1,720,954 research outputs found
Produção de biossurfactante por Bacillus subtilis ATCC 21332 em condição anaeróbia
Get PDFTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2015.Biossurfactantes são compostos anfifílicos de origem biológica que possuem capacidade de reduzir a tensão superficial e interfacial. Dentre os mais efetivos estão os lipopeptídeos produzidos por bactérias do gênero Bacillus, especialmente a surfactina. Devido aos seus altos custos de produção sua aplicação ainda é limitada, tornando-se necessário processos que viabilizam economicamente sua produção. A produção de surfactina a partir de processos anaeróbios pode servir como uma alternativa na redução dos custos operacionais e estruturais. Além disso, microrganismos com capacidade de sintetizar surfactina em anaerobiose são de interesse da indústria petroquímica, pois ambos, surfactina e microrganismo podem ser empregados na extração do petróleo a partir de poços esgotados. Este trabalho teve como objetivo realizar o estudo cinético da produção do biossurfactante surfactina por Bacillus subtilis ATCC 21332 em condição anaeróbia. Todos os ensaios foram realizados em biorreator operado de forma descontínua, em meio salino baseado na composição da água do mar (meio MM), acrescido de glicose e de NaNO3 como fontes de carbono e nitrogênio, respectivamente, além de outros micronutrientes. Inicialmente, para efeito comparativo, B. subtilis foi cultivado na presença e na ausência de oxigênio, em meio MM contendo 10 g.L-1 de glicose e 4,25 g.L-1 de NaNO3. Os resultados mostraram que a presença de oxigênio favoreceu a síntese de surfactina, resultando em maior produtividade, 4,92 mg.L-1.h-1, em comparação ao anaeróbio, 1,84 mg.L-1.h-1. Os cultivos com diferentes relações carbono/nitrogênio (C/N) no meio MM, foram realizados com 10 g.L-1 de glicose e diferentes concentrações de NaNO3. Das condições testadas, a que se mostrou mais adequada foi a relação C/N 3,6, resultando em produção de 49,7 mg.L-1 e produtividade de 2,49 mg.L-1.h-1 em surfactina. A partir desta foram realizados dois cultivos no meio MM aumentando-se proporcionalmente as fontes de carbono e nitrogênio. A produtividade média de 1,75 mg.L-1.h-1 de surfactina, obtida nos cultivos contendo 15 e 20 g.L-1 de glicose foi inferior à produtividade alcançada com 10 g.L-1 de glicose, mostrando que houve efeito negativo com o aumento das concentrações. Avaliou-se também a produtividade em surfactina quando B. subtilis foi cultivado no meio mineral adicionado de micronutrientes (MM1) e de micronutrientes suplementado com 1 g.L-1 de extrato de levedura(MM2), acrescido de 20 g.L-1 de glicose. A maior produção de 101,8 mg.L-1 e a maior produtividade de 3,39 mg.L-1.h-1 em surfactina foram obtidas utilizando o meio MM2. Quando se avaliou a influência do aumento proporcional das fontes de carbono e de nitrogênio no MM2, os resultados mostraram efeito negativo sobre a produtividade emsurfactina a partir do aumento na concentração de glicose. A produtividade foi de 3,18 mg.L-1.h-1 e 1,63 mg.L-1.h-1 de surfactina, nos cultivos contendo 30 e 40 g.L-1 de glicose, respectivamente. Os resultados mostraram que a maior produtividade em surfactina (3,39 mg.L-1.h-1) foi obtida cultivando B. subtilis ATCC 21332 em biorreator anaeróbio no meio MM2 contendo 20 g.L-1 de glicose. As velocidades específicas de crescimento (µX), de consumo de substrato (µS) e de produção de biossurfactante (µP) correlacionaram-se bem, podendo-se então afirmar que a surfactina produzida por Bacillus subtilis ATCC 21332 está associada ao crescimento celular. A análise de espectroscopia de infravermelho por transformada de Fourier (FTIR) confirmou que o biossurfactante produzido é um lipopeptídeo do tipo surfactina. A surfactina semipurificada se mostrou efetiva e eficaz, pois apresentou CMC de 10 mg.L-1 e foi capaz de reduzir a tensão superficial da água de 72,0 para 29,9 mN.m-1. A solução aquosa de surfactina exibiu excelente capacidade emulsificante e estabilidade das emulsões formadas e, apresentou estabilidade na faixa de pH entre 6 e 8, salinidade de até 10 % de NaCl e tempo de exposição de 140 min a 100 °C.Abstract : Biosurfactants are amphiphilic compounds that have the ability to lower the surface and interfacial tension. Among the most effective biosurfactants are the lipopeptides produced by Bacillus, especially the surfactin. Due to their high production costs, its implementation is still limited, making necessary processes that economically allow its production. The production of surfactin from anaerobic processes can serve as an alternative in reduction of operational and structural costs. In addition, microorganisms capable of synthesizing surfactin anaerobically are interesting for petrochemical industry since both, surfactin and microorganism can be employed in the extraction of oil from depleted wells. This study aimed to perform a kinetic study of the production of surfactin by Bacillus subtilis ATCC 21332 