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KMID : 0613820040140050868
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Journal of Life Science
2004 Volume.14 No. 5 p.868 ~ p.873
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Hyperproduction of L-Threonine by Adding Sodium Citrate as Carbon Source in Transformed Escherichia coli Mutant
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Lee Man-Hyo
Kim Byung-Jin
Jeong Weol-Kyu
Choi Sun-Uk
Park Hae-Ryong
Hwang Yong-Il
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Abstract
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The efficient fermentative production of L-threonine fermentation was achieved by using Escherichia coli MT201, transformed a plasmid carrying pyruvate carboxylase gene. It is an attempt to supply oxaloacetate to the L-threonine biosynthetic pathway. In order to improve the L-threonine productivity of E. coli MT201, a plasmid pPYC which is an expression vector of the pyruvate carboxylase gene of Corynebacterium glutamicum, was introduced. When E. coli MT/pPYC was incubated with medium containing only glucose as a carbon source, both the cell growth and L-threonine production were reduced, compared to the results from fermentation of E. coli MT201. In order to circumvent this effect, we attempted the addition of a mixed carbon source, composed of glucose and sodium citrate at a ratio of 1.5:3.5. It was shown that L-threonine production and cell growth (OD660) with E. coli MT/pPYC reached up to 75.7 g/l and 48, respectively, at incubation for 75 hr under fed-batch fermentation conditions. It is assumed that overproduction of L-threonine by anaplerotic pathway leads unbalance of TCA cycle and sodium citrate might play a role to recover normal TCA cycle.
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KEYWORD
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Escherichia coli MT201, L-threonine, E. coli MT/pPYC, sodium citrate
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