Abstract
(1) With regard to the constituents of the fermentation medium, various nitrogen sources, glucose and their optimum concentrations, as well as the additive influences of various growth substances and metals, were examined.
Solely considering its worth in industrial application, urea seems to be a satisfactory nitrogen source. Its optimum concentration in the medium containing 5% of glucose was found to lie between 0.67 to 0.9%. The growth of cells should be suppressed when the initial con-centration of glucose exceeds 12.5%; therefore a level of 10% gives a better result. Data show-ed that addition of meat and bran extracts gave an increment of about 26% in acid yield.
(2) As for the fermentation condition, after experiments on the incubation temperature, pH and the influence of oxygen supply, etc., reveal that the aerobic condition is favorable for cell growth and accumulation of L-glutamic acid. An oxygen supply around 5 × 10-6 of Kd is desirable. The optimum incubation temperature was found to lie at 30°C.
A reasonable quantity of L-glutamic acid will be produced if the culture is kept neutral or preferably slightly alkaline by feeding a proper amount of urea aqueous solution throughout in-cubation.
(3) As a conclusion of the above experimental results, the yield of L-glutamic acid reached 45%, on basis of glucose supplied after 30 hours' in-cubation.
(4) By-products such as alanine, α-ketoglutaric acid, pyruvic acid and succinic acid were found at the same time, in the fermentation of L-glu-tamic acid employing Brevibactcrium divaricatum nov. sp.
By observing the time of formation, the kind and the amount of these by-products it was presumed that the L-glutamic acid formation with this strain most probably proceeds from glucose to pyruvic acid, and then to α-ketoglu-taric acid via Krebs TCA Cycle. L-Guutamic acid could be considered to be formed from α-keto-glutaric acid. The reductive amination reaction of α-ketoglutaric acid is assumed to be the main pathway of L-glutamic acid synthesis.
