Steady-state shear characteristics ofAspergillus niger broths

It can be difficult to obtain reliable rheological data for filamentous fermentation broths using conventional instruments. One common approach is to measure the torque drawn by an impeller rotating in the suspension (1–7). Many previous workers have assumed that the applicable shear rate in such a device is related to the impeller speed by a fluid-independent constant determined by calibration with Newtonian and non-Newtonian fluids (1–9). The rheology ofAspergillus niger broths have been characterized using the impeller viscometer approach. The changes in the broth rheology were measured, and used to interpret the growth of biomass and the evolution of the microorganism morphology.