A fluidized-bed, immobilized-cell bioreactor is used for the conversion of glucose to ethanol by Z. mobilis cells immobilized in k-carrageenan gel beads. The dimensions of the bed are 10 cm (diameter) by 200 cm. Since the reactor is fed from the bottom of the column and because of CO2 gas evolution, substrate and cell concentrations decrease with the height of the column. The average cell concentration at the bottom of the column is X0 = 45 g/l, and the average cell concentration decreases with the column height according to the following equation: where Z is the column height (cm). The specific rate of substrate consumption is qS = 2 g S/g cells. h. The feed flow rate and glucose concentration in the feed are 5 l/h and 160 g glucose/l, respectively. Determine the substrate (glucose) concentration in the effluent -triyambak.org