Studies on the Fermentative Preparation of L-Aspartic Acid from Fumaric Acid

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A number of organisms were screened to test activity of accumulating aspartate from fumarate and ammonium salts and, Pseudomonas fluorescens 6009-2 and mutant Ki-1023 derived from Escherichia coli K-12 by ultraviolet radiation were chosen as the suitable strains.
By employing these strains various cultural conditions suitable for the production of L-aspartic acid were investigated and, the results obtained are as follows:
a) Ammonium fumarate is the most favorable as ammonium salts.
b) On the molar ratio of fumarate and ammonium ion in the medium, the ratio 1:1.5_??_2.0 gives the best result.
c) On the effect of pH, culture without pH adjustment starting from initial pH 7.0, is preferable for Pseudomonas fluorescens than in case of pH adjustment during incubation, while on Escherichia coli the addition of calcium carbonate results in better accumulation of aspartate.
d) The addition of glucose causes formation of amino acids other than aspartic acid and lowers the yield of aspartate.
e) On the concentration of fumarate in the medium, 5.% gives the best result.
f) Of the various organic nitrogen compounds in the medium, peptone is most favorable.
g) Of the wild strain and mutants of Escherichia coli K-12, Ki-1023 is ascertained to be the most suitable strain.
h) Incubation at 37°C accelerates formation of aspartate than incubation at 30°C, though there is no difference of the attained conversion rate.
i) On the influence of shaking, partially stationary culture, that is, after shaking at initial day stationary culture is done, enables better result than stationary or shaking culture throughout the period of incubation.
Under the optimum conditions revealed by the above experiments, practical formation of aspartate was carried out, and formation over 95% conversion rate from consumed fumarate was attained by both strains. The formed aspartate was readily isolated from the culture broth and identified as L-aspartic acid. This method is considered to be an advantageous procedure for the production of L-aspartic acid.