Summary
Anaerobic breakdown of sugars producing products like lactic acid or ethanol, used in yogurt and bread.
In depth
Fermentation regenerates NAD+ so glycolysis can continue without oxygen, giving only 2 ATP per glucose. Lactic acid fermentation is used in yoghurt, cheese and sauerkraut; alcohol fermentation in bread and beer. Other fermentations produce acetone, butanol or propionic acid.
Fermentation products give flavour and preserve food. Starter cultures standardise quality. Industrial fermentations produce acids and solvents.
Key idea: fermentation recycles NAD+ without oxygen.
Types include lactic acid (Lactobacillus in yoghurt, sauerkraut, kimchi; muscle cells under strain), alcoholic (yeast making ethanol and CO2), and others such as propionic acid in Swiss cheese (which forms its holes) and butyric acid. Industrial fermentation in large bioreactors produces antibiotics, citric acid, amino acids, enzymes and biofuels.
In the broad industrial sense, fermentation means any large-scale microbial culture, even aerobic. Biochemically, the process uses an organic molecule as the final electron acceptor, so it has a low energy yield compared with aerobic respiration (2 ATP versus around 30 per glucose). Fermented foods can preserve food because acid or alcohol inhibits spoilage organisms.
Example: lactic acid made by muscles during hard exercise is carried to the liver, where it is converted back to glucose.
Frequently asked questions
What is Fermentation?
Anaerobic breakdown of sugars producing products like lactic acid or ethanol, used in yogurt and bread.
Which area of biology covers Fermentation, and how advanced is it?
Fermentation is one of the 54 topics in Microbiology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Bacteria, Microorganisms, Bacterial Metabolism.
Can you give an example of Fermentation?
Swiss cheese holes come from CO2 produced by Propionibacterium.
What should I learn before Fermentation?
Fermentation is a Beginner topic, so no earlier topic is required. Other Beginner topics in Microbiology that pair well with it include Microorganisms, Bacteria, Archaea.
What topics are related to Fermentation?
The closest topics to Fermentation are Bacteria, Microorganisms, Bacterial Metabolism, Probiotics. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Fermentation?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Fermentation. To practise the whole of Microbiology, use the Microbiology quiz.
How is Fermentation different from Bacteria?
Fermentation: Anaerobic breakdown of sugars producing products like lactic acid or ethanol, used in yogurt and bread. Bacteria: Single-celled prokaryotes found everywhere, vital for nutrient cycling, digestion and some disease. Read both side by side and note what each one explains.
How should I study Fermentation step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Bacteria and explain the difference aloud. Finally, take the Microbiology quiz and come back to this page for any question you miss.