1,720,960 research outputs found
Sugar-glycerol cofermentations by lactobacillus hilgardii isolated from wine
Full text linkGlycerol catabolism was studied in Lactobacillus hilgardii X1B from wine, growing on glycerol and limiting glucose or fructose concentrations in anaerobiosis and microaerophilia. Glycerol consumption occurred simultaneously with sugar use, and it was higher with fructose as a cofermenting sugar in microaerophilia. Enzymatic activities of the glycerol kinase and glycerol dehydratase pathways were detected in both incubation conditions. In anaerobiosis, the main products were lactate, acetate, ethanol, and the intermediary product of the glycerol dehydratase pathway, 3- hydroxypropionaldehyde. However, in microaerophilia, 1,3-propanediol was also detected. In anaerobic glucose + glycerol and fructose + glycerol cultures as in microaerophilic glucose + glycerol cultures, glycerol was degraded mainly through the reductive pathway. However, when L. hilgardii X1B was grown on fructose + glycerol cultures in microaerophilia, glycerol dissimilation occurred mainly via the glycerol kinase way. According to these results, L. hilgardii X1B can degrade glycerol by producing 3-hydroxypropionaldehyde and acetic acid, both undesirable products for wine sensorial quality. © 2009 American Chemical Society.Fil: Pasteris, Sergio Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Strasser de Saad, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentin
Antioxidant capacity and antibacterial activity of phenolic compounds from argentinean herbs infusions
Full text linkArgentinean herbs infusions have been studied for their phenolic content, antioxidant and antibacterial activities in order to find out new natural products. Among the 13 infusions assayed Ilex paraguaiensis present the highest amount of total phenolic compounds and flavonoid fraction. The high correlation between antioxidant capacities and total phenolic contents indicate that phenolic compounds are the major contributors of these capacities. I. paraguaiensis infusion is the most effective to reduce the viability of Escherichia coli and Staphylococcus aureus. The antibacterial effect is related with phenolic compounds concentration but also with it profile. These results permit propose these herbs as new sources of safe natural antioxidants and preservatives for food industry. © 2009 Elsevier Ltd. All rights reserved.Fil: Rodriguez Vaquero, Maria Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Tomasini Serravalle, Ligia R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Manca, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Strasser de Saad, Ana Maria. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentin
Effect of phenolic compounds from Argentinean red wines on pathogenic bacteria in a meat model system
Full text linkIn this work, the effectiveness of phenolic compounds of different varieties of wines as antibacterial agent in a meat model system was determined. Total phenolic, flavonoid and flavanol compounds concentrations were greater inMerlot andMalbec wines compared with Cabernet Sauvignon variety. In meat, the best antibacterial effect of wine phenolic compounds against both bacteria was observed withMerlot and Malbec wine varieties at 4C, even when inhibitory effect was also observed at 20C. The lowest decimal reduction time was obtained withMerlot wine for Listeriamonocytogenes and with Malbec and Merlot wines for Escherichia coli. From our results,we propose the use of wine phenolic compounds as natural biopreservatives for meat in combination with low temperatures. These natural products provide the additional human health benefit inherent to polyphenols properties. The exploration of natural antimicrobials for food preservation receives increased attention due to a growing microbial resistance towards conventional preservatives, added to consumer awareness of natural food products. The antibacterial effect of individual phenolic compounds in culturemedia has been largely studied,, but there is no information about the antibacterial effect of natural combinations of polyphenols fromdifferent varieties of wines in meat. In thiswork,we demonstrate that phenolic compounds combination of Argentinean wines were effective in inhibiting the growth of two pathogenic bacteria that produce food contamination and illness in the consumer.Natural polyphenol combinations found in Argentinean wines could act as natural biopreservatives for meat in combination with low temperatures, achieving extension of the shelf life of food.Fil: Rodriguez Vaquero, Maria Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Centro de Referencia para Lactobacilos (i); Argentina. Universidad Nacional de Tucuman. Facultad de Bioquimica, Quimica y Farmacia. Instituto de Microbiologia;Fil: Aredes Fernández, Pedro Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Centro de Referencia para Lactobacilos (i); ArgentinaFil: Manca, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Centro de Referencia para Lactobacilos (i); Argentina. Universidad Nacional de Tucuman. Facultad de Bioquimica, Quimica y Farmacia. Instituto de Microbiologia;Fil: Strasser de Saad, Ana Maria. Universidad Nacional de Tucuman. Facultad de Bioquimica, Quimica y Farmacia. Instituto de Microbiologia; . Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Lactic acid bacteria-yeast interactions
