THE GROWTH OF ESCHERICHIA-COLI IN GLUCOSE-LIMITED CHEMOSTAT CULTURES - A REEXAMINATION OF THE KINETICS

The relationship between specific growth rate (CL) and steady-state gl ucose concentration was investigated for Escherichia coli ML30 in carb on-limited chemostat culture. This was made possible by the developmen t of a method for measuring reducing sugars in culture media in the mu g.l(-1)-range. Cells initially cultivated in batch culture at high gl ucose concentrations required long-term adaptation to nutrient-limited growth conditions in the chemostat (between 100-200 volume changes at D = 0.6 h(-1)) until steady-state with respect to residual glucose co ncentration was reached; for adapted cells, however, new steady-state glucose concentrations were usually obtained within less than 10 volum e changes. A statistical evaluation of different kinetic models showed that between 0.2 h(-1) < D < 0.8 h(-1) the three models proposed by M onod (1942), Shehata and Marr (1971), and Westerhoff et al. (1982) des cribed the data equally well and the applicability of the different mo dels is discussed. Depending on the model used, calculated glucose con centrations supporting half maximum growth rate (K-s) Were in the rang e of 40-88 mu g.l(-1). The data strongly suggest that the large differ ences in K-s constants reported in the literature (ranging from 40 mu g.l(-1) up to 99 mg.l(-1)) are due to the use of E. coli cells adapted to different degrees to nutrient-limited growth conditions. This indi cates that it is probably not possible to describe the kinetic propert ies of a bacterium with a single set of kinetic 'constants'.