Modeling Bioreactors for Lunar and microgravity applications

Microbes and enzymes are promising biocatalysts to produce fuels, chemicals, and biopolymers in zero and Lunar gravity environments. To produce usable quantities of these products, continuous stirred tank reactor (CSTR)-style vessels are commonly used to ensure efficient mixing and to control key parameters such as pH, temperature, and dissolved gas levels (e.g., oxygen, CO2). Understanding CSTR performance in microgravity will provide critical insights into the feasibility and limitations of conventional Earth-based bioreactor systems in low -gravity environments and will guide future bioreactor designs and predictive models for biomanufacturing created specifically for these conditions. In this work, we present a computational study on the effects of gravity on the mixing process and bacterial growth in continuous stirred tank bioreactors. More specifically, we investigate how key quantities such as the gas holdup, the mass transfer coefficient, and the uptake rate are modified under Lunar and zero gravity conditions. Distribution of gases dissolved in the liquid phase is also a key parameter to ensure efficient bioreactions. Our modeling approach is based on NREL open-source framework BiRD (Bioreactor Design), which leverages the OpenFOAM finite volume library.