Turkish Journal of Biology




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^{-1}h^{-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^{-1}h^{-1} ) were obtained in the continuous stirred bioreactor.


ethanol, beet molasses, calcium alginate, immobilization, packed-bed bioreactor

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