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Pol. J. Food Nutr. Sci. 2002;52(3):51–56
Saccharomyces cerevisiae yeast was immobilized on Al-70 ceramic supports with and without changing their surface zeta-potentials via silylation. Preliminary ethanol fermentation was carried out with yeast cells immobilized on a silylated support. The immobilization technique involved recirculation of the yeast suspension through a column packed with ceramic support material. With a low (under 1.7 g/L) initial biomass concentration in the suspension, cell immobilization was a single-stage process where the amount of yeast cells fixed on the ceramic bed can be expressed as an exponential time function. With high (greater than 3.1 g/L) initial biomass content in the suspension, immobilization was a two-stage process. In each stage, the quantity of the yeast fixed on the carrier can also be regarded as an exponential time function. Specific immobilization rate was proposed as a main criterion for assessing the course of the cell immobilization process. The increase of the initial yeast concentration in the suspension brought about a decrease of the specific immobilization rate in the single-stage process and in the first phase of the two-stage process. Silylation (in order to achieve opposite zeta-potential for the support and the yeast cells) accounted for a noticeable increase of specific immobilization rate both in the single-stage process (by 144%) and in the first phase of the two-stage process (by 61%). Ethanol fermentation involving yeast cells immobilized on a silylated ceramic carrier had an efficiency which accounted for 83.5% of the theoretical efficiency.