Abstract: In this contribution results are presented from the control of glucose during a yeast fed-batch cultivation. For glucose measurements a special flow injection analysis (FIA) system was employed, which uses a glucose oxidase solution instead of immobilized enzymes. To avoid the large delay time caused by probing systems samples containing cells, i.e., samples containing the ordinary culture broth, are injected into the FIA system. Based on a special evaluation method the glucose concentration can be measured with a delay time of about 60 s. Employing an extended Kalman filter, the biomass, the glucose concentration as well as the µ(max) (Monod model) are estimated. Based on the estimation a feed forward and a PI-control with a set point of 0.5 g/l was carried out. The mean deviation of the set point and the estimated value as well as the set point and the measured value were 0.05 and 0.11 g/l respectively for a control period of 8 h producing a cell dry mass of more than 6 g/l.

Abstract: A flow injection analysis method for determination of the enzyme β-galactosidase produced in a fermentation process has been developed. The analytical range was 10^-1000 U/mL and the sample throughput was 40 h-1. The FIA set up was connected directly to the down-stream process and the enzyme activity in the extraction step was measured online. The viscosity of the samples from the process is high causing certain physical effects on the FIA system.