Fig. 8 shows the time courses of glucose, ethanol and total sugar concentrations in SSF using immobilized cells of Z. mobilis.In contrast to SSF using freely suspended cells where the ethanol could not be produced even after 24 h of incubation (Fig. 2),the amount of ethanol produced reached 18 g/L in SSF with Ca-alginate immobilized cells after 48 h of incubation and the total sugar con-centration increased as same as the ethanol production rate with the incubation time and reached 20.5 g/L after 48 h of incubation,while the glucose concentration
remained at a low constant level.This behavior could to be attributed to the ethanol production by immobilized cells sequentially from the produced glucose and the accumulation of the nonfermentable causing the increase of total sugar concentration. This result indicated that the immobilization entrapped in Ca-alginate improved the ethanol production as the metal ions were adsorbed in Ca-alginate gel beads and the inner cells were protected from the inhibitory effect of metal ions and/or impurities included in the paper sludge.