(331a) Experiments and Simulations of Microbial Growth in a Rotating Bioreactor

Enhanced microbial growth on space flight has been reported. The increased population is believed to be caused by a decrease in settlement under microgravity in space, resulting in a more even distribution of microorganisms. Ground-based counterparts have been developed to provide a cheaper alternative for investigating in-space experiments. For example, a rotating wall vessel (RWV) can operated at precision conditions to generate forces that counteract the gravitational force by rotating the wall. Studies of RWV have been conducted both theoretically and experimentally. However, to date, most investigations have neglected the particle-wall and particle-particle interaction or treated the interactions empirically. Thus, a fundamental model needs to be developed to determine the distribution of microbial particles, which can provide information for predicting microbial growth.

Coupled with detailed experiments, we utilize Stokesian dynamics to accurately describe the suspension mechanics of microbes (spherical and aspherical) in a RWV. Using a spherical particle as a building block, we can construct any pseudoshape that we desire. For this work, we construct aspherical particles and the rotating wall so that the hydrodynamic interactions can be accurately calculated. Furthermore, we develop scaling arguments for the parameters that control the operating regime to direct efficient operation of RWV. These parameters consist of dimensionless groups that include the aspect ratio of the sizes of the microorganism and the bioreactor, the rotational velocity of the bioreactor, and the material properties of the suspending media.