Direct ethanol production from dextran industrial waste water by Zymomonas mobilis

The direct production of ethanol from dextran industrial waste water was investigated by using Zymomonas mobilis via batch and semi-continuous fermentation mode. In batch fermentation, pretreated waste water (unsterilized and sterilized), pH value (3.8 and 6.0), and Mg2+ (with and without) was compared with OD600, sugar and ethanol concentration. After 24 h fermentation, sugar in the dextran waste water was almost exhausted, and the amount of ethanol accumulated reached 24.33–29.92 g/l, which is nearly 99% of the theoretical yield of ethanol. Kinetic parameters of Z. mobilis in batch fermentation were also investigated. The raw dextran waste water was also used in semi-continuous fermentation. After 48 h fermentation, the production of ethanol was 28.65 g/l. These results indicated that dextran waste water may be used as a candidate substrate and Z. mobilis could convert the raw material into ethanol directly.