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Fermentation kinetics for xylitol production by a Pichia stipitis D-Xylulokinase mutant previously grown in spent sulfite liquor

RODRIGUES, Rita C. L. B.; LU, Chenfeng; LIN, Bernice; JEFFRIES, Thomas W.
Fonte: HUMANA PRESS INC Publicador: HUMANA PRESS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.33%
Spent sulfite pulping liquor (SSL) contains lignin, which is present as lignosulfonate, and hemicelluloses that are present as hydrolyzed carbohydrates. To reduce the biological oxygen demand of SSL associated with dissolved sugars, we studied the capacity of Pichia stipitis FPL-YS30 (xyl3 Delta) to convert these sugars into useful products. FPL-YS30 produces a negligible amount of ethanol while converting xylose into xylitol. This work describes the xylose fermentation kinetics of yeast strain P.stipitis FPL-YS30. Yeast was grown in rich medium supplemented with different carbon sources: glucose, xylose, or ammonia-base SSL. The SSL and glucose-acclimatized cells showed similar maximum specific growth rates (0.146 h(-1)). The highest xylose consumption at the beginning of the fermentation process occurred using cells precultivated in xylose, which showed relatively high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49). However, the maximum specific rates of xylose consumption (0.19 g(xylose)/g(cel) h) and xylitol production (0.059 g(xylitol)/g(cel) h) were obtained with cells acclimatized in glucose, in which the ratio between xylose reductase (EC 1.1.1.21) and xylitol dehydrogenase (EC 1.1.1.9) was kept at higher level (0.82). In this case...

Carotenoids production from a newly isolated Sporidiobolus pararoseus strain by submerged fermentation

CABRAL, Maria Marina Serrao; CENCE, Karine; ZENI, Jamile; TSAI, Sui Mui; DURRER, Ademir; FOLTRAN, Lillian Liva; TONIAZZO, Geciane; VALDUGA, Eunice; TREICHEL, Helen
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.19%
This work aimed at evaluating the total carotenoids production by a newly isolated Sporidiobolus pararoseus. Bioproduction was carried out in an orbital shaker, using 10% (w/v) of inoculum (25 A degrees C, 180 rpm for 35 h), incubated for 120 h in a dark room. Liquid N(2) and dimethylsulphoxide (DMSO) were used for cell rupture, and carotenoids were extracted with a solution of acetone/methanol (7:3, v/v). Optimization of carotenoids bioproduction was achieved by experimental design technique. Initially, a Plackett-Burman design was used for the screening of the most important factors, after the statistical analysis, a complete second-order design was carried out to optimize the concentration of total carotenoids in a conventional medium. Maximum concentration of 856 mu g/L of total carotenoids was obtained in a medium containing 60 g/L of glucose, 15 g/L of peptone, and 15 g/L of malt extract, 25 A degrees C, initial pH 4.0 and 180 rpm. Fermentation kinetics showed that the maximum concentration of total carotenoids was reached after 102 h of fermentation and that carotenoids bioproduction was associated with cell growth.

Influence of milk type and addition of passion fruit peel powder on fermentation kinetics, texture profile and bacterial viability in probiotic yoghurts

Perego, R.; Converti, A.; Oliveira, M. N.; Santo, A. P. Espirito do
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.27%
The effect of the addition of passion fruit peel powder (PFPP) on the fermentation kinetics and texture parameters, post-acidification and bacteria counts of probiotic yoghurts made with two milk types were evaluated during 28 days of storage at 4 degrees C. Milks were fermented by Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (CY340), and one strain of probiotic bacteria: Lactobacillus acidophilus (L10 and NCFM), Bifidobacterium animalis subsp. lactis (8104 and HN019). The addition of PFPP reduced significantly fermentation time of skim milk co-fermented by the strains L10, NCFM and HN019. At the end of 28-day shelf-life, counts of B. lactis Bl04 were about 1 Log CFU mL(-1) higher in whole yoghurt fermented with PFPP regarding its control but, in general, the addition of PFPP had less influence on counts than the milk type itself. The titratable acidity in yoghurts with PFPP was significantly higher than in their respective controls, and in skim yoghurts higher than in the whole ones. The PFPP increased firmness, consistency (except for the NCFM strain of L acidophilus) and cohesiveness of all skim yoghurts. The results point out the suitability of using passion fruit by-product in the formulation of both skim and whole probiotic yoghurts. (C) 2012 Elsevier Ltd. All rights reserved.; FAPESP; FAPESP; CNPq; CNPq; CAPES; CAPES

