LB contains glucose?

Cornelius Krasel krasel at
Mon Feb 24 05:26:02 EST 1997

hbkg at wrote:
> Glucose is known to repress lac promoter expression.
> LB media (1% tryptone, 0.5% yeast extract, 1% NaCl) is largely
> used for media for overproducing cloned gene products.
> gene expression under the regulation of lac promoter is repressed by
> glucose in the media.
> I am curious how much glucose exists in LB.

The only possible source of glucose could be the yeast extract, but
I don't think it contains appreciable amounts. At the place where I
learned my microbiology people would add a bit of glucose to the LB
if they wanted to make their lac-based promoters more tighter.


/* Cornelius Krasel, U Wuerzburg, Dept. of Pharmacology, Versbacher Str. 9 */
/* D-97078 Wuerzburg, Germany   email: phak004 at  SP3 */
/* "Science is the game we play with God to find out what His rules are."  */

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