Influence of lactate, ammonia, and osmotic stress on adherent and suspension BHK cells.

Adherent and suspension Baby Hamster Kidney (BHK) 21c13 cells were cultivated in a 2.5-1 stirred-tank reactor with indirect aeration. Cell concentration and viability as well as glucose, lactate, ammonia, and protein concentrations in the medium and intracellular and extracellular activities of the intracellular enzymes were determined off-line. The concentrations of glucose, lactate, ammonia, and the activity of lactate dehydrogenase in the culture medium were monitored on-line. The cell/cell fragment size distribution was determined by laser flow cytometer off-line. In several runs, the size distributions were ascertained on-line by a laser flow cytometer. The influence of lactate, ammonia, and osmotic pressure on the viability and biological parameters of the suspension cells was evaluated. In Roux flasks, lactate and ammonia had considerable influence on the cell properties; in stirred tank reactors, these influences were negligible up to 9.5 g l-1 lactate and 150 mg l-1 NH+4 ion concentrations. The influence of high osmolarity on the biological parameters of the cells was much less in the stirred-tank than in the Roux flasks. The adhesion of adherent cells on a surface was impeded neither by the lactate (up to 6 g l-1) nor by the ammonia concentration (up to 150 mg l-1). However, with increasing osmolarity, the fraction of the cells adhered to a surface reduced to below 5% (at 680 mOsmol l-1).