a) The time required to reach substrate limitation is shown in dependence of the temperatures in 5 parallel fermentations. The CO2 concentration in the exhausted air increased in dependency of the cell number as a consequence of metabolism of the carbon source. The faster the growth velocity, the earlier the carbon source became limiting resulting in a drop in CO2 concentration measured in the exhausted air. The period of time to reach this turning point is an indirect measure for growth velocity. b) Effect of maltose on growth and CO2 liberation compared to a control fermentation without alternative carbon source. The QCO2 was determined by balancing the exhausted air (see curves of exhausted air) as described. Growth was determined by measuring the optical density (black circle = control culture, open circle = culture with maltose added).