No abstract

Heat evolution during the growth of Escherichia coli in a stationary culture on bouillon mediumwas continuously monitored with a conduction-type batch calorimeter at different pHs and temperatures. The growth thermograms were found to be reproducible within percent errors of +2.1%, ±0.8% and ± 1.5% for the peak time ofa thermogram, the peak height and the total heat evolution, respectively. The meanheat evolution for the formation of a unit E. coli cell was co= (1.69±0.08) x 10~8Jceir1 at pH 6.2 and 37°C. The mean heat evolution rate per unit cell during growth was g^^pwcell"1, which was consistent with values calculated for other microbial cells. The growth rate constant calculated on kinetic analysis of the growth thermograms was /i= 0.532±0.068 hr"1 at pH 6.2 and 37°C. The pH dependence of the growth rate constant showed that the growth activity of E. coli cells on bouillon medium is maximumin the pH range of 5.5 to 6.5. From the temperature-dependent variations in the growth rate constant, the apparent activation energy of E. coli growth was found to be £a=65.3±7.1 kJmol"1.