Fermentation - wikipedia Fermentation For other uses, see Fermentation ( disambiguation ). Fermentation in progress : Bubbles of CO form a froth on top of the fermentation mixture. Overview of ethanol fermentation. One glucose molecule breaks down into two pyruvate molecules ( 1 ). The energy from this exothermic reaction is used to bind inorganic phosphates to ATP and convert NAD+ to NADH. The two pyruvates are then broken down into two acetaldehyde molecules and give off two CO2 molecules as a waste product ( 2 ). The acetaldehyde is then reduced into ethanol using the energy and hydrogen from NADH ; in this process the NADH is oxidized into NAD+ so that the cycle may repeat ( 3 ). Fermentation is a metabolic process that consumes sugar in the absence of oxygen. The products are organic acids, gases, or alcohol. It occurs in yeast and bacteria, and also in oxygen - starved muscle cells, as in the case of lactic acid fermentation. The science of fermentation is known as zymology. In microorganisms, fermentation is the primary means of producing ATP by the degradation of organic nutrients anaerobically. Humans have used fermentation to produce drinks and beverages since the Neolithic age. For example, fermentation is used for preservation in a process that produces lactic acid as found in such sour foods as pickled cucumbers, kimchi and yogurt ( see fermentation in food processing ), as well as for producing alcoholic beverages such as wine ( see fermentation in winemaking ) and beer. Fermentation occurs within the gastrointestinal tracts of all animals, including humans. Contents 1 Biochemical overview 2 Definitions 3 Examples 4 Chemistry 4.1 Ethanol fermentation 4.2 Lactic acid fermentation 4.3 Aerobic respiration 5 Hydrogen gas production in fermentation 6 Methane gas production in fermentation 7 History of human use 8 Etymology 9 See also 10 References 11 External links Biochemical overview Fermentation turns NADH and pyruvate produced in glycolysis into NAD+ and an organic product ( which varies depending on the type of fermentation ; see examples below ). In the presence of O, NADH and pyruvate are used to generate ATP in respiration. This is called oxidative phosphorylation, and it generates much more ATP than glycolysis alone. For that reason, fermentation is rarely utilized when oxygen is available. The exception being obligate anaerobes, which can not tolerate oxygen. The first step, Embden - Meyerof - Parnas glycolysis, is common to many fermentation pathways : C H O + 2 NAD + 2 ADP + 2 P → 2 CH COCO + 2 NADH + 2 ATP + 2 H O + 2H Pyruvate is CH COCO. P is inorganic phosphate. Two ADP molecules and two P are converted to two ATP and two water molecules via substrate - level phosphorylation. Two molecules of NAD are also reduced to NADH. In oxidative phosphorylation, the energy for ATP formation is derived from an electrochemical proton gradient generated across the inner mitochondrial membrane ( or, in the case of bacteria, the plasma membrane ) via an electron transport chain. Glycolysis has substrate - level phosphorylation ( ATP generated directly at the point of reaction ). Definitions Fermentation simply means the production of alcohol : grains and fruits are fermented to produce beer and wine. If a food soured, one might say it was ' off ' or fermented. Here are some definitions of fermentation. They range to informal, general usage to more scientific definitions. Preservation methods for food via microorganisms ( general use ). Any process that produces alcoholic beverages or acidic dairy products ( general use ). Any large - scale microbial process occurring with or without air ( common definition used in industry ). Any energy - releasing metabolic process that takes place only under anaerobic conditions ( becoming more scientific ). Any metabolic process that releases energy from a sugar or other organic molecule, does not require oxygen or an electron transport system, and uses an organic molecule as the final electron acceptor ( most scientific ). Examples Fermentation is a process which does not necessarily have to be carried out in an anaerobic