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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Discovering Roles In The Evolution Of Collaboration Networks

Bharath Kumar, M 10 1900 (has links)
Searching the Web involves more than sifting through a huge graph of pages and hyperlinks. Specific collaboration networks have emerged that serve domain-specific queries better by exploiting the principles and patterns that apply there. We continue this trend by suggesting heuristics and algorithms to mine the evolution of collaboration networks, to discover interesting roles played by entities. The first section of the dissertation introduces the concept of nurturers using the computer science research community as a case study, while the second section formulates three roles - scouts, promoters and connectors, played by ratings in collaborative filtering systems. Nurturers: Nurturing, a pervasive mammalian trait, naturally extends to most association networks that involve humans. The increased availability of digital and online data about associations lets researchers experiment with algorithms to gain insight into such phenomena. Consider some examples of nurturing: • Slashdot endorsement. Slashdot was not the first site to link to Firefox, but the publicity Firefox received from this association surely helped it become popular quickly. The phenomenon of many small websites crashing due to publicity received through Slashdot has become well known as the Slashdot Effect. • A VC (Venture Capitalist) seed-funding a new startup. This event has a high nurturing value if the startup’s valuation increases rapidly after the funding. • A blogger writing about a topic. Kim Cameron has nurtured the “Laws of Identity” topic if it later becomes the buzz in blog circles. A nurturer need not always be the innovator or originator. The evangelist who adopts a prodigal idea and launches it on its way to success can also be a nurturer. • A professor guiding his student through the art of scientific research and bootstrapping him into a vibrant research community. New nodes not only emerge around these nurturers, but also become important in the network. Knowing nurturers is useful especially in vertical search, where algorithms exploit the structure of specialized collaboration networks to make search more relevant: knowing early adopters of good web pages can make web-search fresher; a list of VCs ranked by their nurturing value is useful to people with new startup ideas; the list of top nurturers in computer science is a valuable resource for a student seeking to do research. This dissertation presents a framework for discovering nurturers by mining the evolution of an association network, and discusses heuristics and customizations that can be applied through a case study: finding the Best Nurturers in Computer Science Research. Roles of Ratings in Collaborative Filtering: Recommender systems aggregate individual user ratings into predictions of products or services that might interest visitors. The quality of this aggregation process crucially affects user experience and hence the effectiveness of recommenders in e-commerce. The dissertation presents a novel study that disaggregates global recommender performance metrics into contributions made by each individual rating, allowing us to characterize the many roles played by ratings in nearest neighbor collaborative filtering. In particular, we formulate three roles - scouts, promoters, and connectors that capture how users receive recommendations, how items get recommended, and how ratings of these two types are themselves connected (respectively). These roles find direct uses in improving recommendations for users, in better targeting of items, and most impor -tantly, in helping monitor the health of the system as a whole. For instance, they can be used to track the evolution of neighborhoods, to identify rating subspaces that do not contribute (or contribute negatively) to system performance, to enumerate users who are in danger of leaving, and to assess the susceptibility of the System to attacks such as shilling. The three rating roles presented here provide broad primitives to manage a recommender system and its community.
132

Synthesis and Characterization of Pyrrole Based Adhesion Promoter Systems on Oxide Substrates

