Minimal Glucose media colour - autoclave surprises . . . (Jan/07/2008 )

I haven't worked with minimal glucose media before, but today I had a project student make some up for a future procotol and it turned dark red in the autoclave. Is that colour normal?

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generally glucose should be filtered through 0.22 um and added to the medium after autoclave.

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Sigh. I figured.

Is it still usable or should we just toss it?

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Glucose reacted with amines groups in your tryptone, no good anymore.

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Thank you!

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So true. The millard reaction is more intence when the pH of the medium is in alkaline region. And for a number of bacteria species, millard reaction products is growth retardant and for some, an outright growth inhibitor.

Genehunter-1's suggestion is the best. Add the glucose after the autoclave run. However if you must add the glucose prior to autoclaving, consider autoclaving the medium on a sugar run (at a lower temperature 117 Celsius rather then the usual 121 Celsius). The lower temperature reduces the millard reaction somewhat.

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The minimal glucose medium we use is sterilized at 110ºC and pressure slightly <1. It's usually enough to make it sterile without compromising it.

Sometimes it comes out a bit darker though (yellowish to be more precise) - probably because the person who autoclaved it wasn't careful enough.

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