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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.
151

CFD MODELING OF MULTIPHASE COUNTER-CURRENT FLOW IN PACKED BED REACTOR FOR CARBON CAPTURE

Yang, Li 01 January 2015 (has links)
Packed bed reactors with counter-current, gas-liquid flows have been considered to be applicable in CO2 capture systems for post-combustion processing from fossil-fueled power production units. However, the hydrodynamics within the packing used in these reactors under counter-current flow has not been assessed to provide insight into design and operational parameters that may impact reactor and reaction efficiencies. Hence, experimental testing of a laboratory-scale spherical ball, packed bed with two-phase flow was accomplished and then a meso-scale 3D CFD model was developed to numerically simulate the conditions and outcomes of the experimental tests. Also, the hydrodynamics of two-phase flow in a packed bed with structured packing were simulated using a meso-scale, 3D CFD model and then validated using empirical models. The CFD model successfully characterized the hydrodynamics inside the packing, with a focus on parameters such as the wetted surface areas, gas-liquid interactions, liquid distributions, pressure drops, liquid holdups, film thicknesses and flow regimes. The simulation results clearly demonstrated the development of and changes in liquid distributions, wetted areas and film thicknesses under various gas and liquid flow rates. Gas and liquid interactions were observed to occur at the interface of the gas and liquid through liquid entrainment and droplet formation, and it became more dominant as the Reynolds numbers increased. Liquid film thicknesses in the structured packing were much thinner than in the spherical ball packing, and increased with increasing liquid flow rates. Gas flow rates had no significant effect on film thicknesses. Film flow and trickle flow regimes were found in both the spherical ball and structured packing. A macro-scale, porous model was also developed which was less computationally intensive than the meso-scale, 3D CFD model. The macro-scale model was used to study the spherical ball packing and to modify its closure equations. It was found that the Ergun equation, typically used in the porous model, was not suitable for multi-phase flow. Hence, it was modified by replacing porosity with the actual pore volume within the liquid phase; this modification successfully accounted for liquid holdup which was predicted via a proposed equation.
152

Development of a Packed-bed Reactor Containing Supported Sol-gel Immobilized Lipase for Transesterification

Meunier, Sarah M. January 2012 (has links)
The objective of this work was to develop a novel enzyme immobilization scheme for supported lipase sol-gels and to evaluate the potential of the immobilized biocatalyst for the production of biodiesel in a packed bed reactor. Two sources of lipase (EC 3.1.1.3 triacylglycerol hydrolase) were used in this study and the transesterification of methanol and triolein to produce glycerol and methyl oleate was used as a model reaction of biodiesel production. A commercially available form of immobilized lipase, Novozym® 435, was used as a basis for comparison to the literature. Upon establishing a lipase sol-gel formulation technique, the experimental methodology for the transesterification reaction using Novozyme® 435 was developed. Subsequently, a series of inert materials were considered based on their suitability as supports for immobilized lipase sol-gels and the synthesis of methyl oleate. The value of a supported lipase sol-gel is to improve the activity and stability of the enzyme and develop an immobilized biocatalyst that is practical for use under packed bed reactor conditions. Of the six support materials considered (6-12 mesh silica gel, Celite® R633, Celite® R632, Celite® R647, anion exchange resin, and Quartzel® felt), the diatomaceous earth supports (Celite® R633, R632 and R647) exhibited high enzymatic activity, were thermally stable, and possessed high sol-gel adhesion. From the three types of diatomaceous earth considered, Celite® R632 supported lipase sol-gels were identified as the most promising supported lipase sol-gels for methyl oleate production via transesterification. Upon further evaluation, the Celite® R632 lipase sol-gels were found to achieve high methyl oleate percent conversions, glycerol-water absorption was only significant at glycerol levels higher than 75%, and the immobilized lipase had high stability upon storage at 4°C for 1.5 years. To determine the effects of methanol and glycerol inhibition as well as temperature on the reaction kinetics, a ping-pong bi-bi kinetic model was developed and validated over a range of methanol concentrations and temperatures. The optimal methanol concentration for the conditions tested was in the range of 1.3 M to 2.0 M, and increased with increasing temperature. The model developed was consistent with the experimental data and confirmed that glycerol inhibition and the presence of products had significant effects on the reaction kinetics. The methyl oleate production capabilities of the Celite® supported lipase sol-gel were investigated using a packed bed reactor and compared with Novozym® 435 under similar operating conditions. A kinetic and mass transfer based model was developed for the reactor system using a novel efficiency correlation to account for the effect of glycerol on the enzymatic activity. Increasing the flow rate (1.4 mL/min to 20 mL/min) increased the reaction rate, presumably due to the reduction of the glycerol inhibition effect on the immobilized biocatalyst. The Celite® supported lipase sol-gel was found to have superior performance over Novozym® 435 both under batch stirred tank reaction conditions and in a packed bed reactor (83% conversion for Celite® sol-gel vs. 59% conversion for Novozym® 435 at 20 mL/min in the packed bed reactor). Based on the results obtained, Celite® supported lipase sol-gels exhibited good performance for the transesterification of triolein with methanol to produce methyl oleate in both batch and packed bed reactors, and warrant further exploration for the enzymatic production of biodiesel.
153

