def media turn yellow

George W. Chang changlab at nature.berkeley.edu
Tue Oct 31 21:53:34 EST 1995

In article <46g47p$9vd at mserv1.dl.ac.uk>, trond.moretro at nlh10.nlh.no (Trond
Moretro) wrote:

> I am working with defined medium for Lactobacillus sp. Fresh medium is=20
> colourless. But when incubated and specially at 30 degrees celsius it turn=
> =20
> yellow. The medium contains 20 amino acids,...<snip> glucose...

> Why do medium turn yellow???. 
Hi Trond,
   My guess is that the glucose is reacting with the amino acids to give
you what the food technologists call "Maillard Reaction" or "non-enzymatic
browning."  I used to have a similar problem with a defined lactobacillus
   I solved my problem by using sucrose instead of glucose.  The bacterium
ate the glucose just fine, and there was very little browning.
   Let us know if this works for you!

George Chang      <Changlab at nature.berkeley.edu>

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