EN
Changes of the main hydrodynamical and <oxygen transfer> parameters during. <A.Niger cultivation> in a pilot plant external-loop <air-lift bioreactor> were investigated. the final average concentrations of biomass and citric acid obtained in experimental fermentations were 10.5g/l and 96.6 g/l, respectively. Significant influence of the increasing biomass concentration on the apparent viscosity of the broth, gas holdup, liquid velocity and volumetric oxygen transfer coeficient was found.