No full textIn complex microbial ecosystems constituted by a mixture of different species and strains, interactions will occur between individual microorganisms determining the final ecology. The general environment from which raw food products originate and the microbiological quality of the products in its processed state admits yeast growth. Only part of the primary microflora survives under the selective pressures exerted by the intrinsic and extrinsic biotic factors present in the ecosystem. Eventually, a particular yeast community will develop, and if the environmental factors permit, a specific association would contribute positively or negatively to the final product. Considering wine production, the habitat presents an ecosystem where yeast-yeast, yeastfilamentous fungi and yeast-bacteria interactions can be produced. The symbiosis of them depend on the yeast strain used providing amino acids, peptides and vitamins available as growth factors for lactic acid bacteria (LAB) development, or by the yeast ability to produce metabolic compounds which can act as inhibitors. The flocculation is a phenomenon wherein the cells adhere in clumps and sediments rapidly from the medium in which they are suspended. This property could modify the metabolic behavior of the interacting cells. It is know that many microbes use extracellular signals to transmit information about population density and environmental conditions. As microbes continually need to respond to varying medium conditions, it is not surprising that quorum-sensing regulation that is modulated by physical factors and nutrients availability affect the interactions produced between microorganisms. Recently the reproducible and simple techniques were formulated to study yeast-LAB interaction in simultaneous (both microorganisms in the same medium) and in sequential (growth of LAB in the supernatant modified by yeast growth) growth.Fil: Farias, Marta Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Strasser de Saad, Ana Maria. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Manca, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentin
Biogenic amines production by lactic acid bacteria
No full textBiogenic amines (BAs) are organic bases with aliphatic, aromatic or heterocyclic structures that can be found in several foods. They are mainly produced by microbial decarboxylation of amino acids. Removal of the alpha-carboxyl group from amino acids leads to the corresponding BA. The most common amines, histamine, tyramine, tryptamine, putrescine and cadaverine are formed from histidine, tyrosine, tryptophan, ornithine and lysine, respectively. BAs are undesirable in all foods and beverages. They are related to the quality of foods their quantities are considered a marker of the level of microbiological contamination. BA can induce headaches, respiratory distress, heart palpitations, hyper or hypotension, and several allergenic disorders. Histamine is physiologically the most important BA. It is a substance with pharmacological activity (mediator) and is involved in pathophysiological processes such as allergies and inflammations. Histidine/histamine exchange due to a decarboxylation of the amino acid is a secondary energy transducing processes in lactic acid bacteria (LAB) that can contribute to the generation of a proton motive force. In this process additional H+ consumption occurs during metabolism leading to the generation of a pH gradient. Strains of Oenococcus oeni and heterofermentative lactobacilli from wine are able to produce BAs. In cheese this production has often been linked to nonstarter LAB which produces histamine, tyramine, putrescine and cadaverine and Enterobacteriaceae that mainly produces tyramine. The high amounts of proteins present in dry fermented sausages can potentially support the accumulation of BAs. The proteolytic activity during ripening provides the precursors for decarboxylase activity of starter cultures and/or wild microflora.Fil: Farias, Marta Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Strasser de Saad, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Manca, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentin
Glycerol production by Oenococcus oeni during sequential and simultaneous cultures with wine yeast strains
Full text linkGrowth and fermentation patterns of Saccharomyces cerevisiae, Kloeckera apiculata, and Oenococcus oeni strains cultured in grape juice medium were studied. In pure, sequential and simultaneous cultures, the strains reached the stationary growth phase between 2 and 3 days. Pure and mixed K. apiculata and S. cerevisiae cultures used mainly glucose, producing ethanol, organic acids, and 4.0 and 0.1 mM glycerol, respectively. In sequential cultures, O. oeni achieved about 1 log unit at 3 days using mainly fructose and L-malic acid. Highest sugars consumption was detected in K. apiculata supernatants, lactic acid being the major end-product. 8.0 mM glycerol was found in 6-day culture supernatants. In simultaneous cultures, total sugars and L-malic acid were used at 3 days and 98% of ethanol and glycerol were detected. This study represents the first report of the population dynamics and metabolic behavior of yeasts and O. oeni in sequential and simultaneous cultures and contributes to the selection of indigenous strains to design starter cultures for winemaking, also considering the inclusion of K. apiculata. The sequential inoculation of yeasts and O. oeni would enhance glycerol production, which confers desirable organoleptic characteristics to wines, while organic acids levels would not affect their sensory profile.Fil: Ale, Cesar Emmanuel. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Microbiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Farias, Marta Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Microbiología; ArgentinaFil: Strasser de Saad, Ana Maria. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Microbiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pasteris, Sergio Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentin
Effect of physicochemical factors on glycerol production by simultaneous cultures of wine micro-organisms using the response surface method
