Genetic analysis of the metabolic pathways responsible for aroma metabolite production by Saccharomyces cerevisiae

Gustav Styger, Dan Jacobson, Bernard A. Prior, Florian F. Bauer

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

During alcoholic fermentation, higher alcohols, esters, and acids are formed from amino acids via the Ehrlich pathway by yeast, but many of the genes encoding the enzymes have not yet been identified. When the BAT1/2 genes, encoding transaminases that deaminate amino acids in the first step of the Ehrlich pathway are deleted, higher metabolite formation is significantly decreased. Screening yeast strains with deletions of genes encoding decarboxylases, dehydrogenases, and reductases revealed nine genes whose absence had the most significant impact on higher alcohol production. The seven most promising genes (AAD6, BAT2, HOM2, PAD1, PRO2, SPE1, and THI3) were further investigated by constructing double- and triple-deletion mutants. All double-deletion strains showed a greater decrease in isobutanol, isoamyl alcohol, isobutyric, and isovaleric acid production than the corresponding single deletion strains with the double-deletion strains in combination with †bat2 and the †hom2-†aad6 strain revealing the greatest impact. BAT2 is the dominant gene in these deletion strains and this suggests the initial transaminase step of the Ehrlich pathway is rate-limiting. The triple-deletion strains in combination with BAT2 (†bat2-†thi3- †aad6 and †bat2-†thi3-†hom2) had the greatest impact on the end metabolite production with the exception of isoamyl alcohol and isovaleric acid. The strain deleted for two dehydrogenases and a reductase (†hom2-†pro2-†aad6) had a greater effect on the levels of these two compounds. This study contributes to the elucidation of the Ehrlich pathway and its significance for aroma production by fermenting yeast cells.

Original languageEnglish
Pages (from-to)4429-4442
Number of pages14
JournalApplied Microbiology and Biotechnology
Volume97
Issue number10
DOIs
StatePublished - May 2013
Externally publishedYes

Funding

Acknowledgments This work was supported by the National Research Foundation, South Africa. The authors thank Andreas Tredoux for technical assistance and Martin Kidd for statistical analysis.

Keywords

  • Aroma compounds
  • Deletion mutants
  • Ehrlich pathway
  • Yeast

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