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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.
1

Transport and metabolism of carbohydrates by anaerobic gut bacteria

Degnan, B. A. January 1992 (has links)
No description available.
2

The Impact of Bifidobacterium bifidum and its Surface Protein BopA on the Murine Intestinal Barrier and Endogenous Microbiota Composition

Villa, Christopher 03 January 2012 (has links)
Bifidobacterium bifidum MIMBb75 is a novel strain whose behavior within the intestinal tract is not known. This work attempts to determine the survival and molecular determinant responsible for its colonization through two studies involving administration to mice of 1) B. bifidum MIMBb75 or 2) engineered B. longum NCC2705 expressing the B. bifidum-specific surface protein BopA. MIMBb75 was able to transiently colonize the murine intestinal tract. As a result, endogenous bifidobacteria increased significantly in the proximal colon whereas Clostridia clusters were differentially affected in a region-dependent fashion. Genetically engineered B. longum NCC2705, expressing the BopA gene, did not impact endogenous bacterial groups in the proximal colon or feces, albeit, it down-regulated the gene expression of KC and mucin 4 in the proximal colon. These outcomes indicate that MIMBb75 encompasses characteristics of a probiotic, but further studies are required to assess the role of BopA as the molecular determinant of its action.
3

The Impact of Bifidobacterium bifidum and its Surface Protein BopA on the Murine Intestinal Barrier and Endogenous Microbiota Composition

Villa, Christopher 03 January 2012 (has links)
Bifidobacterium bifidum MIMBb75 is a novel strain whose behavior within the intestinal tract is not known. This work attempts to determine the survival and molecular determinant responsible for its colonization through two studies involving administration to mice of 1) B. bifidum MIMBb75 or 2) engineered B. longum NCC2705 expressing the B. bifidum-specific surface protein BopA. MIMBb75 was able to transiently colonize the murine intestinal tract. As a result, endogenous bifidobacteria increased significantly in the proximal colon whereas Clostridia clusters were differentially affected in a region-dependent fashion. Genetically engineered B. longum NCC2705, expressing the BopA gene, did not impact endogenous bacterial groups in the proximal colon or feces, albeit, it down-regulated the gene expression of KC and mucin 4 in the proximal colon. These outcomes indicate that MIMBb75 encompasses characteristics of a probiotic, but further studies are required to assess the role of BopA as the molecular determinant of its action.
4

Otimização das propriedades reológicas e sensoriais de iogurtes probióticos enriquecidos com proteínas lácteas / Optimization of the rheological properties of probiotic yoghurts supplemented with milk proteins

Marafon, Ana Paula 21 May 2010 (has links)
Este estudo teve como objetivo otimizar as propriedades reológicas dos iogurtes probióticos suplementados com leite em pó desnatado (SMP), concentrado proteico de soro (WPC) e caseinato de sódio (Na-Cn), usando desenho experimental tipo simplex centroide, para modelagem de misturas. O estudo das interações entre os ingredientes (proteína concentrada de soro, caseinato de sódio e leite em pó) incluiu sete experimentos sendo três com os ingredientes puros, dois correspondentes a misturas binárias e um para a uma mistura ternária. Em paralelo aos sete experimentos delineados, foi realizado ensaio controle com leite não suplementado. Os leites foram fermentados a 42 °C até pH 4,5 empregando-se as culturas Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus e Bifidus lactis. A cinética de acidificação foi determinada bem como as análises físico-químicas, contagem de bactérias viáveis e características reológicas dos iogurtes. Modelos foram ajustados para os resultados (respostas cinética, contagem de bactérias viáveis e parâmetros reológicos) através de três métodos de regressão (linear, quadrático e cúbico especial) e aplicados às misturas. Os resultados deste estudo mostraram que a fortificação da base de leite com proteína concentrada de soro, caseinato de sódio e leite em pó desnatado, para o mesmo nível de teor de proteína, afetou o perfil de acidificação, a contagem de bactérias viáveis e reologia de iogurtes probióticos. Além disso, foi possível estimar o perfil de acidificação e a contagem de bactérias no leite suplementado com proteínas do leite em pó, concentrado proteico de soro e caseinato de sódio por metodologia de superfície de resposta, bem como calcular aproximadamente as propriedades viscoelásticas dos iogurtes probióticos. Pode-se ressaltar que a otimização das propriedades reológicas dos iogurtes probióticos suplementados com proteínas do leite depende da fonte de proteína utilizada. Por fim, a substituição parcial de 55% de leite em pó desnatado por concentrado proteico de soro e caseinato de sódio simultaneamente poderá reforçar as propriedades reológicas dos iogurtes probióticos, considerando a cinética de acidificação e a contagem de bactérias viáveis. Os resultados foram validados ao longo da vida de prateleira dos produtos, confirmando os valores estimados pelos modelos para a cinética de acidificação, a contagem de bactérias viáveis e as propriedades viscoelásticas, além da avaliação sensorial e da análise de microestrutura. / This study aimed to optimize the rheological properties of probiotic yoghurts supplemented with skim milk powder, whey protein concentrate and sodium caseinate throughout an experimental design type centroid simplex for mixture modeling. It included seven trials: three with the pure ingredients, three corresponding to the binary mixtures and one to the ternary one. A control experiment was accomplished with non supplemented milk. Milk was fermented at 42°C until pH 4.5 by Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidus animalis subsp. lactis. The kinetics of acidification was followed as well as physicochemical analyses, enumeration of viable bacteria and rheological characterization of the yoghurts. Models were adjusted to the results (kinetic responses, counts of viable bacteria and rheological parameters) through three regression models (linear, quadratic and cubic special) applied to mixtures. The results showed that the addition of milk proteins affected acidification profile and counts, and enhanced rheological properties of probiotic yoghurt. The estimated results were validated during shelf-life and were confirmed by for the kinetics of acidification, bacterial counts of viable and viscoelastic properties in addition to sensory evaluation and analysis of microstructure.
5

