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?
generally glucose should be filtered through 0.22 um and added to the medium after autoclave.
Sigh. I figured.
Is it still usable or should we just toss it?
Glucose reacted with amines groups in your tryptone, no good anymore.
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.
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.