Percorrer por autor "Cardoso, Beatriz"
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- Assessing the prebiotic potential of xylooligosaccharides produced by one-step fermentation using agro-residuePublication . Cordeiro, Ana; Fernandes, Andreia; Sousa, Joana; Cardoso, Beatriz; Alves, Joana; Silvério, Sara; Peres, António M.; Rodrigues, Lígia R.; Amorim, CláudiaA prebiotic is defined as a substrate that is selectively utilized by host microrganisms, conferring a health benefit
- Assessing the prebiotic potential of xylooligosaccharides produced by one-step fermentation using agro-residuesPublication . Cordeiro, Ana; Fernandes, Andreia; Sousa, Joana; Cardoso, Beatriz; Alves, Joana; Silvério, Sara; Peres, António M.; Rodrigues, Lígia R.; Amorim, CláudiaThe prebiotic effect is a fundamental concept in the fields of nutrition and gut health, referring to the beneficial effects of specific non-digestible dietary components on the gut microbiota, including xylooligosaccharides (XOS). These compounds function as food sources for beneficial gut bacteria, fostering their growth and activity. In this work, in vitro studies were performed to evaluate the prebiotic potential of XOS produced from olive stones (OS) and coffee silver skin (CSS) via a one step fermentation using a recombinant Bacillus subtilis 3610 harbouring the xylanase gene xyn2 from Trichoderma reesei. This potential was compared with a commercially available prebiotic oligofructose (Orafti®, BENEO, Germany). A mixture of human faeces from four healthy donors aged between 24 and 28 years old was used as inoculum. The pH variation and the production of short-chain fatty acids (SCFAs), gases, and ammonia were analysed during the 48 hours fermentations. The prebiotic supplementation resulted in a reduction of the pH value over time, with oligofructose presenting the most significant pH drop at 48 hours (ΔpH=3.65). The addition of prebiotics also significantly increased the production of beneficial SCFAs, with oligofrutose exhibiting a notable increase in the production of lactic and acetic acid production after 48 hours (28.0±0.1 and 28±1 mM, respectively), while OS-XOS and CSS-XOS demonstrated a more prominent rise towards the production of acetic acid (14.8±0.4 and 20.4±0.1 mM, respectively), butyric acid (2.5±0.3 and 3.29±0.04 mM, respectively), and valeric acid (75±1 and 110±14 mM, respectively) at 48 hours. Remarkably, the gas analysis revealed that the addition of OS/CSS-XOS fully suppressed the production of CH4 and increased the CO2 generation after 48 hours (2.6±0.7 and 5.20±0.05 mmol.L-1medium, respectively). These findings strongly suggest that the XOS produced from OS and CSS holds potential prebiotic properties for human health.
- Green synthesis of copper ferrite-based nanofluids using Chlorella vulgaris for heat transfer enhancementPublication . Cardoso, Beatriz; Nobrega, Glauco; Machado, Mariana; Lima, Rui A.This study investigates the green synthesis of copper ferrite nanoparticles (CuFe2O4 NPs) using an aqueous extract of Chlorella vulgaris as a reducing agent and their application in enhancing heat transfer through nanofluids. The successful formation of CuFe2O4 NPs was confirmed through UV–vis spectroscopy, revealing a progressive blue shift in absorption peaks from 380 nm to 350 nm over 4 h, accompanied by a reduction in band gap energy from 2 eV to 1.83 eV, indicating increased particle size and crystallinity. Scanning electron microscopy demonstrated relatively uniform morphology with an average particle size of 130 nm. The EDS analysis revealed strong Cu, Fe, and O peaks, consistent with the expected spinel ferrite composition. Water-based nanofluids containing 0.1 wt%, 0.5 wt%, and 1 wt% CuFe2O4 NPs were prepared and characterized. The 1 wt% nanofluid showed a 4.8 % improvement in thermal conductivity compared to water, while viscosity remained within a manageable range (~1.1 mPa⋅s), ensuring low pumping power requirements. In heat transfer experiments using a serpentine heat exchanger, the CuFe2O4 1 wt% nanofluids achieved a significant increase in heat absorption capacity, increasing the outlet temperature by at least 0.5 ◦C at all volumetric flow rates tested and with a significant improvement in heat storage capacity at the highest flow rate. These results highlight the efficacy of green-synthesized CuFe2O4-based nanofluids in significantly improving heat transfer performance while maintaining practical fluid properties, making them ideal for sustainable and efficient thermal management applications, and suitable for monophasic and biphasic applications.
- Sustainable green synthesis of metallic nanoparticle using plants and microorganisms: A review of biosynthesis methods, mechanisms, toxicity, and applicationsPublication . Cardoso, Beatriz; Nobrega, Cardoso; Afonso, Inês S.; Ribeiro, J.E.; Lima, Rui A.Green synthesis provides a sustainable approach to producing metallic nanoparticles (MNPs) using biological entities such as plants, algae, bacteria, yeast, and fungi. While extensive research has explored these biosynthetic processes, an integrated review is needed to systematically consolidate knowledge on biosynthesis mechanisms, key synthesis parameters, and the comparative advantages and limitations of green versus chemical synthesis methods. This review addresses these gaps by examining the roles of biological entities and their metabolites in reducing and stabilizing MNPs. Plants use polyphenols and sugars to reduce metal ions, while algae utilize compounds such as chlorophylls and carotenoids. Bacteria produce enzymes like nitrate reductase to reduce metal ions inside and outside the cell. Yeast, for instance, employs nitrate reductase for extracellular synthesis and metallothioneins for intracellular synthesis while fungi use enzymes like laccase and reductase to reduce metal ions and stabilize MNPs. It also examines how reaction factors—such as solvent type, pH, precursor concentration, and temperature—affect size, shape, and stability. The comparative analysis highlights the structural, functional, and environmental differences between green and chemical synthesis, emphasizing that green-synthesized MNPs exhibit improved biocompatibility and biological activity. While green synthesis avoids toxic chemicals and harsh conditions, reducing environmental impact, it may result in broader size distributions and less precise shape control compared to chemical methods. This review also addresses current limitations, including batch variability, differences in biological extracts, and challenges in maintaining consistent MNP properties. It emphasizes the need for advanced characterization techniques for reproducibility and quality control, proposing solutions such as bioprocess engineering, real-time monitoring, and lifecycle assessments to improve industrial scalability. In summary, this review provides a comprehensive resource for researchers and industries seeking to use green synthesis for sustainable, large-scale applications in medical, environmental, and biotechnological fields, supporting global sustainability goals and green chemistry principles.