New Techniques for Sample Preparation in Analytical Chemistry : Microextraction in Packed Syringe (MEPS) and Methacrylate Based Monolithic Pipette Tips

Altun, Zeki January 2008 (has links)
Sample preparation is often a bottleneck in systems for chemical analysis. The aim of this work was to investigate and develop new techniques to address some of the shortcomings of current sample preparation methods. The goal has been to provide full automation, on-line coupling to detection systems, short sample preparation times and high-throughput. In this work a new technique for sample preparation that can be connected on-line to liquid chromatography (LC) and gas chromatography (GC) has been developed. Microextraction in packed syringe (MEPS) is a new solid-phase extraction (SPE) technique that is miniaturized and can be fully automated. In MEPS approximately 1 mg of sorbent material is inserted into a gas tight syringe (100-250 μL) as a plug. Sample preparation takes place on the packed bed. Evaluation of the technique was done by the determination of local anaesthetics in human plasma samples using MEPS on-line with LC and tandem mass spectrometry (MS-MS). MEPS connected to an autosampler was fully automated and clean-up of the samples took about one minute. In addition, in the case of plasma samples the same plug of sorbent could be used for about 100 extractions before it was discarded. A further aim of this work was to increase sample preparation throughput. To do that disposable pipette tips were packed with a plug of porous polymer monoliths as sample adsorbent and were then used in connection with 96-well plates and LC-MS-MS. The evaluation of the methods was done by the analysis of local anaesthetics lidocaine and ropivacaine, and anti-cancer drug roscovitine in plasma samples. When roscovitine and lidocaine in human plasma and water samples were used as model substances, a 96-plate was handled in about two minutes. Further, disposable pipette tips may be produced at low cost and because they are used only once, carry-over is eliminated.
154

Associação de bactérias da família Enterobacteriaceae e Clostridium estertheticum com a deterioração blown pack em cortes cárneos embalados a vácuo

