Single Cell Biology

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Glucose Mass Transfer in Alcoholic Fermentation Using Stirred Beds of Immobilized S. Cerevisiae Cells

Anca-Irina Galaction, Marius Turnea and Dan Cascaval

The external and internal mass transfers of substrate have been analyzed for alcoholic fermentation using a bioreactor with mobile beds of immobilized yeast cells. The experiments have been carried out under glucose inhibition limitation for different sizes and concentrations of biocatalysts particle. By means of the substrate mass balance for a single particle of biocatalysts, considering the kinetic model adapted for the inhibitory effect of glucose, a specific mathematical model has been developed for describing the profiles of the substrate concentration in the outer and inner regions of biocatalysts and, implicitly, for estimating its mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of the mass flows are significantly influenced both by the internal diffusion velocity of substrate, and by the rate of the biochemical reaction of substrate consumption. These cumulated influences led to the appearance of “biological inactive region” near the particle centre, its magnitude varying from 0.34 to 1.22% from the overall volume of particles. The use of mixing diminished considerably the extent of this region compared to that recorded for similar substrate conversion in a fixed bed bioreacto