environment. For example, even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to aerobic respiration, as long as sugars are readily available for consumption ( a phenomenon known as the Crabtree effect ). The antibiotic activity of hops also inhibits aerobic metabolism in yeast. Fermentation reacts NADH with an endogenous, organic electron acceptor. Usually this is pyruvate formed from the sugar during the glycolysis step. During fermentation, pyruvate is metabolized to various compounds through several processes : ethanol fermentation, aka alcoholic fermentation, is the production of ethanol and carbon dioxide lactic acid fermentation refers to two means of producing lactic acid : homolactic fermentation is the production of lactic acid exclusively heterolactic fermentation is the production of lactic acid as well as other acids and alcohols. Sugars are the most common substrate of fermentation, and typical examples of fermentation products are ethanol, lactic acid, carbon dioxide, and hydrogen gas ( H ). However, more exotic compounds can be produced by fermentation, such as butyric acid and acetone. Although yeast carries out the fermentation in the production of ethanol in beers, wines, and other alcoholic drinks, this is not the only possible agent : bacteria carry out the fermentation in the production of xanthan gum, while mammalian muscle carries out the fermentation that occurs during periods of intense exercise where oxygen supply becomes limited, resulting in the creation of lactic acid. Chemistry Comparison of aerobic respiration and most known fermentation types in eucaryotic cell. Numbers in circles indicate counts of carbon atoms in molecules, C6 is glucose C H O, C1 carbon dioxide CO. Mitochondrial outer membrane is omitted. Fermentation products contain chemical energy ( they are not fully oxidized ), but are considered waste products, since they can not be metabolized further without the use of oxygen. Ethanol fermentation Main article : Ethanol fermentation The chemical equation below shows the alcoholic fermentation of glucose, whose chemical formula is C H O. The reaction is catalysed by the enzymes pyruvate decarboxylase and alcohol dehydrogenase. One glucose molecule is converted into two ethanol molecules and two carbon dioxide molecules : C H O → 2 C H OH + 2 CO C H OH is the chemical formula for ethanol. Before fermentation takes place, one glucose molecule is broken down into two pyruvate molecules. This is known as glycolysis. Lactic acid fermentation Main article : Lactic acid fermentation Homolactic fermentation ( producing only lactic acid ) is the simplest type of fermentation. The pyruvate from glycolysis undergoes a simple redox reaction, forming lactic acid. It is unique because it is one of the only respiration processes to not produce a gas as a byproduct. Overall, one molecule of glucose ( or any six - carbon sugar ) is converted to two molecules of lactic acid : C H O → 2 CH CHOHCOOH It occurs in the muscles of animals when they need energy faster than the blood can supply oxygen. It also occurs in some kinds of bacteria ( such as lactobacilli ) and some fungi. It is the type of bacteria that converts lactose into lactic acid in yogurt, giving it its sour taste. These lactic acid bacteria can carry out either homolactic fermentation, where the end - product is mostly lactic acid, or Heterolactic fermentation, where some lactate is further metabolized and results in ethanol and carbon dioxide ( via the phosphoketolase pathway ), acetate, or other metabolic products, e.g. : C H O → CH CHOHCOOH + C H OH + CO If lactose is fermented ( as in yogurts and cheeses ), it is first converted into glucose and galactose ( both six - carbon sugars with the same atomic formula ) : C H O + H O → 2 C H O Heterolactic fermentation is in a sense intermediate between lactic acid fermentation, and other types, e.g. alcoholic fermentation ( see below ). The reasons to go further and convert lactic acid into anything else are : The acidity of lactic acid impedes biological processes ; this can be beneficial to the fermenting organism as it drives out