Improvement of production of l-aspartic acid using immobilized microbial cells
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In our laboratory, EAPc-7 a strain having higher aspartase activity was derived from Escherichia coli ATCC 11303. For the improvement of l-aspartic acid productivity using EAPc-7 cells immobilized in χ-carrageenan, it was necessary to eliminate the fumarase activity which converts fumaric acid to l-malic acid. Several treatments for specifically eliminating fumarase activity from EAPc-7 cells were tested and it was found that when EAPc-7 cells were treated in a culture broth (pH 4.9) containing 50 mM l-aspartic acid at 45° C for 1 h, fumarase activity was almost completely eliminated without inactivation of the aspartase.
The treated cells, immobilized in χ-carrageenan, were used for continuous production of l-aspartic acid from ammonium fumarate. The formation of l-malic acid was negligible and the half-life of the immobilized preparation was 126 days.
Productivity of immobilized preparation of treated EAPc-7 cells in l-aspartic acid production was six times of that of the parent cell preparation.
KeywordsAmmonium Escherichia Coli Acid Production Culture Broth Fumarate
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