ONLINE MONITORING OF AN ANIMAL-CELL CULTURE WITH MULTICHANNEL FLOW-INJECTION ANALYSIS

A multi-channel flow injection analysis system was used for on-line mo nitoring of a continuous animal cell culture with high cell density. W ith this system, the glucose, lactate and glutamine concentration were determined using immobilized dehydrogenases, ammonium using an aqueou s o-phthaldialdehyde solution. Glutamine concentration was determined on the basis of the difference between a glutamine and a glutamate mea surement. To prevent disturbance of the measurement and pollution of t he system, the analytes in the sample were separated from high molecul ar compounds by on-line dialysis. On-line gas dialysis was used to avo id interference of other amino groups with the ammonium determination. In addition, dialysis was used as a dilution step. The measurement ti me for all four components was 42 min. This time included a final wash ing 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 re actor as cultivation system. The concentration of glutamine, glucose a nd ammonium determined with the on-line FIA system were in good agreem ent with the off-line data determined once a day. Only the lactate dat a 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 concentratio ns 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 monit ored. It was noted that a sudden change of the glutamine concentration in the feed caused a fast change of the consumption and production ra te of the measured metabolites.