Cai, Xuediao 24 January 2005 (has links) (PDF)
For grafting polypyrrole on oxidized surfaces, 3-substituted pyrrole alkyl phosphonic acids, 11-(pyrrol-3-yl undecyl) trimethoxysilanes and 1-substituted pyrrole alkyl organosilanes with different chain length were designed and successfully synthesized as adhesion promoters. These new derivatives were studied for their adsorption behavior on oxide substrates and chemical or electrochemical deposition of polypyrrole over modified oxide surface or electrodes. Several analytical techniques such as contact angle measurement, surface plasmon resonance spectroscopy (SPR), UV-VIS Spectroscopy, grazing incident FTIR, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to characterize the adsorbed layers on different substrates. Contact angle measurement and ellipsometry data showed that high concentrations in apolar hydrocarbon solvent and long reaction times are sufficient to form tightly packed monolayer of 1-substituted pyrrole alkyl monochlorosilanes (PMCS) on substrates. Adsorption kinetics were studied by SPR and showed that the adsorption took place within a few seconds, then continuously increased and reached a plateau. The orientation of these synthesized monomers is investigated to be well-suited for use as adhesion promoter. CV-measurements showed that 3-substrated pyrrole derivatives had lower oxidation potential, whereas 1-substituted pyrrole derivatives had higher oxidation potential compared with pyrrole. Surface deposition of polypyrrole on the adhesion promoter modified (silane-modified and phosphonic acid-modified) substrates by chemical and electrochemical polymerization were investigated. PPy films formed on the modified surfaces by surface chemical polymerization showed a better adhesion compared to those on the unmodified surfaces. The morphology of PPy films was influenced by the alkyl chain length of the adhesion promoter and the deposition condition, such as choice of oxidant and solvent. The thickness of the resulting PPy films were controlled by the polymerization conditions, such as choice of solvent, deposition time, pyrrole to oxidant ratio and monomer concentration. The thickness of the deposited PPy film was estimated in the range of 10-400 nm by AFM and ellipsometry. The electrical properties were studied by current-voltage (j-V) measurement. Temperature dependence of j-V characteristics of Si/SiO2/PPy/PMCS-16/Al films revealed that the current increases with temperature, the film shows a typical semiconductor behavior. The use of these adhesion promoters modified electrode for electrochemical polymerization resulted in adhesive polypyrrole films.Also the 3-substituted pyrrole phosphonic acids were found to be homo-and co-polymerizable (with pyrrole) under chemical methods. TGA showed that homopolymers are less stable than polypyrrole due to the 3-substitution. he homopolymer of 3-substituted phosphonic acid derivatives of pyrrole is soluble. Films coated from the MeOH solution of homopolymer could be successfully used as humidity sensors. It is observed that the resistivity of the 3-substituted homopolypyrrole sensors increases and capacitance decreases during exposure to humid air. The polypyrrole films obtained by surface chemical polymerization was also used as humidity sensors.
133

The role of regulatory proteins at the FEPDGC-ENTS promoter region in escherichia coli a new model for the fur-DNA interaction /

Lavrrar, Jennifer L. January 2002 (has links)
Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 179-198). Also issued on the Internet.
134

Synthetic sensing systems in Saccharomyces cerevisiae

Bhattacharyya, Souryadeep 21 September 2015 (has links)
The yeast Saccharomyces cerevisiae is a major chemical production platform in the biotechnological industry. It is also increasingly being used as a whole cell biosensor. One method of developing such whole cell biosensors in yeast is by exploiting its mating pathway, which is normally induced by secreted pheromones leading to downstream expression of various genes. Functional expression of different recognition elements or receptors and their coupling to the yeast mating pathway can enable sensing of a variety of ligands. In this work, we have engineered a yeast strain to functionally express a heterologous human olfactory receptor gene which can be coupled to the pheromone signaling pathway, allowing yeast to detect medium chain length fatty acids, alcohols and aldehydes for the first time. Functionally expressing heterologous olfactory receptors in yeast is a challenging task because no definitive method exists on how to express such receptors on the yeast cell surface and couple them to the downstream signaling pathway. We explore in this work how the yeast cell can selectively respond to two activating ligands via two different receptors. We also demonstrate in this work that a synthetic transcription factor can substitute for the native transcription factor in the yeast mating pathway. We believe our biosensor will not only have various uses as a versatile sensor but also aid in the design of synthetic genetic circuits.
135

Impacts fonctionnels des polymorphismes dans les promoteurs des gènes de l’apoptose

