The viable yeast cells in the VHG medium increased in 12 h (Fig. 5A). These values under the aeration at 0.05 vvm were rela- tively constant throughout the fermentation, while they decreased after 48 h under the aeration at 0.2 and 0.35 vvm. Changes of the sugar consumption in the fermentation broth under all aera- tion conditions were similar. The total sugar concentrations under the aeration rates at 0.2 and 0.35 vvm remained constant at 48 h, whereas it was constant at 60 h under the aeration of 0.05 vvm. The total sugar remaining under the aeration rates at 0.05 and 0.2 vvm were similar at about 22–23 g l−1 , whereas this value was higher at the aeration of 0.35 vvm with the sugar remaining of approximately 43g l−1 . Changes of the ethanol concentration under all conditions were similar in the first 48 h. After that, the ethanol values at the aeration of 0.05 vvm were continuously increased until 72 h with the highest P value of 131.6 g l−1 . However, the Qp value under the aeration at 0.05 vvm was slightly lower than those under the aer- ation at 0.2 and 0.35 vvm due to a longer fermentation time. Yan et al. (2009) found that initial aeration and agitation improved the ethanol production up to 143.8 g l−1 . Interestingly, the nutrient sup- plementation with 13.5 g l−1 of DSY, low-cost nitrogen source, on VHG ethanol production under the lowest aeration rate (0.05 vvm), led to an increase in the final P value (131.6 g l−1 ) at 72 h (Table 2). These results strongly indicated that aeration at appropriate lev- els could improve the ethanol production efficiency under the VHG conditions. In the present study, glycerol productions under the DSY sup- plementation coupled with different aeration rates were similar (9.8–9.9 g l−1 ), but they were lower than that (12.4 g l−1 ) under no aeration (Table 3). Similar glycerol productions under all aeration conditions might be due to the fact that the aeration was sup- plied only during log phase or the first 12 h of the fermentation.