Rheological properties of pullulan fermentation broth in a stirred tank fermentor

The rheological properties of the fermentation broth during pullulan produc tion from synthetic medium by Aureobasidium pullulans P56 in a stirred tank fermenter were investigated. The mycelial forms and the production of extr acellular polysaccharide were responsible for the non-newtonian flow behavi our of the fermentation broth. The rheological behaviour can be characteriz ed by a power law type of equation. The relationship shear rate/sheat stres s and shear rate/apparent viscosity showed a non-newtonian behaviour of the fermentation broth. The power law index was found to be a sensitive factor for the indication of the pseudoplastic behaviour of the broth.