Killer activity of combined toxins from different Saccharomyces cerevisiae strains

MIGUEL FERNÁNDEZ DE ULLIVARRI; LUCÍA M. MENDOZA; RAÚL R. RAYA; MARTA E. FARÍAS

San Miguel de Tucumán

Congreso; VII Congreso Argentino de Microbiología General – SAMIGE del Bicentenario; 2011

Sociedad Argentina de Microbiología General SAMIGE

Some yeast strains are capable to produce proteinaceous or glicoproteinaceous toxins that can kill or inhibit the growth of other microorganisms. In winemaking, these yeasts are being used increasingly as fermentation starters, because of their possible predominance during the process. This could ensure the obtaining of products with controlled quality. We evaluated the killer activity of different Saccharomyces cerevisiae supernatants, obtained from cocultures or mixing monocultures (ratio 1:1) of autochthonous killer strains (Cf5, Cf8, Cf13, Cf19, Cf21, M12) and a reference killer yeast (S. cerevisiae type K1), against the sensitive strain S. cerevisiae P351. In all combinations S. cerevisiae Cf8 was utilized. This strain was selected in previous studies as the best killer toxin producer. Supernatants were prepared from yeasts inoculated into YPD-MB broth (pH 4.2) during 96 h at 18 ºC. The culture supernatants were sterilized by filtration and enriched with sterile 10X YPD-MB broth (final 1x). The filtrates were inoculated with the strain P351 and incubated at 18 ºC, and their killer effects were evaluated by OD600 at 0, 18 and 36 h. Supernatants from monocultures were used as killer activity control, and non fermented medium as growth control. Killer activity was expressed as % reduction of absorbance measured against growth control. The highest killer activities were observed with the mix of the M12 and Cf8 monoculture supernatants, which showed an increase of 19.14 and 55.58% compared with the M12 and Cf8 controls, respectively. Also the supernatant from the coculture Cf19-Cf8 showed an increase of 28.94 and 55.74% with regard to the Cf19 and Cf8 controls, respectively. The other assayed strains did not exhibit significant differences with the controls. This study evidenced that the killer activity of S. cerevisiae Cf8 strain could be improved by combining different toxin-producing strains, being this effect strain-dependent as well as culture-condition dependent.