title: The fate of acetic acid during glucose co-metabolism by the spoilage yeast Zygosaccharomyces bailii.
abstract: Zygosaccharomyces bailii is one of the most widely represented spoilage yeast species, being able to metabolise acetic acid in the presence of glucose. To clarify whether simultaneous utilisation of the two substrates affects growth efficiency, we examined growth in single- and mixed-substrate cultures with glucose and acetic acid. Our findings indicate that the biomass yield in the first phase of growth is the result of the weighted sum of the respective biomass yields on single-substrate medium, supporting the conclusion that biomass yield on each substrate is not affected by the presence of the other at pH 3.0 and 5.0, at least for the substrate concentrations examined. In vivo(13)C-NMR spectroscopy studies showed that the gluconeogenic pathway is not operational and that [2-(13)C]acetate is metabolised via the Krebs cycle leading to the production of glutamate labelled on C(2), C(3) and C(4). The incorporation of [U-(14)C]acetate in the cellular constituents resulted mainly in the labelling of the protein and lipid pools 51.5% and 31.5%, respectively. Overall, our data establish that glucose is metabolised primarily through the glycolytic pathway, and acetic acid is used as an additional source of acetyl-CoA both for lipid synthesis and the Krebs cycle. This study provides useful clues for the design of new strategies aimed at overcoming yeast spoilage in acidic, sugar-containing food environments. Moreover, the elucidation of the molecular basis underlying the resistance phenotype of Z. bailii to acetic acid will have a potential impact on the improvement of the performance of S. cerevisiae industrial strains often exposed to acetic acid stress conditions, such as in wine and bioethanol production.
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal.
authors.forename: Fernando
authors.initials: F
authors.lastname: Rodrigues
authors.forename: Maria João
authors.initials: MJ
authors.lastname: Sousa
authors.forename: Paula
authors.initials: P
authors.lastname: Ludovico
authors.forename: Helena
authors.initials: H
authors.lastname: Santos
authors.forename: Manuela
authors.initials: M
authors.lastname: Côrte-Real
authors.forename: Cecília
authors.initials: C
authors.lastname: Leão
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D018533:Biomass; D002247:Carbon Isotopes; D003470:Culture Media / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D020068:Zygosaccharomyces / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D003470:Culture Media; D005947:Glucose; D019342:Acetic Acid