Issue with turbidostat mode keeping pumps going

[ignaciosparrow]

Hi everyone,

We purchased ChiBio with the reactor assembled and ready to go. It has been in the lab since before I arrived and I got around finally to using it. I want to use turbidostat mode to keep my culture at an OD of 0.4 and to measure the emission of a fluorescence protein as inducer is added.

I am using the white plastic caps which are autoclavable and have one out hole at the top which goes in with a “hard” tube toward the center of the reactor so that waste media can be taken from there. It is my understanding that in turbidostat mode the waste pump should always be running faster than the pump 1. Then, it makes sense that if OD is below the set point, the waste pump will run and run until the level of media is at the point where the “hard” tube is, eventually sucking in and getting air into the pump system. This seems to have made our reactor effectively crash as they are unable to create enough vacuum suction to get liquid to beat the gravity curve until it starts flowing again by the force of the flow, even if pump 1 then can compensate and add media to above the level of the “hard” tube, the waste pump no longer generates force because of the bubbles. Fortunately no overflow occurred as we noticed this in time before Pump 1 could overflow.

I am unsure if this has to do with the tubing that I am using (0.2 mm x 0.4 mm ID x OD), as these have trouble to start the liquid flow too unless helped by tilting the tubing almost horizontally. Could it be that these tubes are too thin to create the vacuum turbidostat mode needs to beat the air bubbles that originate? It would be preferable for our experiment to start with a lower OD, build up to the desired OD and maintain, although I am not sure if it should make much of a difference if a high OD is used to start with. I haven’t tested it, but it seems like starting with a higher OD would bypass this problem as media should stay above the waste removal line?

If anyone has had any similar issues when operating in turbidostat mode, please let me know advice or how you have dealt with this.

Sorry for so many questions. Best wishes,
Ignacio

[ignaciosparrow]

Bumping the post in case someone can see this

[harrison]

Hi Ignacio,
As I mentioned in my email response, you need to use the CORRECT tubing. Which is 2.5mm ID 4.5mm OD as specfied on the Hardware page here: https://chi.bio/hardware/
Then, if you are still having problems, you could add tape to the pump head to make the seal tighter.
Ensure you have fully read the operation manual since it discusses each of these points (e.g. in the setup parts and also troubleshooting guide).
Harrison

[Author]

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