The Formation of I-malic Acid as a Product of Alcoholic Fermentation by Yeast

The occurrence of malic acid in fermented products derived from various fruit juices is common knowledge and it has been generally supposed that this substance was exclusively derived from malic acid preformed in the fruit. The object of the following communication is to establish the fact that I-malic acid is a true product of fermentation by yeast and that significant amounts of the acid are formed when pure yeast cultures ferment pure sugar solutions. Experiments are also recorded in which an endeavor is made to ascertain the origin of the malic acid and also to determine some of the conditions affecting its production. The experiments were originally undertaken with t,he object of obtaining additional evidence as to the structure and stcreochemical configuration of the amino acid isolated from various proteins and regarded as fl-hydroxyglutamic acid (1). It was thought that in view of the well established formation of succinic acid from glutamic acid that P-hydroxyglutamic acid might by analogy furnish malic acid.