Advanced

Dynamic metabolomics differentiates between carbon and energy starvation in recombinant Saccharomyces cerevisiae fermenting xylose

Bergdahl, Basti LU ; Heer, Dominik; Sauer, Uwe; Hahn-Hägerdal, Bärbel LU and van Niel, Ed LU (2012) In Biotechnology for Biofuels 5:34.
Abstract
Background: The concerted effects of changes in gene expression due to changes in the environment are

ultimately reflected in the metabolome. Dynamics of metabolite concentrations under a certain condition can

therefore give a description of the cellular state with a high degree of functional information. We used this

potential to evaluate the metabolic status of two recombinant strains of Saccharomyces cerevisiae during

anaerobic batch fermentation of a glucose/xylose mixture. Two isogenic strains were studied, differing only in

the pathways used for xylose assimilation: the oxidoreductive pathway with xylose reductase (XR) and xylitol

dehydrogenase (XDH) or the isomerization pathway... (More)
Background: The concerted effects of changes in gene expression due to changes in the environment are

ultimately reflected in the metabolome. Dynamics of metabolite concentrations under a certain condition can

therefore give a description of the cellular state with a high degree of functional information. We used this

potential to evaluate the metabolic status of two recombinant strains of Saccharomyces cerevisiae during

anaerobic batch fermentation of a glucose/xylose mixture. Two isogenic strains were studied, differing only in

the pathways used for xylose assimilation: the oxidoreductive pathway with xylose reductase (XR) and xylitol

dehydrogenase (XDH) or the isomerization pathway with xylose isomerase (XI). The isogenic relationship

between the two strains ascertains that the observed responses are a result of the particular xylose pathway

and not due to unknown changes in regulatory systems. An increased understanding of the physiological

state of these strains is important for further development of efficient pentose-utilizing strains for bioethanol

production.

Results: Using LC-MS/MS we determined the dynamics in the concentrations of intracellular metabolites in

central carbon metabolism, nine amino acids, the purine nucleotides and redox cofactors. The general

response to the transition from glucose to xylose was increased concentrations of amino acids and TCA-cycle

intermediates, and decreased concentrations of sugar phosphates and redox cofactors. The two strains

investigated had significantly different uptake rates of xylose which led to an enhanced response in the

XI-strain. Despite the difference in xylose uptake rate, the adenylate energy charge remained high and stable

around 0.8 in both strains. In contrast to the adenylate pool, large changes were observed in the guanylate

pool.

Conclusions: The low uptake of xylose by the XI-strain led to several distinguished responses: depletion of

key metabolites in glycolysis and NADPH, a reduced GTP/GDP ratio and accumulation of PEP and aromatic

amino acids. These changes are strong indicators of carbon starvation. The XR/XDH-strain displayed few such

traits. The coexistence of these traits and a stable adenylate charge indicates that xylose supplies energy to

the cells but does not suppress a response similar to carbon starvation. Particular signals may play a role in

the latter, of which the GTP/GMP ratio could be a candidate as it decreased significantly in both strains. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bioethanol, Starvation, Metabolic status, Xylose fermentation, Yeast metabolism, Metabolomics
in
Biotechnology for Biofuels
volume
5:34
publisher
BioMed Central
external identifiers
  • wos:000309402800001
  • scopus:84860907188
ISSN
1754-6834
DOI
10.1186/1754-6834-5-34
language
English
LU publication?
yes
id
7381c05d-2849-4a01-b99e-ea6781dfc16b (old id 3127018)
date added to LUP
2012-10-09 16:29:03
date last changed
2017-10-08 03:47:41
@article{7381c05d-2849-4a01-b99e-ea6781dfc16b,
  abstract     = {Background: The concerted effects of changes in gene expression due to changes in the environment are<br/><br>
ultimately reflected in the metabolome. Dynamics of metabolite concentrations under a certain condition can<br/><br>
therefore give a description of the cellular state with a high degree of functional information. We used this<br/><br>
potential to evaluate the metabolic status of two recombinant strains of Saccharomyces cerevisiae during<br/><br>
anaerobic batch fermentation of a glucose/xylose mixture. Two isogenic strains were studied, differing only in<br/><br>
the pathways used for xylose assimilation: the oxidoreductive pathway with xylose reductase (XR) and xylitol<br/><br>
dehydrogenase (XDH) or the isomerization pathway with xylose isomerase (XI). The isogenic relationship<br/><br>
between the two strains ascertains that the observed responses are a result of the particular xylose pathway<br/><br>
and not due to unknown changes in regulatory systems. An increased understanding of the physiological<br/><br>
state of these strains is important for further development of efficient pentose-utilizing strains for bioethanol<br/><br>
production.<br/><br>
Results: Using LC-MS/MS we determined the dynamics in the concentrations of intracellular metabolites in<br/><br>
central carbon metabolism, nine amino acids, the purine nucleotides and redox cofactors. The general<br/><br>
response to the transition from glucose to xylose was increased concentrations of amino acids and TCA-cycle<br/><br>
intermediates, and decreased concentrations of sugar phosphates and redox cofactors. The two strains<br/><br>
investigated had significantly different uptake rates of xylose which led to an enhanced response in the<br/><br>
XI-strain. Despite the difference in xylose uptake rate, the adenylate energy charge remained high and stable<br/><br>
around 0.8 in both strains. In contrast to the adenylate pool, large changes were observed in the guanylate<br/><br>
pool.<br/><br>
Conclusions: The low uptake of xylose by the XI-strain led to several distinguished responses: depletion of<br/><br>
key metabolites in glycolysis and NADPH, a reduced GTP/GDP ratio and accumulation of PEP and aromatic<br/><br>
amino acids. These changes are strong indicators of carbon starvation. The XR/XDH-strain displayed few such<br/><br>
traits. The coexistence of these traits and a stable adenylate charge indicates that xylose supplies energy to<br/><br>
the cells but does not suppress a response similar to carbon starvation. Particular signals may play a role in<br/><br>
the latter, of which the GTP/GMP ratio could be a candidate as it decreased significantly in both strains.},
  author       = {Bergdahl, Basti and Heer, Dominik and Sauer, Uwe and Hahn-Hägerdal, Bärbel and van Niel, Ed},
  issn         = {1754-6834},
  keyword      = {Bioethanol,Starvation,Metabolic status,Xylose fermentation,Yeast metabolism,Metabolomics},
  language     = {eng},
  publisher    = {BioMed Central},
  series       = {Biotechnology for Biofuels},
  title        = {Dynamic metabolomics differentiates between carbon and energy starvation in recombinant Saccharomyces cerevisiae fermenting xylose},
  url          = {http://dx.doi.org/10.1186/1754-6834-5-34},
  volume       = {5:34},
  year         = {2012},
}