Fermentation is a metabolic process that produces chemical changes in organic substances through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In microbiology, fermentation is an anaerobic process performed by a cell to generate chemical energy (e.g. ATP) from pyruvate (a product of glycolysis) but without going through the citric acid cycle and the electron transport chain system as cellular respiration does. Fermentation occurs in yeast cells and bacteria and also in the muscles of animals.

Here are some key points about fermentation in microbiology:

• Fermentation is an anaerobic process in which energy can be released from glucose even if oxygen is not available.
• Fermentation is a process that helps break down large organic molecules via the action of microorganisms into simpler ones.
• Fermentation does not use oxygen; thus, it is “anaerobic” .
• Microbial fermentation is used commercially by certain industries. Lactic acid fermentation by certain fungi and bacteria, for instance, is used by the dairy industry to make yogurt and cheese. Alcohol fermentation by yeasts is used in making wine and liquor.
• Fermentation by some bacteria, like those in yogurt and other soured food products, and by animals in muscles during oxygen depletion, is lactic acid fermentation.
• Fermentation products are important commercially outside of the food industry. For example, chemical solvents such as acetone and butanol are produced during acetone-butanol-ethanol fermentation. Complex organic pharmaceutical compounds used in antibiotics (e.g., penicillin), vaccines, and vitamins are produced through mixed acid fermentation.

In summary, fermentation in microbiology is a process that occurs in the absence of oxygen and is used by microorganisms to generate energy from glucose. It is used commercially by various industries to produce a wide range of products, including food, beverages, and pharmaceuticals.