EFFECT OF NH3 ON THE CELL-GROWTH OF A HYBRIDOMA CELL-LINE

Ammonia often has been reported to inhibit cell growth. The aqueous am monia equilibrium between the un-ionized form (NH3) and the ammonium i on (NH4+) depends on the pH of the solution. Extensive studies in batc h and continuous cultivation by varying pH and total ammonia concentra tion were carried out to investigate whether a kinetic model describin g growth inhibition by ammonia has to be based on the total ammonia co ncentration, or the concentration of NH3. A significant relationship b etween the specific growth rate and death rate, respectively, and the NH3 concentration, but not the total ammonia concentration, was detect ed. An adaptation of the cells to high ammonia levels was not observed . Based on these results a new kinetic model for ammonia mediated grow th inhibition is suggested. For high density cultivation it is recomme nded to control the pH at the lower limit of the growth optimum to kee p the NH3 level low.