Figure 1.

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).