Abstract Escherichia coli strain BL21 is commonly used
as a host strain for protein expression and purification. For
structural analysis, proteins are frequently isotopically
labeled with deuterium (2
H), 13C, or 15N by growing E.
coli cultures in a medium containing the appropriate
isotope. When large quantities of fully deuterated proteins
are required, E. coli is often grown in minimal media with
deuterated succinate or acetate as the carbon source because
these are less expensive. Despite the widespread use of
BL21, we found no data on the effect of different minimal
media and carbon sources on BL21 growth. In this study,
we assessed the growth behavior of E. coli BL21 in
minimal media with different gluconeogenic carbon
sources. Though BL21 grew reasonably well on glycerol
and pyruvate, it had a prolonged lag-phase on succinate
(20 h), acetate (10 h), and fumarate (20 h), attributed to the
physiological adaptation of E. coli cells. Wild-type strain
NCM3722 (K12) grew well on all the substrates. We also
examined the growth of E. coli BL21 in minimal media that
differed in their salt composition but not in their source of
carbon. The commonly used M9 medium did not support
the optimum growth of E. coli BL21 in minimal medium.
The addition of ferrous sulphate to M9 medium (otherwise
lacking it) increased the growth rate of E. coli cultures and
significantly increased their cell density in the stationary
phase.