Submitted by Raquel Vergara Gondran (raquelvergara38@yahoo.com.br) on 2016-04-11T17:52:57Z No. of bitstreams: 1 tese_daniele.pdf: 1693586 bytes, checksum: a89420a4bb70aea354ae5524f20ac563 (MD5) / Approved for entry into archive by cleuza maria medina dos santos (cleuzamai@yahoo.com.br) on 2016-05-04T20:39:58Z (GMT) No. of bitstreams: 1 tese_daniele.pdf: 1693586 bytes, checksum: a89420a4bb70aea354ae5524f20ac563 (MD5) / Made available in DSpace on 2016-05-04T20:39:58Z (GMT). No. of bitstreams: 1 tese_daniele.pdf: 1693586 bytes, checksum: a89420a4bb70aea354ae5524f20ac563 (MD5) Previous issue date: 2009 / Ao contrário dos bioprocessos submersos, que são amplamente utilizados e estudados, bioprocessos em estado sólido (BES) ainda são carentes de estudos de modelagem e simulação, o que aponta para o grande potencial de otimização. A dificuldade no aperfeiçoamento de BES está associada a problemas com a dissipação do calor gerado pelas atividades metabólicas do microrganismo durante o crescimento. Esta dificuldade na transferência de calor dentro do biorreator pode levar a zonas de altas temperaturas, que afetam adversamente a produtividade. A modelagem matemática é uma ferramenta essencial para otimizar bioprocessos. Através de modelos matemáticos é possível otimizar as variáveis operacionais para controle do bioprocesso e também analisar o design do biorreator. A otimização geométrica, de acordo com a Teoria Constructal, visa melhorar o desempenho do biorreator através, por exemplo, de minimizar a temperatura no interior do leito a níveis ótimos para o cultivo. O presente trabalho apresenta projetos de biorreatores para BES, todos com geometria otimizada, obtidos a partir de experimentação numérica, através de um software de computational fluid dynamics (CFD). O modelo matemático utilizado era preditivo e significativo ao nível de confiança de 95%. A otimização geométrica foi apresentada em função das condições operacionais do cultivo. Para o biorreator de coluna e leito fixo com paredes isoladas, foram apresentadas as geometrias ótimas em função da velocidade, da vazão e da temperatura do ar de admissão. Para uma temperatura do ar de admissão de 29,5 ºC, as configurações ótimas ((D/L)opt) variaram entre 1,0 e 2,4 para uma faixa de velocidade de admissão do ar entre 0,003 e 0,006 m s-1 . Relacionando com vazão, as razões mostraram-se ótimas entre 2,2 ≤ (D/L) ≤ 2,6 quando operando sob 3,3 a 3,5 10-5 m3 s-1 . Outro biorreator estudado foi o biorreator modular, composto de módulos elementares com geometria otimizada, sendo adaptável a diferentes escalas de produção e de fácil montagem. As configurações ótimas dos módulos de geometria retangular e seção quadrada foram apresentadas para diferentes volumes de módulos, em função da temperatura e da velocidade do ar de admissão. Foi observado que o volume máximo do módulo sem resfriamento externo é 5 L, para uma velocidade do ar de admissão acima de 0,0045 m s-1 e temperatura inferior ou igual 29,0 ºC O último biorreator proposto foi o biorreator hollow, semelhante a um biorreator de coluna e leito fixo, porém com um duto oco inserido nele. O duto interno tem inúmeros furos perpendiculares às suas paredes, mas sua saída é isolada, permitindo que o ar penetre no meio poroso. A geometria otimizada do biorreator hollow foi apresentada em função da fração de volume do duto interno, da razão entre os diâmetros de entrada e saída do duto interno, da vazão e da temperatura do ar de admissão. Em comparação com o biorreator de coluna convencional de mesmas dimensões e sob mesmas condições operacionais, o biorreator hollow apresentou temperatura máxima mais baixa, demonstrando que o projeto é eficiente para resfriar o meio poroso. Concluiu-se, enfim, no presente trabalho, que a geometria é um parâmetro importante e a sua otimização pode beneficiar o desempenho do biorreator. / Unlike the submerged bioprocesses, that was wildly used and studied, solid state bioprocess (SSB) are still poorly studied with respect to modeling and simulation, what indicates a big potential for optimization. The difficulty in the BES improvement is associated to problems with the dissipation of heat generated by metabolic activities of microorganisms during growth. This difficulty in transferring heat from the bioreactor could lead to areas with high temperature, which usually affect the productivity adversely. The mathematical modeling is an essential tool for optimizing bioprocesses. Using mathematical models it is possible to optimize operational variables to control the bioprocess and also explore the design of the bioreactor. The geometric optimization, according Constructal Theory, aims to improve the performance of the bioreactor through, for example, minimizing the temperature inside the bed to optimum levels for the bioprocess. The present work presents designs of bioreactors to SSB, all with optimized geometry, obtained from numerical experiments, by computational fluid dynamics (CFD) software. The mathematical model used has been predictive and