Otimização das propriedades reológicas e sensoriais de iogurtes probióticos enriquecidos com proteínas lácteas / Optimization of the rheological properties of probiotic yoghurts supplemented with milk proteins

Ana Paula Marafon 21 May 2010 (has links)
Este estudo teve como objetivo otimizar as propriedades reológicas dos iogurtes probióticos suplementados com leite em pó desnatado (SMP), concentrado proteico de soro (WPC) e caseinato de sódio (Na-Cn), usando desenho experimental tipo simplex centroide, para modelagem de misturas. O estudo das interações entre os ingredientes (proteína concentrada de soro, caseinato de sódio e leite em pó) incluiu sete experimentos sendo três com os ingredientes puros, dois correspondentes a misturas binárias e um para a uma mistura ternária. Em paralelo aos sete experimentos delineados, foi realizado ensaio controle com leite não suplementado. Os leites foram fermentados a 42 °C até pH 4,5 empregando-se as culturas Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus e Bifidus lactis. A cinética de acidificação foi determinada bem como as análises físico-químicas, contagem de bactérias viáveis e características reológicas dos iogurtes. Modelos foram ajustados para os resultados (respostas cinética, contagem de bactérias viáveis e parâmetros reológicos) através de três métodos de regressão (linear, quadrático e cúbico especial) e aplicados às misturas. Os resultados deste estudo mostraram que a fortificação da base de leite com proteína concentrada de soro, caseinato de sódio e leite em pó desnatado, para o mesmo nível de teor de proteína, afetou o perfil de acidificação, a contagem de bactérias viáveis e reologia de iogurtes probióticos. Além disso, foi possível estimar o perfil de acidificação e a contagem de bactérias no leite suplementado com proteínas do leite em pó, concentrado proteico de soro e caseinato de sódio por metodologia de superfície de resposta, bem como calcular aproximadamente as propriedades viscoelásticas dos iogurtes probióticos. Pode-se ressaltar que a otimização das propriedades reológicas dos iogurtes probióticos suplementados com proteínas do leite depende da fonte de proteína utilizada. Por fim, a substituição parcial de 55% de leite em pó desnatado por concentrado proteico de soro e caseinato de sódio simultaneamente poderá reforçar as propriedades reológicas dos iogurtes probióticos, considerando a cinética de acidificação e a contagem de bactérias viáveis. Os resultados foram validados ao longo da vida de prateleira dos produtos, confirmando os valores estimados pelos modelos para a cinética de acidificação, a contagem de bactérias viáveis e as propriedades viscoelásticas, além da avaliação sensorial e da análise de microestrutura. / This study aimed to optimize the rheological properties of probiotic yoghurts supplemented with skim milk powder, whey protein concentrate and sodium caseinate throughout an experimental design type centroid simplex for mixture modeling. It included seven trials: three with the pure ingredients, three corresponding to the binary mixtures and one to the ternary one. A control experiment was accomplished with non supplemented milk. Milk was fermented at 42°C until pH 4.5 by Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidus animalis subsp. lactis. The kinetics of acidification was followed as well as physicochemical analyses, enumeration of viable bacteria and rheological characterization of the yoghurts. Models were adjusted to the results (kinetic responses, counts of viable bacteria and rheological parameters) through three regression models (linear, quadratic and cubic special) applied to mixtures. The results showed that the addition of milk proteins affected acidification profile and counts, and enhanced rheological properties of probiotic yoghurt. The estimated results were validated during shelf-life and were confirmed by for the kinetics of acidification, bacterial counts of viable and viscoelastic properties in addition to sensory evaluation and analysis of microstructure.
6

