Impact of glutathione-rich inactivated yeast on wine chemical diversity

Abstract

Glutathione-rich inactivated dry yeasts (GSH-IDY) are claimed to accumulate intracellularly and then release glutathione in the must. Glutathione is beneficial to the wine quality, but scientists also highlighted that GSH-IDYs have a greater effect than only increase the pool of this antioxidant in the wine. This work unveils the extent of diversity of compounds potentially released by three different IDYs with increasing GSH contents.

Unsupervised analysis of IDYs released compounds in model wine was performed with the ultra-high-resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). This powerful tool allows to have an instant picture of the released compounds chemical diversity. Bioinformatics strategy (chemometric analysis and network annotation) were then applied to visualize and refine the generated data.

Our results clearly show an impact of the GSH accumulation process not only visible on the glutathione itself, but also on the global diversity of compounds. The ratio of annotated CHONS/CHO ions increased from 0.2 to 2.1 respectively with the accumulation of GSH. The IDY with the highest concentration of GSH released 36 unique CHONS annotated ions compared to the two others IDYs. Since the bioprocess dedicated to accumulate the intracellular glutathione used cysteine rich medium, the possibility to attribute this diversity to notably a larger number of cysteinyl residues in peptides raised. Within the 1699 detected ions by (-)FT-ICR-MS, 193 were annotated as peptide sequences (from 2 to 5 residues). Within this pool of peptides, the IDY specific diversity increased with the level of glutathione from 5 to 45 unique m/z. Besides the global diversity, m/z attributed to cysteine containing peptides were much more abundant in the GSH-rich IDY. Within the 25 peptides containing cysteine, and common to the three IDYs, 64 % were more intense in GSH-rich IDY. Thus, the process leading to accumulate glutathione is also involved in other metabolic pathways which contribute to increase CHONS containing compounds and notably peptides.

This work gives new clues on the potential of biotechnology to improve the efficiency of natural yeast derivatives to produce potential active compounds such as cysteine containing peptides. This could lead to substitute partially the chemical additives and thus leading to a better control of wine quality and a better consumer acceptability.