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Advisor(s)
Abstract(s)
The early death of two non-Saccharomyces wine strains (H. guilliermondii and H. uvarum) during mixed fermentations with S. cerevisiae was
studied under enological growth conditions. Several microvinifications were performed in synthetic grape juice, either with single non-
Saccharomyces or with mixed S. cerevisiae/non-Saccharomyces inocula. In all mixed cultures, non-Saccharomyces yeasts grew together with
S. cerevisiae during the first 1–3 days (depending on the initial inoculum concentration) and then, suddenly, non-Saccharomyces cells began to die
off, regardless of the ethanol concentrations present. Conversely, in both non-Saccharomyces single cultures the number of viable cells remained
high (ranging 107–108 CFU ml− 1) even when cultures reached significant ethanol concentrations (up to 60–70 g l− 1). Thus, at least for these yeast
strains, it seems that ethanol is not the main death-inducing factor. Furthermore, mixed cultures performed with different S. cerevisiae/
H. guilliermondii inoculum ratios (3 :1; 1:2; 1: 10; 1 : 100) revealed that H. guilliermondii death increases for higher inoculum ratios. In order to
investigate if the nature of the yeast–yeast interaction was related or not with a cell–cell contact-mediated mechanism, cell-free supernatants
obtained from 3 and 6 day-old mixed cultures were inoculated with H. guilliermondii pure cultures. Under these conditions, cells still died and
much higher death rates were found for the 6 days than for the 3 day-old supernatants. This strongly indicates that one or more toxic compounds
produced by S. cerevisiae triggers the early death of the H. guilliermondii cells in mixed cultures with S. cerevisiae. Finally, although it has not
been yet possible to identify the nature of the toxic compounds involved in this phenomenon we must emphasise that the S. cerevisiae strain used
in the present work is killer sensitive with respect to the classical killer toxins, K1, K2 and K28, whereas the H. guilliermondii and H. uvarum
strains are killer neutral.
Description
Keywords
Non-Saccharomyces wine yeasts Mixed cultures Cellular death Toxic compounds Yeast–yeast interactions
Pedagogical Context
Citation
PÉREZ-NEVADO, F..[et al.] Cellular death of two non-saccharomyces wine-related yeasts during mixed fermentations with saccharomyces cerevisiae. International Journal of Food Microbiology. ISSN 0168-1605. Vol. 108, n.º 3 (2006), p. 336–345
Publisher
Elsevier