Rheological measurements of three Actinomycete in submerged cultures

Fermentation experiments were performed to obtain time-dependent data on broth rheology for three filamentous microorganisms, Streptomyces rimosus, Actinomadura roseorufa and Saccharopolyspora erythraea, cultivated under standard conditions in a mechanically stirred bioreactor. Rheological data were successfully analysed using Mitschka's technique and flow curves of the cultures described by the power law model in the range of shear rate between 5 and 100 s^–1. Consistency coefficients of the cultures were found to vary continuously with fermentation time while flow behaviour index fell sharply within the first few hours of cultivation and then remained practically unchanged till the end of fermentation. The pH of the biomass was found to have a strong influence on both consistency coefficient and flow behaviour index.List of Symbols kn Mitschka shear rate constant - K consistency coefficient (Pa sⁿ) - n flow behaviour index (–) - N spindle speed (rps) - T torque on spindle (Nm) - gg_A average shear rate (s^–1)