Theory of pH-stat titration.

Innovative techniques are being studied to assess the activity of bioreactors and to improve the performance and operational stability of biological processes. Among these techniques, the pH-stat titration is applicable to any bioreaction involving pH variations. Up to now, the main application of the pH-stat titration has been for nitrification monitoring. In this article, we present a theoretical model of pH-stat titration, which predicts the response to any reaction involving the production or consumption of protons, hydroxyl ions, or inorganic carbon chemical species (CO(2), HCO(3)(-), CO(3)(=)). This model is a useful tool to understand pH-stat titrations, to define their applicability and limits, and to select the best experimental conditions for specific applications. Tests have been performed to compare experimental pH-stat titration rates in the presence of carbon dioxide and HCO(3)(-) producing reactions to the values predicted by the model and a very satisfying correspondence was found. Copyright 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 28-37, 2003.