Lalonde, Marie-Eve 04 1900 (has links)
La susceptibilité ou la résistance aux cancers peuvent impliquer plusieurs mécanismes, incluant l’apoptose, la croissance cellulaire et la différenciation, la réplication et la réparation de l’ADN. Mon projet porte plus particulièrement sur l’apoptose. Une dérégulation dans les voies d’activation de l’apoptose entraîne une accumulation de cellules déréglées, créant ainsi un environnement propice à l’instabilité génétique et au développement du cancer. Comme l’apoptose est une voie biologique hautement régulée, nous proposons l’hypothèse que des polymorphismes « fonctionnels » dans les régions de régulations des gènes (rSNPs) perturberaient cette voie à cause de taux variables de transcrits et des protéines correspondantes dû à la modification des sites de reconnaissances des facteurs de transcription. Les principaux objectifs de mon projet sont : (i) identifier les SNPs présents dans la région promotrice des gènes d’apoptose; (ii) déterminer les haplotypes de promoteurs les plus fréquents présents dans la population générale; (rHaps) (iii) vérifier leurs impacts fonctionnels sur l’expression génique par des essais in vitro (gène rapporteur et retard sur gel). Cette étude permettra d’identifier des rSNPs et rHaps ayant un impact sur le niveau d’expression des gènes d’apoptose, au moins dans un contexte in vitro. Ces différences alléliques au niveau de l’expression de ces gènes d’apoptose pourraient contribuer à la susceptibilité interindividuelle de développer un cancer. / Cancer susceptibility can involve many different mechanisms, including apoptosis, cell growth, cell differentiation, DNA replication and DNA repair. My project focuses on the apoptosis pathway. Decreased apoptosis level can lead to the accumulation of dysregulated cells, creating a favourable environment for genetic instability and tumorigenesis. Since apoptosis is a highly regulated pathway, the hypothesis of this project is that functional polymorphisms (rSNPs) in the regulatory regions of apoptosis genes such as promoters could create or disrupt transcription factor binding sites and modify their transcription levels. The main objectives of my project are: (i) Identify rSNPs in promoter regions of apoptosis genes; (ii) Calculate the frequent promoter haplotypes (rHaps) in general population; (iii) Validate their functional impact on gene expression with in vitro assays (gene reporter and gel shift). This study will allow identification of rSNPs and rHaps that could influence apoptosis gene expression levels, at least in the in vitro context. These allelic differences of expression in apoptosis genes could contribute to interindividual cancer susceptibility.
136

Impacts fonctionnels des variants génétiques dans les promoteurs des gènes associés à la survie et à la mort cellulaire

