Dear Md Howlader,

Apart from the use of anti-foaming agents that can negatively affect fermentation bacteria, you may try to reduce foaming in the bioreactor by reducing the stirring speed and by increasing the pH to 7.5-8, since foaming generally occurs in the acidogenic fermentation. If you refer to aerobic fermentation, the flow of oxygen supplied to the fermenter should be reduced.

Perhaps of some interest for your query: https://www.researchgate.net/post/Is_there_any_substitute_for_Antiform_anti-foaming_agent_used_for_fungi_cultured_in_a_fermenter

Dear Mr. Howlader,

you could try different antifoam types (e.g. Sigma AF204, Ucolub, Tween) and test their toxic effect against the cells prior their use in the bioreactor. There are test kits available (see link below). Find out the mean inhibitory concentration and stay below that level in the fermentation process. Alternatively, you can think about mechanical foam breakers or nozzles or thermal foam disruption. Also a reduction of the aeration rate may be helpful.

https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/Datasheet/1/04686dat.pdf

Good luck

Michael

Dear Carmen,

Thank you for your valuable feedback. Actually, we are doing our culture at high pH (more than 7) and I tried reducing the aeration and agitation. The growth decreased if we decrease the air flow rate and agitation. Hopefully, I will find a solution soon.

Dear Micheal,

Your suggestion is very informative. I have already tried two antifoam (e.g., Sigma 204) from different molecular structure. A certain concentration of both antifoams are normal for the cell in the shaker, but inhibitory in the bioreactor. I might try to use mechanical foam breaker. That might a useful tool if I am able to do that.

Thanks.

Designing the bioreactor rather than adding antifoam.....

Better way is to provide the radially attached stainless stell sieves or nets sized of 5mm attached to the central shaft of stirrer

Dear Anand,

Do you have any particular references for that?

Thanks

Adjusting the bioreactor at first,then minimize the aeration.If still,add few tween 80 as antifoam and does not affect the bacteria.

Dear Md Howlader,

these are the practical adjustment which are done on experimental basis.

Also, this troubleshooting are not mentioned in any textbook. Those method which are there in textbook are performed by you. Still your problem persist.

So there are no references for this adjustments as answered earlier.

If you want than you apply the suggestion.

Thanks

Set the upper stirrer at the liquid/air boundary. It will provide mechanical defoaming, and the bottom in the bottom mixing. Try using vegetable oils (such as sunflower), the surface tension will change, the foam will fall and they are most often non-toxic to microorganisms.

There are classically 3 ways to mitigate the formation of foam in a fermentation. 1) Mechanical system that breaks the foam 2) Put pressure on the top preventing foaming 3) Action (bio)-surfactants (which is my area of expertise) as antifoaming agents, natural surfactants such as vegetable oils (olive, sunflower, etc. ..) but also bioresourcés agents whose value in the balance HLB is labilised as antifoam.

However, if all these solutions exist, it depends primarily on your fermentation (micro-organisms, parameters, fermentor used and your product of interest). I am always available for infomartions complements according to your operating conditions.

I agree with Dr.Benoit Moreau, using and adjusting various conduction parameters could possibly reduce foaming. You may use the following in reducing the foam during fermentation process:

1) Foam breaker could be used effectively along with other impellers

2) During foam formation, you may increase the back pressure in the fermenter vessel (if made of Stainless steel) if you are using glass vessel, please DO NOT TRY TO INCREASE THE BACK PRESSURE.

3) Use vegetable oil/s - normally I use vegetable oil (various vegetable oils viz. Soya Oil, sun-flower oil, ground-nut oil, canola oil etc) but you have to check the suitability of the oil for your process i.e. with no compromise on production.

4) You may also use combination of vegetable oil and also synthetic anti-foam agents. Please take care the concentration of anti-foam for sterilization and feeding in to the fermenter. You will have to validate the suitability of anti-foam agent before taking fermenter batches.

Hi, Dear Md Howla,

I agree with the advices by Dr.Benoit Moreau. Large scale fermentor for industrial production, are generally managed by combination of methods stated above. It also depends on the very internal design of your reactor too, besides the factors mentioned above. Place the mechanical foam breaker (the top shaft) a bit above the liduid surface in your reactor. Reducing aeration may affect the cell growth or productivity, so it may not be suitable always. Large scale cultures are in general, operated under a +pressure (of 0.1- 0.3 Atm, inside), to avoid excessive foam formation, oxygen limitation, and in part, even to avoid any possible in-flow of undesired bacteria (contamination). But, please avoid opreration under increased air pressure in a glass fermentor under laboratory conditions . Please try which aproach(es) suit to your condition best. Good luck.

Dear Respondents,

Thank you for your kind feedback. I have tried to control the foaming in different ways and came out with a solution, which is not using the antifoam at all. The trapping of antifoam helped me to get the high biomass (desired) without inhibiting the cell growth.

Goodluck

I wish you the best in your research and don"t hesitate to contact us for any information in fermentation field or in biobased surfactants

Dear Md Howlader,

I am sorry for my typos in your name. I wish you success in your research works. Best of luck.

No problem, thanks for your kind wish @ Tapan Kumar Mazumder