BIO204 Final Term Handouts Lectures 46-91

A compressor forces the air into the reactor. The compressor will need to generate sufficient pressure to force the air through the filter, sparger holes and into the liquid.

Air compressors used for large scale bioreactors typically

Air compressors used for large scale bioreactors typically produce air at 250 kPa. The air should be dry and oil free so as to not block the inlet air filter or contaminate the medium.

It is very important that an "instrument air" compressor

is not used. Instrument air is typically generated at

higher pressures but is aspirated with oil. Instrument air compressors are used for pneumatic control.

Lecture 47-Advanve in Fermentation Technology · of · the · inlet · air · is · undertaken · to

prevent contaminating organisms from entering the reactor.

The exit air on the other hand is sterilized not only to keep

The exit air on the other hand is sterilized not only to keep contaminants from entering but also to prevent organisms in the reactor from contaminating the air. A common method of sterilizing the inlet and exit air is filtration. For small reactors (with volumes less than 5 litres), disk shaped hydrophobic Teflon membranes housed in a polypropylene housing are used. Teflon is tough, reusable and does not readily block.

For larger laboratory scale fermenters (up to 1000 litres), pleated

membrane · filters · housed · in

polypropylene cartridges are used.

By pleating the membrane, it is possible to create a compact filter with a very large surface area for air filtration. Increasing the filtration area decreases the pressure required to pass a given volume of air through the filter.