St-Cyr, Janick 08 1900 (has links)
La régulation de l’apoptose est importante dans le maintient de l’homéostasie cellulaire et l’intégrité du matériel génétique. L’apoptose est un mécanisme cellulaire qui élimine les cellules endommagées. Le bon fonctionnement de cette voie biologique est crucial pour contrer la propagation des cellules avec leurs anomalies génétiques. La dérégulation des gènes codants pour des composantes de la voie intrinsèque de l’apoptose est fréquemment observée chez divers types de cancers, incluant la leucémie. Nous proposons que des polymor¬phis¬mes fonctionnels localisés dans la région régulatrice (rSNP) des gènes impliqués dans la voie d’apoptose intrinsèque auraient un impact significatif dans l’oncogenèse en modifiant le taux d’expression de ces gènes. Dans cette étude, nous avons validé, à l’aide d’une combinaison d’approches in silico et in vitro, l’impact fonctionnel de la variabilité génétique sous la forme d’haplotypes (rHAPs), au niveau du promoteur proximal, de 11 gènes codant pour des composantes de la voie intrinsèque de l’apoptose. Pour ce faire, nous avons sous-cloné les rHAPs majeurs dans un vecteur contenant le gène rapporteur luciférase (pGL3b). Ces constructions furent utilisées dans des essais de transfections transitoires dans 3 lignées cellulaires (Hela, Jeg3 et Jurkat). Nous avons observé qu’au moins 2 rHAPs influencent significativement l’activité transcriptionelle de façon allèle spécifique. Ces rHAPs sont associés aux gènes YWHAB et YWHAQ. Les analyses de retard sur gel d’électrophorèse (EMSA) ont permis d’identifier 2 sites de liaison ADN-protéine différentielles dans les rHAPs du gène YWHAB. La variabilité du niveau d’expression des gènes étudiés pourrait contribuer à la susceptibilité interindividuelle de développer un cancer, tel que la leucémie de l’enfant. / The regulation of apoptosis is important in maintaining cellular homeostasis and the integrity of the genetic material. Apoptosis is a cellular mechanism that eliminates damaged cells. The operation of this biological pathway is crucial to counter the spread of cells and their genetic abnormalities. Deregulation of genes encoding components of the intrinsic pathway of apoptosis is frequently observed in various types of cancers, including leukemia. We propose that functional polymorphism located in the regulatory region (rSNP) of genes involved in the intrinsic apoptosis pathway would have a significant impact in oncogenesis by altering the expression levels of these genes. In this study, we validated, using a combination of in silico and in vitro approaches, the functional impact of genetic variability (analyzed as haplotypes, rHap) at the proximal promoters of 11 genes encoding components of the intrinsic apoptosis pathway. To do this, we subcloned the major rHaps in a vector containing the luciferase reporter gene (pGL3b). These constructs were used in transient transfection assays in three human cell lines (HeLa, Jurkat and JEG3). We observed that at least 2 rHaps significantly influence the transcriptional activity of a specific allele. These rHaps are associated with genes YWHAB and YWHAQ. Electrophoretic mobility shift assays (EMSA) have identified 2 sites for differential DNA-protein binding with the rHaps of YWHAB. Variability in the level of expression of the genes studied could contribute to interindividual susceptibility to developing cancer, such as childhood leukemia.
137

Évaluation de l'impact de l'utilisation de tylosine et de virginiamycine sur les profils de résistance aux antimicrobiens chez enterococcus SP. et Escherichia coli isolés de porcs

Desranleau Dandurand, Ulysse January 2008 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
138

Transformação genética de Citrus sinensis (L.) Osbeck para resistência a Candidatus Liberibacter ssp / Genetic transformation of Citrus sinensis (L) Osbeck for resistance to Candidatus Liberibacter spp

Eveline Carla da Rocha Tavano 19 February 2013 (has links)
A doença Huanglongbing (HLB) associada a bactéria Candidatus Liberibacter spp., que coloniza os vasos do floema, é considerada uma das mais graves doenças de citros. Uma importante estratégia para o controle desta doença consiste na produção de plantas transgênicas, expressando genes que codificam peptídeos antibacterianos especificamente no local de colonização do patógeno. O objetivo deste trabalho foi obter plantas transgênicas de laranja doce, expressando o gene que codifica o peptídeo antibacteriano atacina A (attA) dirigido por promotores específicos para a expressão gênica no floema. O trabalho foi iniciado com a elaboração de construções gênicas contendo o gene attA (associado ou não ao peptídeo sinal), sob o controle dos promotores AtSuc2 (transportador de sacarose), AtPP2 (proteína de floema 2), clonados de Arabidopsis thaliana, ou CsPP2 (proteína de floema 2), clonado de Citrus sinensis. Os experimentos de transformação genética foram realizados com C. sinensis cv. \'Hamlin\', \'Valência\', \'Pêra\' e \'Natal\', via Agrobacterium tumefaciens, utilizando-se segmento de epicótilo como explante. A identificação de plantas transgênicas foi realizada por meio da análise de PCR. Plantas PCR+ foram aclimatizadas e transferidas para casa-de-vegetação específica para o cultivo de plantas transgênicas. Análises de Southern e Northern blot foram realizadas em plantas aclimatizadas, confirmando-se a integração e transcrição do gene attA, respectivamente. A expressão do gene attA também foi confirmada pela análise de RT-qPCR. Plantas de laranja \'Hamlin\' contendo o gene attA (associado ou não ao peptídeo sinal), sob o controle dos promotores AtSuc2 ou AtPP2 foram propagadas por enxertia, para futura avaliação da resistência a Candidatus Liberibacter asiaticus / Huanglongbing (HLB) associated to Candidatus Liberibacter spp., which colonizes the phloem, is considered one of the most serious diseases of citrus. One important strategy to control this disease consists of producing transgenic plants expressing, in the bacteria colonization tissue, genes encoding antibacterial peptides. The objective of this work was to produce transgenic sweet orange plants expressing genes encoding the antibacterial peptide attacin A (attA) driven by phoem-specific promoters. The work started with the development of the gene constructs, containing the attacin A gene (with or without signal peptide) controlled by either sucrose transporter gene (AtSuc2) or phloem protein 2 gene promoters (AtPP2) from Arabidopsis thaliana, or phloem protein 2 gene promotor (CsPP2) from Citrus sinensis. The genetic transformation of C. sinensis \'Hamlin\', \'Valencia\', \'Pera\' and \'Natal\' cultivars was done via Agrobacterium tumefaciens. Epicotyls segments collected from in vitro germinated seedlings were used as explants. Transgenic plants were identified by PCR analyses. PCR positive plants were acclimatized and transferred to specific greenhouse. Integration and transcription of the attA gene was confirmed in acclimatized transgenic plants by Southern and Northern blot analysis, respectively. The attA gene expression was validated by RT-qPCR analysis. \'Hamlin\' transgenic cultivars containing the AtSuc2 or AtPP2 promoters controlling the expression of attA (with or without signal peptide) were propagated by grafting, for future evaluation of Candidatus Liberibacter asiaticus resistance
139

