Browsing by Author "Cordeiro, Nereida"
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- Agro-industrial byproducts as modification enhancers of the bacterial cellulose biofilm surface properties: an inverse chromatography approachPublication . Faria, Marisa; Mohammadkazemi, Fatemeh; Aguiar, Roberto; Cordeiro, NereidaBacterial cellulose (BC) has remarkable and excellent properties. However, the high-cost production and the use of chemicals for BC modification make its application unattractive. A simple approach to modify the properties of BC during biosynthesis, by using alternative low-cost carbon sources from agro-industrial byproducts, was studied. The carbon source (date syrup, mannitol, sucrose, food-grade sucrose, and glucose) significantly changed the BC network morphology and structure. Date syrup source induces the highest modifications in the surface properties of BC: smaller area (SBET = 4.04 m2 /g), higher hydrophobic (γd s = 45.79 mJ/ m2 ) and basic character (Kb/Ka = 1.10), at 25 ºC. Food-grade sucrose source resulted in the lowest yield of BC production (37% less), however caused an increase in the BC network reticulation and a high crystalline structure (IC = 82.3%). This sustainable and simple methodology presents a low-cost and efficient approach allowing the modulation of the surface properties of BC.
- Assessing the impact of sulfur concentrations on growth and biochemical composition of three marine microalgaePublication . Fernandes, Tomásia; Fernandes, Igor; Andrade, Carlos A. P.; Cordeiro, NereidaThe elemental stoichiometry, growth and biochemical composition of Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp. were studied in batch cultures against different nitrogen and sulfur molar ratios (N:S) imposed in their surroundings. In N. gaditana, treatments with low N:S lead to an increase in carbon:sulfur (C:S) and N:S molar ratios up to 95 and 81%, respectively. This was reflected in lipid and protein contents which increased up to 67 and 55%, respectively. Moreover, polyunsaturated fatty acids, as well as its precursors, increased in low N/S treatments. In R. marina, the treatments applied promptly the decrease of both C:S and N:S ratios to 70 and 68%, respectively. Nevertheless, eicosapentaenoic:arachidonic acid ratio increased with N:S treatments by three and a half fold. In Isochrysis sp., the elemental stoichiometry was constrained against treatments until the highest sulfur input. Overall, sulfur supply highlighted microalgae taxonomic differences and suggested that biochemical control is required, even in nutrient replete conditions, to fully exploit their potential as added value biomachineries.
- Assessment of the changes in the cellulosic surface of micro and nano banana fibres due to saponin treatmentPublication . Cordeiro, Nereida; Faria, Marisa; Abraham, Eldho; Pothan, Laly A.The effect of saponin on the surface properties of banana fibres was studied by Inverse Gas Chromatography (IGC). Parameters including the dispersive component of the surface energy, surface heterogeneity, surface area, as well as acid-base surface properties were determined for saponin modified banana micro and nanofibres. These parameters show a more extensive saponin coating on the nanofibres with a network formation which is explained by the higher reactivity of nanofibres due to the higher surface energy, specific interaction and higher surface area presented by the nanofibres. The energetic profile indicates that both micro and nanofibres coated with saponin interact with the same, or similar, energy active sites. Saponin treatment reduces considerably the surface area of the fibres, with the consequent decrease in the monolayer capacity. The interaction with the polar probes clearly indicates that saponin treatment creates new polar active sites for specific interactions in both samples. However, the treatment increases predominately the basicity of the fibre surface with more relevance to the nanofibres. This behaviour will lead to better polymer/fibre interaction during composite preparation.
