Improving Food Preservation: Biodiversity and Heterogeneity of Spoilage Yeasts
Fact file
| Duration |
4 years; 100% FTE |
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| Eligibility |
Home and EU |
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| Supervisor(s) |
Prof Simon Avery |
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| Application deadline |
Friday 5th July 2019 |
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About the project
Food spoilage by microorganisms has major impacts on the security of our food supply. Yeasts and moulds are estimated to cause annual food losses sufficient to feed 600 million people. This PhD project tackles this problem through an academia-industry international collaboration, which offers cross-sector co-supervision and expertise together with a stipend uplift for the successful candidate. Food preservation helps to protect foods, but spoilage microorganisms such as yeasts may co-evolve to enable growth with common preservatives. Specific yeast species, strains and cell-subpopulations are still able to resist the major preservation methods. This is particularly true for preservation with weak acids and low pH, methods that are widely used in food design. However, the contributions of different resistance mechanisms to the overall risk of food spoilage by wild spoilage yeasts are not known. Recent work in our laboratories has shown significant differences in preservative resistance between strains of the same species, and even between individual cells of the same strain. This indicates that the phenotypic status of food spoilage yeasts enables them to overcome preservatives, e.g., by adopting semi-dormant states. The application of these insights for improving food preservation is still in its infancy, presenting a need that that this studentship will address by implementing a broad, quantitative strategy to investigate preservative resistance in spoilage yeasts.
The main project tasks will be:
• Characterise the phenotypic diversity of spoilage yeasts at low pH and in the presence of food acids.
• Identify key genetic elements responsible for acid resistance and its regulation in different spoilage yeast strains.
• Quantify the heterogeneity of acid resistance in genetically-uniform yeast populations and determine the mechanistic basis for formation of cell subpopulations.
• Estimate the prevalence of these mechanisms and importance for food spoilage, using predictive modelling.
• Quantify the minimum preservation level (pH and acid concentration) that is needed to reduce spoilage risk to acceptable levels.
Training:
The project will provide outstanding training opportunities for the successful candidate, with supervision by a cross-disciplinary and cross-sector team. Training will be provided in molecular genetics tools as applied to yeasts, bioinformatics, whole-genome sequencing, single-cell transcriptomics, and flow cytometry complemented by quantitative and predictive modelling approaches. The student will benefit from access to state-of-the-art facilities and dynamic research environments at the University of Nottingham, UK and at Unilever’s Global Foods Innovation Centre, Netherlands. There will be opportunities for travel and training credits for transferable skills relevant to diverse future-career destinations.
Funding notes
Funded for 4 years; 100% FTE; sponsored through BBSRC-CASE
References
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Stratford, M., Steels, H., Nebe-von-Caron, G., Avery, S.V., Novodvorska, M., Archer, D.B. (2014) Population heterogeneity and dynamics in starter culture and lag phase adaptation of the spoilage yeast Zygosaccharomyces bailii to weak acid preservatives Int. J. Food Microbiol., 181:40-47.
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Den Besten, H.M.W., Wells-Bennik, M.H.J., Zwietering, M.H. (2018) Natural diversity in heat resistance of bacteria and bacterial spores: Impact on food safety and quality. Ann. Rev. Food Sci. Technol. 9:383-410
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Stratford, M., Steels, H., Novodvorska, M., Archer, D.B., Avery, S.V. (2019) Extreme osmotolerance and halotolerance in food-relevant yeasts and the role of glycerol-dependent cell individuality. Frontiers Microbiol. 9 art. 3238
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Improving Food Preservation: Biodiversity and Heterogeneity of Spoilage Yeasts