Airlift bioreactor

Airlift bioreactors are used for cell culturing, pallet form fermentation, and immobilized enzyme reactions. Typically, airlift bioreactors are used when the desired reactants and/or final products are in a gaseous state and for aerobic cell cultures.

An airlift bioreactor works by agitating the contents of the bioreactor pneumatically using gas. The gas used for agitation can act to either, introduce new molecules to the mixture inside of the bioreactor, or remove specific metabolic molecules produced by microorganisms. Airlift bioreactors have a built in bubble column designed to release gas into the bioreactor. Gas is usually injected into the bubble column at the bottom of the bioreactor. Mixing occurs as the bubbles rise through the bubble column to the top of the bioreactor.

Simple diagram of an airlift bioreactor

The pattern of of fluid circulation inside of airlift bioreactors can be customized through the design of it's bubble column and shape. There are two separate channels within an airlift bioreactors; one channel for gas/liquid up-flow and one channel for gas/liquid down-flow. Both channels create a closed gas/liquid circuit, and has a mechanism for removing gaseous substances at the top of the bioreactor called the gas separator.

There are two types of airlifts bioreactors: 1) external loop vessels, 2) baffled vessels. External loop vessels have distinct and separate conduits for circulation of gases and liquids. Baffled vessels draw upon spider diffraction techniques to customize gas and liquid through the bioreactor flow by including channels, vanes, and/or other methods of obstruction. Baffled vessels allow for greater control of gas and liquid circulation patterns within bioreactors through the creation of customized bubble disengagement and gas/liquid flow rates.

The primary advantage of airlifts bioreactors over other bioreactors is due to the nature of how the contents inside airlift bioreactors are mixed. They have no focal points of energy dissipation, and have homogenous shear and stress forces throughout the entire bioreactor. Making airlift bioreactors ideal for culturing shear sensitive cells.