ESULTS
Acclimatization of strain WW by long-term-continuous under acidic conditions Fig. 1A shows the changes in PH, cell number, cell viability, and the concentrations of residual glucose and ethanol during continuous fermentation under acidic conditions. The cell number, cell viability, and decreased as the PH was lowered, however, they reached stable under each PH condition. The ethanol and residual glucose concentrations were maintained at 60 9/L and 10 gjL, respectively, when the PH was in the range of 3. 7-2. 7 for days 1-25. When the PH was lowered to 2. 5, the ethanol concentration decreased concomitantly with the increase in residual sugar concentration. At day 26, the day immediately after PH adjustment, the ethanol concentration was 48 gjL which was 10 9/L less than that of the previous day ; the residual sugar concentration was 28 9/L, which was 2-Sold higher than that at day 25. The ethanol concentration continuously decreased to 39 9/L by day 41, whereas the residual sugar concentration increased to 56 gjL. However, the ethanol yields, calculated based on consumed glucose, at stable states of each PH condition, maintained at 85-87%, in spite of the change of PH. Compared to the ethanol fermentation ability, growth of cellswas more sensitive to PH conditions. The number of viable cells