Initial studies have been carried out on the scale-up of a medium-scale (2-5 m tall with a 10.2-cm id), fluidized-bed reactor (FBR) designed for fuel ethanol fermentation using immobilized Zymamonas mobilis. These results suggest that further improvements in ethanol productivity along with good operability may be possible when compared with previous results at the bench scale (40-110 g ethanol/L/h) and present industrial reactors (2-10 g ethanol/L/h). On-line and offline measurement and control systems are also described. Z. mobilis was immobilized in kappa-carrageenan at cell loading of approx 60 g (dry wt)/L of biocatalyst. The system is designed for determining optimal operating conditions for achieving high conversion and productivity with variations in feedstocks, temperature, flow rate, and column sizes.