Fermentation

Lore & Background

Fermentation has been used by humans for food production and preservation for 13,000 years, associated with health benefits, unique flavor profiles, and improved texture. It is also beneficial through gut microbes that release end products used by the host for energy. At an industrial level, fermentation produces commodity chemicals such as ethanol (used in alcoholic beverages like beers, wine, and spirits) and lactate (neutralized to lactic acid for food preservation, curing, or flavoring).

Louis Pasteur described fermentation in 1876 as 'la vie sans air' (life without air), before the discovery of anaerobic respiration. The metabolism utilizes a wide variety of substrates and can form nearly 300 different combinations of end products. Fermentation occurs in both prokaryotes and eukaryotes, and the discovery of new end products and organisms suggests it is more diverse than previously studied.

Fermentation does not need an exogenous electron acceptor, allowing it to occur regardless of environmental conditions, but it is relatively inefficient, producing 2 to 5 ATP molecules per glucose versus 32 during aerobic respiration. Over 25% of bacteria and archaea carry out fermentation, especially in the phylum Bacillota, and it is most rare in Actinomycetota. Fermenting microbes are frequently found in host-associated habitats like the gastrointestinal tract, as well as sediments and food.

Reader's Guide

Fermentation's significance lies in its dual role as a fundamental biological process and a cornerstone of human industry. Biologically, it allows organisms to generate ATP from organic molecules without oxygen, providing energy for periods ranging from 10 seconds to 2 minutes in humans during exercise or disease states like sepsis and hemorrhagic shock. This anaerobic pathway augments aerobic metabolism but is limited by lactate buildup, necessitating rest.

Its legacy in human society is profound: for 13,000 years, fermentation has been used to preserve food and create products with distinct flavors and textures, including cereal, dairy, bread, and beers. Industrial fermentation has been engineered to produce ethanol for alcoholic beverages and fuel, and lactate for food preservation. The process is also critical in gut microbiomes, where microbial fermentation releases end products used by the host for energy. The diversity of fermentation—with nearly 300 possible end products and its occurrence across bacteria, archaea, and eukaryotes—underscores its adaptability and ongoing relevance in both natural ecosystems and human technology.

Did You Know?

• Fermentation can produce nearly 300 different combinations of end products.
• In humans, fermentation pathways provide energy for a period ranging from 10 seconds to 2 minutes.
• Louis Pasteur described fermentation as 'la vie sans air' (life without air) in 1876.