Effects of Delivery Mode on Initial Infant Gut Colonization And Subsequent Immune System Development

Kang, Christina 01 January 2014 (has links)
Since the 1970s, the United States has encountered an increasing proportion of Cesarean deliveries (CS), surpassing the advised 10-15% maximum rate established in 1985 by the World Health Organization (World Health Organization, 1985). This increasing rate has fueled correlational and causational studies observing the impact of Cesarean delivery on several aspects of infant health. Previous studies on CS infants have observed a delay in gut colonization by beneficial bacteria – for instance Bifidobacteria – traditionally transmitted from the mother’s gut and vaginal microbiome as other environmental factors have influenced the initial microflora (Biasucci et al., 2010; Dong, Yang, & Wang, 2010; Penders et al., 2006). In addition, an increasing proportion of births are occurring within a home setting, providing an opportunity to study how these possible environmental factors may influence bacterial colonization. This initial gastrointestinal colonization is considered one of the most important factors towards immune system development and general health. This thesis proposes an examination of how the mode and setting of delivery influence the diversity of Bifidobacterium species in infants’ initial gut microbiomes. Additionally, while several studies have examined the impact of specific bacterial species on immune system development, this study will provide an approach to understanding how differences in the overall gastrointestinal (GI) ecologies of CS and vaginal delivery (VD) infants impact immune system development.
7

Leites fermentados por streptococcus thermophilus adicionados de lactobacillus acidophilus e bifidobacterium longum : isolamento diferencial dos microrganismos, multiplicação em diferentes condições e efeitos nas caracteristicas sensoriais dos leites fermentados naturais ou modificados / Fermented milk for Streptococcus thermophilus added of Lactobacillus acidophillus and Bifidobacterias longum: distinguishing isolation of the microrganismos, multiplication in different conditions and effect in the sensorial characteristics of fermented natural or modified milk

Zacarchenco, Patricia Blumer 02 May 2004 (has links)
Orientador: Salvador Massaguer Roig / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T20:56:04Z (GMT). No. of bitstreams: 1 Zacarchenco_PatriciaBlumer_D.pdf: 905521 bytes, checksum: 6d2849e2b69ed715dda0573bad474ece (MD5) Previous issue date: 2004 / Doutorado / Doutor em Tecnologia de Alimentos
8

