Reactors (or bioreactors or fermenters as they are often called) are at the heart of the fermentation process. They are used for growing cells. Reactors are designed to meet the specific needs of the cells namely: optimal mixing, optimal temperature and optimal pH. In some cases, reactors continuously supply nutrients or precursors to produce a particular product. Bioreactors are often computer controlled to ensure that optimal conditions are met.

Reactors are available in a number of designs including bubble column, airlift, flocculated bed, fluidized bed, packed bed, and stirred tank.  Bubble column reactors are tall reactors, which use air alone to mix the contents. Airlift reactors are similar to bubble column reactors, but differ in that they contain a draft tube. The draft tube is typically an inner tube, which improves circulation and oxygen transfer and equalizes shear forces in the reactor.

Reactors (or bioreactors or fermenters as they are often called) are at the heart of the fermentation process. They are used for growing cells. Reactors are designed to meet the specific needs of the cells namely: optimal mixing, optimal temperature and optimal pH. In some cases, reactors continuously supply nutrients or precursors to produce a particular product. Bioreactors are often computer controlled to ensure that optimal conditions are met.

Reactors are available in a number of designs including bubble column, airlift, flocculated bed, fluidized bed, packed bed, and stirred tank.  Bubble column reactors are tall reactors, which use air alone to mix the contents. Airlift reactors are similar to bubble column reactors, but differ in that they contain a draft tube. The draft tube is typically an inner tube, which improves circulation and oxygen transfer and equalizes shear forces in the reactor.

Flocculated cell reactors retain cells by allowing them to flocculate. These reactors are used mainly in wastewater treatment. In fluidized bed reactors, cells are "immobilized" small particles, which move with the fluid. The small particles create a large surface area for cells to stick to and enable a high rate of transfer of oxygen and nutrients to the cells. In packed bed reactors, cells are immobilized on large particles. These particles do not move with the liquid. Packed bed reactors are simple to construct and operate but can suffer from blockages and from poor oxygen transfer.

Stirred tank reactors use mechanical stirrers (impellers) to mix the reactor to distribute heat and materials (such as oxygen and substrates).

Reactors use different measurement scales to read the reactions taking place.  From smallest to largest they are laboratory scale, pilot scale, and production or industrial scale. The laboratory scale is used for small-scale experiments of kinetics and yield studies.  They are primarily shake flasks and small bioreactors.  This scale is used to complete a preliminary economic evaluation of experiments. Pilot scale reactors are usually in the range of 100 to 1,000 liters and are utilized in kinetic and mass transfer studies.  They are used for economic evaluations, scale-up studies and downstream processing.  Reactors using the industrial scale are for commercial production applications in the range of 1,000 to 1,000,000 liters.  Their uses include commissioning, troubleshooting, improvement and optimization.