competitors that are unadapted to the acidity ; as a result, the food will have a longer shelf life ( part of the reason foods are purposely fermented in the first place ) ; however, beyond a certain point, the acidity starts affecting the organism that produces it. The high concentration of lactic acid ( the final product of fermentation ) drives the equilibrium backwards ( Le Chatelier 's principle ), decreasing the rate at which fermentation can occur, and slowing down growth. Ethanol, into which lactic acid can be easily converted, is volatile and will readily escape, allowing the reaction to proceed easily. CO is also produced, but it is only weakly acidic, and even more volatile than ethanol. Acetic acid ( another conversion product ) is acidic, and not as volatile as ethanol ; however, in the presence of limited oxygen, its creation from lactic acid releases additional energy. It is a lighter molecule than lactic acid, that forms fewer hydrogen bonds with its surroundings ( due to having fewer groups that can form such bonds ), thus is more volatile and will also allow the reaction to move forward more quickly. If propionic acid, butyric acid, and longer monocarboxylic acids are produced ( see mixed acid fermentation ), the amount of acidity produced per glucose consumed will decrease, as with ethanol, allowing faster growth. Aerobic respiration In aerobic respiration, the pyruvate produced by glycolysis is oxidized completely, generating additional ATP and NADH in the citric acid cycle and by oxidative phosphorylation. However, this can occur only in the presence of oxygen. Oxygen is toxic to organisms that are obligate anaerobes, and is not required by facultative anaerobic organisms. In the absence of oxygen, one of the fermentation pathways occurs in order to regenerate NAD ; lactic acid fermentation is one of these pathways. Hydrogen gas production in fermentation Hydrogen gas is produced in many types of fermentation ( mixed acid fermentation, butyric acid fermentation, caproate fermentation, butanol fermentation, glyoxylate fermentation ), as a way to regenerate NAD from NADH. Electrons are transferred to ferredoxin, which in turn is oxidized by hydrogenase, producing H. Hydrogen gas is a substrate for methanogens and sulfate reducers, which keep the concentration of hydrogen low and favor the production of such an energy - rich compound, but hydrogen gas at a fairly high concentration can nevertheless be formed, as in flatus. As an example of mixed acid fermentation, bacteria such as Clostridium pasteurianum ferment glucose producing butyrate, acetate, carbon dioxide and hydrogen gas : The reaction leading to acetate is : C H O + 4 H O → 2 CH COO + 2 HCO + 4 H + 4 H Glucose could theoretically be converted into just CO and H, but the global reaction releases little energy. Methane gas production in fermentation Acetic acid can also undergo a dismutation reaction to produce methane and carbon dioxide : CH COO + H → CH + CO ΔG ° = - 36 kJ / reaction This disproportionation reaction is catalysed by methanogen archaea in their fermentative metabolism. One electron is transferred from the carbonyl function ( e donor ) of the carboxylic group to the methyl group ( e acceptor ) of acetic acid to respectively produce CO and methane gas. History of human use The use of fermentation, particularly for beverages, has existed since the Neolithic and has been documented dating from 7000 -- 6600 BCE in Jiahu, China, 5000 BCE in India, Ayurveda mentions many Medicated Wines, 6000 BCE in Georgia, 3150 BCE in ancient Egypt, 3000 BCE in Babylon, 2000 BCE in pre-Hispanic Mexico, and 1500 BC in Sudan. Fermented foods have a religious significance in Judaism and Christianity. The Baltic god Rugutis was worshiped as the agent of fermentation. The first solid evidence of the living nature of yeast appeared between 1837 and 1838 when three publications appeared by C. Cagniard de la Tour, T. Swann, and F. Kuetzing, each of whom independently concluded as a result of microscopic investigations that yeast is a living organism that reproduces by budding. It is perhaps because