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Ethanol synthesis from glycerol by Escherichia coli redox mutants expressing adhE from Leuconostoc mesenteroides.

Abstract：

AIMS:Analysis of the physiology and metabolism of Escherichia coli arcA and creC mutants expressing a bifunctional alcohol-acetaldehyde dehydrogenase from Leuconostoc mesenteroides growing on glycerol under oxygen-restricted conditions. The effect of an ldhA mutation and different growth medium modifications was also assessed. METHODS AND RESULTS:Expression of adhE in E. coli CT1061 [arcA creC(Con)] resulted in a 1.4-fold enhancement in ethanol synthesis. Significant amounts of lactate were produced during micro-oxic cultures and strain CT1061LE, in which fermentative lactate dehydrogenase was deleted, produced up to 6.5 +/- 0.3 g l(-1) ethanol in 48 h. Escherichia coli CT1061LE derivatives resistant to >25 g l(-1) ethanol were obtained by metabolic evolution. Pyruvate and acetaldehyde addition significantly increased both biomass and ethanol concentrations, probably by overcoming acetyl-coenzyme A (CoA) shortage. Yeast extract also promoted growth and ethanol synthesis, and this positive effect was mainly attributable to its vitamin content. Two-stage bioreactor cultures were conducted in a minimal medium containing 100 microg l(-1) calcium d-pantothenate to evaluate oxic acetyl-CoA synthesis followed by a switch into fermentative conditions. Ethanol reached 15.4 +/- 0.9 g l(-1) with a volumetric productivity of 0.34 +/- 0.02 g l(-1) h(-1). CONCLUSIONS:Escherichia coli responded to adhE over-expression by funnelling carbon and reducing equivalents into a highly reduced metabolite, ethanol. Acetyl-CoA played a key role in micro-oxic ethanol synthesis and growth. SIGNIFICANCE AND IMPACT OF THE STUDY:Insight into the micro-oxic metabolism of E. coli growing on glycerol is essential for the development of efficient industrial processes for reduced biochemicals production from this substrate, with special relevance to biofuels synthesis.

journal_name

J Appl Microbiol

journal_title

Journal of applied microbiology

authors

Nikel PI,Ramirez MC,Pettinari MJ,Méndez BS,Galvagno MA

doi

10.1111/j.1365-2672.2010.04668.x

subject

Has Abstract

pub_date

2010-08-01 00:00:00

pages

492-504

issue

eissn

1364-5072

issn

1365-2672

pii

JAM4668

journal_volume

109

pub_type

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Ethanol synthesis from glycerol by Escherichia coli redox mutants expressing adhE from Leuconostoc mesenteroides.