Cell immobilization techniques for the preservation of probiotics

Thantsha, Mapitsi Silvester 28 January 2008 (has links)
Incorporation of probiotic cultures in products in order to replenish or supplement the normal gastrointestinal microflora is a well known and accepted practice. However survival of these cultures is a problem due to a number of reasons including effects of storage conditions. Various researchers from different countries around the world have reported probiotic product instability. Microencapsulation has been used in an attempt to solve this problem. However, most methods involve the use of organic solvents which is not ideal because their toxicity may cause destruction of the microbial cells. A novel encapsulation method for probiotics, which excludes the use of organic solvents, was developed by the Council for Scientific and Industrial Research (CSIR) (US Patent Application no. 20050112205). This thesis investigated the efficiency/potential of this new method for increasing stability of sensitive probiotic cultures, specifically bifidobacteria. Early studies using both culture dependent and culture independent techniques showed reduced numbers of viable cultures in probiotic products, mainly yoghurts, from all around the world. These results were confirmed in this study for similar products sold in South Africa. Most of the product labels did not specify viable numbers of probiotics nor the identity (genus and species names) of the microorganisms incorporated. Successful encapsulation of bifidobacteria was achieved using the CSIR patented method. Complete encapsulation was indicated by absence of cells on surfaces of the encapsulated particles and production of a product with an acceptable particle size distribution was obtained. It was also demonstrated that the encapsulation process produced no visible morphological changes to the bacterial cells nor did it have a negative effect on cell viability over time. The potential of interpolymer complex formation in scCO2 for the encapsulation of sensitive probiotic cultures was demonstrated for the first time. Once ingested, probiotic cultures are exposed to unfavourable acidic conditions in the upper gastrointestinal tract. It is desired that these cultures be protected from this in order to increase the viability of the probiotics for efficient colonization. Interpolymer complex encapsulated B. longum Bb-46 cells were therefore exposed to simulated gastric fluid (SGF) and subsequently to simulated intestinal fluid (SIF). It was found that the interpolymer complex protected bifidobacteria from gastric acidity, displaying pH-responsive release properties, with little to no release in SGF and substantial release in SIF. Thus the interpolymer complex demonstrated desirable characteristics retaining the encapsulated bacteria inside when conditions were unfavourable and only releasing them under favourable conditions. Survival was improved by the incorporation of glyceryl monostearate (GMS) in the matrix and by use of gelatine capsules. Protection efficiency of the interpolymer matrix was better when higher loading of GMS was used. Use of polycaprolactone (PCL) as an alternative to poly (vinylpyrrolidone) (PVP) and incorporation of ethylene oxide-propylene oxide triblock copolymer (PEO-PPO-PEO) affected the interpolymer complex negatively, rendering it swellable in the low pH environment exposing the bifidobacteria to gastric acidity. The use of beeswax seemed to have a more protective effect though results were inconclusive. Probiotic cultures must also remain viable in products during storage. Encapsulated bacteria were either harvested from the reactor after 2 h of equilibration followed by depressurization, and then ground to a fine powder or after 2 h of equilibration the liquefied product was sprayed through a capillary tube with a heated nozzle at the end, into the product chamber. Encapsulated bacteria were stored in either sterile plastic bags or glass bottles under different conditions and then viable counts were determined over time. Survival of bacteria was generally better when the products were stored in glass bottles than in plastic bags. Bacteria encapsulated in an interpolymer complex formed between PVP and vinyl acetate-crotonic acid copolymer (VA-CA), (PVP:VA-CA) survived better than non-encapsulated bacteria under all storage conditions when the product was recovered from the reaction chamber. When the product was recovered from the product chamber, numbers of viable non-encapsulated bacteria were higher than the encapsulated bacteria for all interpolymer complex formulations. This was probably due to some exposure to high shear during spraying into the product chamber. The interpolymer complex between PCL and VA-CA i.e. PCL:VA-CA seemed weaker than the PVP:VA-CA nterpolymer complex as viable counts of bacteria released from it were lower than those from the latter complex. Addition of PEO-PPO-PEO to both the PVP:VA-CA and PCL:VA-CA complexes decreased the protection efficiency. However, results indicated that sufficient release of encapsulated bacteria from the interpolymer complexes was obtained when the encapsulated material was incubated in SIF rather than in Ringer’s solution. When SIF was used for release of encapsulated bacteria, the shelf life of B. longum Bb-46 was doubled. Encapsulation in an interpolymer complex therefore provided protection for encapsulated cells and thus has potential for improving shelf life of probiotic cultures in products. Further studies will investigate the effects of encapsulating probiotics together with prebiotics in the interpolymer complex as well as effects of encapsulating combinations of different probiotic strains together, both on survival in simulated gastrointestinal tract and during storage. The unique particles produced using the patented encapsulation technique increased the stability of probiotic cultures. This technique may find significant application in industries manufacturing probiotic products, especially food and pharmaceuticals, thereby improving the well being of consumers. / Thesis (PhD(Microbiology))--University of Pretoria, 2008. / Microbiology and Plant Pathology / PhD / unrestricted
9

Vliv probiotických bakterií na alergickou senzibilizaci v modelu alergie I. typu / Impact of Probiotic Bacteria on Allergic Sensitization in Type I Allergy Model

