Production of aspartic and malic acids

Aspartic acid is produced on an industrial scale in Japan using non-viable immobilized cells of E. coli and ammonium fumarate as substrate of die one-step reaction  

Immobilized cells of E. coli also produce malic acid in the following 

In general, endogenous metabolism of anaerobic bacteria was found to be more stable, when biocatalysts based on immobilized cells of P. shermanii and E. coli were compared with respect to the reactions shown above (Ikonnikov, 1985). P. shermanii had a higher aspartase activity than P. pentosaceum, P. petersonii and P. technicum (Kalda and Vorobjeva, 1981). After 3 days of incubation with continuous stirring at 37°C and pH 8.5, the extent of substrate conversion (ammonium fumarate) was 95-96% and 75-90% in the case of E. coli K-12 and P. shermanii, respectively. In addition to aspartic acid, the reaction mixtures of the two strains also contained malic acid. Heat treatment of the biomass of P. shermanii (50 C, 1.5 h, pH 5.0) resulted in a complete inactivation of fumarase, while the activity of aspartase was retained (Kalda and Vorobjeva, 1980, 1981). As a result of the elimination of fumarase activity, the yield of L-aspartic acid from ammonium fumarate was increased up to 96-98% the incubation time was also shortened since no substrate was diverted to the side reaction forming malate. 

Preparations of P. shermanii showed a number of advantages over E. coli as biocatalyst, being more stable (Kalda, 1984), not requiring aeration, and producing more biomass in a cheaper medium. Living cells of P. shermanii can also be used for malic acid production. The yield of malic acid in 5 days 

L-aspartic acid is used in pharmaceutical and food industries, and malic acid is used in food industry as a substitute for citric acid. The cells of P. shermanii immobilized in PAAG can be recommended for the production of L-aspartic acid with an expected cost reduction of 25%. 

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