Characterization and stress-protective action of Saccharomyces cerevisiae extracellular peptide factors on propionic acid bacteria

Abstract

Protective effect of Saccharomyces cerevisiae exometabolites (RF₁ and RF₂) on seven strains of propionic acid bacteria under exposure to bile salts and acid stress was studied. RF₂ had a stronger protective effect than RF₁. Comparison of the analytical profiles of RF₁ and RF₂, separated by RP-HPLC, showed that nearly 80% of RF₁ components were present in RF₂. Separation of S. cerevisiae RF₁ into individual components by means of semi-preparative RP-HPLC was used for structural characterization of the active component of the RF₁ fraction. It was found to contain two pentapeptides (<1 kDa) with identical amino acid sequences (¹Gly-Pro-Tre-Gly-Pro⁵), differing in one hexose residue. The RF₂ separation method based on three-stage liquid chromatography at low and high pressure was developed, which involved analytical high-pressure gel chromatography. The use of the latter method made it possible to separate high-molecular components and perform enrichment of low-molecular peptides. Peptide origin of the RF₂ active substances with molecular masses allegedly below 300 Da was confirmed.