Hey all,
I wanted to start a discussion about maximizing gas transfer inside the pioreactors, and hear your thoughts/solutions on this. In our case the issue is mainly oxygen transfer. We experience that our strain grows significantly slower in pioreactors compared to shake flask experiments. On this forum, some things have been discussed and we’ve tried several things but also run into some issues.
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Initially we have tried the method described here, where the stirring rpm is significantly increased to create a V-cone shaped liquid surface to maximize the surface area. Both with the standard stirrer and with bigger stirrer bars:
Stop stirring while measuring OD?
However, using this method our OD readings got a lot more noisy and it frequently caused the Pioreactors to get a stirring error (‘‘WARNING Stirring RPM is 0’’). Therefore we decided this method is not ideal. But maybe people are having more succes with it in a way? -
Alternatively, we used the pumps to continuously bubble air into the liquid with a needle. This does seem to help the cells, but we still have clear oxygen limitation and no exponential growth.
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Finally, we tried using a baffle. But using this meant having a larger total volume & vial to completely submerge the baffle. Also, the baffle couldn’t be anywhere near the bottom as to not interfere with the readings. These two issues combined turned out to only further hamper oxygen transfer and cells in these conditions grew ever slower. Somehow the magnet & baffle combination doesn’t allow for any turbulence created by the stirrer.
So, TL:DR: Does anybody have ideas/experience on how to maximize oxygen transfer without introducing more noise into your readings.
Greetings from a fellow Pio fanatic!