| Abstract: | The continuous production of ethanol from carob pod extract by immobilized Saccharomyces cerevisiae in a packed-bed reactor has been investigated. At a substrate concentration of 150 g dm?3, maximum ethanol productivity of 16 g dm?3 h?1 was obtained at D = 0·4 h?1 with 62·3% of theoretical yield and 83·6% sugars′ utilization. At a dilution rate of 0·1 h?1, optimal ethanol productivity was achieved in the pH range 3·5–5·5, temperature range 30–35·C and initial sugar concentration of 200 g dm?3. Maximum ethanol productivity of 24·5 g dm?3 h?1 was obtained at D = 0·5 h?1 with 58·8% of theoretical yield and 85% sugars′ utilization when non-sterilized carob pod extract containing 200 g dm?3 total sugars was used as feed material. The bioreactor system was operated at a constant dilution rate of 0·5 h?1 for 30 days without loss of the original immobilized yeast activity. In this case, the average ethanol productivity, ethanol yield (% of theoretical) and sugars′ utilization were 25 g dm?3 h?1, 58·8% and 85·5%, respectively. |
