Bioreactor Controls-II

In bioreactors, oxygen is essential for aerobic fermentations.

Broth saturated with oxygen can supply it only briefly to highly aerobic organisms.

To improve oxygen availability, sterile or filtered air is injected under pressure through a sparger located below the lowest impeller.

The sparger holes must be small enough to create fine bubbles but not so small that they clog from the solids in the culture medium.

Mechanical devices called agitators stir the fluid using mixing arms known as impellers. These ensure uniform air distribution and help maintain a consistent temperature throughout the broth.

Agitation enhances oxygen transfer efficiency by breaking down large bubbles into fine bubbles and increasing the surface area where oxygen can dissolve. It also helps reduce cellular aggregation in organisms prone to clumping.

To further improve mixing and bubble dispersion, baffles are inserted into the fermentor. These disrupt vortex formation by interfering with the circular motion of the liquid.