Fermentation is a chemical process that occurs in living organisms, where molecules such as glucose are broken down anaerobically. More broadly, fermentation is the process by which sugars are transformed into a new product through chemical reactions carried out by microorganisms. Fermentation is a natural process that converts sugars into products that can be useful to humans. The process of fermentation is used in many industrial applications, including the production of beer, wine, cheese, yogurt, bread, and biofuels.

In biochemistry, fermentation is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. Fermentation is a metabolic process that produces chemical changes in organic substances through the action of enzymes. In most cells, the enzymes involved in fermentation occur in the soluble portion of the cytoplasm. The reactions leading to the formation of ATP and pyruvate are common to sugar transformation in muscle, yeasts, some bacteria, and plants.

There are different types of fermentation, including lactic acid fermentation and alcoholic fermentation/Metabolism/Catabolism/Fermentation). Lactic acid fermentation occurs by converting pyruvate into lactate using the enzyme Lactate dehydrogenase and producing NAD+ in the process/Metabolism/Catabolism/Fermentation). Alcoholic fermentation, on the other hand, is the process by which yeast converts sugars into ethanol and carbon dioxide.

In summary, fermentation is a process by which living organisms recycle NADH to NAD+ and extract energy from carbohydrates without using oxygen. It is a natural process that has been used by humans for thousands of years to produce food and beverages. Fermentation is also used in many industrial applications to produce a wide range of products.