Ureia de liberação controlada, cinética e os produtos da fermentação in vitro de Brachiaria brizantha cv. Marandu em duas idades de rebrotação; Slow-release urea and the kinetics of in vitro fermentation of Brachiaria brizantha cv. Marandu in two regrowth ages

Padovani, Kathya Regina Fioravanti
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/06/2014 PT
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36.47%
Foi realizado no Laboratório de Ciências Agrárias da Faculdade de Zootecnia e Engenharia de Alimentos, um bioensaio de fermentação in vitro para avaliar a inclusão de doses crescentes de ureia de liberação controlada (ULC) em lâminas foliares de Brachiaria brizantha cv. Marandu em duas idades de rebrotação. Amostras colhidas em duas idades de rebrotação (28 e 65 dias, S28 e S65, respectivamente) foram incubadas em frascos com doses crescentes de ureia de liberação controlada (ULC - D0, D5, D10 e D20), em três inóculos distintos. O delineamento experimental foi em blocos casualizados fatorial 2 x 4. Foram realizadas análise de regressão e comparação entre médias pelo teste Tukey 5%. Durante 96 horas de fermentação foram colhidas s informações de leitura da produção de gases (tempos 4, 8, 12, 18, 24, 30, 36, 48, 60, 72, 84 e 96 h), concentração de N-NH3 (tempos 6, 12, 24, 48 e 96 h), e AGCC no fluido ruminal (tempos 24 e 48 h), pH (tempo 0 e 96h) e desaparecimento da FDN e MO (tempos 24, 48 e 96 h). Foram calculadas e analisadas as variáveis matemáticas geradas a partir do modelo exponencial indicando tempo de colonização (L), assíntota da curva de produção de gases (A), taxa de fermentação (µ)...

Chemical Composition, Rumen Fermentation Kinetics, Digestibility and Energy Value of Cassava Leaves Hay at Different Storage Times

Guimaraes Beelen, Patricia. M.; Santos, D. F.; Teixeira, I. A. M. A.; Amorim, P. L.; Lira Junior, W. B.; Paula, T. A.; Beelen, R. N.; Fraga, A. B.
Fonte: Int Buffalo Information Ctr Publicador: Int Buffalo Information Ctr
Tipo: Artigo de Revista Científica Formato: 928-928
ENG
Relevância na Pesquisa
46.17%
Cassava leaves have been widely used as a protein source for ruminants in the tropics. However, these leaves contain high level of hydro-cyanic acid (HCN) and condensed tannins (CT). There are evidences that making hay can eliminate more than 90% of HCN and that long-term storage can reduce CT levels. A complete randomized design with four replicates was conducted to determine the effect of different storage times (0-control, 60, 90 and 120 days) on chemical composition, in vitro rumen fermentation kinetics, digestibility and energy value of cassava leaves hay. Treatments were compared by analyzing variables using the GLM procedure (SAS 9.1, SAS Institute, Inc., Cary, NC). Crude protein (CP) and ether extract (EE) of the cassava hay were not affected (P > 0.05) by storage time (17.7% and 3.0%, respectively). Neutral detergent fiber, acid detergent fiber, total carbohydrate and non-fiber carbohydrate were not affected either (P>0.05) by storage time (47.5, 32.6, 72.3 and 25.8% respectively). However, other parameters were influenced. CT was lower (P<0.05) in hay after 120 days of storage compared with control (1.75% versus 3.75%, respectively). Lignin and insoluble nitrogen in neutral detergent, analyzed without sodium sulfite...

Procedimento para o desenvolvimento de um modelo matematico robusto para o processo de fermentação alcoolica; Procedure for development of a robust mathematical model for alcoholic fermentation process

