metabolic versatility in bacterial than in fungal endophytes. While all fungi and most bacteria produced IAA, traits such as siderophore production, phosphate solubilization, and nitrogen fixation were mainly bacterial, with Bacillus velezensis and Pseudomonas spp. showing the highest activity. Fungi exhibited cellulase activity and limited amylase production but lacked phosphate solubilization, nitrogen fixation, and HCN production. Overall, the olive cultivar genotype strongly influenced the diversity and function of root endophytic communities. Notably, Pseudomonas spp. and Bacillus velezensis showed promising plant growth-promoting and biocontrol traits, suggesting their potential as microbial inoculants to enhance olive growth and stress resilience.
- Breakfast snacks made from extruded leguminous flourPublication . Chouikh, Ali Seif; Caleja, Cristina; Rocha, Luís; Charfi, IchrakAlthough legumes are recognized as nutritionally richer than cereal grains, contributing a higher content of protein, dietary fiber, complex carbohydrates, and bioactive compounds, their global consumption often remains below recommended levels. Many countries, particularly in Europe, do not meet the suggested intake targets. In this regard, it becomes crucial to address alternatives that allow for offering nutritionally more attractive, convenient, and healthy foods that can be included in the daily diet and contribute to the maintenance of consumer health. From this perspective, the present study aims to address the need for highly nutritious snacks, leveraging extrusion technology to enrich corn semolina flour and rice flour with chickpea flour in order to obtain protein-enriched ready-to-eat snacks. The specific objectives encompassed defining the optimized extrusion parameters as well as the proportions of each flour in the mixture to ensure not only the improvement of the protein content but also the organoleptic and texture characteristics expected by the consumer of this type of product. Additionally, the study intended to characterize the resulting snacks physically and nutritionally (fat, ash, protein, carbohydrates, and energy value) as well as to determine the chemical composition, and evaluate the bioactive properties, specifically antibacterial and antifungal activities. The extrusion process was achieved using a twin-screw extruder to combine chickpea flour with rice flour or corn semolina. The process parameters, including screw speed, water flow, and a multi-zone temperature profile, were meticulously recorded to correlate with the resulting product characteristics, such as desirable color, crunchy texture, homogeneous flow, particle diameter, and protein content. For the Rice:Chickpea (AGE) flour mixture, the optimized characteristics (white color, crunchy texture, homogeneous flow, and good particle diameter) were achieved using a high screw speed of 600 rpm and a die temperature of 180°C (AGE4). In turn, the Corn Semolina:Chickpea (SGE1) flour mixture achieved optimized physical attributes (golden color, crunchy texture, homogeneous flow, and medium particle diameter) at a lower screw speed of 400 rpm and a relatively lower die temperature of 120°C. Protein content was evaluated using the Kjeldahl method. Among all tested conditions, measured protein levels ranged from 10.23 g/100 g PS (DW) to a maximum of 13.39 g/100 g PS (AGE 4). Specifically, the Corn Semolina:Chickpea (50:50) mixtures reached up to 12.58 g/100 g PS (SGE 1). The two formulations with the best performance in terms of physical characteristics and protein content were selected for complete nutritional and chemical characterization: SGE1 (Corn Semolina:Chickpea, 50:50) and AGE4 (Rice:Chickpea, 50:50). Both SGE and AGE are classified as ready-to-eat snacks with low fat content, high carbohydrate content, and high protein content. They exhibited very low moisture (SGE:3.97%; AGE: 3.63%) and very low fat content (SGE: 0.048 g/100 g fresh weight; AGE: 0.043g/100 g fresh weight), which are desirable attributes for shelf stability and health. The AGE formulation demonstrated a statistically higher protein content (13.39 ± 0.01 g/100 g dry weight) compared to SGE (12.58 ± 0.10 g/100 g dry weight), suggesting that the Rice:Chickpea mixture offers a more protein-rich snack option. Carbohydrates were the main macronutriente (SGE: 83.28 g/100 g fresh weight; AGE: 82.81 g/100 g fresh weight), resulting in