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Wei Sheng Wu Xue Bao. 2009 May;49(5):591-6.

[Construction of recombinant plasmids containing threonine operon and their effects on L-threonine accumulation].

[Article in Chinese]

Author information

1
College of Biological Engineering, Tianjin University of Science & Technology, Tianjin 300457, China. meixiabe@yahoo.com.cn

Abstract

OBJECTIVE:

We reconstructed two recombinant plasmids and studied their effects on L-threonine accumulation of Escherichia coli W3110.

METHODS:

We amplified the threonine operon containing ThrLp promoter, lead peptide thrL, thrA, thrB and thrC genes by PCR from E. coli W3110 chromosome and ligated it into the pMD19 T-vector. Site-directed mutation were carried out by gene splicing by overlap extension PCR to release the feedback inhibition of aspartokinase I (thrA). Two recombinant plasmids pWYE112 and pWYE134 were transformed into E. coli W3110 by electroporation. Fed-batch cultures of E. coli W3110 were carried out in 5-Liter fermentors and the L-threonine concentration was measured by HPLC.

RESULTS:

Fed-batch fermentation results showed that E. coli W3110 could accumulate little L-threonine (0.036 +/- 0.004 g/L) but recombinant E. coli W3110 harboring the plasmid pWYE112 containing a threonine operon exhibited a L-threonine production of 2.590 +/- 0.115 g/L. Furthermore, L-threonine production reached 9.223 +/- 1.279 g/L when the feedback inhibition of thrA was released.

CONCLUSION:

Overexpression of threonine operon can lead to the accumulation of L-threonine. Further release of feedback inhibition of aspartokinase I can enhance its accumulation.

PMID:
19637565
[Indexed for MEDLINE]

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