significant at .95 level of confidence. The geometric optimization was presented as function of operational conditions of the cultivation. For the column fixed bed bioreactor with isolated wall, the optimal configurations are shown as function of flow, velocity and temperature of inlet air. For a inlet air temperature of 29.5 ºC, the optimal configurations ((D/L)opt) varied between 1.0 e 2.4 to a range of inlet velocity between 0.003 e 0.006 m s-1 . Relating with the volumetric flow, the optimal ratios presented between 2.2 ≤ (D/L) ≤ 2.6 when operating under 3.3 a 3.5 10-5 m3 s-1 . Other studied bioreactor was the modular bioreactor, consisting of elementary modules with optimized geometry, being adaptable to different scales of production and easy assembly. The optimal configurations of the modules with rectangular geometry and square section were shown depending on the volume of modules and the temperature and velocity of inlet air. It was observed that the maximum volume of the module without external cooling was 5 L, for a inlet velocity upper 0.0045 m s-1 and temperature smaller or equal to 29.0 ºC. The last proposed bioreactor was the hollow bioreactor, similar to a column fixed bed bioreactor, but with an empty duct inserted on it. The internal duct has innumerable holes perpendicular to its wall (the inlet port), but its end is insulated, allowing the air penetrates into the porous medium. The optimized geometry of hollow bioreactor was presented in function of the volume fraction of internal duct, the ratio between the diameters of inlet and outlet of the internal duct, the flow rate and temperature of the inlet air. Comparing with the conventional column bioreactor with the same configuration and same operational conditions, the hollow bioreactor showed a lower maximum temperature. This demonstrates that the project is efficient at cooling the porous medium. Finally, it was concluded that the geometry is an important parameter and its optimization can benefit the performance of the bioreactor.

Mikroalgen bieten eine hohe Variation unterschiedlichster Wertstoffe. Hochwertige Lipide, wie Omega-3- Fettsäuren, oder Antioxidantien, wie Astaxanthin und Phycocyanin, werden schon heute in großen Mengen aus Mikroalgen gewonnen. Um diese und weitere Stoffe auf dem europäischen Markt anbieten zu können, sind unterschiedliche Normen und Regelungen zu beachten. Die Einhaltung von Normen und Regelungen wird mit Zertifizierungen bestätigt. Dieser Praxisleitfaden bietet einen ersten Einstieg für alle, die in das Feld der zertifizierten Mikroalgenproduktion eintreten wollen. Er gibt einen Überblick über geltende Regelungen verschiedener Ziel-Märkte und damit verbundene Maßnahmen der Qualitätssicherung. Weiterhin werden detaillierte Checklisten sowie Muster für Standardarbeitsanweisungen und Prozessbeschreibungen (via Prozess-Turtle) zur Verfügung gestellt.:Kurzinformationen Einführung Unternehmensorganisation und Qualitätsmanagement Absatzmärkte, Normen und Verordnungen für Herstellung und Vertrieb von Mikroalgen Ausgewählte Vorschriften für zertifizierte Mikroalgenproduktion Handlungsempfehlung für die Erfüllung von GMP-Anforderungen Typische Standardarbeitsanweisungen Planung von Audits Zusammenfassung

Biomass is a valuable and limited resource that should be used efficiently. The potential of replacing fossil-based products with bio-based ones produced in biobased industrial systems is huge. One important aim of increasing the share of biobased products is to improve the sustainability of systems for production and consumption. Therefore, it is important to evaluate what solutions are available to improve the sustainability performance of bio-based industrial systems, and if they also bring negative impacts. The thesis focuses on assessing the role of biogas solutions in developing sustainable bio-based systems. Such assessments are often quite narrow in their scope and focus on quantitative environmental or economic aspects. This thesis aims at also including feasibility related aspects involving the contextual conditions that are assessed more qualitatively. Biogas solutions are identified as a versatile approach to treat organic materials which are generated in large volumes in bio-based industrial systems. The results show that biogas solutions in bio-based industrial systems (i) improve circular flows of energy and nutrients, (ii) are especially viable alternatives when the quality of the by-product streams become poorer, and (iii) may improve the profitability of the bio-based industrial system. To perform better assessments of these systems, it seems valuable to broaden the set of indicators assessed and include feasibility-related indicators, preferably through the involvement of relevant stakeholders as they contribute with different perspectives and can identify aspects that influence the sustainability in different areas. Future studies could benefit from applying those broader assessments on more cases to build on a more generalisable knowledge base.

