Respiration of sugars by non-Saccharomyces yeasts has been recently proposed for lowering alcohol levels in
wine. Development of industrial fermentation processes based on such an approach requires, amongst other
steps, the identification of yeast strains which are able to grow and respire under the relatively harsh conditions
found in grape must. This work describes the characterization of a collection of non-Saccharomyces yeast strains
in order to identify candidate yeast strains for this specific application. It involved the estimation of respiratory
quotient (RQ) values under aerated conditions, at low pH and high sugar concentrations, calculation of yields
of ethanol and other relevant metabolites, and characterization of growth responses to the main stress factors
found during the first stages of alcoholic fermentation. Physiological features of some strains of Metschnikowia
pulcherrima or two species of Kluyveromyces, suggest they are suitable for lowering ethanol yields by respiration.
The unsuitability of Saccharomyces cerevisiae strains for this purposewas not due to ethanol yields (under aerated
conditions they are low enough for a significant reduction in final ethanol content), but to the high acetic acid
yields under these growth conditions. According to results from controlled aeration fermentations with one
strain of M. pulcherrima, design of an aeration regime allowing for lowering ethanol yields though preserving
grape must components from excessive oxidation, would be conceivable.