• Applied Biological Chemistry
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• v.38 no.1
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• pp.13-19
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• 1995

In order to produce phenylalanine without tyrosine co-production, we constructed various temperature-controllable expression vectors by insertion of lower expression of the tyrA gene into the plasmid pSY130-14. And tyrosine revertant to cultivate without addition of tyrosine, was selected from Escherichia coli strain AT2471[tyrA , thi ] by spontaneous mutation. The strain AT2471 harbouring plasmid pSY146A and the tyrosine revertant 5 harbouring plasmid pSY111-14 produced 12 g/l and 15 g/l of phenylalanine respectively in a 2.5 l jar fermenter at a constant temperature of $39^{\circ}C$ after 55 hours cultivation.

• Microbiology and Biotechnology Letters
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• v.19 no.5
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• pp.433-438
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• 1991

The plasmid pSY130-14 for the high production of phenylalanine is a temperaturecontrollable expression vector composed of the $P_R$ and the $P_L$ promoter and a temperature sensitive repressor, $cI_{857}$ of bacteriophage lambda. Strain AT2471 harbouring plasmid pSY13O- 14 is induced the phenylalanine production by shifting up the incubation temperaure to $38.5^{\circ}C$. Plasmid stability of E. coli AT2471 harbouring pSY130-14 was very low, it was about 30% after 48 h cultivation at $38.5^{\circ}C$ without kanamycin. The plasmid disappeared immediately at $40^{\circ}C$ without kanamycin, and at $40^{\circ}C$ adding kanamycin, the plasmid stability decreased at the beginning, but rose with the extension of the culture time. For the improvement of plasmid stability, the plasmid obtaind was designated as pSY15O-1 by changing origin region (ori) pACYC 177 of pSY130-14 for ori pSC101. E. coli AT2471 harbouring pSY150-1 was stable at $38.5^{\circ}C$ without tetracycline, and the plasrnid stability was about 40% after 48 h cultivation at $40^{\circ}C$.