L’acide 3-hydroxypropionique (3-HP) est une molécule plate-forme, particulièrement visée pour ses dérivés acrylés et les polyesters. Sa production par voie biotechnologique fait l’objet de nombreuses études, afin de les obtenir de manière biosourcée. Cependant, dans ces procédés, le 3-HP est dilué dans des milieux de fermentation contenant de nombreuses impuretés. De plus, l’accumulation de l’acide dans les milieux crée une forte inhibition sur les microorganismes producteurs. Nous proposons alors un procédé visant à extraire sélectivement le 3-HP du milieu de fermentation en même temps qu’il est produit afin de limiter son accumulation et de le purifier en continu. Les propriétés du 3-HP ainsi que les meilleures conditions de fermentation actuelles ont permis d’identifier l’extraction liquide-liquide réactive en contacteur membranaire comme une technique de choix. Nous avons tout d’abord élucidé le mécanisme réactionnel impliqué dans le système puis modélisé les équilibres associés afin de pouvoir prédire les rendements d’extraction en fonction de paramètres opératoires. Plusieurs méthodes de désextraction ont été testées, ce qui a permis de coupler les étapes d’extraction et de désextraction dans un procédé semi-continu mimant une production fermentaire. La modélisation dynamique de ce mode de fonctionnement a permis de prédire précisément les résultats expérimentaux. Les milieux ont alors été complexifiés afin de mieux représenter la réalité d’un milieu biologique en identifiant l’impact de chaque constituant. / 3-hydroxypropionic acid (3-HP) is a platform molecule targeted for its acrylated derivatives and polyesters. Its production through biological pathways is widely studied in order to make them bio-based. However, in such processes, 3-HP is diluted in fermentation broths containing many impurities. Moreover, the accumulation of the acid in the broths generates a strong inhibition towards the producing microorganisms. We suggest here a process aiming at extracting 3-HP selectively as soon as it is produced in order to reduce its accumulation and have it purified continuously. 3-HP properties as well as the current best fermentation conditions made us identify reactive liquid-liquide extraction in membrane contactors as promising technique. First, we elucidated the reaction mechanism of extraction in our system and then modeled the associated thermodynamic equilibria as a function of operating paramaters. Several back-extraction methods were tested and it allowed the coupling of the extraction and back-extraction steps in a semi-continuous process mimicking a biological production. The dynamic modeling of this operating mode made possible the accurate prediction of experimental results. The aqueous phase were then made more and more complex in order to better describe an actual fermentation broth and identify the influence of each component on the process efficiency in terms of yield, kynetics and selectivty.

