, Volume 42, Issue 2-3, pp 256-262

On-line growth measurements in bioreactors by titrating metabolic proton exchange

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Recording the amount of titrant required to maintain constant pH in a bioreactor where cell metabolism causes acidity changes allows on-line determinations of growth kinetics in computer-controlled batch cultures. A system for making such measurements is described and its performance is investigated. Transient bicarbonate accumulation occurs if the culture produces CO2 at high pH values and low gas transfer rates. We have developed a mathematical model for the titrant requirement as a function of the cell growth rate, the gas transfer properties of the bioreactor and the culture pH. According to this model, bicarbonate accumulation affects the stoichiometry between titrant and biomass but does not prevent determination of growth rate constants. These predictions are confirmed using model experiments and measurements during batch growth of microbial cultures.