Redirecting reductant flux into hydrogen production via metabolic engineering of fermentative carbon metabolism in a cyanobacterium

Kelsey McNeely, Yu Xu, Nick Bennette, Donald A. Bryant, G Charles Dismukes

Research output: Contribution to journalArticle

100 Citations (Scopus)

Abstract

Some aquatic microbial oxygenic photoautotrophs (AMOPs) make hydrogen (H2), a carbon-neutral, renewable product derived from water, in low yields during autofermentation (anaerobic metabolism) of intracellular carbohydrates previously stored during aerobic photosynthesis. We have constructed a mutant (the IdhA mutant) of the cyanobacterium Synechococcus sp. strain PCC 7002 lacking the enzyme for the NADH-dependent reduction of pyruvate to D-lactate, the major fermentative reductant sink in this AMOP. Both nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS) metabolomic methods have shown that autofermentation by the IdhA mutant resulted in no D-lactate production and higher concentrations of excreted acetate, alanine, succinate, and hydrogen (up to 5-fold) compared to that by the wild type. The measured intracellular NAD(P)(H) concentrations demonstrated that the NAD (P)H/NAD (P)+ ratio increased appreciably during autofermentation in the IdhA strain; we propose this to be the principal source of the observed increase in H2 production via an NADH-dependent, bidirectional [NiFe] hydrogenase. Despite the elevated NAD(P)H/NAD(P)+ ratio, no decrease was found in the rate of anaerobic conversion of stored carbohydrates. The measured energy conversion efficiency (ECE) from biomass (as glucose equivalents) converted to hydrogen in the IdhA mutant is 12%. Together with the unimpaired photoautotrophic growth of the IdhA mutant, these attributes reveal that metabolic engineering is an effective strategy to enhance H2 production in AMOPs without compromising viability.

Original languageEnglish
Pages (from-to)5032-5038
Number of pages7
JournalApplied and Environmental Microbiology
Volume76
Issue number15
DOIs
Publication statusPublished - Aug 2010

Fingerprint

Metabolic Engineering
hydrogen production
metabolic engineering
reducing agents
Reducing Agents
Cyanobacteria
NAD
cyanobacterium
Hydrogen
Carbon
metabolism
hydrogen
autotrophs
engineering
mutants
carbon
lactates
carbohydrate
ferredoxin hydrogenase
carbohydrates

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Food Science
  • Biotechnology
  • Ecology
  • Medicine(all)

Cite this

Redirecting reductant flux into hydrogen production via metabolic engineering of fermentative carbon metabolism in a cyanobacterium. / McNeely, Kelsey; Xu, Yu; Bennette, Nick; Bryant, Donald A.; Dismukes, G Charles.

In: Applied and Environmental Microbiology, Vol. 76, No. 15, 08.2010, p. 5032-5038.

Research output: Contribution to journalArticle

@article{683b5ef8a0494f6fbf6c82e2cdaa9754,
title = "Redirecting reductant flux into hydrogen production via metabolic engineering of fermentative carbon metabolism in a cyanobacterium",
abstract = "Some aquatic microbial oxygenic photoautotrophs (AMOPs) make hydrogen (H2), a carbon-neutral, renewable product derived from water, in low yields during autofermentation (anaerobic metabolism) of intracellular carbohydrates previously stored during aerobic photosynthesis. We have constructed a mutant (the IdhA mutant) of the cyanobacterium Synechococcus sp. strain PCC 7002 lacking the enzyme for the NADH-dependent reduction of pyruvate to D-lactate, the major fermentative reductant sink in this AMOP. Both nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS) metabolomic methods have shown that autofermentation by the IdhA mutant resulted in no D-lactate production and higher concentrations of excreted acetate, alanine, succinate, and hydrogen (up to 5-fold) compared to that by the wild type. The measured intracellular NAD(P)(H) concentrations demonstrated that the NAD (P)H/NAD (P)+ ratio increased appreciably during autofermentation in the IdhA strain; we propose this to be the principal source of the observed increase in H2 production via an NADH-dependent, bidirectional [NiFe] hydrogenase. Despite the elevated NAD(P)H/NAD(P)+ ratio, no decrease was found in the rate of anaerobic conversion of stored carbohydrates. The measured energy conversion efficiency (ECE) from biomass (as glucose equivalents) converted to hydrogen in the IdhA mutant is 12{\%}. Together with the unimpaired photoautotrophic growth of the IdhA mutant, these attributes reveal that metabolic engineering is an effective strategy to enhance H2 production in AMOPs without compromising viability.",
author = "Kelsey McNeely and Yu Xu and Nick Bennette and Bryant, {Donald A.} and Dismukes, {G Charles}",
year = "2010",
month = "8",
doi = "10.1128/AEM.00862-10",
language = "English",
volume = "76",
pages = "5032--5038",
journal = "Applied and Environmental Microbiology",
issn = "0099-2240",
publisher = "American Society for Microbiology",
number = "15",

