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| Construction of Genetic Engineering Strains for L-threonine Production by Red Recombination |
1.College of Biotechnology, Tianjin University of Science & Technology, Tianjin 300457, China
2.Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China |
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Abstract The threonine genetic engineering strains were constructed by a strategy of cut off branch metabolic pathways and overexpression thr operon in E.coli ITHR. The metA and ilvA genes were knocked out by Red-recombination systems and E.coli ITHR△metA、ITHR△ilvA and ITHR△metA△ilvA were constructed respectively. The pWYE065 containing thr operon were transformed into three mutant strains by electroporation. Red-batch cultures of genetic engineering strains were carried out in 5 L fermentors and the threonine concentration was determined by HPLC. The results showed that E.coli ITHR carrying pWYE065 could accumulated 5.55±0.51 g/L threonine. When metA and ilvA were knocked out respectively, the threonine productions reached 9.77±1.83 g/L and 8.65±1.42 g/L. Both metA and ilvA were knocked out simultaneously, the L-threonine production were increased to 13.6±1.14 g/L. The productivity of L-threonine by E.coli ITHR can be enhanced through the knocking out the gene of the key enzymes in branch metabolic pathways, including the methionine and isoleucine synthesis pathway.
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Received: 23 September 2009
Published: 25 March 2010
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Corresponding Authors:
Tingyi Wen
E-mail: wenty@im.ac.cn
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