Oxygen levels/aerobic cultivations

[Dahlin]

Hello,

I’m considering getting some Chi.Bio reactors. I need them for aerobic cultivations, but I’m concerned that the stirring/reactor design is not providing enough aeration. Did anyone measure the levels of dissolved oxygen at different ODs?

Thanks in advance!
Jonathan

[harrison]

Interesting question! I am not aware of anyone that has directly measured dissolved oxygen at different ODs, but that would certainly be useful data to have (though highly dependent on strain/media).

The top of the reactor is by default open to the atmosphere, and due to the outflow pump’s regular action, the air in the head-space is replenished very regularly. Therefore, if there will be oxygen limitation it would have to arrive at the point of stirring it in to the media. Generally stirring is (if set to a high rate) about as vigorous as physically possible: With the right stir bar you can get a vortex that runs the length of the media column. If you think that would be fine I expect it would work well for your needs!
From my own experience, I have used fast-growing bacteria (E. coli, V. Natriegens) at continuous ODs of up >0.5 without seeing any significant slowdown…

[Ari]

Hi Harrison,
first of all, great job on creating this accessible platform, much appreciated!

I have also been curious about the issue of oxygen-supply in the Chi.Bio reactors. Can you explain what you mean by “the top of the reactor is by default open to the atmosphere”? Is the screw-cap not air-tight or do you mean that some of the inlets can be left open (i.e. not connected to any tubing)? How come that the frequent pumping to the waste outflow doesn’t create underpressure?

If air flows in, are you not worried about sterility?

On a related topic: Are you aware of elegant solutions on how to supply a desired atmosphere (e.g. increased CO2 or some (pressurized) gas mix) to the reactor? Glad if you have some ideas or know of successful applications.

[Ari]

Thanks in advance!
– Ari

[Mike Lanz]

Any update on this dissolved oxygen question? I have not measured dissolved O2 directly, but I have tried using either pump 3 or 4 to periodically push fresh air directly into the chamber. I cap the hose with a filter and thus far not contaminated my cells

[Author]

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