Dielec. spectroscopy was applied to two industrial high cell d. culture processes and used to det. online the concn. of CHO cells immobilized on macroporous microcarriers in a stirred bioreactor and in a packed-bed of disk carriers. The cell concn. predicted from the spectroscopic data was in excellent agreement with off-line cell counting data for both processes. Deviations between the two counting methods only occurred in the case of a significant decrease of the cell viability, from 93% to 64%, which induced a change of the av. cell size in the culture. Results for the packed-bed process were further confirmed by the application of indirect yield models based on the measurement of glucose, lactate, and the protein of interest. Moreover, dielec. spectroscopy was used as a tool to characterize the packed-bed process. It was possible to det. both the max. cell concn. that could be reached in the culture system, 2.0 1011 cell per kg of disk carrier, and to quantify the increase of specific protein productivity induced by the prodn. phase, from 5.14 10-8 g cell-1 h-1 to 4.24 10-7 g cell-1 h-1. [on SciFinder (R)]