Scale up challenges in bioreactors

This video builds on our series of video on Bioreactors (see playlist) where we discuss important aspects such as design considerations, oxygen transfer rate and uptake rate, and sensors. In this video, I will discuss scale up of bioreactors and what different approaches you can take. As you will see each method has it is own (dis)advantages and the physiological parameters will change once you scale up the bioreactor. At the end of each video, you should know common methods of scale up and compare them against each other and be able to make an informed decision depending on the scenario (for instance cell culture used).

[@mariamahmed3843]

Thank you for the video, I took practical lesson on the mechanism of bioreactors when I studied food fermentation in my undergraduate programme.

[@MarloesPeeters]

Thanks, hope the video was interesting!

[@mariamahmed3843]

@@MarloesPeeters yes and informative

[@tinailc7068]

Thank you very much for all of your excellent bioprocessing videos! You mention towards the end of the video the simple geometric scaling of airlift bioreactors. Could you recommend any undergrad-level literature on the subject? Textbooks abound with STR scale-up examples, but I could not find much on the subject of airlift bioreactors!

[@MarloesPeeters]

I struggled to find a book chapter on this topic - most of it are journal articles. Perhaps this link might be useful?web.archive.org/web/20140801141653id_/chem.engr.utc.edu:80/ench435/2004/FromTablet/bioreactors.pdf

[@taniat3014]

Hi, in 06.14 you mentioned if you keep N constant, P/V would decreased, hence the oxygen transfer within the liquid would also decreased. But is it not the other way around? From the table, If we keep N constant (N=1) during scale-up, then P/V value increases from 1 to 25. Also, the same case, if we keep P/V constant then wouldn't N value decreased from 1 to 0.34?
Please let me know if I was mistaken cos I am a bit confused now.
Thank you for the video!

[@MarloesPeeters]

Hi! Thanks for the comment. I think you might be reading the table the wrong way around. Keeping N constant (third line from the top), you can see P/V decreases to 0.34. If we want to keep P/V constant (second line from the top), you can see N will have to go up by a factor of 25. Just think of it this way. If you keep the speed the same but your reactor will go bigger, it means parts of the reactor will not be mixed properly (as you can see at 2:24). So generally, this will mean oxygen transfer will go down. Hope that explains it

[@taniat3014]

@@MarloesPeeters Hi! didn't think you would reply, thanks a lot!
I was reading the table vertically at first, e.g.
if P/V is kept constant in scale-up, then these parameters would change such as N=0.34, P input = 125 and so on.
But from you explanation, the correct way is to read the data horizontally e.g.
if P/V is constant, then N = 25, N*Di = 0.2, etc.
Your point about oxygen transfer will decrease at constant N when scaling up, therefore N should be increased makes sense to me. But say we have bigger tank with larger impeller diameter and we would like to find the appropriate N value using constant P/V strategy. The N value calculated for bigger tank is always found to be lower (due to larger impeller diameter). Practically, do you think applying lower N in bigger tank with larger diameter will give similar oxygen transfer? Sorry if i'm asking too much and thanks again!