Fermentation

Fermentation or fermentation (Latin fermentum fermentation ') referred to in biology, a form of enzymatic conversion of organic substances. The fermentation is used deliberately in biotechnology. This is done either by adding the required enzymes or by the addition of bacteria, fungus or other biological cell cultures that perform the fermentation as part of its enzyme-catalyzed metabolism. Some of these microorganisms are already naturally present in the starting materials, such as the spontaneous fermentation. However, pure culture cell cultures are added to control the fermentation better and exclude undesired side products, especially in the industrial fermentation.

Definition

Originally fermentation with a biotic response in the absence of air means [ " fermentation, c'est la vie sans l' air" ( Pasteur ) ]. Today the fermentation includes any technical bio-reaction. To enable medical products such as insulin, hyaluronic acid, streptokinase, and a variety of antibiotics, such as penicillin, synthesized by microorganisms in bioreactors on a large scale. Microorganisms - optionally after genetic engineering change - in the position to form materials which can be difficult to make by chemical means. Devices and bioreactors for fermentation hot fermenter.

Fermentation is a portion of the fermentation and runs exclusively from anaerobic, ie oxygen-free. Frequently fermentation is used as a synonym for fermentation. However, the latter includes both aerobic processes as well as entirely different microbial or autolytic enzymatic processes, such as the young herring maturation. Aerobic processes, such as the acetic acid fermentation, are respectively designated as an oxidative fermentation.

Areas of application

Fermentation in the food and beverage manufacturing

In food production, the fermentation plays a central role in the production and preservation of food, such as the production of sauerkraut, kimchi, Tsukemono, miso or natto. Furthermore, the flavors, like soy sauce and fermented beverages or develop the tannins are reduced, such as in tea, cocoa, coffee, and tobacco. Other operations are the manufacture of dairy products such as cheese or yogurt, the production of tofu or raw sausage (such as salami) and ultimately the production of alcoholic beverages such as beer, wine, whiskey and tequila.

Production of dairy products and vegetables lactofermentiertem

A number of foods are directly produced by lactic acid fermentation. This includes especially the sour milk products such as sour milk, yogurt, kefir and buttermilk. These are prepared by inoculation of pasteurized milk with starter cultures of lactic acid bacteria. Other products are also lactofermentierte vegetables such as sauerkraut, borscht or Gimchi and sourdough sourdough and related products. Silages preserved by fermentation of fresh feed, based on the lactic acid fermentation.

Fermentation of tea leaves

Under fermenting tea was understood in the older Teesprache unlocking and oxidation of the tea leaves in a wet environment. This is not a true fermentation, as this process occurs without microorganisms. Today Teetechnologie speaks increasingly correct oxidation, even at a boundary to real microbial fermentation in Pu -erh teas to ensure.

For this, the tea leaves are crushed by rolling and thus partially destroyed the plant cells. The separate enzymes in the intact cell (especially phenol oxidases ) and other ingredients of the tea plant (especially polyphenols) come together and react with oxygen, the dark-colored polyphenols and aroma substances. The process takes about three hours. In contrast to black tea oolong tea is only briefly and the green tea not fermented.

Fermentation of raw tobacco

Fermentation of tobacco is a fermentation process, the dried raw tobacco from a consumption of finished tobacco is produced. The nicotine content is reduced and leaf own protein compounds, which would mask the characteristic aroma of each variety in smoking are degraded.

After assembling the respective tobacco batch ( at least 1000 kg) is the fermentation process by itself or is set by supply of heat in motion. The ideal process temperature is between 50 ° C and 60 ° C, higher temperatures harm the quality of tobacco. At a natural fermentation, the tobacco batch can be four to five times shifted respectively from the pile edge in the middle of the stack and vice versa. Until all the leaves evenly fermented are pass four to six months.

Technical fermentation

The main field of fermentation is the technical biotechnology for the production of various fermentation products. Products ranging from bioethanol, amino acids, organic acids, such as lactic acid, citric acid and acetic acid, to enzymes such as phytase, antibiotics and other pharmaceutical products to biomonomers and polymers such as polyhydroxyalkanoates. Such technical products, polyhydroxyalkanoates, PHA or polyhydroxy butyric acid, PHB. Technical bioethanol for use as biofuel, is in addition to beer and the yeast production and biogas currently Represents the main product of the fermentation industry

Raw materials are mainly starch and sucrose substrate for production by bacteria or fungi. Bioethanol is produced in Brazil, mainly on the basis of sugar from sugar cane, corn in the U.S. is the main raw material dar. According to the German bioethanol economy in Germany almost two-thirds of bioethanol from starch crops, especially wheat, won. Production is usually independent of the substrate, in almost all fermentation processes so both starch and sucrose, and various other sugary products can be used, in particular thick juice and molasses. And cellulose as the main component of the wood is a sugar polymer of the substrate as an alternative to the discussion is for future applications, especially for cellulose - ethanol and, when used in the biorefinery.

Biogas production

The production of biogas by anaerobic digestion of biomass in biogas plants is a fermentation process. This product is used for the production of bioenergy. With the help of bacteria in an anaerobic fermentation process, a gas mixture containing primarily of methane (CH4) and carbon dioxide ( CO2) and traces of nitrogen (N2 ), oxygen ( O2), hydrogen sulfide (H2S ), hydrogen ( H2) and ammonia ( NH3) produced. In most cases, is purified through a biogas upgrading. For biogas formed during the fermentation proportion of methane is important because combustion releases most of the energy.

Also, landfill gas and sewage gas produced during fermentation or digestion known as anaerobic decomposition of organic material. These gases are sometimes grouped under the names digester gas or biogas.

Bioreactors

Especially microorganisms may be cultured in known bioreactors, or fermentors. These are containers in which the reaction conditions are controlled and optimized. To produce the cultured organisms the desired substances under optimal conditions or in higher concentrations. In the reactors different parameters such as pH, temperature, oxygen, nitrogen source, glucose or Rührereinstellungen can be controlled.

Since the usable organisms have very different claims, are diverse fermenter types are available:

• Stirred tank reactors
• Loop reactors
• Airlift reactors
• Photobioreactors for the cultivation of algae and plants