Bioreactors and Fermentation for Chemical Engineers: fermenters and their operation - Assignment Example

Airlift fermenter (ALF) is generally classified as pneumatic reactors without any mechanical stirring arrangements for mixing. The turbulence caused by the fluid flow ensures adequate mixing of the liquid. The draft tube is provided in the central section of the reactor. The introduction of the fluid (air/liquid) causes upward motion and results in circulatory flow in the whole reactor. The air/liquid velocities will be low and hence the energy use is also low. ALFs can be used for both free and immobilized cells e.g. (SCP) single cell production.

Fluidized bed bioreactors (FBB) have been given WIDESPREAD ATTENTION in the in recent past because to their advantages over other types of reactors. Most of the FBBs developed for biological systems involving cells as biocatalysts are three phase systems (solid, liquid & gas). The fundamentals of three phase fluidization phenomena have been comprehensively covered in chemical engineering literature. The FBBs are generally operated in co-current up flow with liquid as continuous phase and other more unusual configurations like the inverse three phase fluidized bed or gas solid fluidized bed are not of much importance.

Usually fluidization is obtained either by external liquid re-circulation or by gas fed to the reactor compaction. Packed bed or fixed bed bioreactors are commonly used with attached biofilms especially in wastewater engineering. The use of packed bed reactors gained significance following the possibility of entire cell immobilization technique has been demonstrated (Mcneil, & Harvey, 2008). The immobilized biocatalyst is packed in the column and fed with nutrients either from top or from bottom.

One of the disadvantages of packed beds is the changed flow characteristic due to alterations in the bed porosity during operation. Bubble column fermenter is a simplest type of tower fermenter taking in a tube which is air sparged at the base.Moreover, it is a stretched out