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Yeast Populations (yeast + population)
Selected AbstractsSurvival of inoculated Saccharomyces cerevisiae strain on wine grapes during two vintagesLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2006F. Comitini Abstract Aims:, To investigate the influence of a specific ecological niche, the wine grape, on the survival and development of Saccharomyces cerevisiae. Methods and Results:, A strain with a rare phenotype was sprayed onto the grape surfaces and monitored through two vintages using a specific indicative medium and analysing the internal transcribed spacer regions in the 5·8S rDNA. During the ripening process, there was a progressive colonization of the surface of the undamaged and damaged grapes by epiphytic yeasts, up to the time of harvest. The damaged wine grapes showed a much greater epiphytic yeast population. However, the inoculated S. cerevisiae strain showed a scarce persistence on both undamaged and damaged wine grapes, and the damaged grapes did not appear to improve the grape surface colonization of this strain. Conclusions:, Results indicated that wine grape is not a favourable ecological niche for the development and colonization of S. cerevisiae species. Significance and Impact of the Study:, Results of this work are further evidence that S. cerevisiae is not specifically associated with natural environments such as damaged and undamaged wine grapes. [source] Dynamics of yeast populations recovered from decaying leaves in a nonpolluted stream: a 2-year study on the effects of leaf litter type and decomposition timeFEMS YEAST RESEARCH, Issue 4 2007Ana Sampaio Abstract Here we report on the results of a survey of the yeast populations occurring on submerged leaves (alder, eucalyptus and oak) in a natural mountain stream, during different phases of their decomposition and through two consecutive years. Leaf litter mass loss, total yeast counts, Shannon,Weiner index (H,), yeast community structure and physiologic abilities were analyzed to evaluate the dynamics of yeast communities during decay. Seventy-two yeast taxa were recorded, and in all litter types, species of basidiomycetous affinity predominated over ascomycetous ones. Discriminant analysis of presence/absence data (yeast species) showed significant differences both among substrate types (P<0.0026) and with decomposition time (P<0.0001). Carbon and nitrogen source utilization by yeast strains also varied with the substrate (P<0.0001) and decomposition time (P<0.0001). Further conclusions were that: (1) all litter types have in common ubiquitous yeast species, such as Cryptococcus albidus, Debaryomyces hansenii and Rhodotorula glutinis, among the common 20 yeast species; (2) only a few species were dominant, and most species were rare, being recorded once or twice throughout decomposition; and (3) the order of yeast appearance, and their substrate assimilation patterns, strongly suggest a succession phenomenon. Finally, explanations for the distribution patterns and variations in yeast communities are discussed. [source] Analysis of non- Saccharomyces yeast populations isolated from grape musts from Sicily (Italy)JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008D.P. Romancino Abstract Aims:, The aim of this study was to identify the non- Saccharomyces yeast populations present in the grape must microflora from wineries from different areas around the island of Sicily. Methods and Results:, Yeasts identification was conducted on 2575 colonies isolated from six musts, characterized using Wallerstein Laboratory (WL) nutrient agar, restriction analysis of the amplified 5·8S-internal transcribed spacer region and restriction profiles of amplified 26S rDNA. In those colonies, we identified 11 different yeast species originating from wine musts from two different geographical areas of the island of Sicily. Conclusions:, We isolated non- Saccharomyces yeasts and described the microflora in grape musts from different areas of Sicily. Moreover, we discovered two new colony morphologies for yeasts on WL agar never previously described. Significance and Impact of the Study:, This investigation is a first step in understanding the distribution of non- Saccharomyces yeasts in grape musts from Sicily. The contribution is important as a tool for monitoring the microflora in grape musts and for establishing a new non- Saccharomyces yeast collection; in the future, this collection will be used for understanding the significance of these yeasts in oenology. [source] Saccharomyces cerevisiae wine yeast populations in a cold region in Argentinean Patagonia.JOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2002A study at different fermentation scales Aims: To study the diversity and dynamics of indigenous Saccharomyces wine populations during Malbec spontaneous fermentation, a representative Patagonian red wine, at both industrial and laboratory scale. Methods and Results: Two molecular techniques, including restriction fragment length polymorphism of mitochondrial (mt) DNA and polymorphism of amplified , interspersed element sequences, were used for characterization of indigenous yeasts at strain level. The mtDNA restriction patterns showed the major discriminative power; however, by combining the two molecular approaches it was possible to distinguish a larger number of strains and, therefore, draw more representative conclusions about yeast diversity. Although a great diversity of wild Saccharomyces cerevisiae strains was observed, only nine represented more than half of the total Saccharomyces yeast biota analysed; five of these were common and took over the Malbec must fermentation in both vinifications. Conclusions: Many different indigenous S. cerevisiae strains were identified; nevertheless, the dominant strains in both industrial and laboratory vinification processes were just a few and the same. Significance and Impact of the Study: Small-scale fermentation appears to be a valuable tool in winemaking, one especially helpful in evaluating microbiological aspects of as well as possible interactions between inoculated selected strains and native strains. [source] Pasteurization of Beer by a Continuous Dense-phase CO2 SystemJOURNAL OF FOOD SCIENCE, Issue 3 2006Gillian F. Dagan ABSTRACT: Effects on beer quality were studied after pasteurization by a continuous dense-phase carbon dioxide (DPCD) system. Changes in haze formation, foaming capacity and stability, and objective and subjective aroma and flavor were evaluated, after validation of a 5-log reduction in yeast populations. A maximum log reduction in yeast populations of 7.38 logs was predicted at 26.5 MPa, 21°C, 9.6% CO2, and 4.77 min residence time. Haze was reduced by DPCD pasteurization from 146 nephelometric turbidity units (NTU) to 95 NTU. At this same treatment combination, aroma and flavor of beer sample means were not considered significantly different (P= 0.3415) from fresh beer sample means when evaluated in a difference from control test, using fresh beer as the reference. Foam capacity and stability were affected minimally by CO2 processing; however, changes would most likely be unnoticed by consumers. [source] The influence of pre-fermentative practices on the dominance of inoculated yeast starter under industrial conditionsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2002Maurizio Ciani Abstract The influence of pre-fermentative practices on the growth dynamics of a ,natural' starter culture with specific phenotype (H2S,) concurrently with wild yeast populations was evaluated under winery conditions. Different clarification procedures and added SO2 strongly influenced species and cell numbers isolable at the pre-fermentation stage. Independent treatments of must with sulphite addition or vacuum-filtering clarification caused a 30-fold reduction in viable cells. Clarification procedures, enhanced by the selective effect of SO2 addition, induced the appearance of Saccharomyces cerevisiae ,wild' yeasts. Correct application of the inoculum generally guarantees the dominance of fermentation by starter cultures. However, inoculated fermentations using unclarified white and red musts exhibited a consistent presence and persistence of non- Saccharomyces and/or Saccharomyces ,wild' yeasts during fermentation. The extent and composition of the initial wild microflora at the start of fermentation may affect the presence and persistence of wild Saccharomyces and non- Saccharomyces yeasts during guided fermentations under commercial conditions. The above findings confirm the results of previous works carried out at laboratory- or pilot-scale level. Furthermore, they suggest a clear correlation between the modality of pre-fermentative practices and the presence and persistence of ,wild' yeasts during fermentation. © 2002 Society of Chemical Industry [source] | |||||||||||||