A controlled environment used to grow microorganisms. A device or apparatus in which living organism and especially bacteria synthesize useful substances (as interferon) or break down harmful ones (as in sewage). An apparatus, such as a large fermentation chamber, for growing organisms such as bacteria or yeast that are used in the biotechnological production of substances such as pharmaceuticals, antibodies, or vaccines, or for the bioconversion of organic waste.

In a container about the size of a soup can, the clear shell allows scientists to check growth, and the center holds a cylindrical filter that draws off used growth medium as fresh medium is injected. This ensures that the fluid rotates without shear forces that would destroy the cells. The rotating vessel does not really cancel gravity, but constantly reorients the cells so their orientation is constantly changing.