| Line 1: |
Line 1: |
| − | === Fermentation ===
| + | {{stub}} |
| − | Ethanol for use in [[alcoholic beverage]]s, and the vast majority of ethanol for use as fuel, is produced by fermentation: when certain species of [[yeast]] (most importantly, ''[[Saccharomyces cerevisiae]]'') [[metabolism|metabolize]] [[saccharide|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
| |
| | | | |
| − | : [[glucose|C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>]] → 2 CH<sub>3</sub>CH<sub>2</sub>OH + 2 [[carbon dioxide|CO<sub>2</sub>]]
| + | '''Ethanol''', also known as [[grain alcohol]] is a flammable [[chemical compound]] with a strong [[odor]], and is the [[alcohol]] found in [[alcoholic beverage]]s. In common usage, it is often referred to simply as alcohol. The chemical formula is variously represented as EtOH, CH<sub>3</sub>CH<sub>2</sub>OH, C<sub>2</sub>H<sub>5</sub>OH. |
| | | | |
| − | 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 [[toxicity|toxic]] to yeast. The most ethanol-tolerant strains of yeast can survive in up to about 15% ethanol by volume.
| + | Ethanol is also a [[biofuel]] made from [[alcohol]] and is an [[oxygenate]] that is added to [[gasoline]] to increase the [[octane]] rating. The product is produced through the [[fermentation]] of [[corn]], or other cellulosic material. |
| | | | |
| − | During the fermentation process, it is important to prevent oxygen from 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.
| + | ==Process== |
| | | | |
| − | In order to produce ethanol from starchy materials such as [[cereal grain]]s, 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 [[enzyme]]s that can break its starches into sugars.
| + | |
| | + | |
| | + | ==Co-products== |
| | + | |
| | + | A co-product of the fermentation process is [[distillers grains]] which can be used as cattle feed. Distillers grains is termed either [[wet distillers grains]] or [[dried distillers grains]] or simply [[DDGs]]. Wet distillers grains have a very short shelf life as they are susceptible to microorganisms that can pollute the material and render it unfit for cattle consumption. |
| | + | |
| | + | ==Ethanol Industry== |
| | + | |
| | + | In the [[United States]] ethanol is most commonly made through the fermentation of corn. Other countries, such as [[Brazil]] use sugar as a [[catalyst]] for the fermenting process. Currently, the US has the highest production numbers for ethanol in the world, but some analysts forecast China as being a potential world player in the ethanol market. [[China]] currently uses [[casava]] and [[wheat]] among other material for producing ethanol. |
| | + | |
| | + | [[Category:Chemistry]] |