The rheology of mycelial broths

An experimental investigation on the rheology of penicillin broths was undertaken in order to obtain more understanding of this important aspect of the fermentation process. The measuring technique consisted in observation of the torque exerted upon a rotating turbine impeller. The experimental data were interpreted in terms of a model which basically is a synthesis of a known relationship for the rheological behavior of printing ink (Casson equation) and some considerations analogous to the rheological description of polymer solutions (excluded volume concept). One of the key variables in the model is a morphology factor, which can be used for a quantitative description of mycelial morphology. The value of the morphology factor can be determined experimentally by a simple viscosity measurement in combination with a mycelial dry weight determination. There are strong indications that the model may be applicable to mycelial broths other than those of penicillin.