- Bacterial cellulose biopolymers: the sustainable solution to water-polluting microplasticsPublication . Faria, Marisa; Cunha, César; Gomes, Madalena; Mendonça, Ivana; Kaufmann, Manfred; Ferreira, Artur; Cordeiro, NereidaMicroplastics (MPs) pollution has become one of our time’s most consequential issue. These micropolymeric particles are ubiquitously distributed across all natural and urban ecosystems. Current filtration systems in wastewater treatment plants (WWTPs) rely on non-biodegradable fossil-based polymeric filters whose mainte nance procedures are environmentally damaging and unsustainable. Following the need to develop sustainable filtration frameworks for MPs water removal, years of R&D lead to the conception of bacterial cellulose (BC) biopolymers. These bacterial-based naturally secreted polymers display unique features for biotechnological applications, such as straightforward production, large surface areas, nanoporous structures, biodegradability, and utilitarian circularity. Diligently, techniques such as flow cytometry, scanning electron microscopy and fluorescence microscopy were used to evaluate the feasibility and characterise the removal dynamics of highly concentrated MPs-polluted water by BC biopolymers. Results show that BC biopolymers display removal effi ciencies of MPs of up to 99%, maintaining high performance for several continuous cycles. The polymer’s characterisation showed that MPs were both adsorbed and incorporated in the 3D nanofibrillar network. The use of more economically- and logistics-favourable dried BC biopolymers preserves their physicochemical properties while maintaining high efficiency (93–96%). These polymers exhibited exceptional structural preservation, conserving a high water uptake capacity which drives microparticle retention. In sum, this study provides clear evidence that BC biopolymers are high performing, multifaceted and genuinely sustainable/circular alternatives to synthetic water treatment MPs-removal technologies.
- Biodegradable nanocomposite films based on sodium alginate and cellulose nanofibrilsPublication . Deepa, B.; Abraham, Eldho; Pothan, Laly; Cordeiro, Nereida; Faria, Marisa; Thomas, SabuBiodegradable nanocomposite films were prepared by incorporation of cellulose nanofibrils (CNF) into alginate biopolymer using the solution casting method. The effects of CNF content (2.5, 5, 7.5, 10 and 15 wt %) on mechanical, biodegradability and swelling behavior of the nanocomposite films were determined. The results showed that the tensile modulus value of the nanocomposite films increased from 308 to 1403 MPa with increasing CNF content from 0% to 10%; however, it decreased with further increase of the filler content. Incorporation of CNF also significantly reduced the swelling percentage and water solubility of alginate-based films, with the lower values found for 10 wt % in CNF. Biodegradation studies of the films in soil confirmed that the biodegradation time of alginate/CNF films greatly depends on the CNF content. The results evidence that the stronger intermolecular interaction and molecular compatibility between alginate and CNF components was at 10 wt % in CNF alginate films.
- Changes in fatty acid biosynthesis in marine microalgae as a response to medium nutrient availabilityPublication . Fernandes, Tomásia; Fernandes, Igor; Andrade, Carlos A. P.; Cordeiro, NereidaTo maximize and enhance the fatty acid (FA) profiles of microalgae, it is crucial to understand the metabolic path ways that lead to high levels of the desired product. Nannochloropsis gaditana, Rhodomonas marina, and Isochrysis sp. were cultivated in media with various nutrient concentrations, and the biomass was analyzed for protein and fatty acid contents. The long chain polyunsaturated fatty acid (LC-PUFA) and protein contents were maximized in media with high nutrient concentrations. Under these conditions, the reduction in the (SFA + MUFA)/PUFA ratio (by as much as 83%) indicated that R. marina and N. gaditana shifted preference towards PUFA synthesis. The ∑ω3/∑ω6 ratio indicated that R. marina preferentially synthesized ω3 FA towards high nutrient concentrations (depicted by an eightfold increase) in contrast to Isochrysis sp. (which yielded a 35% reduction). In addition, the limitations of LC-PUFA biosynthesis at the level of its precursors (e.g. C18:2ω6, C18:3ω3, C18:4ω3) and further conversion to LC-PUFA as nutrients were increased, suggesting that external variations induced changes in the sets of enzymes that maintain the desaturation and elongation pathways of FA. The present study provides novel insights into the regulation of LC-PUFA biosynthesis and facilitates the modeling of microalgal FA patterns depending on the field of application.
- Changes in the mesocarp of Annona cherimola Mill. ‘Madeira’ during postharvest ripeningPublication . Cordeiro, Nereida; Sousa, Lúcilia; Freitas, Nélia; Gouveia, ManuelaPhysicochemical changes during postharvest ripening of cherimoya (Annona cherimola Mill. ‘Madeira’), were investigated to follow the principal modifications occurring during this process and to determine nutritional value. Fruit harvested atthe mature green stage were analyzed during ripening using standard methods. Significant (P < 0.05) changes in chlorophyll, starch, titratable acidity, total free sugars and uronic acids were obtained, but no significant changes were found in ash, protein, lignin and lipid contents during ripening. The most obvious changes were chlorophyll degradation, an accentuated decrease of starch and an increase in total free sugars, with glucose the predominant sugar in the mesocarp, as revealed by GC analyses. Firmness loss was mainly attributed to depolymerization of pectin and lipid deterioration rather than hemicellulose degradation. Results also showed that the cherimoya variety evaluated in this study is a good source of minerals (mainly potassium), palmitic acid, linoleic acid, -linolenic acid and sitosterol.
