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Aerobic expression of Vitreoscilla hemoglobin efficiently reduces overflow metabolism in Escherichia coli
Author(s) -
Pablos Tania E.,
Sigala Juan Carlos,
Le Borgne Sylvie,
Lara Alvaro R.
Publication year - 2014
Publication title -
biotechnology journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.144
H-Index - 84
eISSN - 1860-7314
pISSN - 1860-6768
DOI - 10.1002/biot.201300388
Subject(s) - metabolism , escherichia coli , citric acid cycle , biochemistry , hemoglobin , biology , yield (engineering) , mutant , chemistry , gene , materials science , metallurgy
Overflow metabolism is a prevalent problem for aerobic cultivations of Escherichia coli. Although several process and molecular approaches have been applied to prevent overflow metabolism, these approaches often result in reductions in growth rate, biomass yield or accumulation of other byproducts. In this report, we present an alternative approach based on increasing the efficiency of aerobic metabolism by the expression of the Vitreoscilla stercoraria hemoglobin (VHb) to avoid overflow metabolism. VHb is expected to increase the consumption of NADH in the respiratory chain, leading to increased activity of the tricarboxylic acid (TCA) cycle. This would result in a faster consumption of acetyl Co‐A and a decrease in acetate production. When this strategy was tested in E. coli strains, acetate production decreased by 50% in MG1655 and more than 90% in W3110, without affecting growth rates or biomass yields. VHb expression in mutant strains with higher TCA activity and reduced acetate formation resulted in a significant increase in growth and glucose consumption rates, whereas acetate production did not increase. The results presented here show that enhancing the efficiency of aerobic metabolism is a valuable approach to avoid overflow metabolism in E. coli and to attain high cell densities in batch mode.