ITQB: AEM - MA Dissertations
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- SuberSkin - plant defensive polymers in wound healingPublication . Barras, Ricardo"A method for the extraction of suberin from cork using two different ionic liquids, cholinium hexanoate and cholinium decanoate, was optimised through the use of a home-built reactor. The use of stirring was essential to enhance the recovery yield of suberin. The extraction of suberin with cholinium hexanoate was fully optimised, whereas that with cholinium decanoate though promising needs further optimisation. Liquid state nuclear magnetic resonance (NMR), gas phase chromatography coupled to mass spectrometry (GC- MS), high pressure liquid chromatography (HPLC), differential scanning calorimetry (DSC), dynamic light scattering (DLS) were used to characterize the extracted suberin. Limited amounts of suberin samples extracted with cholinium decanoate were attained due to low recovery yields. The most remarkable observation was attained using NMR which allowed us to disclose the different configurations of acyl-glycerol ester bonds present in the extracted polymer (i.e. its degree of cross linking). The obtained suberin was used to cast waterproof films; this process was optimized.(...)"
- New functional materials comprising the plant polymer sporopolleninPublication . Albano, Lúcia Isabel Cordeiro"Sporopollenin is a plant polymer present in the exine of pollen grains. It possesses remarkable mechanical, thermal and chemical stability, and is also highly recalcitrant to hydrolysis. Recent works have provided insight into its molecular structure. Nevertheless, it remained to be fully clarified, since its solubilization is hindered by its extreme inertness. Even after harsh isolation procedures, sporopollenin is recovered as modified/degraded fragments of the native polymer. In this work, we tested both acetolysis and ionic liquid (IL) reaction on bee pollen (BP). The obtained fractions were analyzed by infrared spectroscopy (FTIR) that showed that both methods rendered sporopollenin enriched fractions, regardless of the introduction of acetate on the acetolyzed BP and the incomplete removal of non-sporopollenin material by the ILs. The same workflow was employed for sunflower pollen (SP), plus an innovative approach of combining acetolyzed sunflower pollen (AcetSP) and IL reaction. The SP + IL reaction allowed to obtain endexine capsules. Nuclear magnetic resonance (NMR) and/or FTIR data showed signals for aromatics, primary aliphatic esters and acetals in both precipitated and soluble fractions, indicating that sporopollenin can be partially hydrolyzed with ILs. Polysaccharides and proteins were found as contaminants in the IL-isolated fractions, similar as in BP.(...)"
- Biotechnological strategy for the exploitation of the invasive Asparagopsis armata as an underutilized natural source of bioactive compoundsPublication . Cairrão, André" Microorganism resistance to current antibiotics has increased morbidity and mortality, prompting the search for naturally occurring candidate drugs from terrestrial and marine sources. Algae can produce a wide range of bioactive secondary metabolites, some of which display biomedical potential in the treatment of human diseases. Multiple studies have shown that Asparagopsis spp. are promising sources of antimicrobial compounds. However, to date, the bioactivities of Asparagopsis aqueous extracts have never been tested against pathogenic fungi and bacteria. Additionally, this invasive species is present in several coastlines all over the world making it a sustainable, easily obtainable, natural resource. In this study, the capacity of various steam-based extraction methods to render bioactive extracts against the model microorganisms were thoroughly compared using metabolic activity (MTT) and viability (CFUs) assays.(...)"
- Elucidate the biosy nthesis and the functional role of a new class of antimicrobial peptaibiotics in Neurospora crassaPublication . Sequeira, Patrícia Alexandra Soares"Fungi are generally abundant producers of secondary metabolites. In particular, these organisms are involved in the production of a subclass of nonribosomal peptides - peptaibiotics - which display interesting antibiotic activities. Previous studies demonstrated that some fungal strains are able to grow in media supplemented with ionic liquid and this supplementation leads to alterations in their metabolic footprint. Moreover, in Neurospora crassa, growth media supplementation with either 1-ethyl-3-methylimidazolium chloride or cholinium chloride, led to increased levels of 1-aminocyclopropane-1-carboxylate deaminase, an enzyme involved in the production of the rare amino acid 1-aminocyclopropane-1-carboxylic acid (ACC).(...)"
- Unravelling how the biosynthesis of sphingolipids impacts stress responses in Aspergillus nidulansPublication . Piontkivska, Daryna; Pereira, Cristina Silva"For the past years filamentous fungi have been emerging as critical human-pathogens and have been increasingly provoking deadly invasive infections. The currently available antifungal drugs are inadequate to fight this global threat and the discovery of new antifungal targets are urgently needed. In this context, fungal sphingolipids have come up as potential targets for the development of new antifungal agents; however, knowledge on sphingolipid biosynthetic pathways in filamentous fungi, such as Aspergillus nidulans, is still rather limited. Previous observations demonstrated that some ionic liquids can trigger the accumulation of sphingolipid intermediates of the glucosylceramide biosynthetic pathway, that in response to the induced stress are probably acting as second messengers. In the present thesis we wanted to assess how sphingolipid biosynthesis can impact stress responses in A. nidulans.(...)"