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Browsing by Author "Gaspar, Juliana Antunes"

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  • Seaweed exploration by sustainable technologies - Evaluation of their antifouling and bioremediation potential
    Publication . Gaspar, Juliana Antunes; Martins, Alice Isabel Mendes; Pintéus, Susete Filipa Gonçalves; Homem, Ana Sofia Dias Mestre
    Biofouling is the accumulation and growth of micro- and macroorganisms on submerged artificial structures or living surfaces. This process leads to increased fuel consumption and maintenance costs, reduced efficiency of equipment, and contributes to the spread of invasive species, while increasing greenhouse gas emissions. This study explores the antifouling potential of the invasive seaweed Undaria pinnatifida crude extracts obtained with water, ethanol, n-hexane and ethyl acetate, through evaluation of inhibition of bacteria growth, biofilm formation, quorum sensing, and acetylcholinesterase and tyrosinase activities, two enzymes involved in macroinvertebrates settlement process. The results were compared with the ones obtained with methanol and dichloromethane extracts. A field assay was also carried out. Aiming a circular economy approach, the study also investigates biochar produced from the intact and post-extracted seaweed biomass, by pyrolysis process (800 °C and 400 °C), hydrothermal carbonization (170 °C) and activation by a steam process (700 °C), assessing its properties and potential for water bioremediation through adsorption of ibuprofen, diclofenac and paracetamol. While the ethanol: water (50:50) afforded the highest extraction yield (10.3%), the extracts obtained with n-hexane and ethyl acetate, showed the broadest antimicrobial spectrum, exhibiting the highest potency against Citricoccus sp., (IC50 of 203.1 μg/mL and 435.2 μg/mL, respectively). The n-hexane extract also showed the highest capacity to inhibit the diatoms Chaetoceros calcitrans and Amphora sp. growth (10 mm and 8 mm inhibition halo, respectively). Concerning the anti-enzymatic activity, the ethyl acetate extract exhibited significant tyrosinase inhibition with an IC50 of 643 μg/mL. In the field test, in the assayed conditions, U. pinnatifida extracts did not reduce the biofouling process. Pyrolysis at lower temperatures (400 °C) yielded a higher biochar amount of 30-40%, whereas hydrochar synthesis yielded 27-31%. Biochars showed a range of ash content, with values between 53-80% at high pyrolysis temperatures. Surface areas increased with temperature and post-synthesis washing, yielding a maximum of 138 m²/g in pyrochar of post-extracted biomass. Undaria-derived biochar may be suited as a fertilizer, for adsorption of heavy metals or oxidation processes. This study aligns with the principles of a circular economy by exploring the valorization of U. pinnatifida, an invasive species, to create high-value, sustainable antifouling agents and biochars.
    2024-12-27Master thesis Open access Show more