Effect of Kluyveromyces thermotolerans on Saccharomyces cerevisiae during fermentation processes

MARÍA CRISTINA NALLY; MARÍA LORENA PONSONE; SUSANA DEL CARMEN GODOY; VIRGINIA MERCEDES PESCE; MARÍA EUGENIA TORO; FABIO VAZQUEZ; SOFÍA CHULZE

Simposio; III International symposium on postharvest pathology; 2015

Fungal diseases are one of the main reasons for economic losses in viticulture. Aspergillus section Nigri species have been reported as agents of black grape rot. Antagonistic microorganisms are a sustainable alternative to synthetic fungicides. In previous studies (Ponsone et al., 2013) showed that two yeast strains, Kluyveromyces thermotolerans RCKT4 and RCKT5, inhibited Aspergillus growth and decreased OTA accumulation in wine grapes. However, there are no data about the effects of K. thermotolerans, potential biofungicides, during oenological fermentations. The aim of this work was to evaluate the impact of two selected potential biofungicides in mixed cultures with S. cerevisiae BSc203 (an oenological strain) during microfermentations. Pure and mixed cultures (1%BSc203-99%biofungicide; 50%BSc203-50%biofungicide; 99%BSc203-1%biofungicide) were inoculated in commercial must. All fermentation samples were periodically withdrawn and spread on WLN-Agar plates (Log10UFC/ml), in which both strains colonies can be differentiated. In co-cultures Saccharomyces (BSc203)/Kluyveromyces (RCKT5, RCKT4), BSc203 yeast concentration was no significantly different to pure BSc203 concentration, except in co-culture 99%RCKT4-1%S. cerevisiae, at the end of fermentations (22 days). Cells concentration of BSc203 (in 99%K.th./1%S.c.) was 1.38 Log10 cycle lower than in its pure culture. In all mixed cultures assayed basic quality of wines obtained were according to OIV (2013). Biofungicide yeasts did not affect the fermentative process. Conclusions: K. thermotolerans RCKT4 affected BSc203 growth when was inoculated in high proportions. RCKT5 did not affect S. cerevisiae growth in all conditions assayed.