Über die Vergärung der Brenztraubensäure. (Hefegärungen vom biologischen Standpunkt aus betrachtet. III.

Abstract

Since pyro-racemic acid is toxic in concentrations of 0.5%, if the Neuberg theory of fermentation is accepted the acid either cannot accumulate or it must be changed to an inactive form. Experiments with yeast show that in the presence of Na2HPO4, which acts as a buffer, yeast can ferment pyroracemic acid vigorously. At the end of 5 hrs. all the yeast cells were dead in the unbuffered solution of pyroracemic acid; in the buffered solution 58% remained alive. In the unbuffered glucose solution only 3% of the cells were dead. When lysine dichloride and glycocoll were used as buffers, only 6 and 18%, respectively, of the cells were dead at the end of 5 hrs. Which intermediate product poisons the yeast cell in accordance with the Neuberg formulas is still unknown.