Felipe, Lívia Mara [UNESP] 06 June 2008 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:27:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-06-06Bitstream added on 2014-06-13T19:35:10Z : No. of bitstreams: 1 felipe_lm_me_jabo.pdf: 356871 bytes, checksum: 16d6d5f606db8c2a71fd32fc4c6570dc (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A deterioração “blown pack” é caracterizada por abundante produção de gás, induzindo a completa distensão da embalagem durante o processo de estocagem sob refrigeração. Quando a embalagem é aberta, há um odor desagradável, levemente fecal. O gás presente na embalagem é composto por dióxido de carbono e hidrogênio e por vários tipos butíricos do metabolismo fermentativo. O objetivo deste experimento foi determinar possíveis causadores deste tipo de deterioração, quantificando as populações de bactérias da família Enterobacteriaceae, e caracterizando-as nos principais gêneros e espécies encontradas, o número de bactérias ácido-lácticas, a freqüência de Clostridium estertheticum e do Clostridium gasigenes, em carnes próprias para o consumo e em carnes que apresentaram a deterioração “blown pack”. Para contagem e identificação dos membros da família Enterobacteriaceae e contagem de bactérias ácido-lácticas utilizou-se de técnicas microbiológicas clássicas. Já para pesquisa do C. estertheticum e C. gasigenes fez-se uso de técnicas de biologia molecular. Os microrganismos da família Enterobacteriaceae e bactérias ácido-láticas estavam presentes em populações elevadas e em maior número nas carnes com deterioração “blown pack”. A espécie mais freqüentemente encontrada foi a Hafnia alvei. As amostras com deterioração “blown pack’ apresentaram maior positividade para o C. estertethicum que amostras não deterioradas. Não houve diferença estatística de positividade para a presença do C. gasigenes entre amostras com deterioração “blown pack” e carnes não deterioradas. A principal forma de controle desta deterioração é a prevenção da contaminação da carne por material fecal. / The blown pack spoilage is characterised by abundant gas production, leading to complete gross distention pack during refrigerated storage. When the packaging is opened, there is an unpleasant smell, lightly fecal. The gas present in the package is composed of carbon dioxide and hydrogen and also of several butyric types of metabolism fermentation. The purpose of this experiment was to determine possible causes of this spoilage type, quantifying the populations of bacteria of the family Enterobacteriaceae, and characterizing them in the major genera and species found, the number of lactic acid bacteria, the frequency of Clostridium estertheticum and Clostridium gasigenes in meat proper for consumption and meat which showed the blown pack spoilage. In order to enumerate and identify the members of the Enterobacteriaceae family, and to enumerate the lactic acid bacteria the procedure was classical microbiological techniques. However to search the C. estertheticum and C. gasigenes the procedure was molecular biology techniques. The microorganisms of the family Enterobacteriaceae and lactic acid bacteria were present in large populations and in greater numbers in meat with blown pack spoilage. The species which were found more often was the Hafnia alvei. Samples of blown pack“ spoilage had greater positive features for C. estertethicum than samples not damaged. There was no statistical difference of positive features for the presence of C. gasigenes between samples of blown pack spoilage and not damaged meat. The main way to control this spoilage is the prevention of contamination of meat by fecal material.
155

ELETROCIRURGIA E CLIPES DE TITÂNIO PARA HEMOSTASIA EM PEDÍCULOS OVARIANOS DURANTE OVARIOHISTERECTOMIA VIDEOASSISTIDA COM DOIS PORTAIS EM CADELAS / ELECTROSURGERY AND TITANIUM CLIPS FOR HEMOSTASIS OF OVARIAN PEDICLES ON VIDEO-ASSISTED OVARIOHYSTERECTOMY WITH TWO PORTALS IN BITCHES

Guedes, Rogério Luizari 05 March 2012 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / This study evaluated the use of bipolar electrosurgery and laparoscopic clip applier with respect to surgical time, blood loss and inflammatory response during video-assisted ovariohysterectomy with two portals. Two groups (n=10) assessed each of the hemostatic techniques during castration and a third group (GIII, n=6) evaluated changes in serum promoted only by the clinical and anesthetic protocols used in order to exclude the changes made by them. The surgical times, such as the volume of blood loss were significantly lower in Bipolar Group. The inflammatory response was significantly higher throughout the evaluation period after surgery, but no clinical manifestations different than those presented by the Clipador Group. There were no significant changes in packed cell volume between the groups, but among the times evaluated it reduced about 10% from initial value until four hours after the procedure, in the surgical groups and Group III. Both techniques have good execution by the video-assisted procedure, however, the use of bipolar forceps allows minor surgical times, minimal blood loss and shorter learning curve for the surgeon. The bleeding does not result in physiological changes and that one s on packed cell volume are presented because of the clinical and anesthetic protocols. / Este estudo avaliou a utilização da eletrocirurgia bipolar e do clipador laparoscópico em relação ao tempo cirúrgico, perda sanguínea e resposta inflamatória durante a ovariohisterectomia videoassistida com dois portais. Dois grupos (n=10) avaliaram cada uma das técnicas hemostáticas durante as castrações e um grupo (GIII, n=6) avaliou as alterações séricas promovidas somente pelo protocolo clínico e anestésico utilizado, a fim de excluir as alterações promovidas por estes. O tempo cirúrgico, assim como o volume de sangue perdido foram significativamente menores no Grupo Bipolar. A resposta inflamatória apresentou valores significativamente maiores durante todo o período de avaliação pósoperatório, sem manifestações clínicas diferentes das apresentadas pelo Grupo Clipador. Em relação ao hematócrito não houve alterações significativas entre os grupos, mas entre os tempos de avaliação reduziu cerca de 10% do valor inicial, até quatro horas do final do procedimento, tanto nos grupos cirúrgicos como no Grupo III. Ambas as técnicas são de boa execução através do procedimento videoassistido, porém, o uso da pinça bipolar permite menores tempos cirúrgicos, sangramento mínimo e menor curva de aprendizado do cirurgião. O sangramento não acarreta em alterações fisiológicas e as mudanças apresentadas no hematócrito são provenientes dos protocolos clínico e anestésico instituídos.
156