- Characterization of biodegradable films based on extracellular polymeric substances extracted from the thermophilic microalga Graesiella spPublication . Gongi, Wejdene; Pinchetti, Juan Luis Gómez; Cordeiro, Nereida; Sadok, Saloua; Ouada, Hatem BenIn this research, a new type of biodegradable film based on the extracellular polymeric substances (EPS) and isolated from the thermophilic microalga Graesiella sp., was formulated and characterized. The EPS film was 0.221 mm thick. Atomic force microscopy and scanning electron microscopy images revealed a homogeneous character with a lamellar microstructure. The EPS film displayed yellowish color, high transparency, high ul traviolet barrier properties, and low oxygen (0.008 SI), and water-vapor permeability (0.037 SI). Film tensile strength (16.24 MPa) and elongation at break (4.76%) were in the range of common biofilms and the thermal analyses showed high transition temperature (126 ◦C) and high thermal stability (up to 800 ◦C). Compared to ascorbic acid, results indicated that the EPS film shows a higher antioxidant activity, mainly as β-carotene anti bleaching (84%), DPPH- free radical scavenging ability (80%), and ferrous iron-chelating (55%). Graesiella sp., EPS film effects on beef meat packaging were studied during nine days of cold storage. Compared to polyvinylchloride-packed meat, EPS-packed meat samples showed higher stability of color (redness = 13.6) and pH (5.85) during storage and low proliferation of total viable counts (4.04 CFU⋅g− 1 ) and Pseudomonas bacteria (4.09 CFU⋅g− 1 ). They also exhibit lower drip loss (9%) and less metmyoglobin (32%), heme iron (4.87 μg⋅g− 1 ) total volatile basic nitrogen (TVB-N = 22.96 mg⋅kg− 1 ), and lipid oxidation (MDA = 0.025 mg⋅kg− 1 ). The obtained results highlight the potential for use of microalgae EPS as a new film forming material that could be applied in beef meat preservation.
- Characterization of the cork surface by inverse gas chromatographyPublication . Cordeiro, Nereida; Neto, Carlos Pascoal; Gandini, Alessandro; Belgacem, Mohamed NaceurInverse gas chromatography (IGC) at infinite dilution has been used to study the surface properties of cork from Quercus suber. The dispersive component of its surface energy was determined at different temperatures using n -alkanes as probes, and a γDS value of 38 ± 1 mJ · m-2 at 40°C was obtained. The surface acid (A)/base (B) properties were also evaluated by using polar probes and the results indicate that cork has an amphoteric character, with a KA /KB = 1.1. The advantages of IGC, compared with the technique of contact angle measurements in the characterization of the cork surface, are discussed.
- Chemical composition and pulping of banana pseudo-stemsPublication . Cordeiro, Nereida; Belgacem, M.N.; Torres, I. C.; Moura, J.C.V.P.This paper deals with the determination of chemical composition and the study of the pulping potentialities of banana pseudo-stems growing in Madeira Island (Portugal). First, the raw material was both studied as a whole (type I) and as the outer bark part (type II), which is richer in cellulose fibres. Before starting the cooking of banana wastes, the main components of the two types of material were quantified, and showed that the polysaccharide content was high enough (about 60–70%) to justify the pulping investigations. Moreover, the lignin content was very low (approximately 12%). The only discouraging finding was the relative high amounts of ashes and extractives. The pulping of these residues was carried out using soda, kraft and soda-anthraquinone (AQ) cooking processes and the optimal pulping conditions were established. Thus, pulps with a yield of about 37–38% with a Kappa number (Kappa no.) about 30–32 were obtained when cooking in the presence of 0.25–0.35% of anthraquinone at 120 ◦C for a short cooking time, i.e. 30 min. The longer times and higher temperatures of cooking as well as the use of kraft pulping conditions did not give rise to better performances, comparing to those mentioned above. These severe conditions were detrimental to the hemicellulose preservation.