The proton extrusion of growing yeast cultures as an on‐line parameter in fermentation processes: Ammonia assimilation and proton extrusion are correlated by an 1:1 stoichiometry in nitrogen‐limited fed‐batch fermentations

Abstract

AbstractIn preceding papers (HUTH et al. 1990a, b) the proton extrusion nH+ of growing yeast cultures was shown to be an exact and reliable on‐line parameter for the description of biomass production and consumption of the nitrogen (NH4+) and carbon sources quantitatively in batch and fed‐batch fermentation processes.In the present paper we demonstrate that the biochemical basis of this proton extrusion must be connected with the nitrogen metabolism of growing yeasts: A strong acidification was found only during growth on NH4+ as the source of nitrogen, while the pH‐course was different for other substrates. Using NH4+limited fed‐batch conditions we detected an NH4+/H+ exchange ratio of exactly 1.0.The usefulness of the proton extrusion as an on‐line parameter in fermentation control and its range of application are discussed.