Project description:In conditions of nitrogen limitation, Saccharomyces cerevisiae strains differ in their fermentation capacities, due to differences in their nitrogen requirements. A population of 133 individuals from the F2 segregant population from a cross between two strains with different nitrogen requirements for efficient fermentation has been analyzed for their fermentation capacities. Two groups of 15 strains were defined, one group of High and one of Low Nitrogen requirement. These two groups are compared in order to detect genomic regions involved in the differences of nitrogen requirement. We used a custom isothermal array that has been designed for the detection of SNP at 6317 position on RM11.1a genome sequence http://www.broadinstitute.org/annotation/genome/saccharomyces_cerevisiae.3/Home.html) and obtained from the comparison with the genome sequence of strain Saccharomyces P3-D5.
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.
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:Saccharomyces cerevisiae (SC) is the main driver of alcoholic fermentation however for aroma and flavour formation in wine non-Saccharomyces species can have a powerful effect. This study aimed to compare untargeted volatile compound profiles from SPME-GCxGC-TOF-MS and sensory analysis data of Sauvignon blanc wine inoculated with six different non-Saccharomyces yeasts followed by SC. Torulaspora delbrueckii (TD), Lachancea thermotolerans (LT), Pichia kluyveri (PK) and Metschnikowia pulcherrima (MP) where commercial starter strains, while Candida zemplinina (CZ) and Kazachstania aerobia (KA), were isolated from wine grape environments. Each fermentation produced a distinct profile both sensorially and chemically. SC and CZ were the most distinct in both of these cases. SC had guava, grapefruit, banana, and pineapple aromas while CZ was driven by fermented apple, dried peach/apricot, and stewed fruit as well as sour flavor. Chemically over 300 unique features were identified as significantly different across the fermentations. SC had the highest number of esters in the highest relative concentration but all the yeasts had distinct ester profiles. CZ displayed the highest number of terpenes in high concentration but also produced a large amount of acetic acid. KA was high in ethyl acetate. TD had fewer esters but three distinctly higher thiol compounds. LT showed a relatively high number of increased acetate esters and certain terpenes. PK had some off odor compounds while the MP had high levels of different methyl butyl-, methyl propyl-, and phenethyl esters. Overall, this study gives a more detailed profile of these yeasts than anything previously reported.
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 M-bM-^@M-^XM-bM-^@M-^XmedicinalM-bM-^@M-^YM-bM-^@M-^Y in white wines (due to vinyl phenols) and as M-bM-^@M-^XM-bM-^@M-^XleatherM-bM-^@M-^YM-bM-^@M-^Y, M-bM-^@M-^XM-bM-^@M-^Xhorse sweatM-bM-^@M-^YM-bM-^@M-^Y and M-bM-^@M-^XM-bM-^@M-^XstableM-bM-^@M-^YM-bM-^@M-^Y in red wines (due to ethyl phenols mainly 4-ethylphenol). Apart from the negative aroma nuances imparted by these yeasts, positive aromas such as M-bM-^@M-^XsmokyM-bM-^@M-^Y, M-bM-^@M-^XspicyM-bM-^@M-^Y and M-bM-^@M-^XtoffeeM-bM-^@M-^Y 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 (50 KDa 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 50 KDa pore membrane separating both yeasts allowed the exchange of ethanol, metabolites and sugars during the fermentation. Fermentations were carried out in synthetic wine must in duplicate for both the control S. cerevisiae (strain Lalvin EC1118) and mixed fermentation. Sampling of yeast S. cerevisiae for RNA extractions were performed at 22 h of fermentation, during the exponential growth phase of S. cerevisiae, at 92 h and 144 h of fermentation, during its early and late stationary growth phase and at 187 h of fermentation, during its phase of growth decline.
Project description:Industrial wine yeast strains possess specific abilities to ferment under stressing conditions and give a suitable aromatic outcome. Although the fermentations properties of Saccharomyces cervisiae wine yeasts are well documented little is known on the genetic basis underlying the fermentation traits. Besides, although strain differences in gene expression has been reported, their relationships with gene expression variations and fermentation phenotypic variations is unknown. To both identify the genetic basis of fermentation traits and get insight on their relationships with gene expression variations, we combined fermentation traits QTL mapping and expression profiling in a segregating population from a cross between a wine yeast derivative and a laboratory strain.
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:Saccharomyces cerevisiae’s requirement of reduced sulfur to synthesise methionine and cysteine during alcoholic fermentation, is mainly fulfilled through the sulfur assimilation pathway. S. cerevisiae reduces sulfate into sulfur dioxide (SO2) and sulfide (H2S), whose overproduction is a major issue in winemaking, due to its negative impact on wine aroma. The amount of H2S produced is highly strain-specific and depends as well on the SO2 concentration, often added to the grape must. Applying a Bulk Segregant Analysis to a 96 strain-progeny derived from two strains with different ability to produce H2S, and comparing the allelic frequencies along the genome of pools of segregants producing opposite H2S quantities, we identified two causative regions involved in H2S production in the presence of SO2. A functional genetic analysis allowed the identification of variants in four genes: ZWF1, ZRT2, SNR2 and YLR125W, able to impact H2S formation, involved in functions and pathways until now not associated with sulfur metabolism. This data points that redox status and zinc homeostasis are linked to H2S formation in wine fermentation conditions and provides new insights into the regulation of H2S production during wine fermentation, giving a new vision of the interplay between the sulfur assimilation pathway and cell metabolism. This archive contains the transcriptome data of the result of allelic swp for three genes : ZWF1, ZRT2, YLR125w under fermentation.
Project description:We performed here the transcriptomic profile of 44 segregants from a cross between S288c and 59A (a spore of EC1118 strain). The analysis was performed in wine fermentation condition in stationary phase during nitrogen starvation and in alcoholic stress. These data, associated with an individual genotyping by Affymetrix array allow us to highlight genetic variations involved in perturbation of regulatory network and fermentative behavior.
Project description:Gene expression analysis of time course experiment of [1] a synthetic must (nitrogen-rich) fermentation by a natural wine yeast; [2] a synthetic must (nitrogen-poor) fermentation by a natural wine yeast; and [3] a synthetic must (nitrogen-poor) fermentation by a natural wine yeast, supplemented at 72 hours with 200 mg/l of nitrogen. This SuperSeries is composed of the SubSeries listed below.