ABSTRACT
Power is required for mixing and mass transfer. The intensified circulation improves macroscale mixing. The turbulent dynamic forces cause bubble breakup and this improves mass transfer. The turbulent dissipation scale improves the microscale mixing. In contrast to the positive influence t of increased power consumption, there are also a number of negative effects. Ultimately all energy introduced in the fermenter will be transformed into heat, thus leading to an increase of cooling requirements. Further, due to the high energy costs, it is rational to economize. Finally, the supply of energy to the system, e.g., by means of a stirrer, can lead to intense shear fields which can damage the microorganisms and other type of cells, in particular animal cells. The balancing of negative and positive effects is an important feature in fermentation operations.
