A large tank for growing microorganisms used in industrial production: A bioreactor is a fermentation chamber or vat that is used for growing biochemically active matter or microorganisms which are then used for making drugs or for recycling waste.

A microorganism created in a bioreactor and, through its biochemical reactions, can produce medically or commercially useful materials, e.g., beer from fermentation of yeast or insulin from genetically altered bacteria.

A living cell culture genetically engineered in a bioreactor can be used to produce materials useful for research in biology, medicine, and industrial processes.