Combined Isotopic Tracer and Modelling Approach Reveals Differences in Nitrogen Metabolism in S. cerevisiae, S. uvarum and S. kudriavzevii Species.

The species Saccharomyces uvarum and Saccharomyces kudriavzevii have gained popularity in recent decades due to their interesting oenological properties. However, although it plays a crucial role in yeast fermentation performance and compound synthesis, our understanding of nitrogen metabolism in these species remains limited. Therefore, we compared how three strains of Saccharomyces cerevisiae, Saccharomyces uvarum and Saccharomyces kudriavzevii use relevant nitrogen sources by combining quantitative analysis approaches based on isotopic tracing and modelling. The model we have developed aims to facilitate the calculation and interpretation of stable isotope data for other experiments, by providing easy visualisation of the results and predicting the kinetics of isotope incorporation beyond the sampling points. The three species exhibit significant variations in their nitrogen assimilation profile. They differ in the timing of uptake of ammonium, arginine and glutamine: Saccharomyces cerevisiae prefers glutamine, Saccharomyces kudriavzevii ammonium and Saccharomyces uvarum arginine. This contributes to a different pattern of nitrogen redistribution towards proteinogenic amino acids between strains at the start of the exponential phase, which fades on entering the stationary phase. Additionally, we found that the contribution of leucine and valine to isoamyl alcohol production varies between species; also, Saccharomyces kudriavzevii activates the synthesis of volatile compounds earlier.