In the course of repeated batch fermentation with sucrose medium, using the 50 l external loop bioreactor, the immobilized cell concentration and thus the ethanol productivity continued to increase, the latter reaching 16 g l-1 h-1 in the fourth batch (data not shown). By using the method described here, immobolization of cells uniformly in a larger scale reactor can also be achieved. Depending on the scales, however, the loop may be modified as shown in Fig. 8.