ETHANOL FERMENTATION WITH YEAST CELLS IMMOBILIZED ON GRAINS OF POROUS CERAMIC SINTER
 
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Pol. J. Food Nutr. Sci. 2007;57(Special issue 4B):245–250
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ABSTRACT
A study was undertaken to analyse the kinetics of the course of processes (batch, feed-batch and continuous) of ethanol fermentation with cells of Saccharomyces cerevisiae yeast immobilized on porous ceramic sinter and with free cells. The fermentation with free cells was treated as a reference process. Cells were immobilized with the use of porous ceramic sinter in the form of grains. Three grain fractions were applied: 1.2÷2.5; 2.5÷6.0; and 6.0÷10.0 mm. The study demonstrated that dynamics of batch processes with immobilized and free cells were similar in the logarithmic phase. In contrast, significant differences occurred in the initial phase. For the immobilized cells that period spanned considerably longer than for the free cells. In addition, it differed for each fraction of the support – being the shortest for the smallest grains and the longest for the biggest ones. Analyses of the feed-batch process demonstrated that the best kinetic parameters were obtained for the support with grain size of 2.5÷6.0 mm. The kinetics of the process was also found to depend on hydrodynamic conditions occurring in a reaction – flow rate of liquid through the layer of poured support. In turn, the continuous fermentation was carried out with the support’s fractions characterized by the best kinetic parameters of feed-batch fermentation – 2.5÷6.0 mm in size. During the fermentation process, the concentration of yeast in the reaction medium was high, ca. 14 g/L – including ca. 13 g/L of immobilized cells. The high concentration of biomass enabled reaching reactor’s productivity at a level of ca. 13 g/Lh, as compared to 2.7 g/Lh noted for the reactor with free cells (under the same conditions).
ISSN:1230-0322