ENHANCEMENT OF THE OXYGEN-TRANSFER IN A CIRCULATING 3-PHASE FLUIDIZED-BED BIOREACTOR

The addition of alpha-alumina to the aqueous solution of sodium alginate for immobilization of viable cells allows the production of denser particles than the ones obtained with sodium alginate alone. This biocatalyst was used in the continuous oxidation of ethanol to acetic add, by a strain of Acetobacter isolated from an ethanol plant. The continuous fermentation was carried out in a circulating three-phase fluidized bed bioreactor. Denser particles allow a greater oxygen transfer, resulting in increased volumetric production rate of acetic acid, because oxygen is usually the limiting factor of this process. The performance of the biocatalyst was analyzed in terms of respiration rate, oxyen diffusivity, volumetric mass-transfer coefficient, and global productivity.