Rafael Ramos de Andrade
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/08/2007 PT
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36.46%
Entre os principais problemas relacionados à produção de etanol está a falta de robustez da fermentação em presença de flutuações na qualidade de matéria-prima, o que leva a mudanças no comportamento cinético com impacto no rendimento, produtividade e conversão. Esta falta de robustez pode ser levada em conta através de ajustes operacionais e de controle, que pode ser melhorado com o uso de um modelo matemático preciso. Neste trabalho, um procedimento para o desenvolvimento de um modelo matemático robusto, valido em uma grande faixa de condição operacional foi estabelecido. Este modelo considera o efeito da temperatura na cinética. Experimentos foram executados em modo batelada. O microrganismo utilizado foi Saccharomyces cerevisiae e o meio de cultura, melaço de cana de açúcar. O objetivo foi avaliar a dificuldade em atualizar os parâmetros cinéticos quando se tem mudanças nas condições de fermentação. Rendimento e produtividade foram analisados como funções de temperatura e concentração inicial de substrato. Neste trabalho foi executada também a otimização dos parâmetros cinéticos no processo de fermentação alcoólica. Parâmetros cinéticos foram determinados como função da temperatura para fermentações em batelada na faixa de temperatura de 30 até 38oC. Baseado em dados experimentais...

Estudo da fermentação alcoolica em frascos agitados; Study of fermentation flasks

Leonel Vasco Ferreira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/12/2002 PT
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36.55%
Os experimentos de fermentação alcoólica foram conduzidos com diferentes quantidades de inóculo, pH inicial do mosto e temperatura de fermentação, estudando estas variáveis sob diferentes concentrações de substrato, em substratos de glicose, sacarose, xarope industrial e mel final da produção de açúcar. A cinética de liberação de C02 foi determinada em paralelo, em todos os experimentos. Também se determinou parâmetros cinéticos da fermentação alcoólica em substrato de glicose. As fermentações foram monitoradas com determinação de etanol, glicerol, açúcar residual, massa celular, viabilidade e contagem de leveduras, e outras variáveis; os índices de rendimento e parâmetros cinéticos também foram calculados. Os experimentos foram conduzidos em laboratório, com frascos agitados. O inóculo com 1cf células viáveis I mL resultou em fermentações rápidas (2 a 8 horas) enquanto que com 104células viáveis I mL as fermentações foram lentas (18 a 44 horas). Os pH iniciais de 3,5 e 5,0 mostram influir de forma diversa na fisiologia da levedura, resultando em alterações significativas no rendimento da fermentação. Foi observado que sempre que três fatores desfavoráveis se apresentam - alta concentração de substrato...

Construção de um software de simulação e ajuste de curvas cinéticas para o processo de fermentação em batelada alimentada; Construction of a software for kinetic simulation and curve fitting to fed batch fermentation process

Bernardo Hendler
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/07/2011 PT
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46.4%
Este trabalho teve como objetivo desenvolver um programa computacional capaz de auxiliar o estudo da cinética de fermentação em reator de batelada alimentada ou simples. O resultado foi o programa nomeado FERMENTA, o qual simula fermentação considerando tanto um único substrato, os açúcares redutores totais (ART), como dois substratos, a glicose e a frutose. A descrição cinética resulta de um procedimento computacional de simulação que utiliza equações modelo para a estimativa da velocidade específica de crescimento da levedura ( ? ), resolvendo numericamente, por Runge-Kutta de quarta ordem, as equações diferenciais dos balanços de massa para os componentes no reator. Os dados inseridos são os parâmetros de operação do reator e os valores dos parâmetros cinéticos da equação escolhida. A resposta é apresentada como gráfico das curvas cinéticas da concentração dos componentes, informando qualquer valor em qualquer instante. Se há dados experimentais, também são calculados os desvios entre estes e os valores simulados. Uma estratégia de regressão a partir da simulação utiliza uma matriz do tipo empregado em desenho fatorial completo e permite o ajuste dos parâmetros da equação para ? ao conjunto de dados experimentais...

In vitro rumen fermentation kinetics of diets containing oldman saltbush hay and forage cactus, using a cattle inoculum

Tosto,M.S.L.; Araújo,G.G.L.; Ribeiro,L.G.P.; Henriques,L.T.; Menezes,D.R.; Barbosa,A.M.; Romão,C.O.
Fonte: Universidade Federal de Minas Gerais, Escola de Veterinária Publicador: Universidade Federal de Minas Gerais, Escola de Veterinária
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
46.25%
The aim of this experiment was to evaluate, by means of the semi-automated in vitro gas production technique, fermentation kinetics of carbohydrates and degradability of dry matter (DM) and organic matter (OM) of diets containing oldman saltbush hay levels (8.4; 18.8; 31.2 and 48.3%) associated to forage cactus in natura. Pressure readings of the gases were done with a pressure transducer at 2, 4, 6, 8, 10, 12, 17, 20, 24, 28, 34, 48, 72 and 96h post-inoculation. The rumen kinetics was described by the following parameters: maximum potential of gas production, lag time and production rates of gas (k), fibrous carbohydrates (FC) and non-fibrous carbohydrates (NFC). It could be observed that the addition of oldman saltbush hay to the diets promoted a quadratic effect in the production of gases originated from NFC. However, there was no significant effect on the production of gases originated from FC and on production rates of gases from NFC and FC. The degradability of DM and OM did not differ due to the addition of oldman saltbush hay. The use of 8.4% hay and 74.9% forage cactus promoted the maximum potential of production of gases from the fibrous fraction of diets containing cactus and oldman saltbush hay.

