Resistant yeast from Kraków

"Yeast because of its property to carry out the alcoholic fermentation and CO2 production is inextricably linked to human civilization, and has been used for centuries in the process of baking bread and making wine and beer. Yeast is also one of the most important model organisms used in biological research including genetics, genomics biomedicine and cell cycle" - explained Dr. Dominika Włoch-Salamon from the Institute of Environmental Studies at the Jagiellonian University.

Natural yeast strains of the species Saccharomyces can be isolated from all environments: soil, bark, leaves, flowers, fruit, beer, wine, sourdough, infected organs or skin of patients. These single-celled eukaryotes normally form aggregates, clusters of a large number of closely connected cells. "These aggregates consist of cells that are in different physiological states. They include old cells - the >mother< cells, which have repeatedly gemmated, and newly formed >daughter< cells, which have not yet gemmated. When the population starves, some of the "daughter" cells become so-called quiescent cells" - said Dr. Dominika Włoch-Salamon.

The latter are particularly valuable because they contain spare materials, have thick cell walls, are more resistant to various unfavourable factors and have better survival rate than other cells in the population. "When the environmental conditions improve, these cells resume their physiological processes, resulting in divisions and an increase in the population - its revival" - explained the researcher.

The presence of quiescent cells has been observed mainly in the population of laboratory strains of yeast which do not produce aggregates. Research conducted by scientists from the Institute of Environmental Sciences in Krakow show that quiescent cells are present in strains from various environments. "As more resistant to various stresses, they can be a valuable source of yeast cells for industrial applications, for example the production of bakery strains and cosmetics" - explains Dr. Włoch-Salamon.

Until now, the problem was to isolate a homogeneous fractions of quiescent cells from strains forming aggregates. Researchers have developed a method which allows to reduce the presence of aggregates in yeast populations, thus making it easier to isolate a quiescent cell fraction. They did this through genetic modification, so-called homologous transformation of a gene responsible for the aggregation of the yeast cells. So far modifications have been applied to seven strains of Saccharomyces cerevisiae from various environments: fruit, soil and the human body.

Thus obtained quiescent cells of yeast cells will better survive long-term, adverse conditions, such as: repeated thawing and storage at - 20°C; long-term refrigeration at 4°C; long-term storage at 28°C. Their survival depends on strain, prevailing conditions and population size.

"Obtained yeast cells with a higher survival rate can be used in the production of bakery strains: fresh and dry yeast, probiotics and cosmetics that require >revitalization< of yeast cells after a prolonged >dormant< period" - explained Dr. Dominic Włoch-Salamon.

The study was financed by the National Science Centre. Patent applications for the invention have been submitted to the Polish Patent Office and under the PCT. For several weeks, the inventors have been in talks with an Indian company interested in commercialisation.

PAP - Science and Scholarship in Poland

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