TEMPERATURE-DEPENDENT GROWTH-KINETICS OF ESCHERICHIA-COLI ML-30 IN GLUCOSE-LIMITED CONTINUOUS-CULTURE

Detailed comparison of growth kinetics at temperatures below and above the optimal temperature was carried out with Escherichia coli ML 30 ( DSM 1329) in continuous culture. The culture was grown with glucose as the sole limiting source of carbon and energy (100 mg liter(-1) in fe ed medium), and the resulting steady-state concentrations of glucose w ere measured as a function of the dilution rate at 17.4, 28.4, 37, and 40 degrees C. The experimental data could not be described by the con ventional Monod equation over the entire temperature range, but an ext ended form of the Monod model [mu = mu(max) . (s-s(min))/(K-s + s-s(mi n))], which predicts a finite substrate concentration at 0 growth rate (s(min)), provided a good fit. The two parameters mu(max) and s(min) were temperature dependent, whereas, surprisingly, fitting the model t o the experimental data yielded virtually identical K-s, values (appro ximately 33 mu g liter(-1)) at all temperatures. A model that describe s steady-state glucose concentrations as a function of temperature at constant growth rates is presented. In similar experiments with mixtur es of glucose and galactose (1:1 mixture), the two sugars were utilize d simultaneously at all temperatures examined, and their steady-state concentrations were reduced compared with to growth with either glucos e or galactose alone. The results of laboratory-stale kinetic experime nts are discussed with respect to the concentrations observed in natur al environments.