Biochemistry and Biotechnology
Wiley InterScience Backfile Collection 1832-2000
Process Engineering, Biotechnology, Nutrition Technology
Studies were made of oxygen transfer and power in 20-1. novobiocin fermentations with five sizes (23-60% of the tank diameter) of geometrically similar flatblade turbine impellers. The influence of changes in apparent viscosity on oxygen transfer and power was found to be related to impeller diameter. At constant agitator speed the oxygen availability rate (OAR) decreased with increase in apparent viscosity, but the magnitude of the reduction was less with a small impeller than with a large one. At constant power input the small-diameter impeller (23% of tank diameter) gave an OAR about 8 times that of the large one (60% of tank diameter) when tested in viscous beer, whereas with sulfite or yeast all impeller diameters gave the same OAR. Impeller tip velocity correlated with OAR independently of diameter for the five turbine sizes examined. The power required for optimal novobiocin yields increased with increase in turbine diameter, but the yields were independent of diameter at equal OAR.
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