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CO2 incubator need help bad - (Apr/07/2006 )

I just bought a CO2 incubator. My boss had me put in complete medium in teh incubator. Does anyone know why. My guess is to detect growth or contamination. Is this right? What color should it change to if there is growth? What should I look for? WHat color would the comkplete medium turn if there is too much CO2 in the incubator.


standard medium doesnot change pH itself in a CO2 incubator. If turns purple or yellow pH is respectively too high or too acidic.
If CO2 is too high in the air, the fraction solubilized increase leading to more HCO3- wich increases the ph


if you have contamination, it will possibly turn the media yellow/orange

however, the easiest way to tell will be that you will see turbidity, or possibly even floaters...some hyphae if you have fungi...anyhow, it will likely be very obvious within a few days, up to a week or so for fungi

oh, hey, do you have access to a fyrite CO2 tester? they can tell you if your CO2 guages are off and need to calibrated


My guess is that your boss is just checking the CO2 using the color indicator (phenol red) in your medium. If there is too much CO2 in the incubator the medium will turn yellow (acidic), too little and it will turn a bright pink/purple (alkaline).

We grow our cell lines (human) with between 5% and 6% CO2 in air. We actually prefer the pH a little more acidic (hence 6%).

As an example put 2ml of complete medium into a sterile tube, leave the lid very loose and sit it on the bench for a couple of hours - it should turn a pinkish color. If you then add several drops of acetic acid to the tube it will turn yellow (or just put it into your CO2 incubator and the color will revert to a more orange/salmon color).

The only time I would incubate medium in a tube would be to check if the medium was contaminated prior to use. As aimikins has pointed out, the media will turn a turbid yellow after a day or two. Again, test this by putting your finger in a tube of sterile medium and leave it on the bench for a couple of days - the media will turn a putrid yellow pretty quickly.

I'd also try to get hold of a fyrite to periodically check the CO2 although the medium color gives you a ballpark figure. And lastly, why not just ask your boss why he/she was adding it!.....a homework question perhaps?