WEBSITE:www.fermentor.co.in Fermentation …

1 (biochemistry)From Wikipedia, the free encyclopediaFor other uses, seeFermentation (disambiguation). Fermentation in progress:scumformed byCO2gas bubbles and fermenting a form ofanaerobic digestionthat generatesATPby theoxidationof certainorganic compounds, such ascarbohydrates. Fermentation usesanendogenous,organicelectron acceptor.[1]In contrast,respirationis where electrons are donated to anexogenouselectron acceptor, such as oxygen, via anelectron transport chain. Fermentation is important inanaerobicconditions when there is nooxidative phosphorylationto maintain the production of ATP(adenosine triphosphate) byglycolysis. During Fermentation ,pyruvateis metabolized to various compounds.

2 Homolactic Fermentation is the productionoflactic acidfrom pyruvate;alcoholic fermentationis the conversion of pyruvate intoethanolandcarbon dioxide; and heterolactic Fermentation is theproduction of lactic acid as well as other acids and alcohols. Fermentation does not necessarily have to be carried out in ananaerobicenvironment. Forexample, even in the presence of abundant oxygen,yeastcells greatly prefer Fermentation tooxidative phosphorylation, as long assugarsare readily availablefor consumption (a phenomenon known as theCrabtree effect).[2]The antibiotic activity ofhopsalso inhibits aerobic metabolism in are the most commonsubstrateof Fermentation , and typical examples of Fermentation products areethanol,lactic acid,lactose, , more exotic compounds can be produced by Fermentation , such asbutyric outfermentationin the productionofethanolinbeers,wines, and other alcoholic drinks, along with the production oflarge quantities ofcarbon dioxide.

3 Fermentation occursinmammalianmuscleduring periods of intense exercise where oxygen supply becomes limited, resulting in the creation oflactic acid.[3]Contents[hide] acid respiration 2 Hydrogen gas production infermentation 3 Methane gas production infermentation 4 History 5 Etymology 6 See also 7 References 8 External links[edit]ChemistryComparison ofaerobic respirationand most known Fermentation types ineucaryoticcell.[4]Numbers in circles indicate counts of carbon atoms in molecules, C6isglucoseC6H12O6, C1carbon membrane is products contain chemical energy (they are not fullyoxidized), but are considered waste products, since they cannot be metabolized furtherwithout the use of equationbelow shows the alcoholic Fermentation ofglucose, whosechemical formulais C6H12O6.

4 [5]One glucose molecule is converted intotwoethanolmolecules and twocarbon dioxidemolecules:C6H12O6 2 C2H5OH + 2 CO2C2H5OH is thechemical Fermentation takes place, oneglucosemolecule is broken down into twopyruvatemolecules. This is known asglycolysis.[5][6][edit]Lactic acid fermentationLactic acid fermentationis the simplest type of Fermentation . In essence, it is aredoxreaction. In anaerobic conditions, the cell s primary mechanismofATPproduction is glycolysis. Glycolysis reduces ( transferselectronsto)nicotinamide adenine dinucleotide(NAD+), forming NADH. However there is alimited supply of NAD+available in any given cell.

5 For glycolysis to continue, NADH must be oxidized ( have electrons taken away) toregenerate theNAD+that is used in glycolysis. In an aerobic environment, where oxygen is available, oxidation of NADH is usually done through anelectrontransportchainin a process calledoxidative phosphorylation, but oxidative phosphorylation cannot occur in anaerobic environments because oxygen is absent dueto the pathway's dependence on the terminal electron acceptor of oxygen.[7]Instead, the NADH donates its extra electrons to thepyruvate moleculesformed during glycolysis. Since the NADH has lost electrons, NAD+regenerates and is again available for acid, for which this process isnamed,is formed by the reduction of pyruvate.

