FAD in culture medium?

Scott Mulrooney mulrsb at umich.edu
Sat Nov 14 17:31:58 EST 1998

Hi Georg

I have had experience with getting expression of flavoproteins (FAD) to
very high levels without adding any precursors  of FAD to the growth
medium. Levels of over 10 micromoles of FAD per liter of culture are normal
(typical protein yield about 350 mg per liter). Apparently, E. coli can
synthesize FAD to very high levels: about 95% of the enzyme is holoenzyme
and 5% apoenzyme. In fact, I often find that after harvesting the
recombinant E. coli, they have a slight dark green color, probably because
some the enzyme is in the blue neutral semiquinone form. My understanding
is that FAD or FMN will not enter the E. coli cell, but riboflavin can. I
tried to suppliment the growth medium with riboflavin, but it did not help.
You can get more details in Protein Expression and Purification (1997) 9,

Hope this is of some help

Scott B. Mulrooney
Department of Biological Chemistry
University of Michigan
Ann Arbor, MI 48109-0606 USA
mulrsb at umich.edu

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