Influência do tipo de adubação na produção de aminoácidos e de ácido indol-3-acético, etileno e poliaminas por bactérias fixadoras de nitrogênio isoladas de cana-de-açucar (Saccharum sp.). / Influence of the type of fertilization on the production of amino acids and indole-3-acetic acid ethylene and polyamines by nitrogen fixing bacteria isolated from sugarcane (Saccharum sp.)

Felipe Ibañez de Santi Ferrara 13 October 2010 (has links)
Para se avaliar a influência da adubação orgânica, a que foi submetida cana-de-açúcar, na fisiologia de bactérias diazotróficas endofíticas foram identificados e estudados 36 isolados de plantas submetidas a tratamentos orgânico e convencional ou sem tratamento (controle). Foi evidenciado predomínio da família Enterobacteriaceae (75%). Essas bactérias foram avaliadas quanto à excreção de substâncias promotoras de crescimento vegetal (aminoácidos, poliaminas, AIA e etileno), escolhidas como indicadoras da ação do tratamento. Os resultados mostraram que foram significativamente maiores: a excreção de aminoácidos por bactérias provenientes do tratamento orgânico assim como a produção de etileno por bactérias isoladas de plantas controle. Além das 36 linhagens acima citadas, foram identificadas sete linhagens de Rhizobium por sequenciamento dos genes 16S rRNA, recA e gapA. Três dessas linhagens foram identificadas como Rhizobium trifolii, Rhizobium etli e Rhizobium hainanense. O gênero Rhizobium ainda não havia sido descrito como endofítico de cana-de-açúcar. / Aiming to evaluate the influence of the organic fertilization, applied to sugarcane, on the physiology of endophytic nitrogen-fixing bacteria, 36 isolates of plants submitted to organic and conventional fertilization or not fertilized (control) were identified and studied. Results showed that the major part of the strains belong to the Enterobacteriaceae family (75%). The excretions of amino acids, polyamines, IAA and ethylene substances chosen as indicators of the action of the treatment were evaluated in the 36 strains. The release of amino acids was significantly higher in cultures of bacteria isolated from organic treated plants and the production of ethylene was produced in greater amounts by strains isolated from control plants. Seven isolates, different from the 36 tested for the release of plant growth promoters, were identified as Rhizobium strains through 16S rRNA, recA and gapA sequences. Three strains were identified as Rhizobium trifolii, Rhizobium etli and Rhizobium hainanense. This genus was not described as endophytic of sugarcane previously.
140

