Citric acid accumulation by cycloheximide-sensitive mutant strains of Aspergillus niger |
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Authors: | S Rugsaseel K Kirimura S Usami |
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Institution: | (1) Department of Applied Chemistry, School of Science and Engineering, Waseda University, Ohkubo 3-4-1, Shinjuku-ku, Tokyo 169, Japan. Fax: +81 3 3232 3889, JP |
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Abstract: | Mutants having impaired protein synthesis, that is cycloheximide-sensitive mutants of a citric-acid-hyper-accumulating strain,
were induced from Aspergillus niger WU-2223L. Selection was on the basis of a presumption that the mutants should be more sensitive to cycloheximide than WU-2223L.
In shake culture without methanol as a promotor substance, seven mutants accumulated approximately 1.8–3.5 times as much citric
acid as WU-2223L. The best mutant, CHM I-C3, accumulated 69.4 mg citric acid/ml from 120 mg glucose/ml in shake culture without
methanol, this amount being 1.1 times the amount accumulated by WU-2223L with methanol. Furthermore, under the conditions
without methanol the mutants appeared to be more efficient than WU-2223L in employing the consumed glucose for the accumulation
of citric acid. It was also confirmed that CHM I-C3 exhibited a significantly increased level of intracellular NH+
4 accumulation. The addition of 2% (v/v) methanol or 20 μg cycloheximide/ml to the medium caused a remarkable increase of citric
acid accumulation by WU-2223L: about 3.1 and 2.4 times respectively. However, the addition of these substances produced negative
effects on citric acid accumulation by the mutants. With 2% (v/v) methanol, WU-2223L showed a remarkably decreased level of
protein accumulation but a substantially increased level of intracellular NH+
4 accumulation. However, these phenomena were also observed in CHM I-C3 without methanol. These results indicate that the intracellular
circumstances of the cycloheximide-sensitive mutants without methanol were similar to those of WU-2223L with methanol, and
that the impairment of protein synthesis contributed to increased citric acid accumulation by the mutants in the absence of
methanol.
Received: 21 November 1994 / Received last revision: 10 July 1995 / Accepted: 26 July 1995 |
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