Material degradation and a decrease of fuel quality are common phenomena when storing biomass. A magnitude of 7.8% has been reported to degrade over five months when storing spruce wood chips in the winter in Central Europe. This thesis presents a theoretical study of biomass storage. It includes investigations of bio-chemical, chemical and physical processes that occur during storage of chipped woody biomass. These processes lead to degradation caused by micro-activity, chemical oxidation reactions and physical transformation of water. Micro-activity was modeled with Monod kinetics which are Michaelis-Menten type of expressions. The rate expressions were complemented with dependency functions describing the impact of oxygen, moisture and temperature. The woody biomass was divided into three fractions. These fractions represent how hard different components of the wood are to degrade by microorganisms. Chemical oxidation was modeled as a first order rate expression with respect to the active components of the wood. Two different cases have been simulated during the project. Firstly, an isolated system with an initial oxygen concentration of air was considered. This case displayed a temperature increase of approximately 2˚C and a material degradation less than 1%. The second case considered an isolated system with an endless depot of oxygen. This case resulted in degradation losses around 0.45-0.95% in the temperature range between 65-80˚C during approximately 300 days of storage. The temperature increased slowly due to chemical oxidation.

Since the 1900’s it has been known that microorganisms are capable of generating electrical power through extracellular electron transfer by converting the energy found organic compounds (Potter, 1911). Microbial fuel cells (MFCs) has garnered more attention recently, and have shown promise in several applications, including wastewater treatment (Yakar et al., 2018), bioremediation (Rosenbaum & Franks, 2014), biosensors (ElMekawy et al., 2018) desalination (Zhang et al., 2018) and as an alternative renewable energy source in remote areas (Castro et al., 2014). In MFCs catalytic reactions of microorganisms oxidize an electron donor through extracellular electron transfer to the anode, under anaerobic conditions, with the cathode exposed to an electron acceptor, facilitating an electrical current (Zhuwei, Haoran & Tingyue, 2007; Lovley, 2006). For energy production in remote areas a low cost and easily accessible feed stock is required for the MFCs. Sweet sorghum is a drought tolerant feedstock with high biomass and sugar yields, good water-use efficiency, established production systems and the potential for genetic improvements. Because of these advantages sweet sorghum stalks were proposed as an attractive feedstock (Rooney et al., 2010; Matsakas & Christakopoulos, 2013). Dried sweet sorghum stalks were, therefore, tested as a raw material for power generation in a MFC, with anaerobic sludge from a biogas plant as inoculum (Sjöblom et al., 2017a). Using sorghum stalks the maximum voltage obtained was 546±10 mV, the maximum power and current density of 131±8 mW/m2 and 543±29 mA/m2 respectively and the coulombic efficiency was 2.2±0.5%. The Ohmic resistances were dominant, at an internal resistance of 182±17 Ω, calculated from polarization data. Furthermore, hydrolysis of the dried sorghum stalks did not improve the performance of the MFC but slightly increased the total energy per gram of substrate. During the MFC operation, the sugars were quickly fermented to formate, acetate, butyrate, lactate and propionate with acetate and butyrate being the key acids during electricity generation. Efficient electron transfer between the microorganisms and the electrodes is an essential aspect of bio-electrochemical systems such as microbial fuel cells. In order to design more efficient reactors and to modify microorganisms, for enhanced electricity production, understanding the mechanisms and dynamics of the electron transport chain is important. It has been found that outer membrane C-type cytochromes (OMCs) (including omcS and omcZ discussed in this study) play a key role in the electron transport chain of Geobacter sulfurreducens, a well-known, biofilm forming, electro-active microorganism  (Millo et al., 2011; Lovley, 2008). It was found that Raman microscopy is capable of providing biochemical information, i.e., the redox state of c-type cytochromes (cyt-C) without damaging the microbial biofilm, allowing for in-situ observation. Raman microscopy was used to observe the oxidation state of OMCs in a suspended culture, as well as in a biofilm of an MFC. First, the oxidation state of the OMCs of suspended cultures from three G. sulfurreducens strains (PCA, KN400 and ΔpilA) was analyzed. It was found that the oxidation state can also be used as an indicator of the metabolic state of the cells, and it was confirmed that PilA, a structural pilin protein essential for long range electron transfer, is not required for external electron transfer. Furthermore, we designed a continuous, anaerobic MFC enabling in-situ Raman measurements of G. sulfurreducens biofilms during electricity generation, while poised using a potentiostat, in order to monitor and characterize the biofilm. Two strains were used, a wild strain, PCA, and a mutant, ΔOmcS. The cytochrome redox state, observed through the Raman spectra, could be altered by applying different poise voltages to the electrodes. This change was indirectly proportional to the modulation of current transferred from the cytochromes to the electrode. This change in Raman peak area was reproducible and reversible, indicating that the system could be used, in-situ, to analyze the oxidation state of proteins responsible for the electron transfer process and the kinetics thereof.

