Navegando por Data de Publicação, começando com "2021-05-06"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 3 de 3

Produção de etanol 2g em reator de leito fixo e por bioprocessamento consolidado utilizando leveduras de alta performance
(Universidade Federal de São Carlos, 2021-05-06) Perez, Caroline Lopes; Esteves, Thais Suzane Milessi; https://lattes.cnpq.br/7000002745065879; Zangirolami, Teresa Cristina; https://lattes.cnpq.br/4546701843297248; https://lattes.cnpq.br/4188788274676361
In order to enable the industrial production of second generation (2G) ethanol, the development of processes with high productivity using hydrolysates of lignocellulosic material containing high concentration of inhibitors, with minimum enzymes concentration due to its impact on the total cost of the process, are some of the main challenges to be overcome. In this sense, researches in genetic engineering have been working towards obtaining yeast strains that are more tolerant to inhibitors present in hydrolysates and to the ethanol produced, as well as strains presenting capacity to produce and secrete enzymes, in addition to ferment pentoses and hexoses. The immobilization of cells in calcium alginate contributes to protect cells from the harmful effects of inhibitors, besides allowing the use of high cell densities, facilitating the recovery of products and the reuse of iocatalysts. Thus, the present work aimed to contribute to the development of a high productivity 2G ethanol production process using hemicellulose hydrolysates and superior recombinant yeast cells. At the first step of the research, after toxic and irreversible effects to the immobilized cells caused by the use of fermentative medium composed by concentrated hemicellulose hydrolysate during continuous fermentation were evidenced, experiments in mini-reactors unveiled the strong and synergistic effects between the high inhibitors load in fermentative medium and ethanol produced during ermentation, associated to the exposure time and the yeast strain characteristics. The results led the study to searching more robust and promising yeast strains, along with fermentative media presenting reduced inhibitors’ load. Three superior recombinant yeasts (S. cerevisae T18, HAA1 and MDS130) modified for xylose consumption, kindly donated by Prof. Johan Thevelein (KU Leuven and NovelYeast®, Belgium), were evaluated in different fermentative media formulated with concentrated crude hydrolysate (HC), detoxified hydrolysate (HD) and crude hydrolysate supplemented with molasses (MHB). The most encouraging results were achieved by the use of MDS130 strain and MHB medium, being this combination selected for further scale up in fixed bed bioreactors (BLF). Promising data regarding ethanol productivity (up to 20 g/L/h) and yield (up to 100% of the theoretical), besides high sugar conversion during the 20 recycles performed were reached with BLF. These results confirm the feasibility of the industrial application of the 2G ethanol production process from hemicellulose hydrolysate and molasses using recombinant yeast. In the second step of the present study, the superior recombinant yeast strain S. cerevisiae AC14, with capacity to secrete 7 hydrolytic enzymes, was evaluated for 2G ethanol production in a Consolidated Bioprocessing (BPC) system. Preliminary studies showed that free cells in high load enabled the hydrolysis and sequential fermentation of substrates such as cellobiose, corncob xylan and hydrothermal liquor (LH). Complementary experiments revealed that hydrolysis and fermentation steps from synthetic medium and solid (BTH) and liquid (LH) fractions obtained after hydrothermal pretreatment of sugarcane bagasse occurred in less than 10 hours in the presence of high cell load (optical density of 100), surpassing productivities from industrial enzymatic cocktails. Although the hydrolysis of the oligomers present in LH was not complete, the results here obtained are promising, indicating that the AC14 strain has potential of being used in BPC, enabling the 2G ethanol production from pretreated biomass.
Oxidação direta de metano a metanol sobre espécies [CuxOy] incorporadas em zeólitas ferrierita
(Universidade Federal de São Carlos, 2021-05-06) Passini, Ricardo José; Urquieta-González, Ernesto Antonio; https://lattes.cnpq.br/2389975677904655; https://lattes.cnpq.br/0176904791584331
The development of technologies to minimize the CO2 emissions, which are generated by the indiscriminate burning of fossil fuels, remains a relevant research topic in the context of the planet's sustainability. Thus, it is strategic to avoid the methane’s burning and even its proper emission, therefore being interesting valorize it as raw material to produce chemical and intermediates. In this scenario, the conversion of methane to methanol has gained strong relevance due to its wide application possibilities. However, the strong carbon and hydrogen bond in the methane molecule becomes a challenge in the search for routes to promote its reactivity. Another drawback to overcome is the methanol overoxidation because it is more reactive than methane itself. Considering the promising results of conversion and selectivity of methane to methanol over cationic clusters [CuxOy] incorporated in zeolites, this work evaluated ferrierite zeolites containing those species. The Cu-ferrierites were characterized by X-ray diffraction, nitrogen physisorption, scanning electron microscopy with energy dispersive X-ray spectroscopy, and temperature-programmed reduction with hydrogen. The catalytic evaluation involved three steps: (i) activation of the Cu-ferrierites under air flow at 550 ºC; (ii) reaction of methane to methanol at 210 ºC, and (iii) extraction of the adsorbed methanol. The results confirmed that cationic [CuxOy] complexes were the active species in the conversion of methane to methanol, since physical mixtures of copper oxide with the precursor ferrierites did not show methanol yield. With the aim to identify the active species, the Cu-ferrierites were analyzed in situ by FTIR and DRS UV-Vis in the same conditions used during the activation and reaction steps. The results showed bands attributed to dimeric copper species in the FTIR spectra and, in the DRS-UV-Vis spectra, bands corresponding to cationic complexes bis(μ-oxo) dicopper and μ-(η2:η2)peroxo dicopper, with the last being the precursor of the active species mono(μ-oxo) dicopper.
Caracterização e monitoramento de voçoroca associada a técnicas de controle através do método de estaqueamento
(Universidade Federal de São Carlos, 2021-05-06) Silva, Tayne Samara Machado da; Rotta, Cláudia Marisse dos Santos; https://lattes.cnpq.br/8142167187580488; https://lattes.cnpq.br/5831470828031789
Erosion consists in a natural geological process that is part of the terrestrial surface dynamics. However, human actions such as deforestation, agricultural activities without the adoption of conservationist techniques and excessive grazing, are the main responsible for the appearance of erosive features in rural areas. Such actions, associated with certain geological-geotechnical and environmental characteristics, can develop small and large erosive processes. Gullies are the most evolved and complex stage of linear erosion. For this reason, the recovery of areas degraded by these erosive features is, in general, difficult and expensive. Currently, there are several erosion control techniques, which can be adopted in different contexts, however, it is common, in rural areas such as the study sub-basin, to find these techniques associated with erosive processes, indicating misapplication. In this scenario, this work aimed to characterize and monitor by the staking method the evolution of the erosive processes of a sub-basin, where there are erosion control techniques. It was expected to identify if the erosive features are active, the conditions for their development and the reason for the failure of erosion control techniques. To develop this study, several materials were gathered, such as topographic map, satellite images, geological, pedological and geomorphological maps, as well as bibliographic materials. In addition, fieldworks were carried out to characterize and monitor erosive features, identify and evaluate erosion control techniques, and to verify and identify environmental aspects previously evaluated in office works. It was found in the study area an active gully erosion, continuous to the drainage channel. Analyzing the satellite images of the different years, it was verified a significant increase in the gully dimensions, while the staking method identified that the evolution of the gully is due to the destabilization of its walls. The geological-geotechnical and environmental characteristics of the study area, mainly the land use, explain the development of the gully erosion, at the same time the erosion control techniques proved to be inefficient, either by arbitrary use, as is the case of the brush barrier technique, or due to execution failures, as it was verified in the case of terracing.