Robust and reproducible processes are necessary to achieve a constant and high quality of biotechnological products. Thus, suitable online measurement systems and an increased understanding of the parameters influencing the process are required. In this study, two online measurement devices were used to detect the influence of the initial pH value on the lag phase of three E. coli and one B. licheniformis strains cultivated in buffered mineral media. It was shown that the initial pH value, the type of buffer and its concentration have to be carefully chosen to avoid differences in the lag phase, unsuitable pH values during the cultivation, and osmotically inhibiting high buffer concentrations.