wine, beer, and bread were each basic foods in Europe that most of the early studies on fermentation were done on yeasts, with which they were made. Soon, bacteria were also discovered ; the term was first used in English in the late 1840s, but it did not come into general use until the 1870s, and then largely in connection with the new germ theory of disease. Louis Pasteur in his laboratory Louis Pasteur ( 1822 -- 1895 ), during the 1850s and 1860s, showed that fermentation is initiated by living organisms in a series of investigations. In 1857, Pasteur showed that lactic acid fermentation is caused by living organisms. In 1860, he demonstrated that bacteria cause souring in milk, a process formerly thought to be merely a chemical change, and his work in identifying the role of microorganisms in food spoilage led to the process of pasteurization. In 1877, working to improve the French brewing industry, Pasteur published his famous paper on fermentation, `` Etudes sur la Bière '', which was translated into English in 1879 as `` Studies on fermentation ''. He defined fermentation ( incorrectly ) as `` Life without air '', but correctly showed that specific types of microorganisms cause specific types of fermentations and specific end - products. Although showing fermentation to be the result of the action of living microorganisms was a breakthrough, it did not explain the basic nature of the fermentation process, or prove that it is caused by the microorganisms that appear to be always present. Many scientists, including Pasteur, had unsuccessfully attempted to extract the fermentation enzyme from yeast. Success came in 1897 when the German chemist Eduard Buechner ground up yeast, extracted a juice from them, then found to his amazement that this `` dead '' liquid would ferment a sugar solution, forming carbon dioxide and alcohol much like living yeasts. Buechner 's results are considered to mark the birth of biochemistry. The `` unorganized ferments '' behaved just like the organized ones. From that time on, the term enzyme came to be applied to all ferments. It was then understood that fermentation is caused by enzymes that are produced by microorganisms. In 1907, Buechner won the Nobel Prize in chemistry for his work. Advances in microbiology and fermentation technology have continued steadily up until the present. For example, in the late 1970s, it was discovered that 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. Strain selection and hybridization developed as well, affecting most modern food fermentations. Other approaches to advancing the fermentation industry has been done by companies such as BioTork, a biotechnology company that naturally evolves microorganisms to improve fermentation processes. This approach differs from the more popular genetic modification, which has become the current industry standard. Etymology The word `` ferment '' is derived from the Latin verb fervere, which means to boil. It is thought to have been first used in the late 14th century in alchemy, but only in a broad sense. It was not used in the modern scientific sense until around 1600. See also Biotechnology portal Acetone - butanol - ethanol fermentation Chemostat Dark fermentation Ethanol fermentation Fed - batch Fermentation in food processing Fermentation ( wine ) Fermentation lock Fermentative hydrogen production Gut fermentation syndrome Industrial fermentation Non-fermenter Photofermentation References ^ Jump up to : Klein, Donald W. ; Lansing M. ; Harley, John ( 2006 ). Microbiology ( 6th ed. ). New York : McGraw - Hill. ISBN 978 - 0 - 07 - 255678 - 0. Jump up ^ http://www.vivo.colostate.edu/hbooks/pathphys/digestion/largegut/ferment.html ^ Jump up to : AP Biology. Anestis, Mark. 2nd Edition. McGraw - Hill Professional. 2006. 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Jump up ^ Vogels, G.D. ; Keltjens J.T. ; Van Der Drift C. ( 1988 ). `` Biochemistry of methane production ''. In Zehnder A.J.B. Biology of anaerobic microorganisms. New York : Wiley. pp. 707 -- 770. Jump up ^ McGovern, P.E. ; Zhang, J. ; Tang, J. ; Zhang, Z. ; Hall, G.R. ; Moreau, R.A. ; Nunez, A. ; Butrym, E.D. ; Richards, M.P. ; Wang, C. - S. ; Cheng, G. ; Zhao, Z. ; Wang, C. ( 2004 ). `` Fermented beverages of pre - and proto - historic China ''. Proceedings of the National Academy of Sciences. 