Rheological characteristics of filamentous cultivation broths and suitable model fluids

Abstract

The rheological characteristics of cultivations with filamentous microorganisms define many other crucial process parameters in the system, such as the cell morphology and the productivity. The present study aims to determine the rheological changes of broths during batch cultivations of three filamentous microorganisms: the fungus Aspergillus niger, and the two actinomycetes Lentzea aerocolonigenes and Actinomadura namibiensis. Focus is given on establishing measurement methodologies to characterize these heterogeneous filamentous systems. For the rheological characterisation the Ostwald-de Waele power law approach is used. All examined biological filamentous broths exhibit a non-Newtonian shear thinning behavior. The effect of biomass concentration and cell morphology on the rheology of the broth is further enlightened. Finally, the rheology of the cultivation broths is compared with that of various model fluids to test the suitability of the last ones to mimic rheologically the biological broths in further technical applications.