Abstract
Winemaking is a stressful procedure for yeast cells. The presence of high levels of carbohydrates at the beginning of the fermentation and the subsequent increase of ethanol levels alongside with other environmental factors force the cell to undergo a continuous adaptation process. Ideally, yeast strains should be able to adapt to this changing environment fast and they must be able to ferment at low temperatures with the highest possible fermentation rates. Additionally, the balanced utilization of glucose and fructose—the two major hexoses in grapes—is also important as any residual fructose may confers unwanted sweetness. As proteins, Msn2/4 are known to play pivotal roles in cell stress response, the question that arise regards the differentially cell response driven by specific point mutations in these two proteins, and the subsequent effects on alcoholic fermentation. Four different mutants in which serine residues have been replaced by alanine are studied in this paper. Our results indicate that substitution at position 533 of Msn4 protein (W_M4_533) significantly increases the fermentation rate even at low temperatures (12 °C), by lowering the fermentation’s activation energy. Similar results but to a lesser extent were obtained by the S582A substitution in Msn2 protein. In addition, W_M4_533 seems to have a more balanced utilization of must hexoses. From the present work it is concluded that genetic modification Msn2/4 represents a promising procedure for shortening the fermentation time, even at low temperatures, which in many cases constitutes an important technological requirement.
Highlights
Indigenous yeasts are responsible for the fermentation process during traditional winemaking
Msn2/4 are targets of Protein kinase A (PKA) and their phosphorylation at specific serine residues results in their inability to translocate to the nucleus [5]
As the depletion of these transcription factors seems to affect the metabolic function of the cell, a more targeted intervention to PKA/Msn2/4 system may contribute to the improvement of alcoholic fermentation
Summary
Indigenous yeasts are responsible for the fermentation process during traditional winemaking. As the depletion of these transcription factors seems to affect the metabolic function of the cell, a more targeted intervention to PKA/Msn2/4 system may contribute to the improvement of alcoholic fermentation In this concept, there have been a couple of studies from our lab, in order to partially inhibit the Msn2/4 inactivation through the PKA phosphorylation and subsequently help yeast cells to ferment more efficiently and faster, using synthetic substrate. There have been a couple of studies from our lab, in order to partially inhibit the Msn2/4 inactivation through the PKA phosphorylation and subsequently help yeast cells to ferment more efficiently and faster, using synthetic substrate In these studies, several Msn2/4 serine residues that had been thought to undergo phosphorylation and hold these transcription factors to the cytosol, have been replaced by alanine. An effort was made to calculate the physicochemical characteristics of the fermentation’s efficiency of each strain
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