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- Ability of Gordonia alkanivorans strain 1B for enhanced desulfurization of dibenzothiophene and its derivatives using fructose as carbon sourcePublication . Alves, Luís; Silva, Tiago; Fernandes, A. S.; Paixão, Susana M.In order to keep up the strict sulfur limits on fossil fuels and their derivatives, refineries commonly use a desulfurization method, which combines high temperatures and pressures with molecular hydrogen known as hydrodesulfurization (HDS). However, the effectiveness of HDS to desulfurize recalcitrant organic aromatic compounds such as dibenzothiophene (DBT) or its derivatives is low. Biodesulfurization (BDS) has been described as a promising complementary technique to HDS. Using microorganisms, BDS is able of desulfurize several recalcitrant compounds usually present in fossil fuels at mild temperatures and pressures without hydrogen, making it a simple and eco-friendly process. In this context and based in the fructophilic behavior of the desulfurizing bacterium, Gordonia alkanivorans strain 1B, several recalcitrant sulfur sources were tested in BDS assays using fructose as carbon source. So, strain 1B was used in desulfurization assays testing 4-mDBT, 4,6-dmDBT and 4,6-deDBT, as sulfur source, in comparison with DBT. Growth and desulfurization kinetics using the different sulfur sources were evaluated and the desulfurization rates were determined by GC analysis of x-DBT consumed. The results showed that the strain 1B using fructose as carbon source was able to fully desulfurize all the sulfur compounds tested in less than 121 hours. For 4-mDBT, 4,6-dmDBT and 4,6-deDBT the maximal bacterial growth rates obtained were 0.072 h-1, 0.069 h-1 and 0.095 h-1 with maximum desulfurization rates of 1.58, 4.84 and 4.30 umol g(DCW)-1 h-1, respectively. In comparison with previous results obtained for max of strain 1B in glucose as carbon source and DBT as sulfur source (0.025 h-1), all the m_ max obtained in this study highlight once more the importance of use fructose as carbon source, independently of sulfur source. In addition, contrary to what has been described for other strains, the desulfurization rates obtained for the compounds with two alkyl groups were higher than for DBT (2.12 umol g(DCW)-1 h-1). In fructose, the desulfurization of 4,6-dmDBT and 4,6-deDBT by strain 1B were more than 2-fold in comparison with that for DBT. These promising results indicate the high potential of use this bacterium towards fossil fuels BDS.
- Anaerobic digestion of enzymatically treated dairy cow effluent [Resumo]Publication . Eusebio, Ana; Marques, Susana; Marques, Isabel PaulaABSTRACT: In Portugal, cattle production increased up to 91,000 t in 2016 (EUROSTAT, 2016) and has been contributing to the increase of methane emissions into the atmosphere. As an appropriate process for the treatment of organic effluents, anaerobic digestion is ideal to minimize this negative impact since it provides the agricultural and energetic valorisation of the substrate through the production of digestate and biogas. Heating, cooling and electricity supply constitute different applications for this energy carrier gas with a relevant social, environmental and economic importance, mainly for the region and neighbouring areas where it is produced. Dairy cow effluent is an example of lignocellulosic biomass, whose recalcitrant compounds, such as lignin and phenols, must be previously hydrolysed and made available for subsequent anaerobic digestion. The use of laccase and hemicellulase may be of great interest as pre-treatment for a wide range of pollutant compounds of effluents.
