The effect of oxygen partial pressure in bioreactors on cell proliferation and subsequent differentiation of somatic embryos of Cyclamen persicum

The effect of the relative oxygen partial pressure (pO(2)) in bioreactors on cell proliferation and subsequent differentiation of somatic embryos from suspension cultures of Cyclamen persicum Mill. was investigated. The growth rate of cell line 3738-VIII in growth-regulator containing medium in bioreactors at 5% pO(2) was slightly reduced in comparison to 10% and 20% pO(2). Cultures growing at 40% pO(2) had a lower growth rate, a markedly reduced cell viability and showed a decrease of the medium pH to 3.5. Because a pH-control with a setpoint of 3.3 caused cell death within 4 days, it was assumed, that the reason for the poor cell proliferation and viability in the cultures at 40% pO(2) was an effect of medium acidification rather than of the high O-2 partial pressure. A significantly higher number of germinating embryos was obtained from the cultures grown at 40% pO(2) than from those grown in flasks or in bioreactors at 5%, 10% and 20% pO(2). These results were specific for cell line 3738-VIII. Another cell line, 3736-12, did not show marked differences in cell proliferation, viability, pH or subsequent regeneration of somatic embryos when grown at different O-2 partial pressures.