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Avaliação de parâmetros globais de desempenho de biorreatores pneumáticos através de fluidodinâmica computacional
(Universidade Federal de São Carlos, 2015-03-25) Rodriguez, Guilherme Youssef; Béttega, Rodrigo; https://lattes.cnpq.br/1379682125857376; Badino Júnior, Alberto Colli; https://lattes.cnpq.br/6244428434217018; https://lattes.cnpq.br/3444129592454266
Pneumatic bioreactors are devices free of moving parts which have the purpose of converting raw materials in bio-products of commercial interest by the action of enzymes or cells. They are promising in the biochemical industry, ensuring good oxygen transfer and consuming less energy. Global performance parameters such as global gas hold up and the volumetric oxygen transfer coefficient are important criteria in the design and selection among different geometries of the mentioned devices. In the present work it was carried out modeling and simulation of pneumatic bioreactors based on Computational Fluid Dynamics (CFD) in order to estimate the global gas hold up and the volumetric oxygen transfer coefficient in three different geometries of pneumatic bioreactors: bubble column, concentric tube airlift and split tube airlift. The simulated results of each performance parameter were verified by comparison with the experimental values reported by Thomasi et al. (2010) and Mendes and Badino (2015) for the fluids distilled water, glycerol solution 10 cP and xanthan gum solution 0.2% w/v (weight/volume) in a wide range of specific air flow rate (0 to 5 min- 1). Application suite ANSYS® 14.5 was used for numerical simulations in CFD. Important parameters such as the bubble diameter played a great influence on results of the volumetric oxygen transfer coefficient. It can be observed by the experimental and simulated results that the concentric tube airlift bioreactor was the best alternative to the global gas hold up and the volumetric oxygen transfer coefficient (reaching 14% and 0.06 s-1 for distilled water, respectively). It was found that the results obtained via the CFD agreed with the majority trend of experimental data, capturing the most important hydrodynamic phenomena and mass transfer characteristics, showing that the modeling of different systems with different fluids fulfilled the main objective of obtaining reliable models design and performance of other geometries of pneumatic bioreactors.
Estudo da estrutura de complexos de polieletrólitos sobre as propriedades de transporte de água e sais
(Universidade Federal de São Carlos, 2015-03-25) Vale, Rayane da Silva; Silva, Caio Marcio Paranhos da; https://lattes.cnpq.br/7793686262868668; https://lattes.cnpq.br/9352007529619570
Polyelectrolytes complexes (PECs) are defined as materials formed by combining oppositely charged polyelectrolytes together via ionic interaction. PECs have some unique physical properties such as non-solubility in common organic solvents, high surface hydrophilicity, tunable surface charge, and stable structures. A new type of PEC based on chitosan (CS) and sulfonate poly(ethylene terephthalate) (SPET) were synthesized in two different media, buffer solution and salt solution acidified with acetic acid. Fourier transform infrared spectroscopy (FTIR), zeta potencial, X-ray diffraction, thermal gravity analysis and differential scanning calorimetry were used to characterize the chemical structure, particle charge, crystallinity and thermal stability. To assess how the internal structure of the PEC and the subsequent membrane formation can affect water and salts transport capacity of microporous polycarbonate membrane, PECs solutions were spread via casting in commercial membranes with pore size of 5 μm. These membranes were characterized by Scanning Electron Microscopy (SEM), Water Vapor Flux, Resistance to Ion Migration and Membrane Potential. FTIR results indicated the electrostatic interaction of polyelectrolyte to form the polyelectrolyte complex. From the results of zeta potential it was found that the surfaces of CS/SPET nanoparticles have positive charges of about 25 to 44 mV. TGA curves showed that the PECs were more stable than their polyelectrolytes. The deposition of the PEC on the membranes was confirmed by SEM images and the increase of water vapor flux of membranes indicated that the presence of the complex significantly alter the hydrophilic profile of the polycarbonate matrix. The microfiltration of Saccharomyces cerevisiae cells demonstrated that membranes modified with PECs retained more of these organisms than the commercial membrane without modification.