Estudo cinetico da cloracao do silicio

SEO, EMILIA S.M. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:42:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:35Z (GMT). No. of bitstreams: 1 05027.pdf: 12073377 bytes, checksum: 07fdd3a7ed9e60cb7be90d8745f24034 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
157

Produção de hidrogênio em reator anaeróbio de leito fixo / Hydrogen production using up-flow anaerobic packed bed reactor

Bruna Soares Fernandes 16 May 2008 (has links)
O hidrogênio é estudado como alternativa ao uso de combustíveis fósseis para geração de energia, uma vez que é um combustível renovável, apresenta alta concentração de energia por unidade de massa e não gera gases causadores do efeito estufa. Entre os processos de produção de hidrogênio destaca-se o processo fermentativo, pois é um processo de baixo custo quando comparado com outros processos e possibilita unir tratamento de efluente e geração de energia. Neste sentido, este trabalho teve como proposta estudar parâmetros envolvidos no processo de produção fermentativo do \'H IND.2\'. O trabalho envolveu três etapas. Na primeira etapa, foi estudada a produção de hidrogênio a partir de sacarose empregando reatores anaeróbios de leito fixo de fluxo ascendente. Na primeira fase, comparou-se o desempenho de diferentes matérias suportes (argila, carvão vegetal e polietileno) e tempos de detenção hidráulica (TDH) (0,5 e 2h). Na segunda fase, testaram-se diferentes porosidades (50, 75 e 91%) do leito de polietileno TDH de 0,5 h. Os resultados mostraram que TDHs menores e maiores porosidades promovem maiores e contínuas produções de \'H IND.2\'. Na segunda fase, avaliou-se a produção de \'H IND.2\' a partir de quatro inóculos: metanogênico tratamento termicamente e três provenientes de biomassa aderidas aos materiais suportes empregados na primeira etapa. Todos inóculos produziram \'H IND.2\'. Na terceira etapa, avaliou-se a viabilidade de produzir \'H IND.2\' a partir de diferentes águas residuárias (sacarose, esgoto sanitário, vinhaça e glicerina). Houve conversão de hidrogênio a partir de todas as águas residuárias e a vinhaça mostrou ser o efluente mais promissor para esta finalidade. As análises biológicas mostraram baixa diversidade de fungos e bactérias, porém todos associados com o processo de formação de \'H IND.2\'. A varredura dos parâmetros estudados neste trabalho proporcionou o entendimento do processo, assim como, o mapeamento das variáveis adequadas para o projeto e viabilidade da aplicação de reatores desenvolvidos para geração de hidrogênio. / The hydrogen obtained by fermentative production is studied as an alternative process to provide energy instead of fossil fuel application. Moreover, hydrogen is a renewable fuel, has high energy content per unit weight (122 kJ/g), generates clean energy without pollution and produces no greenhouse gases. The fermentative process has low cost when it is compared with traditional process and photosynthetic process, because hydrogen can be produced from wastewater by anaerobic treatment process. For that reason, the aim of this research was to study some parameters involved in the hydrogen production by fermentative process. Three steps were developed. In the first step, it was studied the hydrogen production from sucrose using up-flow anaerobic packed-bed reactor, this step was divide in two phases. In the first phase three support materials (clay beads, vegetal coal and polyethylene) and two hydraulic retention times (0.5 and 2 h) were tested. In the second phase three porosities (50, 75 and 91%) of polyethylene bed were tested. The results demonstrated that the low HRT and high porosities provided high hydrogen production, although, the support materials did not show significant difference in the hydrogen production and in the biomass developed. In the second phase, four inocula were used in order to produce hydrogen: thermal pre-treated methanogenic sludge; and the others three came from the reactors used in the first phase. All inocula were able to produce hydrogen. In the third step hydrogen production was obtained from three wastewaters (domestic wastewater, vinasse and glycerol) and a control (sucrose) in batch reactors. The wastewaters and control produced hydrogen and the vinasse showed the highest production. This research makes available the comprehension on the influence of the different parameters in processes projected for hydrogen production and it makes viable to apply in full-scale.
158

