Browsing by Author "Arez, B. F."
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- Advances in the reduction of the costs inherent to fossil fuel biodesulfurization towards its potential industrial applicationsPublication . Paixão, Susana M.; Silva, Tiago; Arez, B. F.; Alves, LuísABSTRACT: The biodesulfurization (BDS) process consists of 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.
- Advances in the reduction of the costs inherent to fossil fuel biodesulfurization towards its potential industrial applicationsPublication . Paixão, Susana M.; Silva, Tiago; Arez, B. F.; Alves, LuísABSTRACT: The biodesulfurization (BDS) process consists of 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.
- 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.
- Enhancement of dibenzothiophene biodesulfurization by Gordonia alkanivorans strain 1B using fructose rich culture mediaPublication . Alves, Luís; Silva, Tiago; Arez, B. F.; Paixão, Susana M.The removal of sulfur mediated by microorganisms or biodesulfurization (BDS) is already an extensively studied approach. The first studies were reported in the 50’s and 60’s, but only in the last 20 years have been successful breakthroughs. Through BDS it is possible to remove most of the recalcitrant sulfur compounds to the commonly physico-chemical process at mild operating conditions without molecular hydrogen, resorting to microorganisms. These microorganisms can remove sulfur from dibenzothiphene (DBT), a model compound, and other polycyclic aromatic using them as their sulfur source, making BDS an easy and environmental friendly process. Gordonia alkanivorans strain 1B [1] has been described as a desulphurizing bacterium, able to desulfurize DBT to 2-hydroxybiphenyl (2-HBP), the final product of the 4S pathway, using D-glucose as carbon source. However, both the cell growth and the desulphurization rate can be largely affected by the nutrient composition of the growth medium [2,3,4], due to cofactor requirements of many enzymes involved in BDS biochemical pathway.
- KOH for enhanced sugarcane bagasse delignification and further production of sugar-rich hydrolyzates by enzymes applicationPublication . Paixão, Susana M.; Ladeira, S. A.; Arez, B. F.; Martins, M. L. L.; Roseiro, J. Carlos; Alves, LuísLignocellulosic biomass is envisaged as an important raw material for bioethanol production due to its low cost and high availability. Sugarcane bagasse (SCB), a fibrous residue of cane stalks left over after crushing and extraction of the juice from sugarcane; it is one of the largest cellulosic agro-industrial by-products. Tons of SCB are produced in Brazil as a waste of sugar and ethanol industries. This lignocellulosic by-product is a potential renewable source for 2G-bioethanol production. Usually, SCB is pretreated using alkaline and/or acid treatments viewing higher ethanol yields. The main goal of this study was to optimize the delignification of SCB towards the higher availability of glucans and xylans for further enzymatic hydrolysis to obtain sugar-rich syrups that will be more readily fermented to bioethanol. The delignification was carried out by autoclaving the biomass with KOH and the influence of KOH concentration (1-10%) and the autoclave time (10-60 min) were evaluated through a statistical design. Experimental distribution for two factors according to the Doehlert uniform design was used to produce response surfaces. The responses studied in this design were the percentage of hemicellulose, lignin and total polysaccharides. The results showed that from the two factors evaluated, the KOH concentration was the one that most influenced the response observed and that the treatments of SCB with KOH 5-10% for 35 minutes of autoclave at 121ºC and 1 atm led to the highest rates of lignin extraction. Using KOH treatment, a significant reduction of lignin content in SCB was observed, namely from 19% to 5%. Scanning electron micrographs of SCB pre-treated with 10% KOH for 35 minutes demonstrated a change in the structure of the material, with the appearance of broken structures, which can be attributed to the alkaline treatment. To validate the experiments, the SCB pretreated in the optimal conditions (95% of total polysaccharides) was further hydrolyzed with commercial enzymes and the enzymatic hydrolysis performance was evaluated.
- Optimization of a SSF process using invertase applied to fossil fuels biodesulturizationPublication . Arez, B. F.; Alves, Luís; Roseiro, J. Carlos; Paixão, Susana M.