101 ( 51 ) : 17593 -- 17598. doi : 10.1073 / pnas. 0407921102. PMC 539767. PMID 15590771. Jump up ^ Vouillamoz, J.F. ; McGovern, P.E. ; Ergul, A. ; Söylemezoğlu, G.K. ; Tevzadze, G. ; Meredith, C.P. ; Grando, M.S. ( 2006 ). `` Genetic characterization and relationships of traditional grape cultivars from Transcaucasia and Anatolia ''. Plant Genetic Resources : characterization and utilization. 4 ( 2 ) : 144. doi : 10.1079 / PGR2006114. Jump up ^ Cavalieri, D ; McGovern P.E. ; Hartl D.L. ; Mortimer R. ; Polsinelli M. ( 2003 ). `` Evidence for S. cerevisiae fermentation in ancient wine '' ( PDF ). Journal of Molecular Evolution. 57 Suppl 1 : S226 -- 32. doi : 10.1007 / s00239 - 003 - 0031 - 2. PMID 15008419. 15008419. Archived from the original ( PDF ) on December 9, 2006. Retrieved 2007 - 01 - 28. ^ Jump up to : `` Fermented fruits and vegetables. A global perspective ''. FAO Agricultural Services Bulletins - 134. Archived from the original on January 19, 2007. Retrieved 2007 - 01 - 28. Jump up ^ Dirar, H., ( 1993 ), The Indigenous Fermented Foods of the Sudan : A Study in African Food and Nutrition, CAB International, UK Jump up ^ `` Gintaras Beresneviius. M. Strijkovskio Kronikos '' lietuvi diev sraas ``. spauda.lt. Jump up ^ Rūgutis. Mitologijos enciklopedija, 2 tomas. Vilnius. Vaga. 1999. 293 p. Jump up ^ A brief history of fermentation, East and West. Soyinfocenter.com. Retrieved on 2011 - 01 - 04. Jump up ^ Accomplishments of Louis Pasteur Archived 2010 - 11 - 30 at the Wayback Machine... Fjcollazo.com ( 2005 - 12 - 30 ). Retrieved on 2011 - 01 - 04. Jump up ^ HowStuffWorks `` Louis Pasteur ''. Science.howstuffworks.com ( 2009 - 07 - 01 ). Retrieved on 2011 - 01 - 04. Jump up ^ Louis Pasteur ( 1879 ) Studies on fermentation : The diseases of beer, their causes, and the means of preventing them. Macmillan Publishers. ^ Jump up to : Modern History Sourcebook : Louis Pasteur ( 1822 -- 1895 ) : Physiological theory of fermentation, 1879. Translated by F. Faulkner, D.C. Robb. Jump up ^ New beer in an old bottle : Eduard Buchner and the Growth of Biochemical Knowledge. Cornish - Bowden, Athel. Universitat de Valencia. 1997. ISBN 978 - 84 - 370 - 3328 - 0. p. 25. Jump up ^ The enigma of ferment : from the philosopher 's stone to the first biochemical Nobel prize. Lagerkvist, Ulf. World Scientific Publishers. 2005. ISBN 978 - 981 - 256 - 421 - 4. p. 7. Jump up ^ A treasury of world science, Volume 1962, Part 1. Runes, Dagobert David. Philosophical Library Publishers. 1962. p. 109. Jump up ^ Wang, H.L. ; Swain, E.W. ; Hesseltine, C.W. ( 1980 ). `` Phytase of molds used in oriental food fermentation ''. Journal of Food Science. 45 ( 5 ) : 1262. doi : 10.1111 / j. 1365 - 2621.1980. tb06534. x. External links Wikimedia Commons has media related to Fermentation. Works of Louis Pasteur Pasteur Brewing. The chemical logic behind fermentation and respiration Metabolism, catabolism, anabolism General Metabolic pathway Metabolic network Primary nutritional groups Energy metabolism Aerobic respiration Glycolysis → Pyruvate decarboxylation → Citric acid cycle → Oxidative phosphorylation ( electron transport chain + ATP synthase ) Anaerobic respiration Electron acceptors are other than oxygen Fermentation Glycolysis → Substrate - level phosphorylation ABE Ethanol Lactic acid Specific paths Protein metabolism Protein synthesis Catabolism Carbohydrate metabolism ( carbohydrate catabolism and anabolism ) Human Glycolysis ⇄ Gluconeogenesis Glycogenolysis ⇄ Glycogenesis Pentose phosphate pathway Fructolysis Galactolysis Glycosylation N - linked O - linked Nonhuman Photosynthesis Anoxygenic photosynthesis Chemosynthesis Carbon fixation Xylose metabolism Radiotrophism Lipid metabolism ( lipolysis, lipogenesis ) Fatty acid metabolism Fatty acid degradation ( Beta oxidation ) Fatty acid synthesis Other Steroid metabolism Sphingolipid metabolism Eicosanoid metabolism Ketosis Reverse cholesterol