Microalgae are considered as a potential feedstock for many promising applications. Some active substances in microalgae have plant biostimulation effects potentially useful in agriculture. However, to produce such a microalgal biomass, specific microalgae cultivation and post-treatment processes must be designed to preserve active substances. A particular focus is provided on cultivation (tubular photobioreactor) and different plausible post-treatment scenarios for microalgae separation (flocculation and centrifugation) and preservation (sterilization and drying). For each step, yield and energy consumption are modeled using data taken from literature or lab and pilot scale experiments. Industrial equipment for scale-up process is also studied by comparing existing systems. These models enable to make an economic evaluation of the whole process and to study its profitability for each scenario. The breakeven price is calculated as a function of the production rate. Several parameters are suggested to improve system efficiency and profitability at the end of this study. However, a better microalgae characterization and more experiments on potential post-treatment systems are required to improve the accuracy of the model.

Submitted by Caroline Periotto (carol@ufscar.br) on 2016-09-21T20:12:40Z No. of bitstreams: 1 TeseFFF.pdf: 5653411 bytes, checksum: 875bb8d2ed23313c792c9c246e285a85 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-23T18:31:05Z (GMT) No. of bitstreams: 1 TeseFFF.pdf: 5653411 bytes, checksum: 875bb8d2ed23313c792c9c246e285a85 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-23T18:31:11Z (GMT) No. of bitstreams: 1 TeseFFF.pdf: 5653411 bytes, checksum: 875bb8d2ed23313c792c9c246e285a85 (MD5) / Made available in DSpace on 2016-09-23T18:31:20Z (GMT). No. of bitstreams: 1 TeseFFF.pdf: 5653411 bytes, checksum: 875bb8d2ed23313c792c9c246e285a85 (MD5) Previous issue date: 2016-03-18 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Lignocellulosic ethanol, also called second generation ethanol, is a promising alternative for decreasing fossil fuel dependency globally. Nevertheless, its production process still needs further improvements in order to achieve industrial feasibility. Despite the massive experimental effort in this area, threshold values to be pursued in order to attain an economically feasible process are still missing. In this context, this study focused on constructing a methodology for economic evaluation of early-stage developing processes, such as second generation ethanol, aiming to show the R&D area directions to be followed for a successful industrial implementation of the process. The systematic procedure integrates bioprocess systems engineering (PSE) and economic engineering tools to perform a “retro” tecno-economic analysis. This analysis is able to identify the main process variables that influence the economic feasibility of the process and their target values. Initially, the methodology was tested on a case study involving the production of succinic acid from sucrose by fermentation. The methodology was able to eliminate one of the variables initially considered (sucrose conversion), due to its low influence on the process feasibility. Additionally, target values were obtained for the succinic acid concentration in the fermenter as a function of the selectivity and the specific productivity (the process variables chosen). Finally, the integrated production of ethanol from sugarcane juice and bagasse (first and second generation ethanol, respectively) was assessed. The three variables with the highest effect on the economic feasibility of the process were: the biocatalyst yield, the sucrose conversion and the solid mass fraction, both in the hydrolysis reactor. The reactor productivity, on the other hand, had little impact on the process feasibility. Besides, the experimental results already achieved the values needed for this variable. In general, the methodology was able to yield important information about both case studies required improvements for achieving economic feasibility. Although used in biochemical processes, the methodology is general, applying to all types of chemical processes. / A produção de etanol lignocelulósico, o chamado etanol de segunda geração, é uma alternativa promissora para diminuir a dependência energética global dos combustíveis fósseis. Entretanto, um desenvolvimento maior de seu processo de produção ainda é necessário para sua efetiva implementação industrial. Apesar do grande esforço experimental na área, ainda não existem informações claras sobre os valores limites a serem alcançados nas diversas etapas de processo para que esse se torne