CONTINUOUS ETHANOL-PRODUCTION FROM CAROB POD EXTRACT BY IMMOBILIZED SACCHAROMYCES-CEREVISIAE IN A PACKED-BED REACTOR

The continuous production of ethanol from carob pod extract by immobil ized Saccharomyces cerevisiae in a packed-bed reactor has been investi gated. At a substrate concentration of 150 g dm-3, maximum ethanol pro ductivity of 16 g dm-3 h-1 was obtained at D = 0.4 h-1 with 62.3% of t heoretical 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-degrees-C and initial sugar concentratio n of 200 g dm-3. Maximum ethanol productivity of 24.5 g dm-3 h-1 was o btained 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 o perated at a constant dilution rate of 0.5 h-1 for 30 days without los s of the original immobilized yeast activity. In this case, the averag e ethanol productivity, ethanol yield (% of theoretical) and sugars' u tilization were 25 g dm-3 h-1, 58.8% and 85.5%, respectively.