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

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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 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.

Detaljer

Författare
Enheter & grupper
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Industriell bioteknik

Nyckelord

Originalspråkengelska
TidskriftBiotechnology for Biofuels
Volym5:34
StatusPublished - 2012
PublikationskategoriForskning
Peer review utfördJa

Relaterad forskningsoutput

Bergdahl, B., 2013, Applied Microbiology (LTH). 254 s.

Forskningsoutput: AvhandlingDoktorsavhandling (sammanläggning)

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