Abstract
Nitrogen availability and utilization by Saccharomyces cerevisiae significantly influence fermentation kinetics and the production of volatile compounds important for wine aroma. Amino acids are the most important nitrogen source and have been classified based on how well they support growth. This study evaluated the effect of single amino acids on growth kinetics and major volatile production of two phenotypically different commercial wine yeast strains in synthetic grape must. Four growth parameters, lag phase, maximum growth rate, total biomass formation and time to complete fermentation were evaluated. In contrast with previous findings, in fermentative conditions, phenylalanine and valine supported growth well and asparagine supported it poorly. The four parameters showed good correlations for most amino acid treatments, with some notable exceptions. Single amino acid treatments resulted in the predictable production of aromatic compounds, with a linear correlation between amino acid concentration and the concentration of aromatic compounds that are directly derived from these amino acids. With the increased complexity of nitrogen sources, linear correlations were lost and aroma production became unpredictable. However, even in complex medium minor changes in amino acid concentration continued to directly impact the formation of aromatic compounds, suggesting that the relative concentration of individual amino acids remains a predictor of aromatic outputs, independently of the complexity of metabolic interactions between carbon and nitrogen metabolism and between amino acid degradation and utilization pathways.
Highlights
During fermentation, yeast take up and metabolize amino acids and other nutrients to support growth and produce biomass
Previous studies used generation time to evaluate the efficiency of nitrogen sources to support growth (Cooper, 1982; Godard et al, 2007)
This study increased the number of growth parameters evaluated, which allowed for a more rigorous and complete study of the efficiency of single amino acids in a wine-specific context
Summary
Yeast take up and metabolize amino acids and other nutrients to support growth and produce biomass. Amino Acids and Wine Aroma are present during fermentation (Dickinson et al, 1997; Hernández-Orte et al, 2002; Miller et al, 2007; Styger et al, 2011; Torrea et al, 2011; Gutiérrez et al, 2012; Silva Ferreira et al, 2014; Burin et al, 2015; Stribny et al, 2015) In part, for this reason, the metabolic fate and efficiency of amino acids have been studied extensively (Cooper, 1982; Monteiro and Bisson, 1992; Godard et al, 2007; Crépin et al, 2012, 2017; Ljungdahl and Daignan-Fornier, 2012). Arginine, asparagine, aspartate, glutamate, glutamine, and serine were classified as preferred nitrogen sources and all other nitrogen sources as either intermediate or non-preferred (Ljungdahl and Daignan-Fornier, 2012) These studies provide important foundational data sets for elucidating the impact of amino acid composition on yeast growth. Such studies have mostly been carried out with laboratory strains and in conditions that are very different from those encountered during winemaking
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