Nutritional value of forage species from the Central Highlands Region of Mexico at different stages of maturity

Rayas Amor,Adolfo Armando; Estrada Flores,Julieta Gertrudis; Mould,Fergus Lawrence; Castelán Ortega,Octavio Alonso
Fonte: Universidade Federal de Santa Maria Publicador: Universidade Federal de Santa Maria
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2012 EN
Relevância na Pesquisa
36.55%
This paper has two objectives, the first is to determine the chemical composition, gas production parameters and the gas release kinetics, at different stages of maturity, of three grasses and a legume commonly found in long established pastures in Mexico central highland plateau. The second is to combine the gas release kinetics analysis and the GP fitted to a mathematical model in order to improve the biological understanding of the fermentation kinetics obtained from the GP technique. Representative samples of Pennisetum clandestinum (kikuyu grass), Sporobolus indicus (mouse tail), Eleocharis dombeyana (reed), Trifolium amabile (Aztec clover) plus a composite sample were collected in the growing season (July, September and November 2003) and analysed using an in vitro gas production (GP) technique. The accumulated GP was fitted to the model described in PALMER et al. (2005). Significant differences (P<0.001) were observed among species and periods for chemical composition, organic matter and neutral detergent fibre digestibility. Significant differences (P<0.05) were observed regarding fermentation parameters and gas release kinetic, with T. amabile and P. clandestinum being the species with the highest fermentability, whereas S. indicus and E. dombeyana were poorly fermented. P. clandestinum and T. amabile showed higher nutritive value than S. indicus and E. dombeyana. Composite samples were influenced by the chemical and fermentation characteristics of all species. It was concluded that the use of gas release kinetics analysis was useful for differentiating the fermentation kinetic of the soluble and insoluble fraction in the grasses and legume. Therefore by performing both approaches...

Kinetics Study of Extracellular Detergent Stable Alkaline Protease from Rhizopus oryzae

Mushtaq,Zareena; Irfan,Muhammad; Nadeem,Muhammad; Naz,Mammona; Syed,Quratulain
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 EN
Relevância na Pesquisa
46.34%
In this study, extracellular alkaline protease was produced from Rhizopus oryzae in submerged fermentation using dairy waste (whey) as a substrate. Fermentation kinetics was studied and various parameters were optimized. The strain produced maximum protease at initial medium pH of 6.0 medium depth of 26 mm, inoculum size of 2% at incubation temperature of 35ºC for 168 h of fermentation. Alkaline protease was purified to homogeneity by ammonium sulphate fractionation followed by sephadex G-100 chromatography. The molecular mass of alkaline protease was 69 kDa determined by 10% SDS-PAGE. The optimum pH and temperature of alkaline protease was 9.0 and 40ºC, respectively. Metal profile of the enzyme showed that the enzyme was non-metallic in nature. The Km , Kcat , Vmax and Kcat/Km values of purified protease were 7.0 mg/mL, 3.8 x102 S-1, 54.30 µmol/min and 54.28 s-1 mg -1.mL respectively, using casein as substrate. The purified alkaline protease had stability with commercial detergents.

