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Appl. Environ. Microbiol., Jul 1997, 2619-2624, Vol 63, No. 7
K Kovarova, A Kach, AJ Zehnder and T Egli
The fate of pollutants in the environment is affected by the presence of
easily degradable carbon sources. As a step towards understanding these
complex interactions, a model system was explored: the degradation of
mixtures of glucose (i.e., an easily degradable substrate) and
3-phenylpropionic acid (3ppa) (a model pollutant) by Escherichia coli ML 30
was studied systematically in carbon-limited continuous culture. The two
substrates were always consumed simultaneously regardless of the dilution
rate applied. Even at dilution rates higher than the maximum specific
growth rate for 3ppa (0.35 +/- 0.05 h-1), the two carbon substrates were
utilized together. When cells were grown at a constant dilution rate with
different mixtures of 3ppa and glucose, in which 3ppa contributed between 5
and 90% of carbon substrate in the feed medium, the steady-state
concentrations of 3ppa and glucose were approximately proportional to the
ratio of the two substrates in the feed medium. When cells were cultivated
at different dilution rates with a 1:1 mixture (based on carbon) of glucose
and 3ppa, an overall maximum specific growth rate of 0.90 +/- 0.05 h-1 and
a Monod substrate saturation constant for 3ppa (Ks) of 600 to 700
micrograms liter-1, similar to that measured during growth with 3ppa alone,
fitted the experimentally determined steady- state 3ppa concentrations.
However, due to the highly differing substrate affinity constants for 3ppa
and glucose (Ks approximately 30 to 70 micrograms liter-1), the total
steady-state carbon concentration in the culture at a constant dilution
rate was determined mainly by the steady-state 3ppa carbon concentration,
and it increased with increasing proportions of 3ppa in the feed medium.
Copyright © 1997, American Society for Microbiology
Cultivation of Escherichia coli with mixtures of 3-phenylpropionic acid and glucose: steady-state growth kinetics
Swiss Federal Institute for Environmental Science and Technology (EAWAG), Swiss Federal Institute of Technology (ETH), Dubendorf, Switzerland.
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