The opto-electronic device for on-line measurement of pH and DO in shake flasks is using chemical-optical sensor patches. The main unit includes 9 integrated double optic modules measuring both parameters. Special holders suitable for shake flasks of 250, 500 and 1000 ml are used for fixing the flasks. The whole system is mounted on a tray of a conventional shaker and data are transferred to computer by a Wireless Transmission Converter (WTC) allowing real-time display of pH and DO. As all parts of the system are pre-calibrated, no on-site calibration was necessary.

Measuring the dissolved oxygen concentration during the cultivation of C. glutamicum wild type and four L-lysine producing mutants resulted in a clear separation of growth and production phase based on the course of DO. Another application was the physiological characterization of S. cerevisiae strains grown on different sugars. Clear differences were found and DO data were further used to determine the specific oxygen uptake rates using a simple model. A third application was the determination of the minimal buffer requirement for a C. glutamicum cultivation. Several buffer concentrations were used and the course of pH was monitored during cultivation to find a minimal concentration with tolerable pH drop.