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Comparative transcriptome analysis between an original and a recombinant wine yeast strain defective for KNR4/SMI1

ABSTRACT: EKD-13 is among the recently developed mannoprotein overproducing strains. It is a recombinant derivative of the well known EC1118 commercial strain, in which the ORF of all the alleles of KNR4/SMI1 was replaced by different integration cassettes. Lack of Knr4p resulted in a negligible impairment in fermentation kinetics and a net reduction in bentonite requirements to attain complete protein stabilization of white wines made out of natural grape must. In order to improve the technological characterization of this strain, and to better understand the mechanisms underlying mannoprotein oversecretion, we have analyzed kinetics of mannoprotein release and autolysis during fermentation and aging, and we have performed a genome wide expression analysis in two different steps of the fermentation process. The results give some additional clues on KNR4 function in S. cerevisiae as well as on the best application conditions for this recombinant strain.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE26965 | GEO | 2011/02/28

SECONDARY ACCESSION(S): PRJNA136981

REPOSITORIES: GEO

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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.

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Comparative transcriptome analysis between an original and a recombinant wine yeast strain defective for KNR4/SMI1

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