Estudo cinetico da cloracao do silicio

SEO, EMILIA S.M. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:42:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:35Z (GMT). No. of bitstreams: 1 05027.pdf: 12073377 bytes, checksum: 07fdd3a7ed9e60cb7be90d8745f24034 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
159

Avaliação microbiologica e do potencial de estufamento por bacterias acido lacticas e enterobacterias em cortes bovinos embalado a vacuo / Microbiologycal evaluation and assessment of blowing ability by lactic acid bacteria and enterobacteriaceae in vacuum packed re meat

Chaves, Rafael Djalma, 1980- 04 August 2010 (has links)
Orientador: Pilar Rodriguez de Massaguer / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-15T20:08:51Z (GMT). No. of bitstreams: 1 Chaves_RafaelDjalma_M.pdf: 1221605 bytes, checksum: 39b07012e6e51d1b792777e7b85fb78b (MD5) Previous issue date: 2010 / Resumo: Este trabalho teve como objetivos avaliar a microbiota de carnes embaladas a vácuo, em específico bactérias ácido lácticas (BAL) e enterobactérias. Para tanto foram analisadas 12 amostras de carne bovina brasileira embaladas a vácuo, sendo 7 deterioradas (5 contra-filé, 1 cupim e 1 picanha) e 5 não deterioradas (contra-filé). As amostras foram cedidas por 2 frigoríficos do estado de são Paulo, com exceção de 3 amostras não deterioradas adquiridas em mercado localizado na cidade de Campinas. Foi realizada a avaliação visual e sensorial das amostras, bem como a enumeração e identificação dos isolados recuperados, para posterior utilização no ensaio de reprodução do defeito. Foi analisada também a contaminação na linha de produção do frigorífico parceiro, desde o local de confinamento do gado até as esteiras de embalagem. As contagens da superfície da carne e do exsudato foram realizadas em meios específicos para cada grupo estudado: de Mann, Rogosa & Sharpe (MRS Agar, Difco) para BAL e Violet Red Bile Agar (VRBA, Oxoid) acrescido de 1% de glicose para enterobactérias. A incubação se deu a 30°C por 4 dias. As médias das contagens de BAL encontradas para as carnes deterioradas ficaram em torno de 108UFC/mL para o exsudato e 107UFC/100cm2 para a superfície da peça. Já para as enterobactérias, 106UFC/mL e 104UFC/100cm2, respectivamente. Para as carnes não deterioradas as medias de BAL ficaram em 107UFC/mL para o exsudato e 105UFC/100cm2 para a superfície e para as enterobactérias, 102UFC/mL e 102UFC/100cm2 respectivamente. A diferença entre as médias das contagens do exsudato proveniente das amostras deterioradas e não deterioradas, assim como entre as médias da superfície também provenientes dos 2 tipos de amostra, foram consideradas significativamente diferentes (p < 0.01). Os isolados foram identificados pelo sistema API (bioMérieux®), sendo API 50CHL para BAL como: Lactobacillus brevis (1 isolado), Lactobacillus pentosus (2 isolados), Lactococcus lactis (2 isolados) e Leuconostoc mesenteroides (2 isolados) e API 20E para enterobactérias identificadas como: Hafnia alvei (4 isolados), Serratia marcescens (2 isolados), Serratia odorifera (1 isolado), Yersinia enterocolitica (1 isolado), Klebsiella pneumoniae (1 isolado), Escherichia coli (4 isolados), Ewingella americana (1 isolado), Buttiauxella agrestis (1 isolado), Enterobacter sakazakii (1 isolado) e Flavimonas oryzihabitans (1 isolado) sendo que a Hafnia alvei predominou em 50% das amostras de carne embalada a vácuo, já no ambiente de frigorífico a E. coli predominou no corredor de abate. Para a realização do teste de reprodução do defeito, 3 peças de contrafilé foram cortadas, assepticamente, em bifes de 10x5x2cm e inoculadas individualmente com suspensão de células vegetativas pré-ajustada de 108UFC/mL (Densimatic) de 6 diferentes isolados de enterobactérias, 4 de BAL e 1 Pseudomonas sp. O vácuo aplicado nas sacolas plásticas présoldadas (EVA multicamadas) com os bifes inoculados foi de 6mBar, praticado normalmente pela industria, seguido de termo-encolhimento por 4 segundos a 83°C. A incubação foi procedida por 4 semanas a 4 e 15°C. Após 7 dias de incubação a 15°C, foi observado estufamento nas embalagens inoculadas com Hafnia alvei. Todas as outras embalagens inoculadas com enterobactérias, assim como com BAL, iniciaram o estufamento das