Potencial de utilização de vinhaça como meio para o cultivo da microalga Chlorella vulgaris : aspectos toxicológicos e microbiológicos

Bonini, Monica de Albuquerque 04 March 2016 (has links)
Submitted by Luciana Sebin (lusebin@ufscar.br) on 2016-09-27T13:14:48Z No. of bitstreams: 1 TeseMAB.pdf: 527199 bytes, checksum: 9c17c3f72026e7aa20cc36238de2a00a (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-27T19:53:19Z (GMT) No. of bitstreams: 1 TeseMAB.pdf: 527199 bytes, checksum: 9c17c3f72026e7aa20cc36238de2a00a (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-27T19:53:27Z (GMT) No. of bitstreams: 1 TeseMAB.pdf: 527199 bytes, checksum: 9c17c3f72026e7aa20cc36238de2a00a (MD5) / Made available in DSpace on 2016-09-27T19:53:34Z (GMT). No. of bitstreams: 1 TeseMAB.pdf: 527199 bytes, checksum: 9c17c3f72026e7aa20cc36238de2a00a (MD5) Previous issue date: 2016-03-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Microalgae have been cultivated worldwide to obtain biomass for various applications. Nonetheless the production costs of microalgae is still high due to factors such as photobioreactors, water and nutrients to grow the organisms. In recent years the use of wastewaters of several origins for microalgal cultures have been studied. However wastewater generally are more complex than synthetic microalgae culture media. Their characteristics can vary over time and have associated microorganisms such as bacteria, fungi and yeasts. Vinasse is a wastewater generated in large volumes by the ethanol industry of Brazil and it is rich in nutrients and organic materials. The use of this effluent to support microalgae growth can reduce the microalgae production costs at the same time that it decreases the contaminant potential of the effluent through the incorporation of nutrients into biomass. The aim of this research was to evaluate the potential of the use of sugarcane vinasse as culture medium for the growth of the freshwater microalgae Chlorella vulgaris. C. vulgaris is a robust species commonly used in the treatment of effluents. Laboratory tests were initially conducted with two distinct vinasses, a conventional and an originating from a agroecological processing, at different concentrations. Based on these results the conventional vinasse was selected for more detailed studies that aimed at treating the vinasse in defined procedures known as Toxicity Identification Evaluation (TIE). Through such procedure, we attempted to answer why it is so difficult to grow microalgae in sugarcane vinasse and how could the microalgal production be increased in such a complex residue. The results showed that pH adjustment resulted in the highest Chlorella vulgaris biomass in vinasse, whereas the addition of EDTA, sodium thiosulfate and XAD-8 resin to remove specific compounds from the wastewater limited the microalgal final yield. The growth of C. vulgaris was higher at intermediate treated vinasse concentrations (30 - 70%). This demonstrated the possibility of using of this residue as a medium for microalgal cultivation. Once selected the ideal condition for C. vulgaris cultivation (30% vinasse and TIE pH=3.0), there was a screening of the microorganisms present in the vinasse and in non axenic cultures of microalgae after its inoculation with C. vulgaris. The microrganisms were isolated and characterized for indole acetic acid (IAA) production, nitrogen fixation and inorganic phosphate solubilization. The presence of heterotrophic microorganisms in the vinasse did not affect the microalgal production. We obtained promising results about future applications of these microorganisms as growth promoters in microalgal cultures. The biomass produced showed protein productivity of 15.57 mg L-1 day-1 and a decrease of nitrogen, sulfate, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC) and total nitrogen (TN) contents in comparison with the initial vinasse was obtained. The results suggest the possibility of using vinasse as a medium for the cultivation of C. vulgaris, with decrease of the potential contaminant of the effluent and increase of biomass