A single-cell organism, Saccharomyces cerevisiae is part of the mushroom kingdom. Although its common name — bakers’ yeast — comes from the rising of dough during bread-making, its genus name derives from the contraction of the terms saccharose (sugar) and mycelium (mushroom). As for its species name, that references ‘cervoise’, the Gauls’ traditional fermented barley or wheat beer. As with all yeasts, Saccharomyces cerevisiae can reproduce in two ways: identically, by budding a female cell from a mother yeast, if the environment is favorable; or by sexual reproduction, if the conditions are not favorable, by forming resistant spores that will fuse to create a new individual as soon as the environment is more conducive.
Saccharomyces cerevisiae, an anaerobic alcoholic fermentation agent
Identified in 1857 by the chemist Louis Pasteur as the principal alcoholic fermentation agent, Saccharomyces cerevisiae transforms the sugars in grains or fruit into alcohol and carbon dioxide in anaerobic conditions, that is to say in an environment deprived of air. This transformation had been identified in the latter part of the 18th century by Adamo Fabbroni, an Italian agronomist, who suspected that a living substance, naturally present on the grape, was at the origin of wine fermentation.
Controlling the culture of Saccharomyces cerevisiae in a given environment would not however take place until the end of the 19th century, thanks to the work of Robert Koch and Julius Richard Petri, who gave his name to the famous Petri dish. “From that point, the development of the modern fermentation industry became possible, thanks to the isolation and selection of microorganisms of interest, which can be characterized according to nutritional needs and functions,” explains Gilles Stien, R&D fermentation manager at Lesaffre.
Fermentation at the heart of our daily food habits
Today, the Saccharomyces cerevisiae yeast is widely produced and used in the food industry, due to its fermenting metabolism, its total innocuity, its rapid multiplication, its ease of use, and its nutritional benefits.
In bread-making, the strains of Saccharomyces cerevisiae are fermentation agents with an essential role. By partially consuming the flours’ sugar, they produce not only carbon dioxide and ethanol, which facilitate the increase in size during cooking, but also generate more than 200 molecules, which make up baked products’ sought-after aromas. The quantity of aromatic molecules produced varies according to the manufacturing parameters, and also the specific metabolism of the yeast strain used.
The infinite potential uses of yeasts and yeast derivatives
By drawing on this knowledge of strains, growth media and fermentation behavior, it is possible to optimize yeast’s numerous potential applications. For example, in the field of bread-making, certain yeasts are more suited to recipes for sweet or sour doughs, while others are more robust in terms of frozen bread-making techniques. In the winemaking domain, inactive yeasts can be a source of nutrients to facilitate increasingly complicated fermentations in the context of global warming. They are also useful for preserving wine’s aromas and colors throughout the aging process.
Integrated into growth media, yeast extracts are also greatly prized in the manufacture of the lactic ferments used by dairy manufacturers, and also in the creation of diagnostic tests and vaccines in the pharmaceutical sector.
For our food security, yeast fractions rich in mannan-oligosaccharides and β-glucans (1,3 and 1,6) are also allies of choice in poultry production, by diminishing the pressure of certain pathogens like E.Coli or Salmonella.
Lesaffre’s field of research has therefore grown considerably over the past fifty years, given the diversity of possible applications for yeast and its derivatives. In R&D, as the number of potentially interesting candidates for new applications has increased, so the control of their metabolism and growth, and the maintaining of their potential during large-scale production, constitute a daily challenge at manufacturing sites.