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Heterogeneity in spores of food spoilage fungi

 
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Project leader: Prof dr Han Wösten
Time frame: 2017 – 2021
Project code: 16MF02
Research theme: Microbes and Function
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 Summary


Food production should be increased by 70% to feed the human world population in 2050. Reducing post-harvest food spoilage could significantly contribute to this challenge. At the moment, 25% of the food is spoiled, a significant part due to fungal contamination. Fungal food spoilage can be found in all food categories. For instance, Aspergillus niger and Paecilomyces variotii are important spoilage fungi of fruits and processed foods, respectively. Penicillium roqueforti is a spoilage fungus of airtight stored grain and dairy products, while Saccharomyces cerevisiae subsp. diastaticus is the main cause of spoilage of alcohol-free beer and beer-mix beverages. Fungal spoilage not only affects visual and organoleptic properties of food but can also result in the production of toxins. Food preservation methods like sterilization and salt addition reduce spoilage enormously. However, consumers prefer minimal processing of food to maintain taste and composition and to reduce health risks. This, however, leads to increased risk of fungal spoilage. Therefore, new food processing protocols are needed.

Fungal food spoilage often starts with a contamination with spores. These reproductive structures are abundant in the environment. Experimental data strongly indicate the existence of subpopulations of spores with different levels of resistance to preservation methods. The aim of this project is to study the extent of this heterogeneity and to study the underlying mechanisms using spores of Aspergillus niger, Paecilomyces variotii, Penicillium roqueforti, and Saccharomyces cerevisiae subsp. diastaticus as model systems. The role of the genetic background, environmental conditions, and the developmental state of the mycelium and spores will be studied. Quantitative imaging, genome and RNA sequencing, functional gene analysis, and modelling will be used, which should reveal leads for novel mild intervention protocols to prevent food spoilage.

Key objectives

  • Study the impact of the genetic background by using a collection of strains of different geographic origin and originating from contaminated food and beverages.
  • Study the impact of environmental growth conditions by isolating spores from colonies grown at different substrates either or not in the presence of sub-lethal stress conditions.
  • Study the impact of the developmental stage of the colony and the conidia by isolating spores of different age from different zones of colonies.
  • Show a proof of concept of a novel processing treatment that prevents fungal spoilage by making use of a combination of mild interventions.

Main deliverables

  • Description of the impact of the genetic background on variability in stress resistance between strains of the model fungi used in this project.
  • Description of the impact of environmental growth conditions on variability in stress resistance between strains of the model fungi used in this project.
  • Description of the impact of the developmental state of the mycelium and the spores on variability in stress resistance between strains of the model fungi used in this project.
  • Molecules triggering germination of a (sub)population of spores of the model fungi used in this project.
  • Mechanism(s) underlying spore heterogeneity with respect to stress resistance.
  • Generic models describing growth/no growth boundaries and/or germination and outgrowth kinetics.
  • Proof of concept of a novel processing treatment that prevents.

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