Full text linkAim: To evaluate the effect of temperature, pH and SO2 on growth and glycerol production improvement by Saccharomyces cerevisiae mc2, Kloeckera apiculata mF and Oenococcus oeni X2L using the response surface method (RSM). Methods and Results: Multifactorial design of cultures with physicochemical factors variations was performed. The micro-organisms grew in all cultures conditions. Overall, after 6 days yeasts prevailed, especially S. cerevisiae (109 CFU/mL), while O. oeni reached 107 CFU/mL. At initial fixed pH 55,metabolic behaviour of cultures showed a temperature-dependent response. Total malate consumption occurred at 26°C, 50 mg/L SO2. Glucose and pentoses utilization was highly modified when varying SO2. Ethanol showed negative interaction with temperature?SO2 relationship. At low SO2, glycerol and acetate production increased when temperature enhanced. Predictive results of RSM indicate that 26°C, 6024 mg/L SO2 and pH 55 were the optimal conditions for glycerol and organic acids synthesis compatible with wine quality. Conclusions: We propose a predictive condition to improve the performance of mixed cultures for must fermentations. Significance and Impact of the Study: To optimize the culture conditions to design mixed starters containing autochthonous yeasts and O. oeni strains for winemaking and to obtain products with high glycerol content, low acidity and maintenance of regional characteristics.Fil: Ale, Cesar Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucuman. Instituto Superior de Investigaciones Biologicas; ArgentinaFil: Bru Chauve, Elena Magdalena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; ArgentinaFil: Strasser de Saad, Ana Maria. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Microbiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pasteris, Sergio Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucuman. Instituto Superior de Investigaciones Biologicas; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Learning microbiology in biochemistry, chemistry and pharmacy faculty of Universidad Nacional de Tucumán (Argentina)
No full textMicrobiology is part of the biochemistry, chemistry, pharmacy and biotechnology curriculum at the National University of Tucumán, in northwest Argentina. This course is taught for four months in the 4th year of the curriculum, and includes all elements of general microbiology. Each year it is more difficult to teach microbiology because only two labs and one classroom are available for over 250 students. Until 2008, less than 60% were able to complete the course. For this reason, two new strategies were implemented to improve the percentage of the students who can complete the general microbiology exam. The students have the opportunity to take two, free theoretical classes a week. Since 2009, one of the new strategies implemented to encourage students is using multimedia in the lesson for increasing the discussion of the subject with the students. Also to reinforce learning, students can participate in special meetings with the professor where they get the opportunity to know the main subjects they need to study. The hypothesis was that, by implementing these two strategies, more students would be successful in the course. To implement a second strategy, to improve education by having more equipment available, it is essential to reduce the number of students in each group during practical work. The total number of students is divided into 10 groups (no more than 20 students in each) and, because there is only one laboratory, 5 groups per week can take lab class; as a result, each subject is issued for two weeks. In addition, students divided into groups of four must expose a seminar of a research recently published on issues related to practical classes. These strategies have improved by over 10% the number of students who can pass exams in practical classes. For many years, the students take an oral exam related to the entire subject. However, the number of students passing the course since 2009 has increased to 75%, with a remarkable improvement in the grades obtained. Despite only a one-year experience, the results obtained are promising enough to continue with these strategies for improving student learning.th year of the curriculum, and includes all elements of general microbiology. Each year it is more difficult to teach microbiology because only two labs and one classroom are available for over 250 students. Until 2008, less than 60% were able to complete the course. For this reason, two new strategies were implemented to improve the percentage of the students who can complete the general microbiology exam. The students have the opportunity to take two, free theoretical classes a week. Since 2009, one of the new strategies implemented to encourage students is using multimedia in the lesson for increasing the discussion of the subject with the students. Also to reinforce learning, students can participate in special meetings with the professor where they get the opportunity to know the main subjects they need to study. The hypothesis was that, by implementing these two strategies, more students would be successful in the course. To implement a second strategy, to improve education by having more equipment available, it is essential to reduce the number of students in each group during practical work. The total number of students is divided into 10 groups (no more than 20 students in each) and, because there is only one laboratory, 5 groups per week can take lab class; as a result, each subject is issued for two weeks. In addition, students divided into groups of four must expose a seminar of a research recently published on issues related to practical classes. These strategies have improved by over 10% the number of students who can pass exams in practical classes. For many years, the students take an oral exam related to the entire subject. However, the number of students passing the course since 2009 has increased to 75%, with a remarkable improvement in the grades obtained. Despite only a one-year experience, the results obtained are promising enough to continue with these strategies for improving student learning.Fil: Amoroso, Maria Julia del R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Farias, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Perez Chaia, Adriana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Strasser de Saad, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina17th Annual American Society For Microbiology ConferenceCaliforniaEstados UnidosAmerican Society for Microbiolog
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