economicamente viável. Nesse contexto, o objetivo deste trabalho foi construir uma metodologia para avaliação econômica de processos em estágio inicial de desenvolvimento, como é o caso do etanol de segunda geração, indicando à área de P&D direções a serem seguidas para sua viável implementação industrial. Tal procedimento sistemático integra ferramentas de engenharia de bioprocessos e sistemas e engenharia econômica para realizar uma análise tecno-econômica “reversa”, que permite obter as variáveis que mais influenciam a viabilidade do processo, bem como seus valores limites para que tal viabilidade seja alcançada. Inicialmente, a metodologia proposta foi testada em um estudo de caso envolvendo o processo de produção de ácido succínico a partir da sacarose por rota fermentativa. Nesse processo, a metodologia conseguiu eliminar uma das variáveis inicialmente consideradas (a conversão da sacarose), devido a sua baixa influência. Além disso, foram obtidos valores mínimos para a concentração de ácido succínico no fermentador em função da seletividade e da produtividade específica (as variáveis de processo escolhidas). Em seguida, considerou-se a produção integrada de etanol a partir do caldo e do bagaço de cana-de-açúcar, etanol de primeira e segunda geração, respectivamente. As três variáveis com maior impacto na viabilidade econômica do processo foram: o rendimento do biocatalisador, a conversão da celulose no reator de hidrólise e a fração de sólidos nesse reator. A produtividade do reator, por outro lado apresentou baixo impacto na viabilidade, além de os resultados experimentais já estarem no patamar necessário para essa variável. De modo geral, a metodologia foi aplicada com sucesso aos estudos de caso escolhidos, produzindo dados importantes quanto às melhorias necessárias para que os processos alcancem a viabilidade econômica. Apesar de ter sido aplicada a bioprocessos, a metodologia é geral, sendo adequada ao estudo econômico de qualquer processo químico.

L'idée de base est de permettre à deux microorganismes de partager le même environnement tout en les maintenant séparées à l'aide d'une membrane perméable les retenant sélectivement. La principale contrainte résulte du transfert des composées d'intérêts limité par l'écoulement dans et autour des fibres ainsi que dans module et par le colmatage. Le double bioréacteur a membrane étudié dans cette thèse, de par son fonctionnement, alterne les cycles de filtration et rétrofiltration (ou rétrolavage), limitant ainsi en partie le colmatage. Ce travail de thèse s'est donc attaché à approfondir la connaissance des mécanismes de limitation au transfert mis en jeu lors de la filtration de fluide biologique complexes et évolutifs en fonction des conditions opératoires et des caractéristiques géométriques du module de filtration à fibres creuses. Dans cet objectif, sur la base des choix de configuration de module membranaire proposés dans cette étude, et afin de tendre vers une optimisation rationnelle de l'utilisation de ce dispositif, l'étude s'appuya sur l'utilisation d'outils de mécanique des fluides numériques, complétée par une approche expérimentale menée dans des conditions modèles. Les simulations réalisées par cette approche ont ainsi mis en évidence de grandes variations des vitesses de filtration le long de la fibre et ceci en lien direct avec une augmentation de la perte de charge à l'extérieur des fibres due au confinement induisant une baisse des performances de filtration. De manière similaire, un modèle numérique de formation de dépôt nous a permis d'évaluer l'effet du confinement de fibres. Il entraine une augmentation de pression dans la partie fluide externe induisant une forte variation de pertes de charges entrainant une répartition du dépôt le long de la fibre beaucoup plus inhomogène. Le retour du numérique à l'expérimental réalisé s'est attaché à décrire l'influence des conditions de mise oeuvre sur les performances de filtration du pilote. L'analyse méthodique de l'influence du sens de filtration et de la compacité dans le cas de fluides modèles (suspension de différents microorganismes / solutions de protéines modèles) et dans le cas de fluides biologiques évolutifs (milieux de fermentation + micro organismes) fut réalisée. L'ensemble de ces résultats nous permettent de donner des recommandations aux futurs utilisateurs du double bioréacteur à membranes. / This work presents a specific bioreactor previously designed to study microbial interactions. In this process, the microbial species in two tanks are physically separated by a microfiltration membrane. In order to give to the microorganisms a molecular environment in each compartment similar to the one