Browsing by Issue Date, starting with "2016"
Now showing 1 - 10 of 10
Results Per Page
Sort Options
- Advances in the reduction of the costs inherent to fossil fuels’ biodesulfurization towards its potential industrial applicationPublication . Paixão, Susana M.; Arez, B. F.; Silva, Tiago; Alves, LuísBiodesulfurization (BDS) process consists on the use of microorganisms for the removal of sulfur from fossil fuels. Through BDS it is possible to treat most of the organosulfur compounds recalcitrant to the conventional hydrodesulfurization (HDS), the petroleum industry’s solution, at mild operating conditions, without the need for molecular hydrogen or metal catalysts. This technique results in lower emissions, smaller residue production and less energy consumption, which makes BDS an eco-friendly process that can complement HDS making it more efficient. BDS has been extensively studied and much is already known about the process. Clearly, BDS presents advantages as a complementary technique to HDS; however its commercial use has been delayed by several limitations both upstream and downstream the process. This study will comprehensively review and discuss key issues, like reduction of the BDS costs, advances and/or challenges for a competitive BDS towards its potential industrial application aiming ultra low sulfur fuels.
- Novel Bisphosphonates Derived from 1H-Indazole, 1H-Pyrazolo[3,4-b]Pyridine, and 1H-Pyrazolo[3,4-b]QuinolinePublication . Teixeira, Fatima; Lucas, Carla; Curto, Maria João Marcelo; Teixeira, António P. S.; Duarte, M. Teresa; Andre, VaniaNovel tetraethyl ethylene-1,1-bisphosphonate esters derived from 1H-indazole, 1H-pyrazolo[3,4-b]pyridine, and 1H-pyrazolo[3,4-b]quinoline were synthesized by a Michael addition reaction of tetraethyl ethylidene-1,1-bisphosphonate with the corresponding heterocycle, using conventional heating and microwave-assisted methods. The microwave-assisted method provides shorter reaction times and better yields. The hydrolysis of bisphosphonates afforded the corresponding bisphosphonic acids or salt, using concentrated hydrochloric acid or TMSBr/collidine, respectively. All new compounds were fully characterized, and their structures were assigned using 1H, 31P, and 13C NMR and IR spectroscopies and mass spectrometry. The molecular structure of compound 6 was confirmed by X-ray diffraction studies.
- Life cycle assessment of advanced bioethanol production from pulp and paper sludgePublication . Sebastião, Diogo; Gonçalves, Margarida S.; Marques, Susana; Fonseca, César; Gírio, Francisco; Oliveira, Ana Cristina; Matos, Cristina T.This work evaluates the environmental performance of using pulp and paper sludge as feedstock for the production of second generation ethanol. An ethanol plant for converting 5400 tons of dry sludge/year was modelled and evaluated using a cradle-to-gate life cycle assessment approach. The sludge is a burden for pulp and paper mills that is mainly disposed in landfilling. The studied system allows for the valorisation of the waste, which due to its high polysaccharide content is a valuable feedstock for bioethanol production. Eleven impact categories were analysed and the results showed that enzymatic hydrolysis and neutralisation of the CaCO3 are the environmental hotspots of the system contributing up to 85% to the overall impacts. Two optimisation scenarios were evaluated: (1) using a reduced HCl amount in the neutralisation stage and (2) co-fermentation of xylose and glucose, for maximal ethanol yield. Both scenarios displayed significant environmental impact improvements.
- A new methodology for urban wind resource assessmentPublication . Simões, Teresa; Estanqueiro, AnaIn the latest years the wind energy sector experienced an exponential growth all over the world. What started as a deployment of onshore projects, soon moved to offshore and, more recently to the urban environment within the context of smart cities and renewable micro-generation. However, urban wind projects using micro turbines do not have enough profit margins to enable the setup of comprehensive and expensive measurement campaigns, a standard procedure for the deployment of large wind parks. To respond to the wind assessment needs of the future smart cities a new and simple methodology for urban wind resource assessment was developed. This methodology is based on the construction of a surface involving a built area in order to estimate the wind potential by treating it as very complex orography. This is a straightforward methodology that allows estimating the sustainable urban wind potential, being suitable to map the urban wind resource in large areas. The methodology was applied to a case study and the results enabled the wind potential assessment of a large urban area being consistent with experimental data obtained in the case study area, with maximum deviations of the order of 10% (mean wind speed) and 20% (power density).
