HIGH-DENSITY FED-BATCH CULTURES FOR HYBRIDOMA CELLS PERFORMED WITH THE AID OF A KINETIC-MODEL

Hybridoma fed-batch cultures with either standard medium as feed or co ncentrated medium as feed and removal of toxic metabolites through dia lysis were performed by using model calculations for ''a priori'' dete rmination of process parameters. In a first step a kinetic model for s pecific growth and death rate, respectively as well as for substrate u ptake and metabolite production rates was formulated. In a bed-batch c ulture with standard medium as feed the appropriate time for start of the feeding pump and the increase of feed rate were determined ''a pri ori''. The glutamine concentration was controlled at 0.04 mmoll(-1). ' 'A priori'' calculation and course of the culture coincided rather wel l. A cell concentration of 3.210(6) cells ml(-1), a MAb-concentration of 54 mg(MAb)l(-1) and a MAb-time-space-yield of 0.53 mg(MAb)l(-1)h(- 1) were obtained. For further increase of the efficiency a high densit y fed-batch process was developed, where concentrated medium is fed to the cells and the accumulating toxic low molecular weight metabolites are removed through a dialysis membrane into a dialyzing fluid. In a membrane dialysis reactor consisting of a culture chamber and a dialyz ing chamber, which are separated by a cylindrical dialysis membrane, a gain model calculations were used to determine feed rate and exchange rate of dialyzing fluid. A viable cell density of 1.210(7) cells ml(- 1) and a MAb concentration of 425 mg l(-1) were reached in a culture w ith stepwise feeding of 10 x concentrated medium and exchange of dialy zing fluid for removal of low molecular metabolites. The course of the culture could be predicted ''a priori'' rather well. The MAb-time-spa ce-yield was 2.47 mg(MAb)l(-1)h(-1), appr. 5 times higher compared to fed-batch cultures with standard medium as feed.