Improvement of Nitrogen Assimilation and Fermentation Kinetics under Enological Conditions by Derepression of Alternative Nitrogen-Assimilatory Pathways in an Industrial Saccharomyces cerevisiae Strain

Salmon, Jean-Michel; Barre, Pierre
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /10/1998 EN
Relevância na Pesquisa
46.42%
Metabolism of nitrogen compounds by yeasts affects the efficiency of wine fermentation. Ammonium ions, normally present in grape musts, reduce catabolic enzyme levels and transport activities for nonpreferred nitrogen sources. This nitrogen catabolite repression severely impairs the utilization of proline and arginine, both common nitrogen sources in grape juice that require the proline utilization pathway for their assimilation. We attempted to improve fermentation performance by genetic alteration of the regulation of nitrogen-assimilatory pathways in Saccharomyces cerevisiae. One mutant carrying a recessive allele of ure2 was isolated from an industrial S. cerevisiae strain. This mutation strongly deregulated the proline utilization pathway. Fermentation kinetics of this mutant were studied under enological conditions on simulated standard grape juices with various nitrogen levels. Mutant strains produced more biomass and exhibited a higher maximum CO2 production rate than the wild type. These differences were primarily due to the derepression of amino acid utilization pathways. When low amounts of dissolved oxygen were added, the mutants could assimilate proline. Biomass yield and fermentation rate were consequently increased, and the duration of the fermentation was substantially shortened. S. cerevisiae strains lacking URE2 function could improve alcoholic fermentation of natural media where proline and other poorly assimilated amino acids are the major potential nitrogen source...

Oxygen Consumption by Anaerobic Saccharomyces cerevisiae under Enological Conditions: Effect on Fermentation Kinetics

Rosenfeld, Eric; Beauvoit, Bertrand; Blondin, Bruno; Salmon, Jean-Michel
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /01/2003 EN
Relevância na Pesquisa
46.49%
The anaerobic growth of the yeast Saccharomyces cerevisiae normally requires the addition of molecular oxygen, which is used to synthesize sterols and unsaturated fatty acids (UFAs). A single oxygen pulse can stimulate enological fermentation, but the biochemical pathways involved in this phenomenon remain to be elucidated. We showed that the addition of oxygen (0.3 to 1.5 mg/g [dry mass] of yeast) to a lipid-depleted medium mainly resulted in the synthesis of the sterols and UFAs required for cell growth. However, the addition of oxygen during the stationary phase in a medium containing excess ergosterol and oleic acid increased the specific fermentation rate, increased cell viability, and shortened the fermentation period. Neither the respiratory chain nor de novo protein synthesis was required for these medium- and long-term effects. As de novo lipid synthesis may be involved in ethanol tolerance, we studied the effect of oxygen addition on sterol and UFA auxotrophs (erg1 and ole1 mutants, respectively). Both mutants exhibited normal anaerobic fermentation kinetics. However, only the ole1 mutant strain responded to the oxygen pulse during the stationary phase, suggesting that de novo sterol synthesis is required for the oxygen-induced increase of the specific fermentation rate. In conclusion...

Characterisation of carbohydrate metabolism by industrial strains of Saccharomyces cerevisiae yeast.

Meneses, Florante Jon
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2007
Relevância na Pesquisa
36.58%
In the brewing industry, the rapid and efficient utilisation of fermentable carbohydrates are considered important attributes of the culture yeast. However, fermentation capabilities vary widely between brewing strains of yeast, especially with regard to the utilisation of individual sugars. Accordingly, this study was performed to determine the physiological and genetic basis for the differences in fermentation performance by brewing strains of the yeast Saccharomyces cerevisiae when presented with a composite of carbohydrates typical1y present in wort. Additionally, our investigation involved the determination of whether a desirable attribute of one strain is transferable to other strains. A model fermentation system employing a defined medium has been used to study sugar transport and catabolising capabilities. An emphasis has been placed on characterising the kinetics of utilisation of the predominant wort carbohydrate maltose as influenced by the presence of fructose, glucose and sucrose. The first phase of our study involved a survey of twenty eight strains of Saccharomyces cerevisiae consisting of brewing, baking, distilling, wine and laboratory strains, with regard to their fermentation kinetics and pattern of sugar utilisation. Stronger correlations were established between shorter duration of fermentation and biomass formation and rates of maltose or monosaccharide removal. Conversely...

