Fermentation experiments on 15 mL synthetic must with high sugar content (140 g/L glucose, 140 g/L fructose, 1.7 g/L Yeast Nitrogen Base without ammonium sulphate and amino acids, 6 g/L citric acid, 6 g/L malic acid, 1.15 g/L ammonium chloride, 30 mg/L potassium disulphite, pH adjusted at 3.5 with KOH) were carried out at 25 C in 50 mL Falcon tubes capped with fermentation locks filled with mineral oil. Each tube was inoculated with 1% volume of a fresh culture in YPD (grown for 48 h at 28 C and 180 rpm).