Other fermenter types

The stirred tank fermenter gives an efficient means for the growth of most bacteria. However, as culture volumes approach hundreds of liters the power demands of turning the impeller fast enough to ensure sufficient oxygen transfer can become too high. The airlift reactor in Figure 2 has no internal moving parts and stirs the culture via the passage of the air itself. This design of reactor is also useful for cells that are prone to lysis through mechanical shear.

                                                   Figure .  An airlift fermenter with draft  tube.

When oxygenation is not so important example for when using anaerobic or microaerophilic cells or when immobilized enzymes are used, much simpler reactors can be employed in Figure 3, such as fluidized or fixed bed reactors.