蛋白质被震颤产生的气泡，有商用的消泡剂

In most fermentation processes (aerobic) when the protein or protease enzyme-mediated protein fragments are high, foam formation occurs. Hence, if you can adjust the protein concentration in the medium the foam formation is less. Otherwise along with the medium you may add antifoam agents (which do not interfere with microbial growth) and sterilize the medium.

Dear Chakka Lakshmi Prasanna, foam formation in bioreactors can have several causes:

1) Biochemical: As already mentioned by Prabakaran Krishnamurthi, the composition of the medium plays an important role. Substrates (peptides, proteins) can influence foam formation as well as (un-)wanted products like biosurfactants. The composition of the medium cannot usually be changed, or only to a limited extent, and is therefore often not the first choice.

2) Physical: In stirred tank bioreactors, for instance, increasing the stirring rate can lead to the formation of a vortex and thus to the intake of additional air, which favours the formation of foam. In submerged aerated bioreactors, aeration itself via gassing rings/lances also promotes foam formation, with higher aeration rates leading to stronger foam formation. Optimum conditions must be found. However, antifoam agents are often added, but these can cause problems in the downstream process.

3) Bioreactor design: There are various bioreactor designs on the market, with the classic stirred tank bioreactor usually being the first choice. However, the phenomena described above occur in this type of bioreactor. Therefore, for some applications, it makes sense to use alternative bioreactor designs, such as orbital shaken bioreactors. Put simply, these are large shaking flasks with a working volume of up to 2500 litres. As there are no mechanical internals (no stirrer) and aeration takes place via the headspace, foaming is significantly reduced.

I hope this helps you!