The ethanol fermentation under anaerobic condition by a strain of S. cerevisiae was investigated in batch and fed-batch modes at pH 4.0 and 30 ℃． The flask fermentation showed the optimal glucose concentration to be 10 % by weight. With the increase in the initial glucose concentration, the initial lag phase as well as substrate inhibition increased. In batch fermentation, the effect of some fermentation parameters such as the inoculum size and the glucose concentration on the fermentation time and the ethanol production rate was investigated.
The experimental results together with the mathematical model were utilized for finding the optimal strategy for the glucose addition rate.
Fermentations with constant glucose feed rate were undertaken using 50 % glucose solution. The productivity of fed-batch fermentation per cell inoculated was about 30 % higher than that of the batch fermentation. The use of the glucose powder instead of the solution may help reduce the dilution effect and hence the fermentation period required to arrive at the same final ethanol concentration.