transport Amino acid Amino acid synthesis Urea cycle Nucleotide metabolism Purine metabolism Nucleotide salvage Pyrimidine metabolism Other Metal metabolism Iron metabolism Ethanol metabolism Metabolism map Carbon Fixation Photo - respiration Pentose Phosphate Pathway Citric Acid Cycle Glyoxylate Cycle Urea Cycle Fatty Acid Synthesis Fatty Acid Elongation Beta Oxidation Peroxisomal Beta Oxidation Glyco - genolysis Glyco - genesis Glyco - lysis Gluconeo - genesis Decarb - oxylation Fermentation Keto - lysis Keto - genesis feeders to Gluconeo - genesis Direct / C4 / CAM Carbon Intake Light Reaction Oxidative Phosphorylation Amino Acid Deamination Citrate Shuttle Lipogenesis Lipolysis Steroidogenesis MVA Pathway MEP Pathway Shikimate Pathway Transcription & Replication Translation Proteolysis Glycosy - lation Sugar Acids Double / Multiple Sugars & Glycans Simple Sugars Inositol - P Amino Sugars & Sialic Acids Nucleotide Sugars Hexose - P Triose - P Glycerol P - glycerates Pentose - P Tetrose - P Propionyl - CoA Succinate Acetyl - CoA Pentose - P P - glycerates Glyoxylate Photosystems Pyruvate Lactate Acetyl - CoA Citrate Oxalo - acetate Malate Succinyl - CoA α - Keto - glutarate Ketone Bodies Respiratory Chain Serine Group Alanine Branched - chain Amino Acids Aspartate Group Homoserine Group & Lysine Glutamate Group & Proline Arginine Creatine & Polyamines Ketogenic & Glucogenic Amino Acids Amino Acids Shikimate Aromatic Amino Acids & Histidine Ascorbate ( Vitamin C ) δ - ALA Bile Pigments Hemes Cobalamins ( Vitamin B ) Various Vitamin B 's Calciferols ( Vitamin D ) Retinoids ( Vitamin A ) Quinones ( Vitamin K ) & Carotenoids ( Vitamin E ) Cofactors Vitamins & Minerals Antioxidants PRPP Nucleotides Nucleic Acids Proteins Glycoproteins & Proteoglycans Chlorophylls MEP MVA Acetyl - CoA Polyketides Terpenoid Backbones Terpenoids & Carotenoids ( Vitamin A ) Cholesterol Bile Acids Glycero - phospholipids Glycerolipids Acyl - CoA Fatty Acids Glyco - sphingolipids Sphingolipids Waxes Polyunsaturated Fatty Acids Neurotransmitters & Thyroid Hormones Steroids Endo - cannabinoids Eicosanoids Major metabolic pathways in metro - style map. Click any text ( name of pathway or metabolites ) to link to the corresponding article. Single lines : pathways common to most lifeforms. Double lines : pathways not in humans ( occurs in e.g. plants, fungi, prokaryotes ). Orange nodes : carbohydrate metabolism. Violet nodes : photosynthesis. Red nodes : cellular respiration. Pink nodes : cell signaling. Blue nodes : amino acid metabolism. Grey nodes : vitamin and cofactor metabolism. Brown nodes : nucleotide and protein metabolism. Green nodes : lipid metabolism. GND : 4129537 - 7 NDL : 00562847 Metabolism portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Fermentation&oldid=824053843 '' Categories : Fermentation Anaerobic digestion Oenology Fermented drinks Brewing Food science Metabolism Food preservation Alchemical processes Mycology Catalysis Hidden categories : Webarchive template wayback links All articles with unsourced statements Articles with unsourced statements from February 2015 Pages using div col without cols and colwidth parameters Wikipedia articles with GND identifiers Talk Contents About Wikipedia Wikibooks Alemannisch Asturianu বাংলা Bân - lâm - gú Беларуская Български Bosanski Català Čeština Dansk Deutsch Eesti Ελληνικά Español Esperanto Euskara فارسی Français Gaeilge Gàidhlig Galego 한국어 Հայերեն हिन्दी Hrvatski Ido Bahasa Indonesia Íslenska Italiano עברית Basa Jawa Қазақша Latviešu Lietuvių Magyar Македонски Bahasa Melayu Mìng - dĕ̤ng - ngṳ̄ မြန်မာဘာသာ Nederlands 日本 語 Norsk Norsk nynorsk Oʻzbekcha / ўзбекча Piemontèis Polski Português Runa Simi Русский Саха тыла Shqip Sicilianu Simple English Slovenščina Ślůnski Soomaaliga Српски / srpski Srpskohrvatski / српскохрватски Basa Sunda Suomi Svenska Tagalog தமிழ் ไทย Türkçe Українська Vèneto Tiếng Việt 粵語 中文 Edit links This page was last edited on 5 February 2018, at 01 : 40. 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Question: what is necessary for a substance to undergo fermentation
Answer: sugar in the absence of oxygen