Characterization and identification of yeast bioactive peptides released during fermentation and autolysis in model wine

Aging wine on lees is a consolidated practice during which some yeast components (e.g., polysaccharides, proteins, peptides…) are released and solubilized in wine thus, affecting its stability and quality. Apart from the widely studied mannoproteins, the role of other yeast components in modulating wine characteristics is still scarce. Wine peptides have been studied for their contribution to taste, antioxidant, and antihypertensive potentials. However, the variety of peptides detected in wine can be influenced by the interaction between yeast and grape components. Therefore, to study the actual contribution of yeasts to the presence of wine peptides, the concentration and profile of peptides released by yeasts during and after fermentation was studied in model conditions. A synthetic must, prepared replacing amino acids with NH4Cl as the sole nitrogen source, was inoculated with an oenological Saccharomyces cerevisiae strain. The resulting synthetic wine was sampled weekly over the first month, and monthly in the following five months. After centrifugation, each sample was ultrafiltered (3 kDa MWCO), and the peptides on the filtrate were quantified and separated by RP-HPLC. The peptides present in the 7 (end of fermentation) - and 120-day samples, were characterized by LC-MS/MS, thus determining their sequence and the putative origin. Moreover, by using the BIOPEP Database, their potential bioactivity was studied in silico using the BIOPEP Database. Results showed that the total concentration of peptides increased during the first two weeks before plateauing to ≃ 1.1 g/L. Nevertheless, the number of peptides (2263 at day 7; 1978 at day 120) and the amino acid sequence differed over time. Within the released peptides, in silico analysis revealed the presence of potential bioactive sequences in the samples taken at the end of fermentation and collected after 120 days of lees aging. The vast majority (≃ 95%) of the peptides showed a potential antihypertensive activity. Results indicate that yeasts abundantly release different peptides during and after the alcoholic fermentation due to the presence of yeast cells. The high peptide concentration, variety, and bioactive potential reported here deserves further investigation to assess the role of this fraction on wine quality and, possibly, health effects.