- Sugarcane bagasse delignification with potassium hydroxide for enhanced enzymatic hydrolysisPublication . Paixão, Susana M.; Ladeira, S. A.; Silva, Tiago; Arez, B. F.; Roseiro, J. Carlos; Martins, M. L. L.; Alves, LuísThe optimization of an alkaline pretreatment process for the delignification of sugarcane bagasse (SCB) to enhance the subsequent enzymatic hydrolysis was performed according to the Doehlert uniform shell design. In this experimental design, the effect of two factors—potassium hydroxide (KOH) concentration and autoclaving time at 121 C (1 atm)—on cellulose, hemicellulose, or the total polysaccharide and lignin content in SCB was evaluated. This response surface methodology revealed that KOH concentration is the factor that most influences the chemical characteristics of treated SCB (SCBt), with optimal conditions for the highest delignification being KOH in the range 5–10% (w/v) and an autoclaving time of 35 min, which provides an average of 97% total polysaccharides without inhibitor accumulation (furfural, 5-hydroxymethyl furfural) and #5% lignin. SCBt samples from two pretreatment conditions (KOH 3.25% – 13 min; KOH 10% – 35 min) were selected, based on the greatest delignification (70–74%) and polysaccharide availability (95–97%) after pretreatment, and further hydrolysed for fermentable sugar production. High sugar yields were obtained from both the pretreated samples (866 to 880 mg sugar per g biomass, respectively) in contrast with the 129 mg sugar per g raw biomass obtained from untreated SCB. These results demonstrate the effectiveness of KOH alkali pretreatments, which improves the overall digestibility of raw SCB polysaccharides from about 18% up to 91%. However, harsh alkali treatment (KOH 10%) is the most effective if the highest glucose/xylose ratio in the final sugar-rich hydrolysate is the aim. Hence, the use of sugar-rich hydrolysates obtained from SCBt as the carbon source for industrial purposes may provide a sustainable and economic solution for the production of bio-based added-value products, such as second generation (2G) bioethanol.
- Ability of Gordonia alkanivorans strain 1B for high added value carotenoids productionPublication . Silva, Tiago; Paixão, Susana M.; Alves, LuísCurrently, carotenoids are valuable bioactive molecules for several industries, such as chemical, pharmaceutical, food and cosmetics, due to their multiple benefits as natural colorants, antioxidants and vitamin precursors. Hence, the increasing interest on these high added-value products has led to the search of alternatives, more cost-effective and with better yields, towards their industrial production. Indeed, microbial metabolism offers a promising option for carotenoids production. Herein it is shown the potential of the dibenzothiophene desulfurizing bacterium Gordonia alkanivorans strain 1B as a high carotenoid-producer microorganism. The novel carotenoids, produced under different culture conditions, were extracted with DMSO and then further analyzed both through spectrophotometry and HPLC. When grown in glucose-sulfate-light, strain 1B was able of achieving 2015 g carotenoids per g DCW in shake-flask assays, with about 60% corresponding to lutein, canthaxanthin and astaxanthin. Further optimization studies open a new focus of research aiming to get a hyper pigment-producer strain that may be applied towards different industrial sectors.
- Characterization of thermophile xylanase produced by anoxybacillus sp. strain 3M in submerged fermentation using brewers’ spent grainPublication . Alves, Luís; Ladeira, S. A.; Paixão, Susana M.The main goal of this study was the characterization of the extremophile xylanases produced by by Anoxybacillus sp. strain 3M, a thermophilic bacterium isolated from terrestrial hot springs (temperature of 90°C) samples collected on S. Miguel, Azores, Portugal. In this context, several batch fermentations using different agro-industrial wastes as inducer substrates (BSG – Brewers’ spent grain, wheat straw, sugarcane bagasse, and corn cobs) were performed towards an optimal enzyme production. The results for xylanase production showed that the higher enzymatic levels were obtained in the growth medium containing 1% (w/v) BSG (1.34 U mL-1), indicating that the BSG was the best inducer substrate, but the xylanase activity was also observed when wheat straw (1.33 U mL-1), sugarcane bagasse (0.80 U mL-1), corn cobs (0.30 U mL-1) and commercial xylan (0.21 U mL-1) were used as inducers. The extracellular crude enzymatic extract produced by Anoxybacillus sp. 3M in optimized submerged fermentation with BSG, attaining a maximal xylanase activity of 1.41 U mL-1 (i.e. 5-fold higher than with xylan), was further characterized for its optimal temperature and pH and stability. The highest enzyme activity was observed at a temperature of 60ºC and pH 5.3, but the enzyme retained 100% of its original activity after 96 h at 60°C and pH 7.0 and it still maintained 46% activity after 28 days at the same conditions. At 60ºC, the enzyme also retained its activity for pH ranging from 7.0 to 10.5. In addition, a zymogram of native gel analysis of the different culture supernatants revealed the presence of an enzymatic complex with an apparent molecular weight ranging from 400-500 kDa. Further application of strain 3M enzymatic extract to commercial oat spelts xylan revealed the presence of xylose and xylooligosaccharides (XOS), mainly X2 and X3, in the hydrolyzates produced. So, the thermostable and alkalistable extracellular xylanases from Anoxybacillus sp. 3M are biocatalysts with high potential for the development of processes where lignocellulosics are converted to precursors for several biotechnological applications.