that would be obtained if the microbial cells were cultivated in the same reactor, two criteria have to be considered: (i) the flow rates between compartments have to be sufficient with respect to the microbial kinetics and (ii) all the molecular compounds of the medium that have an effect on the microorganism behaviour must pass through the membrane. The main constrain is due to transfer of component limited by the fluid flow in and around the fiber of the filtration module. This thesis has therefore committed to deepening the understanding of the mechanisms limiting the transfer involved during the filtration of biological fluid complex according to operating conditions and geometric characteristics of the hollow fiber module of filtration. For this purpose, based on the choice of membrane module configuration proposed in this study, and to strive for a rational optimization of the use of this device, the study relied on the use of CFD tools, supplemented by an experimental approach conducted under models conditions. The numerical simulations of fluid flow have shown a modification of the axial filtration velocity profile with packing density. Similarly, a numerical model of cake deposit was developed and show difference of cake growth along the fiber with packing density. Two experimental hollow fiber modules with two packing densities were tested with clean water and biological fluid, and showed good agreement with the numerical data. These results underline the variations of filtration velocity along the fiber that will allow some predictions on fouling deposit to be done.

A microalga Spirulina platensis, que possui alto de teor de proteínas, vem sendo cultivada fotoautotroficamente para a produção de biomassa microbiana. Embora as fontes convencionais de nitrogênio utilizadas para a produção de Spirulina sejam os nitratos, há a possibilidade do emprego de fontes alternativas, como a uréia, utilizando o processo descontínuo alimentado, com diminuição do custo de produção. No entanto, o uso exclusivo de uréia, em função de sua hidrólise no meio de cultivo e conseqüente perda de amônia, pode levar as células a crescerem por determinados períodos sob carência da fonte de nitrogênio, uma vez que esta fonte não pode ser adicionada em grandes quantidades devido à toxicidade da amônia proveniente de sua hidrólise. Este trabalho teve como objetivo verificar se a adição de nitrato de potássio em cultivos realizados com uréia podem levar a processos com maior produtividade e/ou aumento na quantidade de biomassa produzida. Foram verificadas várias proporções entre as concentrações iniciais de nitrato de potássio e uréia, utilizando planejamento experimental e a metodologia de superfície de resposta. As variáveis dependentes foram concentração celular máxima (Xm), produtividade em células (Px) e fator de conversão de nitrogênio em células (YX/N), bem como, os teores de clorofila, proteínas e lipídios na biomassa obtida. Os resultados obtidos permitiram concluir que a associação de nitrato de potássio e uréia aumentaram a concentração celular máxima. A condição ótima obtida pela análise de regressão multivariável para Xm foi 17,3 mM de KNO3 e 8,90 mM de uréia, nessas condições foram obtidos 6077 ±199 mg/L. / The cyanobacterium Spirulina platensis, that have high protein content, has been cultivated photoautrophically for microbial biomass production. However nitrates are the conventional nitrogen sources for Spirulina, there is the possibility of use alternative source, as urea by fed batch process, decreasing the costs of production. So, the exclusive use of urea, due to urea hydrolysis in culture medium and consequently loss of ammonia, can cause the cell to growing for specific moments without nitrogen source, because urea can not be added in huge quantity due to the ammonia toxicity provide by its hydrolysis. This work have as objectives verify if the potassium nitrate addition in the culture carried out with urea can lead a process with more productivity and/or increase in the biomass quantity. It was verified many proportion between initial concentration of potassium nitrate and urea, using experimental planning and surface response methodology. The dependent variables were maximum cell concentration (Xm), cell productivity (Px) and nitrogen-cell conversion factor (YX/N), as well as biomass contents of chlorophyll, protein and lipids. The results allowed us concluded that the association of KNO3 and urea was good and improved the maximum cell concentration. The optimal condition otained by statistic analysis for Xm was 17,3 mM of KNO3 and 8,90 mM of urea. In this condition the maximum cell concentration was 6077 ±199 mg L-1.