similar overall energy values (AGE: 385 Kcal/100 g; SGE: 384 Kcal/100 g). Chemical analysis of free sugars revealed sucrose as the only free sugar present in both snacks. The low free sugar contente is favorably aligned with public health recommendations. The fatty acid profiles were distinct: SGE exhibited a lipid profile rich in saturated fatty acids (AGS: 55.3 ± 0.1%), with palmitic acid (C16:0) being the most abundant (45.287 ± 0.42%). Meanwhile, AGE demonstrated a profile rich in polyunsaturated fatty acids (AGPI: 48.4 ± 0.1%), predominantly linoleic acid (C18:2n6c: 48.438 ± 0.07%). Regarding bioactive properties, the evaluation of the extracts showed limited antibacterial activity against most tested foodborne pathogens (including Gram-negative E. coli and Gram-positive S. aureus). Minimum Inhibitory Concentrations (MICs) generally exceeded the maximum concentration tested (> 10 mg/mL). However, both SGE and AGE extracts showed fungistatic activity against Aspergillus species. The MIC values for fungal inhibition against A. brasiliensis and A. fumigatus ranged between 5 mg/mL and 10 mg/mL, although neither reached a fungicidal concentration (MFC > 10 mg/mL). This study successfully demonstrated that extrusion technology can be effectively applied in the development of ready-to-eat snacks, rich in protein, low in fat, and with energy balance, by combining chickpea flour with rice and semolina flours. The rice and chickpea formulation (AGE) showed the highest protein content and a favorable fatty acid profile, confirming the potential of legumes to increase the nutritional value of extruded products. These findings highlight the relevance of legume mixtures in formulating healthy, protein-rich snacks that meet modern consumer demands for nutritious and practical plant-based foods, while also supporting strategies to improve global protein intake and diet quality.
- Natural products as collagenase inhibitors: a molecular modelling approachPublication . Carvalho, Eduardo Miguel Da Costa; Abreu, Rui M.V.; Mateus, CristianoSkin photoaging is a process that involves the degradation of extracellular matrix proteins, including collagen and elastin. These are essential components of the skin, providing sturdiness and elasticity; their degradation leads to the loss of tensile strength, flexibility, and the development of wrinkles. This process is mediated by matrix metalloproteinases (MMPs), including Collagenase (MMP-1). Excessive production of MMP-1 accelerates extrinsic skin ageing, which may be mitigated by applying anti-ageing compounds with anti-collagenase activities. Therefore, there’s interest in discovering better MMP-1 inhibitors, with emphasis on natural compounds, since there’s been a significant shift in market interest towards the usage of natural products in cosmeceutical development. One way to quickly test a wide range of compounds with minimal costs is to rely on in silico methodologies to predict compound bioactivities. This study aimed to explore different molecular modelling approaches to assess the inhibition potential of different natural products against MMP-1, namely molecular docking and quantitative structure-activity relationship (QSAR) modelling. For this purpose, a virtual library of 83 known MMP-1 inhibitors was developed and used to develop QSAR models. QSAR model 2 was selected for further use since it presented solid statistical parameters, with an R² value of 0.96 and a RMSE value of 0.191. A library of natural compounds, with a structure similar to compounds used to develop the QSAR models, was constructed using the COCONUT database of natural compounds. A total of 715 compounds were gathered, and the QSAR model 2 was applied to it. The molecular docking approach was also validated by performing a Re-Docking protocol, and the validated approach was applied in the same library of 715 compounds. Finally, the data from the two methods were combined. Using this data, the tested compounds were ranked according to their combined inhibition probability (%) and the top 10 ranked compounds were analyzed in terms of their structure and binding conformations. In the future, it would be of interest to buy these compounds and test them experimentally to validate these in silico models and confirm the predicted inhibition activity. If this activity is confirmed, then these compounds could be used in cosmeceutical and drug design applications.