}

TY - JOUR

T1 - Redirecting reductant flux into hydrogen production via metabolic engineering of fermentative carbon metabolism in a cyanobacterium

AU - McNeely, Kelsey

AU - Xu, Yu

AU - Bennette, Nick

AU - Bryant, Donald A.

AU - Dismukes, G Charles

PY - 2010/8

Y1 - 2010/8

N2 - Some aquatic microbial oxygenic photoautotrophs (AMOPs) make hydrogen (H2), a carbon-neutral, renewable product derived from water, in low yields during autofermentation (anaerobic metabolism) of intracellular carbohydrates previously stored during aerobic photosynthesis. We have constructed a mutant (the IdhA mutant) of the cyanobacterium Synechococcus sp. strain PCC 7002 lacking the enzyme for the NADH-dependent reduction of pyruvate to D-lactate, the major fermentative reductant sink in this AMOP. Both nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS) metabolomic methods have shown that autofermentation by the IdhA mutant resulted in no D-lactate production and higher concentrations of excreted acetate, alanine, succinate, and hydrogen (up to 5-fold) compared to that by the wild type. The measured intracellular NAD(P)(H) concentrations demonstrated that the NAD (P)H/NAD (P)+ ratio increased appreciably during autofermentation in the IdhA strain; we propose this to be the principal source of the observed increase in H2 production via an NADH-dependent, bidirectional [NiFe] hydrogenase. Despite the elevated NAD(P)H/NAD(P)+ ratio, no decrease was found in the rate of anaerobic conversion of stored carbohydrates. The measured energy conversion efficiency (ECE) from biomass (as glucose equivalents) converted to hydrogen in the IdhA mutant is 12%. Together with the unimpaired photoautotrophic growth of the IdhA mutant, these attributes reveal that metabolic engineering is an effective strategy to enhance H2 production in AMOPs without compromising viability.

AB - Some aquatic microbial oxygenic photoautotrophs (AMOPs) make hydrogen (H2), a carbon-neutral, renewable product derived from water, in low yields during autofermentation (anaerobic metabolism) of intracellular carbohydrates previously stored during aerobic photosynthesis. We have constructed a mutant (the IdhA mutant) of the cyanobacterium Synechococcus sp. strain PCC 7002 lacking the enzyme for the NADH-dependent reduction of pyruvate to D-lactate, the major fermentative reductant sink in this AMOP. Both nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS) metabolomic methods have shown that autofermentation by the IdhA mutant resulted in no D-lactate production and higher concentrations of excreted acetate, alanine, succinate, and hydrogen (up to 5-fold) compared to that by the wild type. The measured intracellular NAD(P)(H) concentrations demonstrated that the NAD (P)H/NAD (P)+ ratio increased appreciably during autofermentation in the IdhA strain; we propose this to be the principal source of the observed increase in H2 production via an NADH-dependent, bidirectional [NiFe] hydrogenase. Despite the elevated NAD(P)H/NAD(P)+ ratio, no decrease was found in the rate of anaerobic conversion of stored carbohydrates. The measured energy conversion efficiency (ECE) from biomass (as glucose equivalents) converted to hydrogen in the IdhA mutant is 12%. Together with the unimpaired photoautotrophic growth of the IdhA mutant, these attributes reveal that metabolic engineering is an effective strategy to enhance H2 production in AMOPs without compromising viability.

UR - http://www.scopus.com/inward/record.url?scp=77955572487&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77955572487&partnerID=8YFLogxK

U2 - 10.1128/AEM.00862-10

DO - 10.1128/AEM.00862-10

M3 - Article

C2 - 20543051

AN - SCOPUS:77955572487

VL - 76

SP - 5032

EP - 5038

JO - Applied and Environmental Microbiology

JF - Applied and Environmental Microbiology

SN - 0099-2240

IS - 15

ER -