1. 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.

1. A fermentation vat, containing microorganisms or biochemically active substances, used for waste recycling or for making drugs.

1. an apparatus in which a suspension of microorganisms in a liquid are used to perform chemical reactions, as in synthesis of pharmaceutical agents or the conversion of harmful waste to less harmful substances. the reactor consists of a vessel to contain the suspension of microorganisms, plus a variety of attached devices used to control the reaction.