Fluxes of carbon, phosphorylation, and redox intermediates during growth of Saccharomyces cerevisiae on different carbon sources

S. Cortassa, J. C. Aon, M. A. Aon

Research output: Contribution to journalArticle

Abstract

In the present work we develop a method for estimating anabolic fluxes when yeast are growing on various carbon substrates (glucose, glycerol, lactate, pyruvate, acetate, or ethanol) in minimal medium. Fluxes through the central amphibolic pathways were calculated from the product of the total required amount of a specified carbon intermediate times the growth rate. The required amount of each carbon intermediate was estimated from the experimentally determined macromolecular composition of cells grown in each carbon source and the monomer composition of macromolecules. Substrates sharing most metabolic pathways such as ethanol and acetate, despite changes in the macromolecular composition, namely carbohydrate content (34% ± 1 and 21% ± 3, respectively), did not show large variations in the overall fluxes through the main amphibolic pathways. For instance, in order to supply anabolic precursors to sustain growth rates in the range of 0.16/h to 0.205/h, similar large fluxes through Acetyl CoA synthase were required by acetate (4.2 mmol/hr g dw) or ethanol (5.2 mmol/h g dw). The V(max) activities of key enzymes of the main amphibolic pathways measured in permeabilized yeast cells allowed to confirm, qualitatively, the operation of those pathways for all substrates and were consistent on most substrates with the estimated fluxes required to sustain growth. When ATP produced from oxidation of the NADH synthesized along with the key intermediary metabolites was taken into account, higher Y(ATP)/(max) values (36 with respect to 24 g dw/mol ATP) were obtained for glucose. The same result was obtained for glycerol, ethanol, and acetate. A yield index (YI) was defined as the ratio of the theoretically estimated substrate flux required to sustain a given growth rate over the experimentally measured flux of substrate consumption. Comparison of YI between growth on various carbon sources led us to conclude that ethanol (YI = 0.84), acetate (YI = 0.77), and lactate (YI = 0.77) displayed the most efficient use of substrate for biomass production. For the other substrates, the YI decayed in the following order: pyruvate > glycerol > glucose. An improvement of the quantitative understanding of yeast metabolism, energetics, and physiology is provided by the present analysis. The methodology proposed can be applied to other eukaryotic organisms of known chemical composition.

Original languageEnglish (US)
Pages (from-to)193-208
Number of pages16
JournalBiotechnology and Bioengineering
Volume47
Issue number2
DOIs
StatePublished - 1995
Externally publishedYes

Fingerprint

Carbon Cycle
Phosphorylation
Yeast
Oxidation-Reduction
Saccharomyces cerevisiae
Acetates
Ethanol
Carbon
Fluxes
Glycerol
Substrates
Growth
Adenosine Triphosphate
Yeasts
Adenosinetriphosphate
Pyruvic Acid
Glucose
Lactic Acid
Chemical analysis
Acetyl Coenzyme A

Keywords

  • amphibolic pathways
  • carbon and phosphorylation fluxes
  • NADH oxidation
  • Saccharomyces cerevisiae
  • yeast intermediary metabolism

ASJC Scopus subject areas

  • Biotechnology
  • Microbiology

Cite this

Fluxes of carbon, phosphorylation, and redox intermediates during growth of Saccharomyces cerevisiae on different carbon sources. / Cortassa, S.; Aon, J. C.; Aon, M. A.

In: Biotechnology and Bioengineering, Vol. 47, No. 2, 1995, p. 193-208.

Research output: Contribution to journalArticle

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