CONTINUOUS BIOREACTOR FOR YEAST CELL CULTIVATION IN SPACE

摘要

In order to allow the study of the adaptation and the effects of several stressors on yeast cells (Saccharomyces cerevisiae) in micro-gravity, RUAG Space site of Nyon is developing a space bioreactor for the continuous cultivation of yeast cells in the frame of an ESA project. A major challenge in the design of such continuous space bioreactor is providing sufficient aeration to the reactor ensuring the required aerobic cultivation conditions. At high cell concentrations, the demands on oxygen transfer rates and carbon dioxide removal rates are significant. For terrestrial bioreactors, the necessary oxygenation is frequently achieved by bubbling, and the excess of CO2 escapes of the liquid as bubbles. Because in micro-gravity, gravity-induced phase separations (buoyancy) cannot be exploited, bubbling represents a challenge due to the need for subsequent phase separation. In this regard, aeration through gas permeable membranes is an interesting alternative. A Gas Exchange Module (GEM) based on a membrane aeration system is presented. Its parametrical model for the O2 mass transfer has been developed with the help of a Finite Element Method (FEM) simulation. This model has been validated by test with a preliminary breadboard model of the GEM. The O2 mass transfer coefficient of several type of membranes and hollow fibres have been experimentally evaluated and the parametrical O2 mass transfer have been extended to the CO2 mass transfer. With the result of this study, RUAG is able to optimize the GEM design in term of power consumption and encumbrance.