Hyperproduction of L-Threonine by an Escherichia coli Mutant with Impaired L-Threonine Uptake.

• OKAMOTO Kazuyuki

• KINO Kuniki

• IKEDA Masato

Bibliographic Information

Other Title

• Hyperproduction of L-Threonine by an Es
• Hyperproduction of<scp>L</scp>-Threonine by an<i>Escherichia coli</i>Mutant with Impaired<scp>L</scp>-Threonine Uptake

Abstract

An efficient production strain for L-threonine fermentation was derived from Escherichia coli by multiple rounds of mutation programs that aimed at deregulation of the L-threonine biosynthetic pathway and blocking of L-threonine degradation pathways. When the optimum amount of DL-methionine was added, this strain KY10935, an L-methionine auxotroph, gave 100 g/liter L-threonine after 77 h cultivation. In this strain, key enzymes in the L-threonine biosynthetic pathway were highly derepressed, but some were inhibited by lower concentrations of L-threonine than the accumulated level. Such incomplete deregulation of the pathway was accounted for by the intracellular concentration of L-threonine being lower than the extracellular level. In an assessment of L-threonine transport in terms of phenotypic growth responses to the amino acid, L-threonine-auxotrophic mutanis with a lesion in the L-threonine operon were derived from strain KY10935 by selection for auxotrophy for dipeptide L-alanyl-L-threonine or glycyl-L-threonine, the transport systems of which were different from those of L-threonine. All three independent mutants isolated needed an extraordinarily high concentration (10mg/ml) of L-threonine, but grew in the presence of a low concentration (10μg/ml) of either dipeptide, indicating that strain KY10935 had impaired L-threonine uptake. These results suggested that the strain had an unusual mechanism of L-threonine hyperproduction: the inability to take up L-threonine that had accumulated extracellularly decreased the steady-state level of intracellular L-threonine, freeing the remaining regulatory steps of feedback inhibition.

Journal

• Bioscience, Biotechnology, and Biochemistry

  Bioscience, Biotechnology, and Biochemistry 61 (11), 1877-1882, 1997

  Japan Society for Bioscience, Biotechnology, and Agrochemistry

Keywords

• threonine production
• transport mutant of Escherichia coli
• threonine uptake
• strain improvement

Details

• CRID: 1390282681452745216
• NII Article ID: 110002678836
• NII Book ID: AA10824164
• DOI: 10.1271/bbb.61.1877
• ISSN: 13476947
• ISSN: 09168451
• NDL BIB ID: 4357348
• PubMed: 9404067
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I4357348
• Web Site: http://www.tandfonline.com/doi/pdf/10.1271/bbb.61.1877
• Text Lang: en
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • PubMed
  • CiNii Articles
• Abstract License Flag: Disallowed