embalagens com 15 dias de incubação. Com incubação a 4°C e somente após 6 semanas, aconteceu perda de vácuo e início de estufamento na embalagem inoculada com H. alvei. Apesar de que, de acordo com a literatura, os Clostridium psicrotróficos estão envolvidos nos episódios de estufamento de embalagens, nesta pesquisa concluímos que linhagens de BAL (homo e heterofermentativas) e enterobactérias também causam este defeito. Além disso, o abuso de temperatura (15°C) reportado ao longo da linha de produção do frigorífico em estudo pode aumentar a contaminação inicial destes organismos, fazendo com que o acondicionamento a vácuo não se torne uma barreira tão eficiente ao desenvolvimento de micro-organismos deterioradores e patogênicos / Abstract: This work aimed to evaluate the bacteria flora of vacuum packed meat, particularly lactic acid bacteria (LAB) and Enterobacteriaceae. For both microorganisms, 12 samples of red vacuum packaged meat were analyzed, seven of which were deteriorated (5 striploin, 1 hump and 1 rump cap) and 5 fresh (striploin). The samples were donated by 2 slaughterhouses located in São Paulo State, except 3 samples which were purchased in a market located in Campinas city. Enumeration and identification of the recovered isolates were performed, followed by inoculation tests to verify the defect. Contamination of slaughterhouse production line was also analyzed, from the stockyard area until the conveyor belt after packaging. Surface and purge counts were made with specific culture medium: de Mann, Rogosa & Sharpe (MRS agar, Difco) for LAB and Violet Red Bile Agar (VRBA, Oxoid), 1% glucose added, for Enterobacteriaceae. Incubation was conducted at 30°C for 4 days, LAB average counts found for deteriorated samples were ~ 108CFU/mL in purge and 107CFU/cm2 in meat surface and 106UFC/mL and 104CFU/100cm2 for Enterobacteriaceae, respectively. For fresh samples, the values for LAB were 107CFU/mL in purge and 105CFU/100cm2 of LAB in the meat surface and for Enterobacteriaceae, 102CFU/mL for purge and 102CFU/100cm2 for meat surface. Mean counts between purge from deteriored and non deteriored samples and mean counts between meat surface from both samples were considered significantly different (p <0.01). Isolates were identified with API system (bioMérieux®): API 50 CHL for LAB: Lactobacillus brevis (1 isolate), Lactobacillus pentosus (2 isolates), Lactococcus lactis (2 isolates) and Leuconostoc mesenteroides (2 isolates) and API 20E for Enterobacteriaceae identified as: Hafnia alvei (4 isolates), Serratia marcescens (2 isolates), Serratia odorifera (1 isolate), Yersinia enterocolitica (1 isolate), Klebsiella pneumoniae (1 isolate), Escherichia coli (4 isolates), Ewingella americana (1 isolate), Buttiauxella agrestis (1 isolate), Enterobacter sakazakii (1 isolate) and Flavimonas oryzihabitans (1 isolate). Hafnia alvei was the dominant species in 50% samples of vacuum packed meat while in the abattoir environment, E. coli was dominant at the slaughter blood conveyor. For the inoculation test to verify the defect, 3 fresh vacuum pack strip loins were aseptically cut in 10x5x2cm beefs and inoculated individually with pre adjusted bacterial suspension 108CFU/mL (Densimatic) of 6 different Enterobacteriaceae isolates, 4 LAB and 1 Pseudomonas sp. were used individually. The applied vacuum in individual packs (EVA multilayer) was 6mBar, as industrial practice, followed by heat-shrinking of 83°C, 4s. Incubation was about 4 weeks at 4 and 15°C. After 7 days incubation at 15°C, blown pack was observed in samples with Hafnia alvei inoculated. In all other samples, the blown pack started after 15 days incubation. After 6 weeks at 4°C, was observed vacuum loss in the sample inoculated with H. alvei. Although, according to literature, the psychrotrophic clostridia are involved in blown pack cases, in this research it is concluded that LAB strains (homo ¿ heterofermentative) and Enterobacteriaceae also cause the defect. Besides, temperature abuse along the slaughterhouse production line (15°C) may increase initial contamination of these organisms, becoming the vacuum packaging a non so efficient barrier against spoilage and pathogenic microorganisms development / Mestrado / Mestre em Ciência de Alimentos
160