- Petrogenesis of a late-Variscan rhyodacite at the Ossa Morena-Central Iberian zones boundary, Iberian Massif, Central Portugal: Evidence for the involvement of lithospheric mantle and meta-igneous lower crustPublication . Henriques, S.B.A.; Neiva, A.M.R.; Dunning, G. R.ABSTRACT: A late-Variscan rhyodacite is exposed at the contact between the Ossa Morena Zone and the Central Iberian Zone of the Iberian Massif, Central Portugal. Dykes of rhyodacite intruded the Serie Negra Unit and the Sardoal Complex that are part of the Cadomian basement. The igneous crystallization age of the rhyodacite (308 +/- 1 Ma) was obtained on igneous monazite by the ID-TIMS U-Pb method. It is broadly coeval with the emplacement of late-Variscan granitoids during the last deformation phase of the Variscan Orogeny (ca. 304-314 Ma) and with the development of the large late-Variscan strike-slip shear zones (ca. 307 Ma). The rhyodacite samples are calc-alkaline, show identical composition and belong to the same magmatic sequence. The rhyodacite isotopic signatures (Sm-Nd and delta O-18) are consistent with depleted-mantle juvenile sources and the contribution of the meta-igneous lower crust. The input of mantle juvenile sources is related to Variscan reactivation of lithospheric fractures. The inherited Neoproterozoic (ca. 619 Ma) and Mesoproterozoic (ca. 1054 Ma) zircon ages, are similar to those of the Central Iberian Zone. This suggests that lower crust of the Central Iberian Zone was involved in the magma generation of the rhyodacite. Coeval late-Variscan magmatic rocks display a larger contribution from ancient crustal components, which may be attributed to the smaller volume and faster cooling rate of the rhyodacite and consequent lower melting of the crust. Mixing of juvenile mantle-derived melts with melts from the lower continental crust was followed by fractional crystallization of garnet and amphibole that remained in the source. Fractional crystallization of plagioclase, biotite, quartz and zircon occurred in shallower magma chambers. Fractional crystallization of zircon was not significant.
- Suppressed hydrogen (H) solubility in body centered cubic vanadium (V) by alloying with molybdenum (Mo), chromium (Cr), iron (Fe) or cobalt (Co) appreciated in terms of statistical thermodynamicsPublication . Shohoji, NobumitsuEquilibrium isothermal pressure-composition relationships reported for H solubility in body centered cubic (bcc) V1-yMyHx (M = Cr, Mo, Fe or Co) by Suzuki et al. recently on this journal were analyzed with statistical thermodynamics under a priori assumption of constant H-H interatomic interaction energy E(H-H) within homogeneity composition range of bcc V1-yMyHx phase at arbitrary temperature T. Results of the present statistical thermodynamic analysis showed that detected H solubility suppression for the examined V1-yMyHx was consistently interpreted in terms of decrease of available number ? for occupation by H atoms per metal atom in the V1-yMy lattice from ? = 0.55 determined for bcc VHx in the earlier work of the author. The extent Q of stabilization of H atoms in the V1-yMy lattice through formation of H-V and H-M bonds was one of principal parameters determined by the statistical thermodynamic analysis. It was intriguing to note that Q(V1-yMyHx) with M = Fe and Co became less negative than Q(VHx) in pure bcc VHx implying that the extent of stabilization of H atoms in V1-yMy lattice with M = Fe or Co increased with reference to that in pure VHx in spite of decreased ? from that (0.55) in VHx. On the other hand, Q(V1-yMyHx) with M = Cr and Mo became less negative (that is decreased stability of H) than Q(VHx) corresponding straightforwardly to the detected decrease of ? value from that in VHx. Noting the promoted H permeability reported for V1-yFey membrane by Suzuki et al., search for alloying element M that induced H solubility drop form that in the bcc V but with effect of enhancing stability of H in the V1-yMy lattice was concluded to be a pragmatic guideline for the screening of alloying constituent towards development of V-based H permeation membrane material.
- Erratum: Corrigendum to “Evolution of a Neoproterozoic suture in the Iberian Massif, Central Portugal: New U-Pb ages of igneous and metamorphic events at the contact between the Ossa Morena Zone and Central Iberian Zone” (Lithos (2015) 220–223 (43–59)Publication . Henriques, S.B.A.; Neiva, A.M.R.; Ribeiro, Maria Luísa; Dunning, G. R.; Tajcmanová, L.