The nature of the nitrogen source added to nitrogen depleted vinifications conducted by a Saccharomyces cerevisiae strain in synthetic must affects gene expression and the levels of several volatile compounds

Abstract

Nitrogen starvation may lead to stuck and sluggish fermentations. These undesirable situations result in wines with high residual sugar, longer vinification times, and risks of microbial contamination. The typical oenological method to prevent these problems is the early addition of ammonium salts to the grape juice, although excessive levels of these compounds may lead to negative consequences for the final product. This addition reduces the overall fermentation time, regardless of the time of addition, but the effect is more significant when nitrogen is added during the yeast exponential phase. In this work we analysed the effect of adding different nitrogen sources (ammonia, amino acids or a combination of both) under nitrogen depletion in order to understand yeast metabolic changes that lead to the adaptation to the new conditions. These studies were carried out in a synthetic must that mimics the composition of the natural must. Furthermore, we studied how this addition affects fermentative behaviour, the levels of several yeast volatile compounds in the final product, arginase activity, and the expression of several genes involved in stress response and nitrogen metabolism during vinification. We found that the nature of the nitrogen source added during yeast late exponential growth phase introduces changes to the volatile compounds profile and to the gene expression. On the other hand, arginase activity and the expression of the stress response gene ACA1 are useful to monitor nitrogen depletion/addition during growth of the wine yeast considered under our vinification conditions.

Linking Post-Translational Modifications and Variation of Phenotypic Traits

“…In addition, winemaking selection appeared to have specially targeted the acidic isoform of Tdh3p. In a recent work, JimenezMarti and coworkers suggested that Tdh3p might account for strain adaptation to enological conditions (84). This could explain why isoforms of this enzyme had been specially targeted for wine strains.…”

Glucose and Fructose Fermentation by Wine Yeasts in Media Containing Structurally Complex Nitrogen Sources

“…Troubled fermentations have been attributed to the nutritional status of grape musts, once they contain suboptimal yeast nutrients, especially assimilable nitrogen 3,17,21,32 . A common practice in the wine industry for nitrogen limited fermentation is the addition of nitrogen supplements, using inorganic salts such as diammonium phosphate 22,27 .…”

“…completion and product quality 14,17,30,32 . The main sources of assimilable nitrogen in grape must are ammonium compounds, α-amino acids and to a lesser extent peptides 31 .…”

Metabolic Responses of Saccharomyces cerevisiae to Valine and Ammonium Pulses during Four-Stage Continuous Wine Fermentations

“…Nitrogen additions in the third stage of FSCF resulted in a substantial increase in the fermentation rate while biomass production was almost unaffected; this is consistent with previous observations during batch cultures (2,11,20). This recovery of an efficient fermentative activity has been explained by the increase of glucose uptake capacity, related to the de novo synthesis of glucose transporters (2,34,35,59). More generally, previous works reported that one of the main consequences of nitrogen supplementation during wine fermentation was an enhanced de novo synthesis of proteins, which involves an increase in the anabolism of amino acids (36,37).…”