STUDIES ON AMINO ACID FERMENTATION. PART VIII. ON THE MECHANISM OF CONVERSION OF L-GLUTAMIC ACID FERMENTAION TO SUCCINIC ACID FERMENTATION. (I)

Abstract

A L-glutamic acid-producing bacterium, Brevibacterium divaricatum nov. sp. S-1627, accumulates a large amount of succinic acid in CSL-rich or insufficiently aerated culture.
In order to obtain a good yield of succinic acid, it is desirable that CSL content is more than 1.5% in the culture medium and that aeration is insufficient so far as cells grow.
Effect of CSL is proved due to biotin content in it.
The optimal condition for the accumulation of succinic acid is also favorable to that of lactic acid and unfit for that of L-glutamic acid, and vice versa.
When the organism is cultivated in CSL-deficient culture, the resting cells oxidize acetic and lactic acids and glucose very rapidly, but oxidize C₄ dicarboxylic acids in the TCA cycle such as malic, fumaric, and succinic acids slowly, while the cells grown in CSL-rich culture have an increased activity of C₄ dicarboxylic acid oxidation.
α-Ketoglutaric acid is generally formed by the resting cells from various organic acids and glucose under fully aerated conditions, but under insufficient aeration succinic acid is formed. From fumaric and malic acids, succinic acid is formed both under fully and insufficiently aerated conditions.
Tracer experiments using the resting or growing cells show that, though a little decreased values are observed under fully aerated conditions, approximately one mole of CO₂ is incorporated into one mole of succinic acid.
The formation of succinic acid by this organism is considered to be performed through the reduction of fumaric acid, quantitatively under insufficiently aerated conditions and mainly under fully aerated ones.