Yeast. that is what causes the fermentation.
Here:
Ethanol is produced both as a petrochemical, through the hydration of ethylene, and biologically, by fermenting sugars with yeast.
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Ethylene hydration
Ethanol for use as industrial feedstock is most often made from petrochemical feedstocks, typically by the acid-catalyzed hydration of ethylene, represented by the chemical equation
C2H4 + H2O → CH3CH2OH
The catalyst is most commonly phosphoric acid, adsorbed onto a porous support such as diatomaceous earth or charcoal; this catalyst was first used for large-scale ethanol production by the Shell Oil Company in 1947.[5] Solid catalysts, mostly various metal oxides, have also been mentioned in the chemical literature.
In an older process, first practiced on the industrial scale in 1930 by Union Carbide[6], but now almost entirely obsolete, ethene was hydrated indirectly by reacting it with concentrated sulfuric acid to product ethyl sulfate, which was then hydrolysed to yield ethanol and regenerate the sulfuric acid:
C2H4 + H2SO4 → CH3CH2SO4H
CH3CH2SO4H + H2O → CH3CH2OH + H2SO4
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Fermentation
Ethanol for use in alcoholic beverages, and the vast majority of ethanol for use as fuel, is produced by fermentation: when certain species of yeast (most importantly, Saccharomyces cerevisiae) metabolize sugar in the absence of oxygen, they produce ethanol and carbon dioxide. The overall chemical reaction conducted by the yeast may be represented by the chemical equation
C6H12O6 → 2 CH3CH2OH + 2 CO2
The process of culturing yeast under conditions to produce alcohol is referred to as brewing. Brewing can only produce relatively dilute concentrations of ethanol in water; concentrated ethanol solutions are toxic to yeast. The most ethanol-tolerant strains of yeast can survive in up to about 25% ethanol (by volume).
During the fermentation process, it is important to prevent oxygen getting to the ethanol, since otherwise the ethanol would be oxidised to acetic acid (vinegar). Also, in the presence of oxygen, the yeast would undergo aerobic respiration to produce just carbon dioxide and water, without producing ethanol.
In order to produce ethanol from starchy materials such as cereal grains, the starch must first be broken down into sugars. In brewing beer, this has traditionally been accomplished allowing the grain to germinate, or malt. In the process of germination, the seed produces enzymes that can break its starches into sugars. For fuel ethanol, this hydrolysis of starch into glucose is accomplished more rapidly by treatment with dilute sulfuric acid, fungal amylase enzymes, or some combination of the two.
At petroleum prices like those that prevailed through much of the 1990s, ethylene hydration was a decidedly more economical process than fermentation for producing purified ethanol. Recent increases in petroleum prices, coupled with perennial uncertainty in agricultural prices, make forecasting the relative production costs of fermented versus petrochemical ethanol difficult at the present time.
2006-07-28 02:04:56
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answer #1
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answered by Robb 5
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You generally don't make the enzyme. Instead, it is isolated from cultures (bacterial or yeast). And usually, that's pretty expensive. Most industrial processes use the microbes and then deal with separating and otherwise cleaning up the fermentation mess.
2006-07-28 02:08:15
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answer #2
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answered by ChemDoc 3
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that wasnt the question. it exchange into merely what enzyme is used interior the production of ethanol based fuels. i positioned carbohydrases, because of the fact they destroy down the strach interior the maize into trouble-free sugars to create an capability source for the yeast :)
2016-11-03 04:41:55
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answer #3
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answered by ? 4
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ethanol is prepared using mollazzes,water and yeast.
mix all the ingredients and store it in a glass bottle with a small hole in the lid
2006-07-28 02:38:52
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answer #4
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answered by pearl 1
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