MEASUREMENT OF BUBBLE SIZE DISTRIBUTIONS IN FERMENTATION MEDIA USING A PHOTOELECTRIC PROBE.

In many aerobic fermentation processes the effective growth rate of micro-organisms is limited by the oxygen transfer rate from the gas to the liquid phase. One of the important parameters affecting the oxygen transfer rate is the interfacial area, which is directly dependent on energy dissipation. Therefore a sterilizable photoelectric probe was developed for this particular type of application. In principle, the method consists of sucking a small sample stream from the dispersion through a transparent capillary tube in which the bubbles are transformed into slugs. The length of these slugs is determined by means of two light sensors on the basis of different light absorption in gas and liquid. The experimental results show that the photoelectric probe is suitable for a fast determination of bubble size distributions under sterile conditions. Therefore the method can be used for process control. 11 refs.