The Aeration ofCatharanthus roseusL. G. Don Suspension Cultures in Airlift Bioreactors: The Inhibitory Effect at High Aeration Rates on Culture Growth

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Abstract
An investigation was carried out to examine the effect of aeration on the growth of Catharanthus roseus suspension cultures in airlift bioreactors. A high aeration rate (0·86 v.v.m.) was found to inhibit the growth of cultures. Venting cultures at a high rate with low oxygen content gas mixtures was equally inhibitory to culture growth, showing that high aeration was not inhibitory as a result of oxygen toxicity. The dissolved carbon dioxide tension was found to be lower in cultures operated at high aeration than those operated at low aeration. Supplying exogenous CO2 to cultures at high aeration restored the CO2 tension to values normally encountered at a low aeration rate, and was found to alleviate the inhibitory effects at high aeration. However, further increasing the CO2 supply to cultures was found to be severely inhibitory to growth. Therefore, the growth of C. roseus cultures is very sensitive to dissolved CO2 concentration, growth being inhibited at values either higher or lower than an optimum.