The cholesterol lowering drug, Lovastatin (Mevacor), acts as an inhibitor of HMGCoA reductase, and is produced from an Aspergillus terreus fermentation.
Pilot scale studies were carried out in 800 liter fermenters to determine the effects of cell morphology on the oxygen transport properties of this fermentation. Specifically, parallel fermentations giving (i) filamentous mycelial cells, and (ii) discrete mycelial pellets, were quantitatively characterized in terms of broth viscosity, availability of dissolved oxygen, oxygen uptake rates and the oxygen transfer coefficient under identical operating conditions.
The growth phase of the fermentation, was operated using a cascade control strategy which automatically changed the agitation speed with the goal of maintaining dissolved oxygen at 50% saturation. Subsequently stepwise changes were made in agitation speed and aeration rate to evaluate the response of the mass transfer parameters (DO, OUR, and kLa ). The results of these experiments indicate considerable potential advantages to the pellet morphology from the standpoint of oxygen transport processes. List of symbols DO % sat. kLa h -1 0 UR mmol/dm 3 h P/V KW/m 3 V~ m/s gapp cP Dissolved oxygen concentration Gas-liquid mass transfer coefficient Oxygen uptake rate Agitator power per unit volume Superficial air velocity Apparent viscosity