Schwarzer, Martin January 2013 (has links)
The main goal in reversing the allergy epidemic is the development of effective prophylactic strategies. Early life events, such as exposures to microbes, have a major influence on the development of balanced immune responses. Due to their ability to interact with host immune system and to modulate host immune responses probiotics, mainly bifidobacteria and lactobacilli have been used with some success in prevention of allergic disease. In order to be referred to as probiotic, bacterial strain has to undergo rigorous testing. We have selected three new Lactobacillus (L.) strains out of 24 human isolates according to their antagonistic activity against pathogenic bacteria, resistance to low pH and milieu of bile salts. Safety of these strains was proven upon intragastric administration to mice; moreover, we have shown their ability to shift cytokine Th1 - Th2 balance towards non-allergic Th1 response in isolated splenic cells. Allergen specific prophylaxis using probiotics as vehicles for mucosal delivery of recombinant allergen is an attractive concept for development of well-tolerated and effective allergy vaccines. We have shown that neonatal mono-colonization of germ-free mice with the L. plantarum NCIMB8826 strain producing the major birch pollen allergen Bet v 1 attenuates the development of...
10

Perfil tecnológico de cepas de bifidobactéria em cultura pura e em co-cultura com Streptococcus thermophilus em leites orgânico e convencional / Technological profile of bifidobacteria strains in pure culture and in co-culture with Streptococcus thermophilus in organic and conventional milks

Ana Carolina Rodrigues Florence 27 March 2009 (has links)
A crescente preocupação com tecnologias sustentáveis e a procura de novos alimentos funcionais despertam o interesse para o desenvolvimento de novos produtos alimentícios que proporcionem, além da nutrição, benefícios à saúde do consumidor. Assim, esse trabalho visa propor o leite orgânico como potencial matéria-prima para a fabricação de leites fermentados probióticos. Para tanto, estudou-se o perfil tecnológico de cepas de bifidobactéria em cultura pura e em co-cultura com Streptococcus thermophilus em leites orgânico e convencional, analisando a composição química dos leites, determinando o perfil de acidificação de quatro cepas de Bifidobacterium animalis subsp. lactis em cultura pura e em co-cultura com Streptococcus thermophilus, verificando a contagem microbiológica das culturas probióticas e iniciadoras nos leites fermentados, examinando o perfil de ácidos graxos e o teor de ácido linoléico conjugado dos leites fermentados e determinando o perfil de textura dos leites fermentados. A maior velocidade de acidificação foi observada para as cepas B94 e BL04 em leite orgânico e para a cepa HN019, para ambos os tipos de leite. As contagens de todas as cepas de B. animalis subsp. lactis foram superiores a 8,58 log10 unidades formadoras de colônia (UFC).mL-1</SUP. O leite orgânico apresentou maiores teores de ferro e proteína, enquanto o leite convencional apresentou maiores teores de gordura e lactose. Os principais ácidos graxos foram pouco influenciados pelo tipo de leite e as maiores quantidades de ácido linoléico conjugado (65 % maior do que o controle) foram encontradas em leite orgânico fermentado com a cepa BB12 em co-cultura com S. thermophilus. Assim, verificou-se que o leite orgânico pode ser empregado como matéria-prima na fabricação de leites fermentados probióticos, agregando qualidade nutricional ao produto final. / The concern about sustainable technologies and demand for new functional foods arouses the interest for the development of new food products in addition to provide nutrition and health benefits to the consumer. Thus, this work aims to offer organic milk as a potential raw material for the manufacture of probiotic fermented milk. Therefore, studying the technological profile of strains of bifidobacteria in pure culture and in co-culture with Streptococcus thermophilus in organic and conventional milks, analyzing the chemical composition of milk; determining the profile of acidification of four strains of Bifidobacterium animalis subsp. lactis in pure culture and in co-culture with Streptococcus thermophilus; checking the counts of starter and probiotic cultures in fermented milks; examining the profile of fatty acids and conjugated linoleic acid content of fermented milks and the profile of texture of fermented milks. The highest rate of acidification profile was observed for the strains BL04 and B94 in organic milk and for the strain HN019 in both milks. The counts of all strains of B. animalis subsp. lactis were higher than 8.58 log10 colony forming units (CFU). mL-1. The organic milk had higher levels of iron and protein, whereas conventional milk had higher levels of fat and lactose. The main fatty acids were not influenced by the type of milk and higher amounts of conjugated linoleic acid (65% higher than the control) were found in organic fermented milk with the strain BB12 in co-culture with S. thermophilus. Thus, it was found that organic milk can be used as raw material in the manufacture of probiotic fermented milk, increasing nutritional quality to final product.

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