Models for predicting wine fermentation kinetics

O'Neill, B.; Van Heeswijck, T.; Muhlack, R.
Fonte: Engineers Australia; online Publicador: Engineers Australia; online
Tipo: Conference paper
Publicado em //2011 EN
Relevância na Pesquisa
36.57%
Fermentation of grape juice by yeast is a critical stage in industrial wine production. However, the kinetics of the process are poorly understood due to the extreme conditions present during such fermentations. Problematic fermentations occur regularly and result in significant cost as a result of wasted tank capacity and low value of the final degraded product. Control of the fermentation process is important to avoid 'stuck fermentations' (a stuck fermentation is a fermentation that has stopped before all the available sugar in the wine has been converted to alcohol and CO2) and clearly, the fermentation unit operation strongly influences the aesthetic endcharacteristics of the wine. A variety of models have been proposed to predict the dynamic behaviour (kinetics) of the process. Two traditional and simple biochemical models (Monod kinetics and the Gompertz model) are predominantly employed and these were investigated in this work. The primary aim of this study was to determine the ability of both models to predict fermentation behaviour when fitted to data from early stages of fermentation. Initially, the Monod and Gompertz models were fitted to sugar consumption data for laboratory scale wine fermentations using least squares regression. The model produced a reasonable qualitative fit for the kinetic (growth and production) data with a root-mean-squared error (RMS) of 21 g/L or less in each case. Both models were then fitted to sugar consumption data from twenty two industrial fermentations over a varying number of time steps following the initial measurement in each data set. The number of time steps required to produce an RMS error less than 20 g/L was 8 days in 19 cases using the Monod model. However...

Modelagem de processo industrial de fermentação alcoolica continua com reatores de mistura ligados em serie; Industrial process modeling of continuous alcholic fermentation in cascade bioreactors

Lia de Mendonça Porto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/12/2005 PT
Relevância na Pesquisa
46.49%
Este trabalho consiste em determinar o modelo que melhor descreve a fermentação alcoólica industrial, em sistemas contínuos de reatores de mistura em série. Para determinação dos parâmetros cinéticos foi desenvolvido um programa utilizando os dados de análises feitas em amostras retiradas de usinas em operação. Dos modelos testados, o Tosseto (2002), Lee; Pagan; Rogers (1983) e Levenspiel (1980), não apresentaram incoerência física nem problema de convergência sendo estes indicados para descrever a cinética da fermentação alcoólica. Os parâmetros cinéticos comuns aos modelos apresentaram valores semelhantes, onde o parâmetro Ks' limitação pelo substrato, foi de 3,0:t 0,4, o valor da concentração limite pelo produto inibidor, Pmáx' foi 92:t 9 e o fator exponencial de inibição pelo produto, YN, foi 5,3:t 0,9. O fator de inibição pelo substrato do modelo Tosseto (2002), Ki, foi 27:t 5 . O parâmetro X máx ' inibição pela massa celular, e YM, fator exponencial desta inibição, para o modelo Lee; Pagan; Rogers (1983) foram 1O0:t 1 e 0,9:t 0,1, respectivamente. A escolha pelo modelo Tosetto (2002) para implementação do programa de simulação do processo foi devido à tentativa de uma maior abrangência na obtenção das constantes cinéticas devido à possibilidade de inibição pelo substrato. A simulação em regime permanente trata-se da resolução equações algébricas dos balanços de massa do sistema e é capaz de dimensionar a etapa de fermentação de novas plantas a serem implantadas...

Regulation of Saccharomyces cerevisiae maltose fermentation by cold temperature and CSF1

Hollatz,Claudia; Stambuk,Boris Ugarte
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2003 EN
Relevância na Pesquisa
46.22%
We studied the influence of cold temperature (10ºC) on the fermentation of maltose by a S. cerevisiae wild-type strain, and a csf1delta mutant impaired in glucose and leucine uptake at low temperatures. Cold temperature affected the fermentation kinetics by decreasing the growth rate and the final cell yield, with almost no ethanol been produced from maltose by the wild-type cells at 10ºC. The csf1delta strain did not grew on maltose when cultured at 10ºC, indicating that the CSF1 gene is also required for maltose consumption at low temperatures. However, this mutant also showed increased inhibition of glucose and maltose fermentation under salt stress, indicating that CSF1 is probably involved in the regulation of other physiological processes, including ion homeostasis.

