Project description:In wine fermentation, the blending of non-Saccharomyces yeast with Saccharomyces cerevisiae to improve the complexity of wine has become common practice, but data regarding the impact on yeast physiology and on genetic and metabolic regulation remain limited. Here we describe a transcriptomic analysis of single species and mixed species fermentations.
Project description:The yeast Dekkera bruxellensis is as ethanol tolerant as Saccharomyces cerevisiae and may be found in bottled wine. It causes the spoilage of wine, beer, cider and soft drinks. In wines, the metabolic products responsible for spoilage by Dekkera bruxellensis are mainly volatile phenols. These chemical compounds are responsible for the taints described as ‘‘medicinal’’ in white wines (due to vinyl phenols) and as ‘‘leather’’, ‘‘horse sweat’’ and ‘‘stable’’ in red wines (due to ethyl phenols mainly 4-ethylphenol). Apart from the negative aroma nuances imparted by these yeasts, positive aromas such as ‘smoky’, ‘spicy’ and ‘toffee’ are also cited. Our goal was to identify the impact that the wine spoilage yeast Dekkera bruxellensis has on fermenting S. cerevisiae cells, especially on its gene expression level. To this end we co-inoculated both yeast species at the start of fermentation in a synthetic wine must, using S. cerevisiae-only fermentations without Dekkera bruxellensis as a control. All fermentations were employed in special membrane reactors (1.2 um pore size cut-off) physically separating Dekkera bruxellensis from wine yeast S. cerevisiae. Biomass separation with this membrane was done to abolish the possibility of hybridizing also D. bruxellensis probes on Agilent V2 (8x15K format) G4813 DNA microarrays designed just for S. cerevisiae ORF targets. The 1.2 um pore membrane separating both yeasts allowed the exchange of ethanol, metabolites and sugars during the fermentation.
Project description:Natural grape-juice fermentations involve the sequential development of different yeast species which strongly influence the chemical and sensorial traits of the final product. In the present study,we aimed to examine the transcriptomic response of Saccharomyces cerevisiae to the presence of Hanseniaspora guilliermondii wine fermentation.
Project description:We used genome-wide expression analyses to study the response of Saccharomyces cerevisiae to stress throughout a 15-day wine fermentation. Forty percent of the yeast genome significantly changed expression levels to mediate long-term adaptation to an environment in which ethanol is both a stressor and a carbon source. Within this set, we identify a group of 223 genes, designated as the Fermentation Stress Response (FSR), that are dramatically and permanently induced; FSR genes exhibited changes ranging from four-to eighty-fold. The FSR is novel; 62% of the genes involved have not been implicated in global stress responses and 28% of the genes have no functional annotation. Genes involved in respiratory metabolism and gluconeogenesis were expressed during fermentation despite the presence of high concentrations of glucose. Ethanol, rather than nutrient depletion, was responsible for entry of yeast cells into stationary phase. Ethanol seems to regulate yeast metabolism through hitherto undiscovered regulatory networks during wine fermentation. Keywords: time course, stress response, fermentation
Project description:Yeast mannoproteins contribute to several aspects of wine quality by protecting wine against protein haze, reducing astringency, retaining aroma compounds and stimulating growth of lactic-acid bacteria. The selection of a yeast strain simultaneously overproducing mannoproteins and showing good fermentative characteristics is a difficult task. In this work, a Saccharomyces cerevisiae x Saccharomyces cerevisiae hybrid bearing the two oenologically relevant features was constructed and a reduction in the amount of bentonite necessary for wine stabilization was observed for wines fermented with the generated strain. Additionally, different copy numbers of some genes probably related with these physiological features were detected in this hybrid. Hybrid share with parental Sc1 similar copy number of genes SPR1, SWP1, MNN10 and YPS7 related to cell wall integrity and with parental Sc2 similar copy number of some glycolytic genes as GPM1 and HXK1 as well as genes involved in hexose transport as HXT9, HXT11 and HXT12. This work demonstrates that artificial hybridization and stabilization in winemaking conditions constitute an effective approach to obtain yeast strains with desirable physiological features as mannoprotein overproducing capacity and improved fermentation performance, characteristics genetically depending on the coordinated expression of a multitude of different genes. In this work, genetically stable mannoprotein overproducing Saccharomyces cerevisiae strains simultaneously showing excellent fermentation capacities were obtained by hybridization methods giving rise to non-GMO strains. The potential relationship between the copy number of specific genes and the improved features was also evaluated by means of aCGH analysis of parental and hybrid strains.
Project description:To characterize the ecological interactions among S. cerevisiae strains coming from the same geographical area, we examined the fitness of two natural isolates from San Giovese grapes, alone or in competition, in synthetic wine must (SWM). We performed genome-wide analyses in order to identify the genes involved in yeast competition and cooperation.
Project description:To characterize the ecological interactions among S. cerevisiae strains coming from the same geographical area, we examined the fitness of two natural isolates from San Giovese grapes, alone or in competition, in synthetic wine must (SWM). We performed genome-wide analyses in order to identify the genes involved in yeast competition and cooperation.
Project description:The aim of this study was to determine how nitrogen repletion affected the genomic cell response of a Saccharomyces cerevisiae wine yeast strain, in particular within the first hour following relief from nutrient starvation. We found almost 4000 genes induced or repressed sometimes within minutes of nutrient changes. Some of the transcriptional responses to nitrogen depended on the TOR pathway which control positively ribosomal protein genes, amino acid and purine biosynthesis or amino acid permease genes and negatively stress-response genes, RTG specific TCA cycle genes and NCR sensitive genes. Some unexpected transcriptional responses concerned all the glycolytic genes, the starch and glucose metabolism and citrate cycle related genes which were down-regulated, as well as genes from the lipid metabolism.
Project description:Transcriptomic study to characterize the interaction of the Penicillium expansum antifungal protein PeAfpA with the the model yeast Saccharomyces cerevisiae. For this, the transcriptome of S. cerevisiae BY4741 strain was compared among samples treated with increasing concentrations of PeAfpA.
Project description:By an evolutionary approach based on long-term culture on gluconate as the sole carbon source, a Saccharomyces cerevisiae wine strains with enhanced flux through the pentose phosphate (PP) pathway were obtained. One of these evolved strains, ECA5, exhibited several novel properties with great potential for wine making, including a higher than wild-type fermentation rate and altered production of acetate and aroma compounds. To describe the mechanisms underlying this complex phenotype, we performed a comparative analysis of transcriptomic profiles between ECA5 and its ancestral strain, EC1118, under low nitrogen, wine fermentation conditions.