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 13C-NMR spectroscopy studies showed that the gluconeogenic pathway is not operational and that [2−13C]acetate is metabolised via the Krebs cycle leading to the production of glutamate labelled on C2, C3 and C4. The incorporation of [U-14C]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.

Mitochondrial proteomics of the acetic acid - induced programmed cell death response in a highly tolerant Zygosaccharomyces bailii - derived hybrid strain

“…Nevertheless, in ISA1307 cells undergoing acetic acid - induced PCD a particular regulation of glutamate metabolism, not seen in S. cerevisiae , seems to play a crucial role upon acetic acid treatment. A negative correlation between the intracellular level of glutamate and the level of propionic acid supplementation was reported and tentatively explained as a mechanism to maintain cytosol electrical neutrality by exchange of glutamate and the counterion propionate under propionic acid stress 46, a mechanism already reported to occur in acetic acid stressed Escherichia coli 47 and suggested to take place in ISA1307 cells growing in the exponential phase in the presence of acetic acid1748. Additionally, glutamate is a precursor for the synthesis of glutathione, which is a compound with important antioxidant properties known to play a role in PCD 4950.…”

Molecular mechanisms of Saccharomyces cerevisiae stress adaptation and programmed cell death in response to acetic acid

“…Thus, yeast is sensitive to acetic acid stress in the presence of glucose. Acetate transport, as its metabolism, is also under glucose repression in S. cerevisiae but not in Zygosaccharomyces bailii that can metabolize acetic acid in the presence of glucose and is known for its high resistance to weak acids in glucose-containing media (Sousa et al, 1998; Rodrigues et al, 2012). …”

Strain-dependent tolerance to acetic acid in Dekkera bruxellensis

“…Saccharomyces cerevisiae has been reported to be unable to co-metabolize glucose and acetic acid simultaneously (Fernandes et al 1997), but co-consumption has been described recently (Lindberg et al 2013). In contrast, the high acetic acid resistance in Z. bailii species has been associated with its ability to metabolise this acid also in presence of glucose (Rodrigues et al 2012), due to a specific and not glucose repressed transport system and a higher metabolic flux through acetyl-CoA synthetase (Sousa et al 1996;Rodrigues et al 2012). In order to investigate the influence of acetic acid on glucose metabolism, the selected strains were cultivated in YPD medium at pH 4.5 supplemented with acetic acid and compared to the control (without acetic acid).…”