production when compared to synthetic culture medium. / Microalgas têm sido cultivadas no mundo todo visando obter biomassa para as mais diversas aplicações. No entanto, seu custo de produção é elevado, pois além de demandarem elevada quantidade de água, exigem nutrientes minerais para que possam crescer satisfatoriamente. A utilização de águas residuárias para cultivos microalgais tem merecido destaque uma vez que, simultaneamente à possibilidade de se reduzir os custos de produção algal, é possível reduzir o potencial eutrofizante e contaminante dos efluentes através da incorporação de nutrientes ali presentes à biomassa microalgal. No entanto, efluentes apresentam maior complexidade do que meios de cultura sintéticos, com características variáveis ao longo do tempo e maior presença de micro-organismos associados como bactérias, fungos e leveduras. O Brasil é o maior produtor mundial de etanol de cana-de-açúcar e a vinhaça é o principal subproduto dessa produção, sendo gerada na proporção de 10 - 12 L vinhaça/L etanol. A presença de nutrientes minerais na vinhaça indica seu uso como adubo vegetal, quer seja para microalgas, quer para vegetais vasculares. Entretanto, cultivar microalgas em vinhaça é ainda um desafio. Se, por um lado, em cultivos fotoautotróficos a coloração escura do efluente pode ser limitante, em cultivos heterotróficos a presença de contaminantes biológicos pode levar à competição por recursos e comprometer a qualidade da biomassa final. O objetivo deste trabalho foi avaliar o potencial de utilização de vinhaça de cana-de-açúcar como meio para o cultivo da microalga Chlorella vulgaris, uma espécie robusta usualmente empregada em tratamento de águas residuárias. Buscou-se desvendar qual constituinte da vinhaça a torna tão problemática aos cultivos microalgais e analisar as possibilidades de cultivo fotoautotrófico objetivando, sempre, maior rendimento de biomassa. Ensaios laboratoriais foram conduzidos inicialmente com duas vinhaças, uma convencional e uma oriunda de um processamento agroecológico, utilizando diferentes concentrações para o cultivo microalgal. Com base nesses resultados, selecionou-se a vinhaça convencional para intensificação dos estudos referentes à toxicidade deste efluente. Ensaios envolvendo avaliação e identificação da toxicidade (TIE) foram conduzidos através de uma série de manipulações físico-químicas da vinhaça, com objetivo de alterar a biodisponibilidade de determinados compostos e, consequentemente, aumentar a produção microalgal. Os resultados mostraram que, dentre os tratamentos, o ajuste de pH foi o principal responsável pelo maior crescimento de Clorella vulgaris quando cultivada em vinhaça, enquanto a adição de EDTA, tiossulfato de sódio e resina XAD-8 ao efluente limitou o crescimento microalgal. O crescimento de C. vulgaris foi maior em concentrações intermediárias de vinhaça (30 – 70%), demonstrando a possibilidade de utilização deste resíduo como meio para o cultivo microalgal. Selecionada a condição ideal de cultivo para C. vulgaris, realizou-se um rastreamento dos microorganismos presentes na vinhaça e nas culturas não axênicas da microalga, com isolamento e caracterização dos mesmos no tocante à produção de ácido indolacético (AIA), fixação de nitrogênio e solubilização de fosfato inorgânico. A presença de micro-organismos heterotróficos na vinhaça não comprometeu o crescimento microalgal e os resultados mostraram-se promissores quanto ao uso dos micro-organismos isolados como promotores de crescimento em cultivos microalgais. A biomassa produzida apresentou produtividade protéica de 15,57 mg L-1 dia-1, com diminuição dos teores de nitrogênio, sulfato, demanda bioquímica de oxigênio (DBO), demanda química de oxigênio (DQO), carbono orgânico total (COT) e nitrogênio total (NT) em relação à vinhaça inicial. Os resultados sugerem a possibilidade de uso de vinhaça como meio para o cultivo de C. vulgaris, com redução do potencial contaminante do efluente e aumento da biomassa produzida em relação ao meio de cultura sintético.

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