Characterization of membrane bioreactor for dry wine production.

Characteristics of yeast growth and ethanol fermentation were examined in membrane bioreactor using a grape juice. After inoculation, batch fermentation was carried out for 24 h. When yeast growth reached the stationary phase, continuous fermentation was initiated. In continuous fermentation, a linear relationship was observed between cell concentration and dilution rate. In single-vessel membrane bioreactor, the cell concentrations of 18.7 g/l and 76.9 g/l (15 and 60 times higher than that of the batch fermentation, respectively) were observed at dilution rates of 0.1 h(-1) and 0.3 h(-1), respectively. The residual sugar concentration was higher than 10 g/l at the dilution rate of 0.1 h(-1), 0.2 h(-1) or 0.3 h(-1), therefore the single-vessel membrane bioreactor was not suitable for producing dry wine (sugar concentration: 4 g/l or less). In the double-vessel membrane bioreactor, it is most suitable to set the recycle ratio at 0.15 for keeping the sugar concentration below 4 g/l. The productivity of dry wine in the double-vessel membrane bioreactor was 28 times higher than that in the batch fermentation.