title: Cultivation of Escherichia coli with mixtures of 3-phenylpropionic acid and glucose: steady-state growth kinetics.
abstract: 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.
authors.affiliation: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Swiss Federal Institute of Technology (ETH), Dübendorf, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Kovárová
authors.forename: A
authors.initials: A
authors.lastname: Käch
authors.forename: A J
authors.initials: AJ
authors.lastname: Zehnder
authors.forename: T
authors.initials: T
authors.lastname: Egli
mesh_terms: D018533:Biomass; D003470:Culture Media / Q000378:metabolism; D004787:Environmental Pollution; D004926:Escherichia coli / Q000254:growth & development* / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D007700:Kinetics; D010666:Phenylpropionates / Q000378:metabolism*
chemical_list: D003470:Culture Media; D010666:Phenylpropionates; C035253:3-phenylpropionic acid; D005947:Glucose