- Production and characterization of a novel yeast extracellular invertase activity towards improved dibenzothiophene biodesulfurizationPublication . Arez, B. F.; Alves, Luís; Paixão, Susana M.The main goal of this work was the production and characterization of a novel invertase activity from Zygosaccharomyces bailii strain Talf1 for further application to biodesulfurization (BDS) in order to expand the exploitable alternative carbon sources to renewable sucrose-rich feedstock. The maximum invertase activity (163 U ml.1) was achieved after 7 days of Z. bailii strain Talf1 cultivation at pH 5.5–6.0, 25 °C, and 150 rpm in Yeast Malt Broth with 25 % Jerusalem artichoke pulp as inducer substrate. The optimum pH and temperature for the crude enzyme activity were 5.5 and 50 °C, respectively, and moreover, high stability was observed at 30 °C for pH 5.5–6.5. The application of Talf1 crude invertase extract (1 %) to a BDS process by Gordonia alkanivorans strain 1B at 30 °C and pH 7.5 was carried out through a simultaneous saccharification and fermentation (SSF) approach in which 10 g l.1 sucrose and 250 ìM dibenzothiophene were used as sole carbon and sulfur sources, respectively. Growth and desulfurization profiles were evaluated and compared with those of BDS without invertase addition. Despite its lower stability at pH 7.5 (loss of activity within 24 h), Talf1 invertase was able to catalyze the full hydrolysis of 10 g l.1 sucrose in culture medium into invert sugar, contributing to a faster uptake of the monosaccharides by strain 1B during BDS. In SSF approach, the desulfurizing bacterium increased its ìmax from 0.035 to 0.070 h.1 and attained a 2-hydroxybiphenyl productivity of 5.80 ìM/h in about 3 days instead of 7 days, corresponding to an improvement of 2.6-fold in relation to the productivity obtained in BDS process without invertase addition.
- Production and characterization of Talf1 yeast invertases and further application to biodesulfurizationPublication . Arez, B. F.; Alves, Luís; Paixão, Susana M.Combustion of fossil fuels generates emissions of numerous toxic gases which in later years have become a major concern internationally. One of the most concerning problems is sulfur and sulfur dioxide, and maximum levels have been established through the years. Biodesulfurization (BDS) could be a complementary technology to the commonly used physico-chemical process. BDS is based on the use of microorganisms for the removal of sulfur even from the most recalcitrant compounds at atmospheric pressure and temperature, making it cheaper and more eco-friendly. However, this bioprocess has a few limitations, such as the high costs of the culture medium, which makes the process very expensive. Thus, in order to reduce its costs, it is important to search for cheaper carbon sources which can contribute to produce the microbial biomass. The goal of this work was the production and characterization of novel Z. bailii strain Talf1 invertases for further application to BDS, in order to expand the usable alternative carbon sources to high sucrose level feedstock, comparing two different approaches: Separated Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) processes.
- Properties of Anoxybacillus sp. 3M Xylanases and further application towards sugar rich hydrolysatesPublication . Alves, Luís; Ladeira, S. A.; Arez, B. F.; Paixão, Susana M.This study aimed to optimize the production of xylanases 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 batch fermentation testing several agroindustrial byproducts as inducer substrates (BSG - Brewer's spent grain, wheat straw, sugarcane bagasse, and corn cobs). In addition, the xylanases produced by this bacterium with the best inducer substrate were characterized for their optimal pH, temperature and stability. The results for xylanase production showed that the higher levels of xylanases were obtained in growth medium containing 1% (w / v) BSG (1.35 U/mL), but the xylanolytic activity was also observed when wheat straw (1.32 U/mL), sugarcane bagasse (0.80 U/mL), corn cobs (0.30 U/mL) and commercial xylan (0.21 U/mL) were used as substrates. The extracellular crude enzymatic extract from Anoxybacillus sp. 3M was then characterized for its optimal temperature and pH and stability. The best enzyme activity was observed at a temperature of 60 ºC and pH 5.3, and the enzyme retained 100% of its original activity after 96 h at 60 °C and pH 7.0. Zymogram of native gel analysis of the different culture supernatants revealed the presence of an enzyme complex with a molecular weight of 420 kDa. This xylanase may be considered as a biocatalyst thermotolerant and it is interesting for biotechnological applications. Further application of Anoxybacillus 3M crude enzymatic extract to BSG and commercial xylan revealed the presence of xylose and xylooligosaccharides, mainly X2 and X3, in the hydrolizates produced.
- Simultaneous saccharification and fermentation: a tool to improve fossil fuels biodesulfurization using Gordonia Alkanivorans strain 1BPublication . Paixão, Susana M.; Silva, Tiago; Arez, B. F.; Alves, Luís