Bioprotection by non-Saccharomyces yeasts in oenology: Evaluation of O consumption and impact on acetic acid bacteria.

Bioprotection by yeast addition is increasingly used in oenology as an alternative to sulfur dioxide (SO). Recent studies have also shown that it is likely to consume dissolved O. This ability could limit O for other microorganisms and the early oxidation of the grape must. However, the ability of yeasts to consume O in a context of bioprotection was poorly studied so far considering the high genetic diversity of non-Saccharomyces. The first aim of the present study was to perform an O consumption rate (OCR) screening of strains from a large multi species collection found in oenology. The results demonstrate significant inter and intra species diversity with regard to O consumption. In the must M. pulcherrima consumes O faster than Saccharomyces cerevisiae and then other studied non-Saccharomyces species. The O consumption was also evaluate in the context of a yeast mix used as industrial bioprotection (Metschnikowia pulcherrima and Torulaspora delbrueckii) in red must. These non-Saccharomyces yeasts were then showed to limit the growth of acetic acid bacteria, with a bioprotective effect comparable to that of the addition of sulfur dioxide. Laboratory experiment confirmed the negative impact of the non-Saccharomyces yeasts on Gluconobacter oxydans that may be related to O consumption. This study sheds new lights on the use of bioprotection as an alternative to SO and suggest the possibility to use O consumption measurements as a new criteria for non-Saccharomyces strain selection in a context of bioprotection application for the wine industry.