Characterization of salt-tolerant mutant for enhancement of l-threonine production in Escherichia coli |
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Authors: | K.-H. Song H.-H. Lee H.-H. Hyun |
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Affiliation: | (1) Department of Bioscience and Biotechnology, Hankuk University of Foreign Studies, Youngin, Kyungki-Do 449-791, Korea e-mail: hhhyun@san.hufs.ac.kr Tel.:+82-335-3304279 Fax:+82-335-3331696, KR |
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Abstract: | Escherichia coli strain HS3, metabolically engineered to have Met–, AHVr, IleL and AECr characteristics, produced 58.0 g/l of l-threonine, but it was neither salt-tolerant nor osmotolerant; and the growth and threonine production of the strain were severely inhibited both by the addition of NaCl with a concentration higher than 2% and by the presence of glucose with a concentration higher than 10%. Therefore, salt-tolerant mutants were isolated. The salt-tolerant mutants, HS454 and HS528 which were derived from strain HS3, were both tolerant to salt (2%) and hyperproductive. The growth and l-threonine production by the mutant strain HS454 were almost unaffected by a glucose concentration lower than 10%, but gradually reduced with increasing glucose concentration, up to 15%. However, the mutant strain HS528 showed slightly enhanced growth and l-threonine production with increasing glucose concentration, up to 10–12.5%. Strains HS454 and HS528 produced 69.8 g/l and 74.0 g/l of l-threonine, respectively in a 5-l jar fermentor. Received: 21 January 2000 / Received revision: 31 March 2000 / Accepted: 5 May 2000 |
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