ABSTRACT
A multi-channel flow injection analysis system was used for on-line monitoring of a continuous animal cell culture with high cell density. With this system, the glucose, lactate and glutamine concentration were determined using immobilized dehydrogenases, ammonium using an aqueous o-phthaldialdehyde solution. Glutamine concentration was determined on the basis of the difference between a glutamine and a glutamate measurement. To prevent disturbance of the measurement and pollution of the system, the analytes in the sample were separated from high molecular compounds by on-line dialysis. On-line gas dialysis was used to avoid interference of other amino groups with the ammonium determination. In addition, dialysis was used as a dilution step. The measurement time for all four components was 42 min. This time included a final washing period after the analysis cycle. The system was calibrated once a day. Two continuous cultivations of a hybridoma cell line immobilized in open-porous glass carriers were monitored, using a fluidized bed reactor as cultivation system. The concentration of glutamine, glucose and ammonium determined with the on-line FIA system were in good agreement with the off-line data determined once a day. Only the lactate data showed some deviation. The immobilized enzyme reactors could be used for up to 3000-5000 injections. During the first cultivation, lasting 200 h, the start up period of the reactor was monitored. The on-line measurements described much better the time-course of the concentrations than the off-line data. It was possible to estimate the growth rate of the cells in the micro-carriers by the on-line data. In the course of the second cultivation, which lasted almost 1000 h, the influence of the dissolved oxygen concentration on the cell metabolism was monitored. It was noted that a sudden change of the glutamine concentration in the feed caused a fast change of the consumption and production rate of the measured metabolites.
