Saccharomyces cerevisiae and Torulaspora delbrueckii Intra- and Extra-Cellular Aromatic Amino Acids Metabolism

Abstract

Tryptophan, phenylalanine, and tyrosine play an important role as nitrogen sources in yeast metabolism. They regulate biomass production and fermentation rate, and their catabolites contribute to wine health benefits and sensorial character through the yeast biotransformation of grape juice constitutes into biologically active and flavor-impacting components. A UHPLC-MS/MS method was applied to monitor 37 tryptophan/phenylalanine/tyrosine yeast metabolites both in extra-and intracellular extracts produced by the fermentation of two Saccharomyces cerevisiae strains and one Torulaspora delbrueckii. The results shed light on the intra-and extra-cellular metabolomic dynamics, by combining metabolic needs, stimuli, and signals. Among others, the results indicated (a) the production of 2-aminoacetophenone by yeasts, mainly by the two Saccharomyces cerevisiae; (b) the deactivation and/or detoxification of tryptophol via sulfonation reaction; and (c) the deacetylation of N-acetyl tryptophan ethyl ester and N-acetyl tyrosine ethyl ester by producing the corresponding ethyl esters.

Modulating Wine Aromatic Amino Acid Catabolites by Using Torulaspora delbrueckii in Sequentially Inoculated Fermentations or Saccharomyces cerevisiae Alone

“…The number of identified and quantified metabolites was higher in extracellular samples than in intracellular ones, which is in accordance with the results of our previous study [9]. The UPLC-MS/MS method used was able to quantify 33 compounds in wine [23], 26 of which were detected and quantified in the extracellular and 8 were detected in the intracellular samples in this experimental design.…”

“…Therefore, using T. delbrueckii as a starting culture in winemaking should not influence the growth and the metabolic activity of S. cerevisiae (Figure 2) too badly. Generally, the results about the three amino acids' consumption during fermentation are in accordance with the literature [9,15,16,24,31], since their concentration decreased quickly mainly during the logarithmic phase of cell growth ( Figure 2) by covering the needs of the yeasts in nitrogen. Finally, chardonnay must fermented by S. cerevisiae QA and RF showed an increase of PHE and NIC concentrations in the last part of fermentation (Table S2 and Figures S3 and S4).…”

“…The majority of published works about non-Saccharomyces use in winemaking focuses on the volatile metabolites and the basic oenological parameters [8][9][10][11]28]. Only a few papers deal with measurement of the metabolites produced by the aromatic amino acids [9,11,29,30], even though they include several important sensorial and biological active compounds (see the Introduction section). This project tried to enrich our knowledge with regard to a big part of the metabolites presented in Figure 1.…”

“…The aromatic amino acids phenylalanine (PHE), tyrosine (TYR) and tryptophan (TRP), which take part in the grape metabolome, can also be consumed but are less preferable [15]. On the other hand, the catabolites of these aromatic amino acids include several sensorial and biological active compounds, such as tryptophol (TOL), tyrosol (TYL), hydroxytyrosol (OH-TYL) kynurenic acid (KYNA), kynurenine (KYN), indole acetic acid (IAA), indole lactic acid (ILA), and ethyl esters of TRP (TRP-EE) and TYR (TYR-EE) ( Figure 1) [9,16]. Via the Ehrlich pathway, the amino acids produce aromatic higher alcohols, like TOL and TYL, for which biosynthesis is positively correlated with ethanol stress-tolerant yeast, and as auto inducers are able to transmit information about the population density and the amount of available nitrogen [17].…”

“…A recent work of our group focused on the intra-and extracellular metabolic dynamics of the three aromatic amino acid catabolites on synthetic media during fermentation of two S. cerevisiae and one non-Saccharomyces strains [9]. The study demonstrated that all three strains were able to produce 2AA and sulfonated tryptophol (TOL-SO 3 H), two previously considered metabolites formed only during wine aging and storage.…”