Scientists Identify Yeast as a Living Agent of Fermentation

In 1837, French physicist Charles Cagniard-Latour and German researchers Theodor Schwann and Friedrich Traugott Kützing independently published observations identifying yeast as a living microscopic organism involved in alcoholic fermentation. Cagniard-Latour observed yeast cells reproducing by budding and connected their activity with fermentation. Schwann concluded from controlled experiments that fermentation depended on living yeast, while Kützing described yeast microscopically as an organized biological entity. Their work challenged influential chemical theories that explained fermentation as decomposition or contact action rather than a biological process. Although many chemists initially rejected this biological interpretation, the three investigations established an important foundation for fermentation microbiology and the later work of Louis Pasteur. Brewers had reused yeast for centuries without understanding its biological nature; the studies of 1837 began transforming this practical brewing ingredient into an object of scientific investigation.