- Anaerobic digestion of pre-treated microalgae biomass [Resumo]Publication . Neves, André; Silva, Teresa Lopes da; Reis, Alberto; Ramalho, Luís; Eusebio, Ana; Marques, Isabel Paula
- Antimicrobial peptides from Saccharomyces cerevisiae induce physiological changes in Hanseniaspora guilliermondiiPublication . Branco, Patricia; Albergaria, Helena; Arneborg, NilsSaccharomyces cerevisiae secretes antimicrobial peptides (AMPs) during alcoholic fermentation that are active against other wine-related yeasts (e.g. Hanseniaspora guilliermondii) (Albergaria et al., 2010) and bacteria (e.g. Oenococcus oeni) (Osborne and Edwards, 2007). In the present study we assessed the physiological changes induced by those AMPs on sensitive yeast cells of Hanseniaspora guilliermondii, namely membrane permeability and intracellular pH (pHi) alterations. Membrane permeability was evaluated by staining cells with propidium iodide (PI) and pHi by the fluorescence ratio imaging microscopy (FRIM) technique (Guldfeldt and Arneborg, 1998). Results showed that after 20 min of incubation with inhibitory concentrations of AMPs, the average pHi of cells dropped from 6.5 to 5.4. After 8 h of incubation, 32% of the cells had lost their ĢpH (=pHi-pHext) and after 24 h that percentage rose to 77%. The culturability (plating) and viability (PI staining) of the sensitive yeast cells also decreased in the presence of the AMPs. After 24 h of exposure to AMPs, 61% of the cells were dead (PI-stained) and the number of viable cells fell from 1 ~105 to 1.5 CFU/ml, which means that virtually all cells (99.999%) became unculturable but a sub-population of 39% of cells remained in a viable but non-culturable (VBNC) state. However, those VBNC cells were able to recover their culturability after incubation at optimal growth conditions. Our study revealed that the mode of action of these AMPs seems to be primarily targeted to the cell membranes, reducing their permeability and preventing cells to maintain pH homeostasis.
- Assessment of a winery effluent microbial community dynamics by LH-PCR/DGGE analysisPublication . Eusebio, Ana; Tacão, M.; Chaves, S.; Gadanho, M.; Duarte, José Cardoso; Almeida-Vara, Elsa; Tenreiro, R.
- Avaliação da conformidade do teor em enxofre em gasóleo e biodieselPublication . Crujeira, Teresa; Calisto, Sandra C.; Trancoso, Maria AscensãoRESUMO: Os transportes rodoviários que utilizam combustíveis de origem fóssil são uma das principais fontes de emissão de poluentes para a atmosfera, conduzindo à degradação da qualidade do ar, em particular nos grandes centros urbanos. A necessidade de utilização de combustíveis de origem renovável levou ao desenvolvimento de combustíveis alternativos, que permitem a redução significativa de emissões de CO2, ou a adição de produtos de origem renovável ao gasóleo. No caso dos óxidos de enxofre, a redução dessas emissões tem sido conseguida como resultado da progressiva diminuição do teor máximo de enxofre permitido nos combustíveis rodoviários.
- Biocatalytic performance of Butyribacterium methylotrophicum in the long-term conversion of synthesis gas produced from low-grade lignin gasification by Butyribacterium methylotrophicum [Resumo]Publication . Pacheco, Marta; Pinto, Filomena; Andre, Rui N.; Marques, Paula; Gírio, Francisco; Moura, PatríciaABSTRACT: Second-generation biorefineries produce large streams of low-grade lignin. Its thermochemical conversion, through gasification, enables the carbon recovery from an otherwise recalcitrant by-product. The main product of gasification is producer synthesis gas (PS), which is mainly composed by carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), methane (CH4) and minor impurities. Carboxydotrophic acetogenic bacteria can utilize CO and CO2 as carbon and energy source, and convert them into biomass, biofuels and biochemicals through the Wood-Ljungdahl pathway.