Modelagem matemática da degradação da glicose, com produção de hidrogênio, em um reator anaeróbio de leito fixo / Mathematical modeling of glycose degradation with hydrogen production in a fixed bed anaerobic reactor

Aline Cardoso Tavares 30 October 2008 (has links)
Modelos matemáticos oferecem grandes benefícios para a compreensão dos mecanismos envolvidos nos processos de tratamento de águas residuárias uma vez que fornecem interpretações e possibilitam previsões de desempenho, comparações de alternativas de tratamento, otimização de futuras plantas ou o aprimoramento das existentes, podendo subsidiar a elaboração de projetos em escala real. Em virtude disto, nesta pesquisa visou-se o desenvolvimento de um modelo bioquímico-matemático para descrever o processo de degradação da glicose em um reator anaeróbio de leito fixo com fluxo ascendente, com a resultante produção biológica de hidrogênio por meio do processo de fermentação. O desenvolvimento do modelo foi baseado em estudos sobre a cinética bioquímica e as características hidrodinâmicas do sistema. Os parâmetros de ajuste do modelo aos dados experimentais foram as constantes de velocidade das reações bioquímicas envolvidas na produção de hidrogênio. A calibração foi realizada manualmente buscando minimizar o desvio global. Para a determinação dos parâmetros foi utilizada a técnica de geração de números aleatórios com distribuição de freqüência uniforme e em seguida, o método de inversão de matrizes. O modelo matemático se revelou bastante adequado para a previsão do perfil de concentrações ao longo do reator, e possibilitou a representação das rotas de utilização da matéria orgânica. A reação de oxidação do ácido propiônico pelas bactérias acidogênicas produtoras de hidrogênio constitui a principal via de produção de \'H IND.2\' no sistema. / Mathematical models bring benefits to the understanding of mechanisms involved on wastewater treatment processes because they provide interpretations and make possible performance predictions, evaluation of design alternatives, optimization of future plants or the improvement to existing systems. Therefore, in this work a mathematical model to describe the glucose degradation process, with hydrogen production through the fermentation, in an upflow anaerobic packed-bed reactor is developed. The model equations were based on studies of biochemical kinetics and hydrodynamics features of the system. The parameters considered were the rates of the biochemical reactions involved in the hydrogen production. The calibration was made through the minimization of the global deviation. The parameters determination was obtained with the use of a technique of generation of aleatory numbers, and after that, the method of matrices inversion for the solution of the system of linear equations. The mathematical model developed showed to be adequate for the concentrations prediction along the reactor, and it made possible the representation of the routes of organic material utilization. The oxidation reaction of propionic acid is the main hydrogen production route in the reactor.

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