The continuous production of ethanol from beet molasses by Ca-alginate immobilized Saccharomyces cerevisiae in a packed-bed bioreactor was investigated. The temperature was maintained at 30°C and the dilution rate was 0.22 h-1. Maximum ethanol (4.62%), theoretical yield (82.9%) and volumetric productivity (10.16 gl-1h-1) were obtained from the beet molasses medium containing 10.90% total sugar with 2.0-2.4 mm diameter beads prepared from 2% (w/v) sodium alginate solution. At higher substrate concentrations, substrate was recirculated through the packed-bed bioreactor to increase yields and to decrease residual sugar content. The bioreactor system was operated at a constant dilution rate of 0.22 h-1 for 25 days without loss of original fermentation capacity. Compared to packed-bed bioreactor, lower ethanol concentration (3.94%), theoretical yield (70.7%) and productivity (8.67 gl-1h-1 ) were obtained in the continuous stirred bioreactor.

The continuous production of ethanol from beet molasses by Ca-alginate immobilized Saccharomyces cerevisiae in a packed-bed bioreactor was investigated. The temperature was maintained at 30°C and the dilution rate was 0.22 h-1. Maximum ethanol (4.62%), theoretical yield (82.9%) and volumetric productivity (10.16 gl-1h-1) were obtained from the beet molasses medium containing 10.90% total sugar with 2.0-2.4 mm diameter beads prepared from 2% (w/v) sodium alginate solution. At higher substrate concentrations, substrate was recirculated through the packed-bed bioreactor to increase yields and to decrease residual sugar content. The bioreactor system was operated at a constant dilution rate of 0.22 h-1 for 25 days without loss of original fermentation capacity. Compared to packed-bed bioreactor, lower ethanol concentration (3.94%), theoretical yield (70.7%) and productivity (8.67 gl-1h-1 ) were obtained in the continuous stirred bioreactor.