Abstract
The yeast Brettanomyces bruxellensis is one of the most dangerous wine contaminants due to the production of phenolic off-flavors such as 4-ethylphenol. This microbial hazard is regularly tackled by addition of sulfur dioxide (SO2). Nevertheless, B. bruxellensis is frequently found at low levels (ca 103 cells/mL) in finished wines. Besides, consumers health concerns regarding the use of sulfur dioxide encouraged the search for alternative biocontrol measures. Recently, we found that Saccharomyces cerevisiae secretes a natural biocide (saccharomycin) that inhibits the growth of different B. bruxellensis strains during alcoholic fermentation. Here we investigated the ability of S. cerevisiae CCMI 885 to prevent B. bruxellensis ISA 2211 growth and 4-ethylphenol production in synthetic and true grape must fermentations. Results showed that B. bruxellensis growth and 4-ethylphenol production was significantly inhibited in both media, although the effect was more pronounced in synthetic grape must. The natural biocide was added to a simulated wine inoculated with 5 × 102 cells/mL of B. bruxellensis, which led to loss of culturability and viability (100% dead cells at day-12). The conjugated effect of saccharomycin with SO2 was evaluated in simulated wines at 10, 12, 13 and 14% (v/v) ethanol. Results showed that B. bruxellensis proliferation in wines at 13 and 14% (v/v) ethanol was completely prevented by addition of 1.0 mg/mL of saccharomycin with 25 mg/L of SO2, thus allowing to significantly reduce the SO2 levels commonly used in wines (150–200 mg/L).
Highlights
The indigenous microbiota of grape musts includes an immense variety of microorganisms that can grow and ferment sugars [1,2]
In previous work [27,28,29,30], we found that several S. cerevisiae strains secrete a natural biocide, which we named saccharomycin, that is active against wine-related non-Saccharomyces yeasts, including B. bruxellensis, as well as lactic acid bacteria
The aim of the present work was to evaluate the effectiveness of saccharomycin to prevent B. bruxellensis growth and 4-ethylphenol production in wine fermentations, as well as to assess its conjugated effect with SO2 against B. bruxellensis proliferation in finished wines, allowing to reduce the chemical levels presently used in winemaking
Summary
The indigenous microbiota of grape musts includes an immense variety of microorganisms that can grow and ferment sugars [1,2]. S. cerevisiae strains usually dominate alcoholic fermentations, some microorganisms such as lactic and acetic acid bacteria and yeasts like Dekkera/Brettanomyces bruxellensis may remain in finished wines and proliferate under certain conditions (e.g., oxygen and/or sugars availability), spoiling the wine [6,7]. B. bruxellensis (anamorphic form) and its ascosporeforming type D. bruxellensis (teleomorphic form) is considered the most dangerous spoilage microorganism and has been isolated from almost every wine-producing area of the world [8,9,10].
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