Breeding of Phenylalanine-producing Brevibacterium flavum Strains by Removing Feedback Regulation of Both the Two Key Enzymes in Its Biosynthesis |
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Authors: | Isamu Shiio Shin-ichi Sugimoto Kazue Kawamura |
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Institution: | Central Research Laboratories, Ajinomoto Co., Inc., Kawasaki-ku, Kawasaki, Kanagawa 210, Japan |
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Abstract: | The growth of a mFP-resistant Brevibacterium flavum mutant, No. 221-43, having PDTR was synergistically and completely inhibited by mFP plus Tyr-Glu, but not by mFP plus tyrosine or pFP plus Tyr-Glu, whereas that of a mutant having was only partially inhibited by mFP plus Tyr-Glu. Tyr-Glu could replace tyrosine required for the growth of a tyrosine auxotroph. The phenylalanine uptake was competitively inhibited by tyrosine and the tyrosine uptake by phenylalanine. The phenylalanine uptake was also inhibited by mFP, but not by Tyr-Glu. Mutants having both PDTR and DSR derived from strain No. 221-43 were effectively selected by the resistance to mFP plus Tyr-Glu, and produced much larger amounts of phenylalanine, with small amounts of tyrosine, than the parent. By the same method, mutants having DSR and PDTR, which produced 23.4 g/l of phenylalanine at maximum, were obtained from a pFP-resistant tyrosine auxotroph having PDTR which produced 18 g/l. Similar mutants were also obtained from a tryptophan-producing strain, but produced smaller amounts of tryptophan than the parent, whereas the total amounts of tryptophan and phenylalanine produced were increased. |
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