Factors affecting cell growth and monoclonal antibody production in stirred reactors

Environmental and cultural factors that could affect growth and cell viability of mouse-mouse hybridoma cells in culture were investigated. The aim was to determine conditions that could prolong viability and result in increased yields of monoclonal antibodies in stirred reactors. Factors studied included temperature, level of dissolved oxygen, nutrient depletion, and waste product accumulation. Growing cells at temperatures 3-9 degrees lower than optimum (37 degrees C) increased viability but monoclonal antibody production was lowered. A low level of dissolved oxygen (25% air saturation compared to 60% for optimum growth) prolonged cell viability and increased the monoclonal antibody yield by about 50%. Feeding cultures daily to maintain the glucose level above 1 mg/ml and at the same time feeding cells glutamine (150 micrograms/10(6) cells per day) maintained the level of viable cells at 1.7 X 10(6)/ml for at least 9 days and resulted in an antibody yield of 290 micrograms/ml, about a 70% increase over cultures fed either glucose or glutamine alone. Ammonium ion, added to cell populations at levels produced in cultures, stopped cell growth and decreased antibody production. Another waste product, lactic acid, had no toxic effect when added to media at levels found in cultures. These results agree with our suggestion that monoclonal antibody production is enhanced by maintaining cell viability over a prolonged period and provide a base for investigating modes of hybridoma cell propagation in fermentors.