Noteworthy, ethanol yields on sugar for S. cerevisiae strains under these experimental conditions were quite below normal values under anaerobic conditions (about 0.45 g/g). This was only partly explained by alcohol stripping (data not shown), and indicates a significant contribution of respiratory metabolism. However, the acetic acid yield for both S. cerevisiae strains was extremely high under these aerated conditions ( Table 2), and the resulting increase in volatile acidity would preclude any practical application of the respiratory capacity of these S. cerevisiae strains. Indeed, these strains showed some of the highest YACE/S values amongst the strains analysed, together with T. delbrueckii AQ249, and K. exigua DBVPG6354. Acetic acid yield for the other yeast strains in Table 2 was lower or much lower than for the above mentioned strains. The correlation between ethanol and acetic acid yields has some noteworthy and interesting exceptions, like K. lactis AQ2166, or M. pulcherrima IFI1459.