Evaluation of Maximum to Specific Power Consumption Ratio in Shaking Bioreactors

Among others, the maximum power consumption in a fermentation broth is one of the most decisive engineering parameters to characterize culture conditions and to scale-up bioprocesses, especially with filamentous microorganisms. Based on the fact that maximum drop diameter in coalescence inhibited two-phase dispersing processes is solely dependent on maximum power consumption, no matter which dispersing machine is used, drop sizes were measured in shaking bioreactors and the ratios between maximum and specific power consumption were calculated. In agreement with two different simplifying theoretical considerations relatively small ratios are obtained. It is concluded that the power consumption in shaking bioreactors is much more evenly distributed than in stirred tank fermentors. As the specific power consumptions in both types of bioreactors are of the same order of magnitude, shaking bioreactors create much lower levels of hydromechanical stress to microorganisms and dispersed phases.