© 1993KluwerAcademicPublishers. Printedin the Netherlands.
Kinetics of growth and sugar consumption in yeasts
J ohannes R van Dijken, Ruud A. Weusthuis & Jack T. Pronk
D epartment of Microbiology and Enzymology, Kluyver Laboratory of Biotechnology, Julianalaan 67,
2628 BC Delft, The Netherlands
K ey words: a lcoholic fermentation, chemostat culture, Crabtree effect, respiration,
Saccharornyces cerevisiae, y easts
A bstract
A n overview is presented of the steady- and transient state kinetics of growth and formation of metabolic b yproducts in yeasts. Saccharomyces cerevisiae is strongly inclined to perform alcoholic fermentation. Even u nder fully aerobic conditions, ethanol is produced by this yeast when sugars are present in excess. This s o-called 'Crabtree effect' probably results from a multiplicity of factors, including the mode of sugar transp ort and the regulation of enzyme activities involved in respiration and alcoholic fermentation. The Crabtree e ffect in S. cerevisiae is not caused by an intrinsic inability to adjust its respiratory activity to high glycolytic fluxes. Under certain cultivation conditions, for example during growth in the presence of weak organic acids, v ery high respiration rates can be achieved by this yeast. S. cerevisiae is an exceptional yeast since, in contrast t o most other species that are able to perform alcoholic fermentation, it can grow under strictly anaerobic c onditions.
' Non-Saccharomyces' y easts require a growth-limiting supply of oxygen (i.e. oxygen-limited growth condit ions) to trigger alcoholic fermentation. However, complete absence of oxygen results in cessation of growth a nd therefore, ultimately, of alcoholic fermentation. Since it is very difficult to reproducibly achieve the right o xygen dosage in large-scale fermentations, non-Saccharornyces y easts are therefore not suitable for larges cale alcoholic fermentation of sugar-containing