The reactor is usually run at 30 minute residence time, an approximate rate of 11.5 mL/min. It is up to you to make sure that the residence time is less than doubling time to select for biofilm growth. 

Dear Connie

Is it fixed for all bacterial species? I mean the 30 min residence time?

Sinan, 

No the residence time can be whatever you set it at. As different species grow at differing rates, the reactor can be run at whatever you need. The SOP for the CDC Reactor is 11.5 mL/min, but I have read articles that use residence times as long as 12 hours. The working volume is approximately 350 mL, so whatever you set your pump at (and select proper tubing) you can run at whatever you need. (350/11.5 is about 30 minutes).

Thank you so much, Connie. I was waiting for an answer to this question for a long time. at last, I got it.

Thanks again

Good luck! There is a Youtube video showing how to set it up, and it covers common mistakes. Just search CDC Reactor. You have the manual I'm assuming? I've attached my version. 

I have problems getting consistent biofilm growth. I'm curious the doubling time I should be looking at is the doubling time with full strength media at optimum temperature or the doubling time with partial strength media (as for the CSTR phase of CBR operation) at whatever temperature you choose? Anyone has any ideas?

And in the manual, it says that the stirring speed is crucial. But how would the change of stirring speed affect the biofilm formation? Is 125 rpm good for all microbes?

Hello! It looks like your question has been answered, but I wanted to mention that there are now training videos available from the Center for Biofilm Engineering. You can find them at CBEVideos.com. They should answer this question for you as well.