Bioreactors with stirred bed of immobilized cells, 2. Studies on distribution of mixing efficiency

Abstract

The influences of the main factors on mixing efficiency and distribution for a bioreactor with stirred bed of S. cerevisiae immobilized cells in alginate have been analyzed. Indifferent of the region inside the suspension or of the biocatalyst volumetric fraction, the most efficient mixing has been obtained for biocatalyst particles with a 4.6 mm diameter. In function of the biocatalyst diameter and concentration, the uniform mixing can be reached in a whole bulk of suspension for certain rotation speed values. Therefore, for biocatalyst particles of 4 and 5.2 mm diameter, the suspensions have been uniformly mixed for solid particles concentration of maximum 15%, the optimum rotation speed being of 100 and, respectively, 200 rpm. For intermediary size of biocatalyst particles, the uniform circulation of the suspension can be obtained for volumetric fraction up to 20%, at 150-200 rpm. Over these levels of solid particles concentration, the mixing becomes nonuniform for the entire considered domain of rotation speed.