KINETICS OF ETHANOL-PRODUCTION FROM CAROB PODS EXTRACT BY IMMOBILIZEDSACCHAROMYCES-CEREVISIAE CELLS

Kinetics of ethanol production from carob pods extract by immobilized S. cerevisiae cells in static and shake flask fermentation have been i nvestigated. Shake flask fermentation proved to be a better fermentati on system for the production of ethanol than static fermentation. The optimum values of ethanol concentration, ethanol productivity, ethanol yield, and fermentation efficiency were obtained at pH range 3.5-6.5 and temperature between 30-35 degrees C. A maximum ethanol concentrati on (65 g/L), ethanol productivity (8.3 g/Lh), ethanol yield (0.44 g/g) , and fermentation efficiency (95%) was achieved at an initial sugar c oncentration of 200, 150, 100, and 200 g/L, respectively. The highest values of specific ethanol production rate and specific sugar uptake r ate were obtained at pH 6.5, temperature 40 degrees C, and initial sug ar concentration of 100 g/L. Other kinetic parameters, biomass concent ration, biomass yield, and specific biomass production rate were maxim um at pH 5.5, temperature 30 degrees C, and initial sugar concentratio n 150 g/L. Under the same fermentation conditions nonsterilized carob pod extract gave higher ethanol concentration than sterilized medium. In repeated batch fermentations, the immobilized S. cerevisiae cells i n Ca-alginate beads retained their ability to produce ethanol for 5 d.