UB - Artigos em revistas internacionais
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- Hemicellulose biorefineries: a review on biomass pretreatmentsPublication . Carvalheiro, Florbela; Duarte, Luís C.; Gírio, FranciscoBiomass pretreatment (BP) plays a crucial role in a lignocellulose feedstock-based biorefinery (LCFBR) for processing of three major output streams (cellulose, hemicelluloses and lignin) into chemicals and biofuels. BP includes processing of lignocellulosic material (LCM) under aqueous, dilute acid or alkaline media to obtain a cellulosic fraction, which is then fermented to produce bioethanol. Hemicellulose is usually treated as a secondary stream due to lack of efficient fermentation of hemicellulosic sugars to ethanol. This review provides BPs assuming that hemicellulose stream should be integrated in LCFBR as a primary fraction for converting into value-added compounds other than bioethanol. Different LCM treatments are analyzed foreseeing bio-based products possible to obtain from hemicellulose path.
- Composition and biological activity of the essential oil peruvian lantana camaraPublication . Benites, Julio; Moiteiro, Cristina; Miguel, Graça; Rojo, Leonel; Lopez, José; Venâncio, Florência; Ramalho, Luís; Feio, Sónia; Dandlen, Susana; Casanova, Hugo; Torres, IvanThe composition of the essential oil from Lantana camara L. (Verbenaceae) obtained by hydrodistillation of the aerial parts was examined by GC, GC/MS, and 13C-NMR. The GC analysis showed that carvone is the most abundant monoterpene 75.9%, together with limonene 16.9%, accounting for 92.8% of the oil. The major components were also tested by 13C-NMR analysis of the essential oil. The L. camara oil was assayed against several microorganisms, showing moderate antibacterial activity against the human pathogen Staphylococcus aureus (MIC 200 μg/ml). High antioxidant activity evaluated by the Trolox equivalent antioxidant capacity assay (TEAC) was found (29.0 mmol Trolox/kg) and relative low anti-inflammatory activity due to its weak ability for inhibiting lipoxygenase (IC50 = 81.5 μg/ml).
- Production of biosorbents from waste olive cake and its adsorption characteristics for Zn2+ IonPublication . Fernando, Ana Luisa; Monteiro, Sofia; Pinto, Filomena; Mendes, BenildeIn this study, waste olive cake (OC) was utilized as the raw material for the production of biosorbents by chemical treatment and its adsorption capacity for zinc ion was evaluated. Tests were conducted with the total biomass (T) and with the fraction > 2.00 mm (P), in order to determinate the influence of this fractionation step on subsequent treatments. Two chemical agents were used: sulfuric acid and sodium hydroxide. The parameters studied include physical and chemical properties of materials, contact time, pH, adsorbent dose and initial concentrations. The kinetic data were best fitted to the pseudo-second order model. Zinc binding is strongly pH dependent, with more zinc ions bound at a higher pH (5-7 in a range of 3-7). Both Langmuir and Freundlich models are well suited to fit the data on sorption of zinc by OC. Data on sorption of zinc by waste olive cake treated with sulfuric acid (OC-H) was better described by the Freundlich model. Zinc sorption by waste olive cake treated with sodium hydroxide (OC-OH) was better described by the Langmuir model. Results show OC-OH is a biosorbent with a superior adsorption capacity for zinc than OC-H. The maximum adsorption capacity obtained from the Langmuir isotherms increases in the order (mg/g): OC-HT (14), OCT (22) and OC-OHT (27). Results also indicate that the previous fractionation step doesn´t produce a biosorbent with a superior adsorption capacity.
- Monitoring rhodotorula glutinis CCMI 145 stress physiological response during fed-batch fermentations using multi-parameter flow cytometryPublication . Silva, Teresa Lopes da; Feijão, Daniela; Reis, AlbertoMulti-parameter flow cytometry was used to monitor R. glutinis stress response during a fed-batch fermentation, through cell viability, lipid content and intrinsic light scatter. During the yeast fermentation, the proportion of cells with permeabilized membrane (dead cells) increased when nutrients and/or oxygen became limiting. Yeast cells showed a higher injury level when grown under other nutrient limitation than under oxygen limiting conditions, as the dead cells reduced their internal content and size in the former situation, suggesting drastic cells lysis. The maximum yeast lipid content was 8% (w/w) at t=38.3 h. Such low lipid content was attributed to oxygen limitation, which highlights the importance of the oxygen transfer rate when producing lipids from aerobic yeast cultures. Changes in Forward and Side scatter light signals were detected during the yeast growth, which can provide a useful and fast way to identify the yeast growth phase. The multi-parameter approach here reported represents a better control system based at the individual cell level that can be used for optimization of yeast bioprocess performance, and may also be used for quick screening of yeast strains for single cell oil production.
