Fermentation
[5] Humans and their livestock have microbes in the gut that carry out fermentation, releasing products used by the host for energy.
In total, fermentation forms more than 50 metabolic end products[2] This process highlights the power of microbial activity.
[citation needed] When glucose is fermented, it enters glycolysis or the pentose phosphate pathway and is converted to pyruvate.
[15] Fermentation of feedstocks, including sugarcane, maize, and sugar beets, produces ethanol that is added to gasoline.
[16] In some species of fish, including goldfish and carp, it provides energy when oxygen is scarce (along with lactic acid fermentation).
The United States began producing ethanol on a large scale in the 1980s and 1990s as a fuel additive to gasoline, due to government regulations.
It is the type of bacteria that convert lactose into lactic acid in yogurt, giving it its sour taste.
Reasons to go further and convert lactic acid into something else include: Hydrogen gas is produced in many types of fermentation as a way to regenerate NAD+ from NADH.
[24][citation needed] In food and industrial contexts, any chemical modification performed by a living being in a controlled container can be termed "fermentation".
It is commonly used to modify existing protein foods, including plant-based ones such as soy, into more flavorful forms such as tempeh and fermented tofu.
Some examples are:[25] Heme proteins such as myoglobin and hemoglobin give meat its characteristic texture, flavor, color, and aroma.
[25][27] Industrial fermentation can be used for enzyme production, where proteins with catalytic activity are produced and secreted by microorganisms.
The development of fermentation processes, microbial strain engineering and recombinant gene technologies has enabled the commercialization of a wide range of enzymes.
Enzymes are used in all kinds of industrial segments, such as food (lactose removal, cheese flavor), beverage (juice treatment), baking (bread softness, dough conditioning), animal feed, detergents (protein, starch and lipid stain removal), textile, personal care and pulp and paper industries.
Batch fermentation has been used for millennia to make bread and alcoholic beverages, and it is still a common method, especially when the process is not well understood.
Once many of the nutrients have been consumed, the growth slows and becomes non-exponential, but production of secondary metabolites (including commercially important antibiotics and enzymes) accelerates.
In particular, production of secondary metabolites can be increased by adding a limited quantity of nutrients during the non-exponential growth phase.
[30]: 1 [31] The high cost of sterilizing the fermentor between batches can be avoided using various open fermentation approaches that are able to resist contamination.
Solid-state fermentation adds a small amount of water to a solid substrate; it is widely used in the food industry to produce flavors, enzymes and organic acids.
[31] If the process works well, there is a steady flow of feed and effluent and the costs of repeatedly setting up a batch are avoided.
[citation needed] In 1837, Charles Cagniard de la Tour, Theodor Schwann and Friedrich Traugott Kützing independently published papers concluding, as a result of microscopic investigations, that yeast is a living organism that reproduces by budding.
However, a lot of chemists, including Antoine Lavoisier, continued to view fermentation as a simple chemical reaction and rejected the notion that living organisms could be involved.
This was seen as a reversion to vitalism and was lampooned in an anonymous publication by Justus von Liebig and Friedrich Wöhler.
[41]: 108–109 The turning point came when Louis Pasteur (1822–1895), during the 1850s and 1860s, repeated Schwann's experiments and showed fermentation is initiated by living organisms in a series of investigations.
For example, in the 1930s, it was discovered microorganisms could be mutated with physical and chemical treatments to be higher-yielding, faster-growing, tolerant of less oxygen, and able to use a more concentrated medium.
[citation needed] The field of fermentation has been critical to producing a wide range of consumer goods, from food and drink to industrial chemicals and pharmaceuticals.
Since its early beginnings in ancient civilizations, fermentation has continued to evolve and expand, with new techniques and technologies driving advances in product quality, yield, and efficiency.
This led to developing new fermentation techniques and genetically engineered microorganisms to improve yields and reduce production costs.
In the 1990s and 2000s, there was a growing interest in fermentation to produce functional foods and nutraceuticals, which have potential health benefits beyond basic nutrition.