Effect of sodium bicarbonate supplementation on feed intake, digestibility, digesta kinetics, nitrogen balance and ruminal fermentation in young fattening lambs; Efecto del bicarbonato sódico sobre la ingestión, digestibilidad, cinética de la digesta, balance de nitrógeno y fermentación ruminal en corderos en crecimiento cebo

Bodas, Raúl; Frutos, Pilar; Giráldez, Francisco Javier; Hervás, Gonzalo; López, Secundino
Fonte: Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (España) Publicador: Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (España)
Tipo: Artículo Formato: 174993 bytes; application/pdf
ENG
Relevância na Pesquisa
46.47%
12 pages, 4 tables.; [EN] Twenty-two Merino lambs (average weight=15.3 kg) were used to study the effects of inclusion of sodium bicarbonate in the concentrate on feed intake, digestibility, rate of passage, nitrogen balance and ruminal fermentation in vivo and in vitro. Lambs were allocated to two experimental groups receiving concentrate and 20 g kg-1 sodium bicarbonate (group Bic) or concentrate alone (group Control). Both groups received barley straw ad libitum. Faeces and urine were collected for 5 days to estimate digestibility, nitrogen balance and rate of passage. After slaughter (at 25 kg live weight), samples of rumen fluid were collected from each lamb to determine parameters of ruminal fermentation and to be used as inocula for batch cultures of rumen microorganisms. There were no significant differences between treatments (P>0.10) in concentrate intake, dry matter digestibility, nitrogen balance and digesta kinetics. However, straw intake was greater (P<0.05) and neutral- detergent fibre digestibility showed a tendency to be higher in the group Bic (P<0.10). No differences, due to the supplementation with sodium bicarbonate, were observed for in vivo pH, ammonia-N and volatile fatty acids concentrations (P>0.10). Results for rumen fermentation parameters determined in in vitro batch cultures and for fermentation kinetics estimated with the gas production technique followed a similar trend to results observed in vivo. Most parameters showed no significant differences between groups. Nevertheless...

Modelagem, simulação e otimização dinâmica aplicada a um processo de fermentação alcoólica em batelada alimentada; Modeling, simulation and dynamic optimization applied to an alcoholic fermentation process in fed-batch

Vilela, Paulo Roberto Chiarolanza
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/10/2015 PT
Relevância na Pesquisa
46.22%
O uso de etanol combustível no Brasil é hoje considerado o mais importante programa de combustível comercial renovável do mundo, sendo um potencial substituto aos derivados de petróleo. O aumento de rendimento fermentativo e a diminuição das perdas são objetivos de estudo em diversos centros de pesquisa, sendo o estudo da modelagem matemática e simulação do processo de grande importância para tal. A presente pesquisa apresenta como função identificar um modelo matemático para a linhagem isolada de Saccharomyces cerevisiae PE-2, de maneira a otimizar a maneira como é realizada a sua alimentação através de um controle H∞ por representação quasi-LPV. São realizados 9 ensaios de fermentação em 3 temperaturas distintas sob mesmas condições de concentração de substrato entrante. Após a finalização dos experimentos e análises, realiza-se a estimativa dos parâmetros componentes das equações diferenciais que modelam a cinética fermentativa, através de um algoritmo Quasi-Newton. De posse do modelo matemático, desenvolve-se um controle otimizado para a temperatura de 33ºC (temperatura usual de controle no processo industrial), considerando os parâmetros \"s\" e \"v\" variantes no tempo e os parâmetros x = 150 g/L e p = 70 g/L fixados...

The diversity and dynamics of indigenous yeast communities in grape must from vineyards employing different agronomic practices and their influence on wine fermentation

Bagheri,B.; Bauer,F.F.; Setati,M.E.
Fonte: South African Journal of Enology and Viticulture Publicador: South African Journal of Enology and Viticulture
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
56.46%
The current study evaluated the diversity of yeast species in Cabernet Sauvignon grape must derived from three neighbouring vineyards from a similar terroir but on which significantly different management practices are employed. The fermentation kinetics and yeast population dynamics were monitored from the beginning to the end of spontaneous fermentation. The grape musts were characterised by distinct yeast populations comprising oxidative, weakly fermentative and strongly fermentative yeasts. Different combinations of dominant non-Saccharomyces yeasts were observed in each must, with significantly different assortments of dominant species, including Starmerella bacillaris (synonym Candida zemplinina), Lachancea thermotolerans, Hanseniaspora uvarum, Candida parapsilosis and Wickerhamomyces anomalus. None of these yeast consortia appeared to affect the growth of Saccharomyces cerevisiae or inhibit the overall progress of fermentation. However, the percentage of fermentative yeasts was positively correlated with the fermentation rate. Glucose and fructose consumption rates suggested active participation of both glucophilic and fructophilic yeasts from the onset of fermentation. The data highlight two parameters, viz. initial cell concentration and yeast community composition...