- Study of membrane ageing and grafting mechanisms using electron paramagnetic resonancePublication . Oliveira, Fábio R. P.; Matos, Cristina T.; Moura, José J. G.; Portugal, Carla A. M.; Crespo, JoãoAn important setback for a wider use of membrane processes in industry is fouling, caused by aggregation of biomolecules at membrane surface and pores. Two important approaches to reduce this effect are the use of chemical cleaning procedures and the functionalisation of the membrane surface. However, both processes may lead to membrane degradation and structure alteration due to free radical formation or radical interaction with membrane polymer chains. In this work, electron paramagnetic resonance (EPR) was used to evaluate and quantify radical formation in both chemical cleaning and membrane functionalisation by UV grafting, allowing for a better understanding of free radical formation processes and their influence on membrane characteristics. Studies under different cleaning and grafting conditions, such as, cleaning agent concentration and pH, light intensity and irradiation were also performed showing the potential of EPR as a technique for monitoring both procedures. The information provided by EPR may contribute significantly to the development of new cleaning strategies which minimise the effect of membrane ageing and to the implementation of new and more efficient grafting procedures
- Biological hydrogen production by Anabaena sp. – Yield, energy and CO2 analysis including fermentative biomass recoveryPublication . Ferreira, Ana F.; Marques, Ana C.; Batista, Ana Paula; Marques, Paula; Gouveia, Luisa; Silva, Carla M.This paper presents laboratory results of biological production of hydrogen by photoautrotophic cyanobacterium Anabaena sp. Additional hydrogen production from residual Cyanobacteria fermentation was achieved by Enterobacter aerogenes bacteria. The authors evaluated the yield of H2 production, the energy consumption and CO2 emissions and the technological bottlenecks and possible improvements of the whole energy and CO2 emission chain. The authors did not attempt to extrapolate the results to an industrial scale, but to highlight the processes that need further optimization. The experiments showed that the production of hydrogen from cyanobacteria Anabaena sp. is technically viable. The hydrogen yield for this case was 0.0114 kgH2/kgbiomass which had a rough energy consumption of 1538 MJ/MJH2 and produced 114640 gCO2/MJH2. The use of phototrophic residual cyanobacteria as a substrate in a dark-fermentation process increased the hydrogen yield by 8.1% but consumed 12.0% more of energy and produced 12.1% more of CO2 showing that although the process increased the overall efficiency of hydrogen production it was not a viable energy and CO2 emission solution. To make cyanobacteria-based biofuel production energy and environmentally relevant, efforts should be made to improve the hydrogen yield to values which are more competitive with glucose yields (0.1 kgH2/kgbiomass). This could be achieved through the use of electricity with at least 80% of renewables and eliminating the unessential processes (e.g.pre-concentration centrifugation).
- Pre-treatment optimization of Scenedesmus obliquus microalga for bioethanol productionPublication . Miranda, J. R.; Passarinho, Paula; Gouveia, LuisaThe present work deals with the optimization of cellular disruption and sugar extraction from the microalgae Scenedesmusobliquus (Sc) for bioethanol production. Among the physical and physicochemical methods tested, the best results were obtained with acid hydrolysis by H2SO4 (2 N), at 120 °C for 30 min and using dried biomass. The sugar extraction efficiency level reached was 95.6% when compared to the harsh quantitative acid hydrolysis. The influence of other parameters such as biomass loading and number of extraction cycles were also evaluated. The results obtained in the latter case showed that a unique hydrolysis step is sufficient.
- Production, purification and characterisation of oligosaccharides from olive tree pruning autohydrolysisPublication . Cara, Cristóbal; Ruiz, Encarnación; Carvalheiro, Florbela; Moura, Patrícia; Ballesteros, Ignacio; Castro, Eulogio; Gírio, FranciscoThe production of oligosaccharides (OS) by olive tree pruning autohydrolysis in the range 170–230 °C was studied. The best results in terms of maximum yield of OS along with a low amount of byproducts were obtained at 180 °C. After purification by preparative gel filtration chromatography a range of OS-fractions with average degree of polymerisation (DP) from 25 to 3 was selected for further characterisation. Gluco-and xylooligosaccharides were the predominant OS in these fractions. OS yields in the range 80–90% were obtained for fractions with average DP between 25 and 7, practically free of low molecular compounds. Both OS total yields and xylooligosaccharides proportion decreased for lower DP fractions while monosaccharides and other products concentrations increased. OS production and the recovery of other high value compounds can be envisaged as an interesting contribution to develop an olive-biomass biorefinery.
- A favourable solubility of isoniazid, an antitubercular antibiotic drug, in alternative solventsPublication . Forte, Andreia; Melo, Catarina I.; Lukasik, Rafal M.; Bogel-Lukasik, EwaThe sufficient solubility of isoniazid in alternative solvents obtained in this work can open new perspectives in pharmaceutical processing. Solid–liquid equilibrium (SLE) measurements have been made using a dynamic (synthetic) method. The melting point and the enthalpy of fusion of isoniazid were acquired using differential scanning calorimetry (DSC). The solubility of isoniazid in bis(trifluoromethylsulfonyl)amide ionic liquids was found to be significantly lower than in the studied trifluoromethanesulfonate ionic liquid. The best solvent amongst studied for this common antibiotic against tuberculosis was discovered. The solid–liquid phase equilibria were described using the six different correlation equations which revealed relatively good description with the acceptable standard deviation temperature range.
- Bioethanol production from Scenedesmus obliquus sugars: the influence of photobioreactors and culture conditions on biomass productionPublication . Miranda, J. R.; Passarinho, Paula; Gouveia, LuisaA closed-loop vertical tubular photobioreactor (PBR), specially designed to operate under conditions of scarce flat land availability and irregular solar irradiance conditions, was used to study the potential of Scenedesmus obliquus biomass/sugar production. The results obtained were compared to those from an open-raceway pond and a closed-bubble column. The influence of the type of light source and the regime (natural vs artificial and continuous vs light/dark cycles) on the growth of the microalga and the extent of the sugar accumulation was studied in both PBRs. The best type of reactor studied was a closed-loop PBR illuminated with natural light/dark cycles. In all the cases, the relationship between the nitrate depletion and the sugar accumulation was observed. The microalga Scenedesmus was cultivated for 53 days in a raceway pond (4,500 L) and accumulated a maximum sugar content of 29 % g/g. It was pre-treated for carrying out ethanol fermentation assays, and the highest ethanol concentration obtained in the hydrolysate fermented by Kluyveromyces marxianus was 11.7 g/L.