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Yeast
About: Yeast is a research topic. Over the lifetime, 31777 publications have been published within this topic receiving 868967 citations. The topic is also known as: yeasts.
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218 citations
TL;DR: The results obtained show that fermentation of cocoa beans is a very inhomogeneous process with great variations in both yeast counts and species composition, which seem to depend especially on the processing procedure, but also the season and the post-harvest storage are likely to influence the Yeast counts and the species composition.
Abstract: Samples of cocoa beans were taken on two separate occasions during heap and tray fermentations in Ghana, West Africa. In total 496 yeast isolates were identified by conventional microbiological analyses and by amplification of their ITS1-5.8S rDNA-ITS2 regions. For important species the identifications were confirmed by sequencing of the D1/D2 domain of the 5' end of the large subunit (26S) rDNA. Assimilations of organic acids and other carbon compounds were conducted. For dominant yeasts intraspecies variations were examined by determination of chromosome length polymorphism (CLP) using pulsed-field gel electrophoresis. For the heap fermentations maximum yeast cell counts of 9.1 x 10(7) were reached, whereas maximum yeast counts of 6.0 x 10(6) were reached for the tray fermentations. Candida krusei was found to be the dominant species during heap fermentation, followed by P. membranifaciens, P. kluyveri, Hanseniaspora guilliermondii and Trichosporon asahii, whereas Saccharomyces cerevisiae and P. membranifaciens were found to be the dominant species during tray fermentation followed by low numbers of C. krusei, P. kluyveri, H. guilliermondii and some yeast species of minor importance. For isolates within all dominant species CLP was evident, indicating that several different strains are involved in the fermentations. Isolates of C. krusei, P. membranifaciens, H. guilliermondii, T. asahii and Rhodotorula glutinis could be found on the surface of the cocoa pods and in some cases on the production equipment, whereas the origin of e.g. S. cerevisiae was not indicated by the results obtained. In conclusion, the results obtained show that fermentation of cocoa beans is a very inhomogeneous process with great variations in both yeast counts and species composition. The variations seem to depend especially on the processing procedure, but also the season and the post-harvest storage are likely to influence the yeast counts and the species composition.
217 citations
TL;DR: Results indicate that the translocation of maltose across the yeast plasma membrane is not dependent on ATP and is coupled to the electrochemical gradient of protons in this membrane, which suggests the electroneutrality during maltose and proton uptake can be maintained.
Abstract: Maltose transport in yeast (Saccharomyces cerevisiae) is inhibited by uncouplers under conditions where the intracellular concentration of the sugar is lower than in the medium. The uncouplers did not deplete the ATP content of the yeast cells and a 50--100-fold reduction in ATP caused by antimycin and 2-deoxyglucose had no effect on maltose transport. In ATP-depleted cells, the maltose transported is partially hydrolyzed to glucose but not further metabolized and therefore a mechanism of transport involving phosphorylation can be discarded. One proton is cotransported with every maltose molecule. The fact that maltose transport is inhibited by KCl but not by NaCl, Tris-Cl or KSCN suggest that the electroneutrality during maltose and proton uptake can be maintained by the exit of K+ from the cells or by the entry of a permeable anion as SCN-. These results indicate that the translocation of maltose across the yeast plasma membrane is not dependent on ATP and is coupled to the electrochemical gradient of protons in this membrane. When this gradient is abolished by uncouplers, the transport system is not able to function even in favour of a concentration gradient of the sugar.
217 citations
TL;DR: An immunological screening technique has been used for the detection of a specific antigen-producing clone in a bank of bacterial colonies containing hybrid plasmids, identified an Escherichia coli colony, containing a yeast DNA insert in plasmid ColE1, that produces antigen which combines with antibody directed against purified yeast 3-phosphoglycerate kinase.
217 citations
TL;DR: There is chemical, cytochemical and ultrastructural evidence that the differences between Y and M walls of C. albicans are essentially quantitative, strongly suggesting that hyphal conversion in this yeast is controlled by the modulation of pre-existing enzymatic activities rather than by any new factors.
Abstract: DIMORPHISM in fungi is generally defined as a reversible transition from a yeast habit of growth (Y) to a mycelial one (M)1. In Candida albicans Y→M transition can occur rapidly in serum2,3, serum substitutes and other natural4–6 and synthetic media7. In a few hours the yeast cell or blastospore forms a germ tube which grows as a true mycelium6,8,9. Since the cellular form depends on wall construction10, marked modifications in the organisation of wall components are expected to, and in fact do, occur during morphogenesis. Nevertheless, there is chemical11, cytochemical and ultrastructural evidence12,13 that the differences between Y and M walls of C. albicans are essentially quantitative, strongly suggesting that hyphal conversion in this yeast is controlled by the modulation of pre-existing enzymatic activities rather than by any new factors.
216 citations