Louis Pasteur Demonstrates the Biological Nature of Fermentation

In 1857, French chemist Louis Pasteur published studies of lactic and alcoholic fermentation that connected particular fermentations with the growth and activity of specific living microorganisms. Working with fermentation mixtures, Pasteur showed that lactic acid formation was associated with a microscopic organism distinct from brewer’s yeast. His experiments challenged the influential chemical theory that fermentation resulted primarily from the decomposition of nonliving organic matter. Earlier researchers had already identified yeast as a living organism, but Pasteur established a broader experimental connection between microbial life and fermentation. His work helped found fermentation microbiology and suggested that brewers could understand unwanted souring and other fermentation failures as the activity of different microorganisms. Pasteur later applied these principles directly to wine and beer, developing methods for controlling contamination and improving the stability of fermented beverages.