In this section, we discuss reactor-level strategies towards the enhanced ethanol productivity in two ways. First, we seek optimal ratios of glucose and xylose in batch and continuous cultures to maximize bioethanol productivity. Second, various configurations combining batch, fed-batch and continuous reactors are considered. Their maximum achievable productivities are assessed using the model for the original recombinant strain S. cerevisiae 1400 (pLNH33) (i. e., with no amplification of EM6 flux).

The ethanol productivity in a batch and continuous reactor is computed as follows:

where xeth, in is the ethanol concentration in the feed (which is zero in our case), ts is the extra time taken for harvesting and preparation for the next batch. The normal range of ts is from 3 to 10 hours (Shuler & Kargi, 2002) and we set it to 6 hours.