The Advantages of Stirred Tank Bioreactor with shaft agitator:
1. Disperse air bubbles
The blades that used as agitator can break the bubbles which produced from the air supply (sparger).
2. Increase oxygen transfer efficiency
Obviously the efficiency of oxygen transfer in liquid will increase during the agitation.
3. Foam Breaker
At the surface of liquid the blades can be use to break the foam. This method can decrease the utility of additive to break the foam.
4. Axial impeller at top to drive liquid downward
Using a special axial impeller to driven the liquid on the surface downward to achieve the optimum circulation.

The Disadvantages of Stirred Tank Bioreactor with shaft agitator:
1. More complicated for scale up with agitator shaft
More detail calculation that involved size, material, energy of the agitator for the scale up this bioreactor.
2. Risk of mechanical damage caused by agitator shaft
3. Need more energy to disperse bubbles and increase Oxygen efficiency
4. Need more energy, time and cost for agitator shaft
For the scale up bioreactor then the energy, time and cost consumptions will needed.