in anaerobic conditions. All assays were performed in a bioreactor operated discontinuously, in saline medium based on the composition seawater (MM medium) supplemented with NaNO3 and glucose as carbon and nitrogen sources, respectively, and other micronutrients. Initially, for comparative purposes, B. subtilis was cultivated with and without oxygen, in MM medium containing 10 g.L-1 of glucose and 4.25 g.L-1 of NaNO3. Results showed that the presence of oxygen favored the surfactin synthesis, resulting in higher productivity, 4.92 mg.L-1.h-1, compared to the anaerobic process that was 1.84 mg.L-1.h-1. Cultures with different carbon/nitrogen (C/N) ratio in MM medium were performed at 10 g.L-1 glucose and different concentrations of NaNO3. Among the tested conditions, the C/N 3.6 had the best result, resulting in surfactin production and productivity of 49.7 mg.L-1 and 2.49 mg L-1.h-1, respectively. Based on these results, two cultures were performed in MM medium by increasing proportionally carbon and nitrogen concentrations. Average productivity in surfactin of 1.75 mg.L-1.h-1, that was obtained in the culture containing 15 and 20 g.L-1 glucose was lower than the productivity achieved with 10 g.L-1 of glucose, showing that there was a negative effect of increasing concentrations. It also evaluated the productivity of surfactin whenB. subtilis was grown on mineral medium supplemented with micronutrients (MM1) and added micronutrients and supplemented with 1 g.L-1 yeast extract (MM2) plus 20 g.L-1 glucose. The highest production of surfactin of 101.8 mg.L-1 and the highest productivity of 3.39 mg.L-1.h-1 were obtained usingMM2 medium. When it was evaluate the influence of the proportional increase of carbon and nitrogen sources in MM2, results showed negative effect on the surfactin productivity. The surfactin productivity was 3.18 mg.L-1.h-1 and 1.63 mg.L-1.h-1, in cultures containing 30 and 40 g.L-1 glucose, respectively. The results showed that the greater surfactin productivity (3.39 mg.L-1.h-1) was obtained by cultivating B. subtilis ATCC 21332 in an anaerobic bioreactor using MM2 as medium containing 20 g.L-1 glucose. From the specific growth rates (µX), substrate consumption (µS) and biosurfactant production (µP) data, it can be said that the surfactin produced by Bacillus subtilis ATCC 21332 its associated with cell growth. Analysis of Fourier transform infrared spectroscopy (FTIR) confirmed that the biosurfactant produced in this work is surfactin. The semi purified surfactin was effective and efficient, since it presented a CMC of 10 mg.L-1 and was able to reduce the surface tension of water from 72.0 to 29.9 mN.m-1. The aqueous solution of surfactin showed excellent emulsifying capacity and stability of emulsions formed and was stable in the pH range between 6 and 8, salinity up to 10 % NaCl and exposure time of 140 min at 100 °C
Emprego da microfiltração tangencial na obtenção de leite fermentado prebiótico
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Alimentos, Florianópolis, 2009.Através do processo de microfiltração (MF) em substituição a pasteurização do leite, foi obtido um microfiltrado com características físico-químicas e microbiológicas adequadas, sendo possível o seu empregado na elaboração de um leite fermentado padrão e de um leite fermentado prebiótico (adição de 5 % de inulina). Através das análises físico-químicas, durante 28 dias de armazenamento sob refrigeração (5 ± 1°C), pôde-se verificar que os teores de lipídios, proteínas e cinzas não foram influenciados (p > 0,05) pela adição de inulina, no entanto, o leite fermentado prebiótico durante o armazenamento, apresentou um aumento (p 0,05) durante os 28 dias de armazenamento, porém a adição de inulina proporcionou uma maior (p 0.05) by the addition of inulin. However, during storage the prebiotic fermented milk showed an increase (p 0.05) over the 28-day storage period, however, the addition of inulin resulted in a product with greater (p < 0.05) firmness and cohesiveness, and also led to a reduction (p < 0.05) in the syneresis index. The prebiotic fermented milk showed a lower tendency toward a greenish coloration, while the storage time led to an increase in a yellowish coloration. Over the 21- day storage period the rheological properties were evaluated at temperatures of 4°C and 6°C and the fermented milk samples had shear thinning, non-Newtonian and thixotropic fluid characteristics. The addition of inulin led to an increase (p < 0.05) in the apparent viscosity, and also a greater thixotropy (p < 0.05), which was represented by a greater area of hysteresis. It was observed that for the two fermented milk samples the apparent viscosity increased (p < 0.05) over a 21-day storage period. An increase in the temperature from 4°C to 6°C resulted in a decrease in the apparent viscosity and the hysteresis (p < 0.05)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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