CONICET | Buscador de Institutos y Recursos Humanos

The increasing of compounds with beneficial biological activities to human health in foods, such as antihypertensive and antioxidant activities, is currently topic of great interest. Peptides with biological activities can be released from inactive precursors (proteins-polypeptides) during food fermentation. Oenococcus oeni X2L from wine is able to express a proteolytic system under the stresses conditions present during winemaking. The aim of this work was to study the ACE-inhibitory and antioxidant activities during the growth of O. oeni X2L sequentially inoculated in grape juice medium fermented by Saccharomyces cerevisiae mc2. Microbial growth and peptide-amino acids modifications was also evaluated. S. cerevisiae mc2 was grown in basal juice medium (grape juice 57.0 ml/l; yeast extract 10.0 g/l; pH 5.5) at 30 °C. Supernatants of S. cerevisiae mc2 obtained at 0 (I) and 24 h (F) were collected, centrifuged, filtered (0.22 µm) and inoculated with O. oeni. Microbial growth was determined by viable cell count in agar plates. Amino acid and peptide concentrations were measured by Doi method. I-ACE activity percentage was measured by Cushman and Cheung method. Antioxidant capacity was evaluated by ferric reducing/antioxidant power (FRAP) and DPPH radical scavenging activity methods. When O.oeni was grown in the medium without yeast fermentation (I), reached a final biomass of 8.20 log cfu/ml at 48 h incubation. At this time, the bacterium increases peptide concentration in 265.9 mg N/L and specific FRAP activity to 1.79 µM FeSO4/mg peptide. DPPH activity did not significantly modify, while I-ACE activity also increase 5.43 % at 48 h. When O. oeni was grown in the medium fermented during 24 h by the yeast (F), even if a diminution of bacterium biomass (3 log cycles) and peptide release (76.02 mg N/L) were detected respect to the I medium, a higher specific antioxidant (FRAP) and I-ACE activities were determined (4,38 µM FeSO4/mg peptide and 40 %, respectively). The growth of O. oeni sequentially inoculated in unfermented and yeast fermented medium, produced a positive effect on the biological activities studied, respect to pure culture of S. cerevisiae. This behavior could be related to the proteolytic activity of the bacterium that release active peptides. Also, the differences observed between I and F medium could due to the higher expression of the O. oeni proteolytic system in the nutritional stress conditions present in the F medium after 24 h yeast growth.