Enhanced monoclonal antibody production by gradual increase of osmotic pressure

The time length required for the adaptation of AFP-27 hybridoma cells to high osmotic pressure and the effect of a gradual increase of osmotic pressure on monoclonal antibody production were investigated. When the cells were subjected to an increase of osmotic pressure from 300 mOsmol kg(-1) to 366 mOsmol kg(-1), the intracellular content of osmoprotective free amino acids reached a maximum level 6 h after the osmotic pressure was increased to 366 mOsmol kg(-1). The same time period of 6 h incubation at 366 mOsmol kg(-1) was required to obtain a high growth rate of AFP-27 cells at 440 mOsmol kg(-1) when the cells were subjected to a two-step increase of osmotic pressure from 300 mOsmol kg(-1) to 366 mOsmol kg(-1) and then to 440 mOsmol kg(-1). The time length for the physiological adaptation of the cells to 366 mOsmol kg(-1) was consequently estimated to be 6 h. Osmotic pressure during batch cultivation was gradually increased from 300 mOsmol kg(-1) to 400 mOsmol kg(-1) with an adaptation time of at least 6 h. The specific growth rates following a gradual increase of osmotic pressure were higher than those at a constant osmotic pressure of 400 mOsmol kg(-1), while the specific monoclonal antibody production rate increased with the increase in the mean osmotic pressure. As a result, the cells grown under a gradual increase of osmotic pressure produced higher amounts of monoclonal antibodies than did those grown under constant osmotic pressure.