Fluid dynamics of anaerobic fermentation

In beer fermentation, yeast cells are kept in suspension, despite their higher density, by natural agitation created by ascending CO₂ bubbles. Yeast cells are unable to nucleate bubbles but instead release CO₂ in a soluble form in such a way that the medium tends to become supersaturated. A higher concentration of yeast cells and the presence of solid particles cause the formation of bubbles at the bottom of the fermenter and practically only there. The rising bubbles grow and accelerate by sweeping the CO₂ formed throughout the fermenter by the suspended yeast cells, thereby creating a fluid regime. A mathematical expression relating the bubble agitation power to the fermentation parameters was obtained and used to design more efficient fermenter shapes.