Abstract.
In previous studies, we showed that cofactor manipulations can potentially be used as a tool in metabolic engineering. In this study, sugars similar to glucose, that can feed into glycolysis and pyruvate production, but with different oxidation states, were used as substrates. This provided a simple way of testing the effect of manipulating the NADH/NAD+ ratio or the availability of NADH on the metabolic patterns of Escherichia coli under anaerobic conditions and on the production of 1,2-propanediol (1,2-PD), which requires NADH for its synthesis. Production of 1,2-PD was achieved by overexpressing the two enzymes methylglyoxal synthase from Clostridium acetobutylicum and glycerol dehydrogenase from E. coli. In addition, the effect of eliminating a pathway competing for NADH by using a ldh – strain (without lactate dehydrogenase activity) on the production of 1,2-PD was investigated. The oxidation state of the carbon source significantly affected the yield of metabolites, such as ethanol, acetate and lactate. However, feeding a more reduced carbon source did not increase the yield of 1,2-PD. The production of 1,2-PD with glucose as the carbon source was improved by the incorporation of a ldh – mutation. The results of these experiments indicate that our current 1,2-PD production system is not limited by NADH, but rather by the pathways following the formation of methylglyoxal.
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Berríos-Rivera, S.J., San, KY. & Bennett, G.N. The effect of carbon sources and lactate dehydrogenase deletion on 1,2-propanediol production in Escherichia coli . J IND MICROBIOL BIOTECHNOL 30, 34–40 (2003). https://doi.org/10.1007/s10295-002-0006-0
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DOI: https://doi.org/10.1007/s10295-002-0006-0