Effects of CO2 and osmolality on hybridoma cells:: growth, metabolism and monoclonal antibody production

CO2 partial pressure (pCO(2)) in industrial cell culture reactors may reach 150-200 mm Hg, which can significantly inhibit cell growth and recombinant protein production. Due to equilibrium with bicarbonate, increased pCO(2) at constant pH results in a proportional increase in osmolality. Hybridoma AB2-143.2 cell growth rate decreased with increasing pCO(2) in well-plate culture, with a 45% decrease at 195 mm Hg with partial osmolality compensation (to 361 mOsm kg(-1)). Inhibition was more extensive without osmolality compensation, with a 63% decrease in growth rate at 195 mm Hg and 415 mOsm kg(-1). Also, the hybridoma death rate increased with increasing pCO(2), with 31- and 64-fold increases at 250 mm Hg pCO(2) for 401 and 469 mOsm kg(-1), respectively. The specific glucose consumption and lactate production rates were 40-50% lower at 140 mm Hg pCO(2). However, there was little further inhibition of glycolysis at higher pCO(2). The specific antibody production rate was not significantly affected by pCO(2) or osmolality within the range tested. Hybridomas were also exposed to elevated pCO(2) in continuous culture. The viable cell density decreased by 25-40% at 140 mm Hg. In contrast to the well-plate cultures, the death rate was lower at the new steady state at 140 mm Hg. This was probably due to higher residual nutrient and lower byproduct levels at the lower cell density (at the same dilution rate), and was associated with increased cell-specific glucose and oxygen uptake, Thus, the apparent effects of pCO(2) may vary with the culture system.