DYNAMIC MIXING AND OXYGEN-TRANSFER IN SMALL, AIRLIFT-LOOP BIOREACTORS- MODEL AND EXPERIMENTAL-VERIFICATION

A mechanistic model for mixing and mass transfer in both airlift bubbl e column and loop bioreactors is described. The model is a useful desi gn tool to improve oxygen-transfer characteristics. It is shown that t he model fits mixing and mass-transfer experimental data closely. The model confirms that the overall oxygen-transfer coefficient in the ris er of a loop airlift fermenter is similar to that in bubble columns an d that lower measured transfer rates are due solely to the dead volume in the downcomer. The effects of parameters such as mass-transfer coe fficient, aeration rate, dispersion coefficient, sparger rotation spee d, and liquid circulation velocity are presented in terms of both the Liquid- and gas-phase oxygen concentrations.