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Reassessment of hydrogen tolerance in Caldicellulosiruptor saccharolyticus

Willquist, Karin LU ; Pawar, Sudhanshu LU and van Niel, Ed LU (2011) In Microbial Cell Factories 10.
Abstract (Swedish)
Abstract in Undetermined

Background



Caldicellulosiruptor saccharolyticus has the ability to produce hydrogen (H2) at high yields from a wide spectrum of carbon sources, and has therefore gained industrial interest. For a cost-effective biohydrogen process, the ability of an organism to tolerate high partial pressures of H2 (PH2) is a critical aspect to eliminate the need for continuous stripping of the produced H2 from the bioreactor.



Results



Herein, we demonstrate that, under given conditions, growth and H2 production in C. saccharolyticus can be sustained at PH2 up to 67 kPa in a chemostat. At this PH2, 38% and 16% of the pyruvate flux was redirected to lactate... (More)
Abstract in Undetermined

Background



Caldicellulosiruptor saccharolyticus has the ability to produce hydrogen (H2) at high yields from a wide spectrum of carbon sources, and has therefore gained industrial interest. For a cost-effective biohydrogen process, the ability of an organism to tolerate high partial pressures of H2 (PH2) is a critical aspect to eliminate the need for continuous stripping of the produced H2 from the bioreactor.



Results



Herein, we demonstrate that, under given conditions, growth and H2 production in C. saccharolyticus can be sustained at PH2 up to 67 kPa in a chemostat. At this PH2, 38% and 16% of the pyruvate flux was redirected to lactate and ethanol, respectively, to maintain a relatively low cytosolic NADH/NAD ratio (0.12 mol/mol). To investigate the effect of the redox ratio on the glycolytic flux, a kinetic model describing the activity of the key glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), was developed. Indeed, at NADH/NAD ratios of 0.12 mol/mol (Ki of NADH = 0.03 ± 0.01 mM) GAPDH activity was inhibited by only 50% allowing still a high glycolytic flux (3.2 ± 0.4 mM/h). Even at high NADH/NAD ratios up to 1 mol/mol the enzyme was not completely inhibited. During batch cultivations, hydrogen tolerance of C. saccharolyticus was dependent on the growth phase of the organism as well as the carbon and energy source used. The obtained results were analyzed, based on thermodynamic and enzyme kinetic considerations, to gain insight in the mechanism underlying the unique ability of C. saccharolyticus to grow and produce H2 under relatively high PH2.



Conclusion



C. saccharolyticus is able to grow and produce hydrogen at high PH2, hence eliminating the need of gas sparging in its cultures. Under this condition, it has a unique ability to fine tune its metabolism by maintaining the glycolytic flux through regulating GAPDH activity and redistribution of pyruvate flux. Concerning the later, xylose-rich feedstock should be preferred over the sucrose-rich one for better H2 yield. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Caldicellulosiruptor saccharolyticus, biohydrogen production, hydrogen tolerance, enzyme levels, glyceraldehyde-3-phosphate dehydrogenase kinetics, redox ratio
in
Microbial Cell Factories
volume
10
publisher
BioMed Central
external identifiers
  • wos:000301576700001
  • scopus:83755187898
ISSN
1475-2859
DOI
10.1186/1475-2859-10-111
language
English
LU publication?
yes
id
ae8a8831-17b9-48c0-ae66-9a74e9a05ab3 (old id 2439062)
date added to LUP
2012-04-16 13:01:06
date last changed
2017-05-14 04:03:42
@article{ae8a8831-17b9-48c0-ae66-9a74e9a05ab3,
  abstract     = {<b>Abstract in Undetermined</b><br/><br>
Background<br/><br>
 <br/><br>
Caldicellulosiruptor saccharolyticus has the ability to produce hydrogen (H2) at high yields from a wide spectrum of carbon sources, and has therefore gained industrial interest. For a cost-effective biohydrogen process, the ability of an organism to tolerate high partial pressures of H2 (PH2) is a critical aspect to eliminate the need for continuous stripping of the produced H2 from the bioreactor.<br/><br>
 <br/><br>
Results<br/><br>
 <br/><br>
Herein, we demonstrate that, under given conditions, growth and H2 production in C. saccharolyticus can be sustained at PH2 up to 67 kPa in a chemostat. At this PH2, 38% and 16% of the pyruvate flux was redirected to lactate and ethanol, respectively, to maintain a relatively low cytosolic NADH/NAD ratio (0.12 mol/mol). To investigate the effect of the redox ratio on the glycolytic flux, a kinetic model describing the activity of the key glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), was developed. Indeed, at NADH/NAD ratios of 0.12 mol/mol (Ki of NADH = 0.03 ± 0.01 mM) GAPDH activity was inhibited by only 50% allowing still a high glycolytic flux (3.2 ± 0.4 mM/h). Even at high NADH/NAD ratios up to 1 mol/mol the enzyme was not completely inhibited. During batch cultivations, hydrogen tolerance of C. saccharolyticus was dependent on the growth phase of the organism as well as the carbon and energy source used. The obtained results were analyzed, based on thermodynamic and enzyme kinetic considerations, to gain insight in the mechanism underlying the unique ability of C. saccharolyticus to grow and produce H2 under relatively high PH2.<br/><br>
 <br/><br>
Conclusion<br/><br>
 <br/><br>
C. saccharolyticus is able to grow and produce hydrogen at high PH2, hence eliminating the need of gas sparging in its cultures. Under this condition, it has a unique ability to fine tune its metabolism by maintaining the glycolytic flux through regulating GAPDH activity and redistribution of pyruvate flux. Concerning the later, xylose-rich feedstock should be preferred over the sucrose-rich one for better H2 yield.},
  articleno    = {111},
  author       = {Willquist, Karin and Pawar, Sudhanshu and van Niel, Ed},
  issn         = {1475-2859},
  keyword      = {Caldicellulosiruptor saccharolyticus,biohydrogen production,hydrogen tolerance,enzyme levels,glyceraldehyde-3-phosphate dehydrogenase kinetics,redox ratio},
  language     = {eng},
  publisher    = {BioMed Central},
  series       = {Microbial Cell Factories},
  title        = {Reassessment of hydrogen tolerance in Caldicellulosiruptor saccharolyticus},
  url          = {http://dx.doi.org/10.1186/1475-2859-10-111},
  volume       = {10},
  year         = {2011},
}