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KMID : 1094719990040030170
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Biotechnology and Bioprocess Engineering
1999 Volume.4 No. 3 p.170 ~ p.170
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Physiological and environmental effects on metabolic flux change caused by heterologous gene expression inEscherichia coli
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Kim Jeong-Yoon
Ryu Dewey D. Y.
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Abstract
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Expression of theZymomonas mobilis pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adh) genes inEscherichia coli has been known to reduce acetate accumulation by shifting carbon flow from acetate to ethanol. In this study, we investigated the effects of physiological and environmental conditions on the metabolic flux alteration caused by the expression of thepdc andadh genes. In the batch cultures, no significant differences, regardless of medium composition, were found in growth rate and glucose uptake rate between the host strains and the recombinant strains expressing thepdc andadh genes. In the continuous cultures performed with glucose minimal medium, however, the recombinant strains gave more biomass than the host strains at the same specific growth rates. On the contrary, in the continuous cultures with complex medium, the host strains yielded more biomass than the recombinant strains. Analysis of the culture supernatants revealed that the effect of thepdc andadh expression on byproduct formation was more significant at low specific growth rates than at high specific growth rates. This study suggests that physiological and environmental conditions should be carefully considered and precisely defined in assessing the effects of heterologous gene expression on metabolic activities of recombinantE. coli.
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KEYWORD
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E. coli, heterologous gene expression, physiological condition, metabolic flux
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