- Biohydrogen fermantative production : energetic valorization of microalgae biomassPublication . Batista, Ana Paula; Ortigueira, Joana; Gouveia, Luisa; Marques, Paula; Alves, Luís; Moura, PatríciaRenewable, sustainable and carbon-neutral energy production is needed to deal with the challenges of growing energy demand and climate change. Hydrogen (H2) is most promising in the succession of fuel evolution, with several technical, socio-economic and environmental benefits to its credit [1]. It is an excellent energy carrier as it has the highest energy content per unit weight/mass of any known fuel (142 kJ/g) and upon oxidation produces only water [1]. H2 is being explored for use in combustion engines and fuel-cell electric vehicles, and it is expected that H2 demand increases significantly in the near and long term [2]. Biological hydrogen production processes are found to be more environmentally friendly and less energy intensive as compared to thermochemical and electrochemical processes [1]. In dark fermentation, carbohydrate-rich substrates can be used to produce bioH2 in a process mediated by hydrogenase enzymes of anaerobic microorganisms. Moreover, residues and byproducts from agricultural and food industries or wastewaters can be used, providing inexpensive energy generation with simultaneous waste treatment [3]. Recently, there has been an increasing interest on using microalgal biomass for biofuels production. Besides oil extraction for biodiesel purposes [4] or sugar extraction for bioethanol production [5-6], microalgal biomass can also be fermented into bioH2. In this work, Scenedesmus obliquus biomass was used as feedstock for biohydrogen production by Enterobacter aerogenes and Clostridium butyricum. The concentration of microalgal biomass used as fermentation substrate was optimized for each microorganism: 2.5 g/L for E. aerogenes and 50 g/L for C. butyricum. The values of hydrogen production by using “wet” (75% moisture) and dried (oven, 80°C) microalgal biomass were compared, as the suppression of an intermediate biomass drying step is economically advantageous. The highest H2 yield (113.1 mL/g algaAFDW) was attained by C. butyricum with dried microalgal biomass. Hydrogen production by E. aerogenes was clearly improved by using S. obliquus wet biomass, generating an H2 yield of 72.3 mL/g algaAFDW
- Bioremediation of piggery effluents using Scenedesmus Obliquus microalga [Resumo]Publication . Batista, Ana Paula; Mirón, Vicente; Ribeiro, Belina; Silva, Teresa Lopes da; Barragán, Blanca E.; Gouveia, Luisa; Marques, Isabel PaulaEffluents from intensive pig farms present high nutrient concentration, mainly ammonium, contributing to water eutrophication and pollution. Microalgae ability to deplete inorganic nutrients makes them an efficient effluent bioremediation tool. Scenedesmus obliquus was grown in piggery effluent (without any pretreatment) diluted with tap water at 5%v/v (187±25mg/L N-NH4+) and compared with growth in synthetic Bristol media. A 21-days trial was performed in 1L bubble-column reactors illuminated by fluorescent and LED lamps(3klux). Microalgae growth was monitored through OD540nm, dry weight and Chlorophyll content and also by flow cytometry in terms of autofluorescence read in FL3 channel (>670 nm), cell size (FSC), internal complexity (SSC) and cell membrane integrity (PI). S. obliquus cells have grown slower in pig effluent (mmax=0.13-19d-1) than in Bristol media (mmax=0.46-0.50d-1) although after 15 days the biomass productivity observed for the pig waste cultivation, operated under LED (0.127gL-1d-1) was similar to those attained for the Bristol media after 8 and 12 days (0.130 and 0.129 gL-1d-1 using Fluorescent and LED lights, respectively). The Chlorophyll content was correlated to FL3 autofluorescence, with R2>0.97 for Bristol and R2>0.92 for pig waste cultures. Regarding cell size and complexity, Bristol cultures did not show significant differences along time, while cells grown on pig waste increased, attaining FSC and SSC values similar to those observed for Bristol cultures. However, pig waste led to higher percentage of cells with permeabilised membrane (up to 18%) than Bristol cultures (7%). For pig waste experiments, ammonium removal rates were 95% with final values within legal limits. S. obliquus cultivations proved to be an efficient system for direct piggery effluent bioremediation, attaining biomass productivities similar to those obtained in synthetic media. Using LED lighting enables to reduce the energy consumption while maintaining microalgae growth and bioremediation performance. Scale-up to an outdoor 150L photobioreactor is underway.
- Brazilian castor oil as raw material for biodiesel productionPublication . Lages, Cléia; Araújo, Eduardo; Oliveira, Ana Cristina