KINETIC-MODELS FOR THE GROWTH OF ESCHERICHIA-COLI WITH MIXTURES OF SUGARS UNDER CARBON-LIMITED CONDITIONS

In natural environments, heterotrophic microorganisms encounter comple x mixtures of carbon sources, each of which is present only at very lo w concentrations. Under such conditions no significant growth could be expected if cells utilized only one of;he available carbon compounds as suggested by the principle of diauxic growth. Indeed, there is much evidence that microbial cells utilize many carbon sources simultaneou sly. In order to predict bacterial growth under such conditions we dev eloped a model describing the specific growth rate as a function of th e individual concentrations of several simultaneously utilized carbon substrates. Together with multisubstrate models previously published, this model was evaluated for its ability to describe growth of Escheri chia coli during the simultaneous utilization of mixtures of sugars in carbon-limited continuous culture. Using the mu(max) and K-s constant s determined for single substrate growth with six different sugars, th e model was able for most experiments to adequately describe the speci fic growth rate of the culture, i.e., the experimentally set dilution rate, from the measured concentrations of the individual sugars. The m odel provides an explanation why bacteria can still grow relatively fa st under environmental conditions where the concentrations of carbon s ubstrates are usually extremely low. (C) 1998 John Wiley & Sons, Inc.