Phenomenological theory of substrate-induced acidification with application to Candida utilis dissimilating ethanol.

The mathematical theory of substrate-induced acidification by microorganisms was based on special formulation of mass and charge conservation laws for distinct species. The strength of the theory was tested on the ethanol-induced acidification by Candida utilis in pure water and in phthalate buffer. We showed that the theory may be used to approximate, extrapolate and predict the course of apparent acidification including the effects of buffering capacity of the broth. It makes it possible to formulate mathematical models that are suitable for process simulation and computer control of bioreactors when pH is used as a state variable.