EFFECT OF CELL PURGE ON THE STABILITY OF MICROFILTRATION CELL RECYCLEFERMENTATION SYSTEMS

Fermentation with complete cell recycle on microfiltration tubular mem branes was studied and its effect upon broth rheology evaluated. The i ncrease in cell concentration was found to be responsible for a contin uous rise in viscosity leading to changes of broth rheology and conseq uent operating problems. A strategy to control the broth rheological b ehaviour with the aim of achieving long-term stable fermentations is p roposed. This strategy involves the use of a cell purge in order to ma intain cell concentration at a manageable level. The results obtained show that the total cell concentration in the fermenter can be stabili sed if the cell bleed rate is calculated to remove exactly the amount of cells produced. To obtain long-term stable fermentations, the time to initiate the bleeding procedure and the cell bleed rate need to be determined and optimised.