THE GROWTH-RATE CONTROL IN ESCHERICHIA-COLI AT NEAR TO MAXIMUM GROWTH-RATES - THE A-STAT APPROACH

The growth characteristics of Escherichia coil K-12 in the continuous culture with a smooth increase in the dilution rate (A-stat) of variou s carbon sources (glucose, acetate, succinate, glycerol, lactate, acet ate + succinate, casamino, acids + glucose) were studied. For all subs trates studied the maximum value of specific respiration rate, Q(O2), remained between 14-18 mmol O-2 h(-1) g dwt(-1) and the maximum growth rate varied from 0.22 h(-1) on acetate to 0.77 h(-1) on glucose + cas amino acids. After the respiratory capacity of the cells was exhausted at growth rates mu > mu(crit), the growth yield Y-XO2, increased slig htly when the dilution rate increased. The maximum growth rate of Esch erichia coli K12 was dependent on growth yield, respiratory capacity a nd glycolytic capacity of the strain. Analysis of the cultivation data using a stoichiometric flux model indicated that ATP synthesis in E. coli exceeds by two-fold that (theoretically) required to build up bio mass. The experimental value of m(ATP) < 4 mmol ATP h(-1) g dwt(-1) de termined from A-stat cultivation data was low compared with the calcul ated 'unproductive hydrolysis' of ATP (64-103 mmole ATP g dwt(-1)).