1,720,966 research outputs found
Dynamics of Enterobacteriaceae and lactobacilli in model sourdoughs are driven by pH and concentrations of sucrose and ferulic acid
No full textThis study aimed to assess, in model sourdough fermentations, the relevance of physico-chemical features of flour for the interactions between Enterobacteriaceae and lactobacilli, and for the interactions within the latter microbial group. Initially, model sourdoughs made with white wheat flour, whole wheat flour or wheat bran were inoculated with Cronobacter sakazakii, Klebsiella pneumoniae, Lactobacillus plantarum and Lactobacillus sanfranciscensis. Subsequently, white wheat sourdoughs were prepared with phosphate buffer, ferulic acid, maltose, sucrose or baker's yeast. During sourdough propagation, C. sakazakii and K. pneumoniae disappeared after few fermentation cycles in white wheat and whole wheat sourdoughs, but persisted in phosphate buffered or in wheat bran sourdoughs. Sucrose, maltose or ferulic acid did not impact on the ecological fitness of Enterobacteriaceae, whereas baker's yeast inhibited these bacteria. In white wheat and in whole wheat sourdoughs, L. sanfranciscensis outcompeted L. plantarum. A variation of sucrose level and the presence of ferulic acid reduced the competitiveness of L. sanfranciscensis, thus favoring L. plantarum.This study demonstrated that the pH is key contributor to the elimination of Enterobacteriaceae in cereal fermentation. In addition, L. sanfranciscensis prevails in wheat sourdoughs, but minor perturbations of the ecosystem reduce its competitiveness
Metabolism of phenolic compounds by Lactobacillus spp. during fermentation of cherry juice and broccoli puree.
No full textThis study aimed to investigate the metabolism of phenolic acids and flavonoids during lactic acid
fermentation of cherry juice and broccoli puree for potential food and pharmaceutical purposes. When
fermenting cherry juice and broccoli puree, Lactobacillus spp. exhibited strain-specific metabolism of
phenolic acid derivatives. The metabolism of protocatechuic, caffeic and p-coumaric acids through
phenolic acid decarboxylases and reductases differed between mMRS and cherry juice and broccoli
puree. The synthesis of reduced compounds was the highest during food fermentations and the substrate
seemed to modulate the metabolism of phenolic compounds. The reduction of phenolic acids involves a
hydrogen donor and the re-oxidation of the reduced co-factor NADH, which may provide a metabolic
advantage through NADþ regeneration. Quinic acid reduction may replace fructose and pyruvate as
hydrogen acceptors, and it may provide an energetic advantage to heterofermentative bacteria when
growing in broccoli puree lacking of fructose. This study demonstrated that phenolics metabolism may
confer a selective advantage for lactobacilli in vegetable and fruit fermentation, and the metabolic routes
are strongly dependent on the intrinsic factors of substrate. Fermented cherry juice and broccoli puree,
due to the selected bacterial bioconversion pathways, are enriched in phenolic derivative with high
human bioavailability and biological activity
Barley malt wort fermentation by exopolysaccharide-forming Weissella cibaria MG1 for the production of a novel beverage
No full textAimsThe growing interest of governments and industry in developing healthy and natural alternative foods and beverages that will fulfil the consumer drive towards a healthy lifestyle and clean-label, natural diet has led to an increase in traditional lactic acid bacteria fermentation research. In particular, this research aims to address the organoleptic modulation of beverages using in situ-produced bacterial polysaccharides. Methods and ResultsWeissella cibaria MG1 is capable of producing exopolysaccharides (dextran) and oligosaccharides (glucooligosaccharides) during sucrose-supplemented barley-malt-derived wort fermentation. Up to 364g l(-1) of dextran was produced in an optimized system, which improved the rheological profile of the resulting fermentate. Additionally, small amounts of organic acids were formed, and ethanol remained below 05%(v/v), the threshold volume for a potential health claim designation. ConclusionsThe results suggest that the cereal fermentate produced by W.cibaria MG1 could be potentially used for the production of a range of novel, nutritious and functional beverages. Significance and Impact of the StudyUsing conventional raw materials and traditional processes, novel LAB-fermented beverages can be produced representing an innovative mechanism towards fulfilling the aim to decrease government and personal costs as well as potentially ameliorating consumer lifestyle regarding dietary-related disease
Biochemical analysis of respiratory metabolism in the heterofermentative Lactobacillus spicheri and Lactobacillus reuteri
No full textAims: This study evaluated the aerobic and respiratory metabolism in Lactobacillus reuteri and Lactobacillus spicheri, two heterofermentative species
used in sourdough fermentation.
Methods and Results: In silico genome analysis, production of metabolites andgene expression of pyruvate oxidase, pyruvate dehydrogenase and cytochrome oxidase were assessed in anaerobic and aerobic cultures of Lact. reuteri and Lact. spicheri. Respiring homofermentative Lactobacillus casei N87 and Lact. rhamnosus N132 were used for comparison.
Aerobiosis and respiration increased the biomass production of heterofermentative strains compared to anaerobic cultivation. Respiration led
to acetoin production by Lact. rhamnosus and Lact. casei, but not in heterofermentative strains, in which lactate and acetate were the major endproducts.
Lactobacillus spicheri LP38 showed the highest oxygen uptake. Pyruvate oxidase, respiratory cytochromes, NADH oxidase and NADH
peroxidase were present in the genome of Lact. spicheri LP38. BothLact. spicheri LP38 and Lact. rhamnosus N132 overexpressed pox in aerobic
cultures, while cydA was up-regulated only when haeme was supplied; pdh was repressed during aerobic growth.
Conclusions: Aerobic and respiratory growth provided physiological and metabolic advantages also in heterofermentative lactobacilli.
Significance and Impact of the Study: The exploitation of oxygen-tolerant phenotypes of Lact. spicheri may be useful for the development of improved
starter cultures
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