6 [7]In heterolactic acid Fermentation , one molecule of pyruvate is converted to lactate; the otheris converted to ethanol and carbon dioxide. In homolacticacid Fermentation , both molecules of pyruvate are converted to lactate. Homolactic acid Fermentation is unique because it isone of the only respirationprocesses to not produce a gas as a fermentationbreaks down the pyruvate intolactate. It occurs in themuscles of animals when they need energy faster than thebloodcansupply oxygen. It also occurs in some kinds ofbacteria(such aslactobacilli) and somefungi. It is this type of bacteria that convertslactoseinto lactic acidinyogurt, giving it its sour taste.

7 These lactic acid bacteria can be classed as homofermentative, where the end-product is mostly lactate, orheterofermentative, where some lactate is further metabolized and results in carbon dioxide, acetate, or other metabolic process of lactic acid Fermentation using glucose is summarized below.[8]In homolactic Fermentation , one molecule of glucose is converted to twomolecules of lactic acid:C6H12O6 2 one molecule of lactose and one molecule of water make four molecules of lactate (as in some yogurts and cheeses):C12H22O11+ H2O 4 heterolactic Fermentation , the reaction proceeds as follows, with one molecule of glucose being converted to one molecule of lactic acid, onemolecule of ethanol, and one molecule of carbon dioxide:[8]C6H12O6 CH3 CHOHCOOH + C2H5OH + CO2 Before lactic acid Fermentation can occur, the molecule of glucose must be split into two molecules ofpyruvate.

8 This process iscalledglycolysis.[9][edit]GlycolysisMa in article:GlycolysisTo extract chemicalenergyfrom glucose, the glucose molecule must be split into two molecules ofpyruvate.[9]This process generates twomolecules ofNADHand also four molecules ofadenosine triphosphate(ATP), yet there is only net gain of two ATP molecules considering thetwo initially consumed.[8]C6H12O6+ 2 ADP+ 2 Pi+ 2 NAD+ 2 CH3 COCOO + 2 ATP + 2 NADH + 2 H2O + 2H+Thechemical formulaofpyruvateis CH3 COCOO . Pistands for the inorganicphosphate. As shown by the reactionequation,glycolysiscauses the reduction oftwo molecules ofNAD+toNADH.[8]TwoADPmolecules are alsoconverted to twoATPandtwo water molecules viasubstrate-level phosphorylation.

9 [edit]Aerobic respirationInaerobic respiration, the pyruvate produced by glycolysis is oxidized completely, generating additional ATP and NADH in thecitric acidcycleand byoxidative phosphorylation. However, this can occur only in the presence of oxygen. Oxygen is toxic to organisms thatareobligate anaerobes, and are not required byfacultative anaerobic organisms. In the absence of oxygen, one of the fermentationpathways occurs in order to regenerateNAD+; lactic acid Fermentation is one of these pathways.[8][edit]Hydrogen gas production in fermentationHydrogengas is produced in many types of Fermentation (mixed acid Fermentation ,butyricacidfermentation,cap roatefermentation,butanolfermentation,gl yoxylatefermentation), as a way to regenerate NAD+ transferred toferredoxin, which in turn is oxidized byhydrogenase, producing H2.

10 [5]Hydrogen gas isasubstrateformethanogensandsulfate reducers, which keep the concentration of hydrogen low and favor theproduction of such anenergy-rich compound,[10]but hydrogen gas at a fairly high concentration can nevertheless be formed, as an example of mixed acid Fermentation , bacteria such asClostridium pasteurianumferment glucoseproducingbutyrate,acetate,carbon dioxideand hydrogen gas:[11]The reaction leading to acetate is:C6H12O6+ 4 H2O 2 CH3 COO-+ 2 HCO3-+ 4 H++ 4 H2 Glucose could theoretically be converted into just CO2and H2, but the global reaction releases little energy.[edit]Methane gas production in fermentationAcetic acidcan also undergo adismutationreaction to producemethaneandcarbon dioxide:[12][13]CH3 COO + H+ CH4+ CO2 G =-36kJ/reactionThisdisproportionationrea ction is catalysed bymethanogenarchaeain their fermentative metabolism.