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Browsing UB - Resumos em livros de actas by Author "Arez, B. F."
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- 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 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.
- Zygosaccharomyces bailii strain talf1 inulinases/invertases towards enhanced bioprocessesPublication . Paixão, Susana M.; Arez, B. F.; Silva, Tiago; Teixeira, Pedro D.; Alves, LuísZygosaccharomyces bailii strain Talf1, a yeast recently isolated in our laboratory, produces a crude enzymatic extract that was determined to have both inulinase/ invertase activities. The properties of these activities were characterized and the crude extract was applied towards bioprocesses. The extracellular crude enzymatic extract presents activity in a range of temperatures from 20 to 60°C and pH from 4.5 to 7. Optimal pH and temperature was 5.5 and 50°C for both activities, with long-term thermostability at 25-30°C and pH 5.5. Maximal activities on crude were obtained when Jerusalem artichoke (JA) was used as inducer, attaining 18 and 156 U/ml of inulinase and invertase activities, respectively. Z. bailii Talf1 was used for bioethanol production through consolidated bioprocessing using JA juice as the only nutrients medium (~130 g/l total hydrolysable sugars), producing 67 g/l of ethanol and attaining the maximum theoretical yield (0.51 g/g hydrolysable sugars). Moreover, the crude enzymatic extract was applied for fossil fuels biodesulfurization. Thus, two renewable agro-materials, sugar beet molasses (SBM) and JA, were exploited as cheaper carbon sources for a cost-effective dibenzothiophene desulfurization process by Gordonia alkanivorans strain 1B through simultaneous saccharification and fermentation (SSF) approach. SSF with invertases/inulinases permitted an increase in 2-hydroxybiphenyl specific production rate of 19.5% from SBM (2.61 to 3.12 µmol g-1DCW h-1) and 64.6% (5.06 to 8.33 µmol g-1DCW h-1) from JA juice in comparison to acidic hydrolysis. These results highlight the potential of Talf1 as a CBP strain towards bioethanol and of its enzymatic crude towards enhanced biodesulfurization.