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  • 酒精发酵 -- -- 高级

    lesson content

    When you combine grapes and yeast, what have you begun to make?
    ::当你们将葡萄和酵母混合的时候,你们有什么收获呢?

    Wine. It may be slightly more complicated than that, but you need to start with grapes and yeast and allow a natural process to occur. Essentially, this is respiration without oxygen.
    ::葡萄酒。它可能比这稍微复杂一些, 但你需要从葡萄和酵母开始, 并允许自然过程发生。 基本上, 这是没有氧气的呼吸。

    Alcoholic Fermentation: A “New” Source of Energy?
    ::酒精发酵:“新的”能源来源?

    Have you fueled your car with corn? You have if you bought gas within the city of Portland, Oregon. Portland was the first city to require that all gasoline sold within the city limits contain at least 10% ethanol. By mid-2006, nearly 6 million “flex-fuel” vehicles – which can use gasoline blends up to 85% ethanol (E85 – Figure  ) were traveling US roads. This “new” industry employs an “old” crew of yeast and to make ethanol by an even older biochemical pathway – alcoholic fermentation . Alcoholic fermentation is a biochemical process in which sugars such as glucose , fructose, and sucrose are converted into small amounts of ATP , producing ethanol and carbon dioxide during the process.
    ::你是否用玉米给汽车加油了? 如果你在俄勒冈州波特兰市购买了天然气,你是否用玉米加油了? 波特兰是第一个要求城市范围内销售的所有汽油至少含有10%乙醇的城市。 到2006年年中,近600万辆“弹性燃料”车 — — 它可以使用高达85%乙醇的汽油混合(E85-图 ) — — 正在美国公路上行驶。 这个“新”工业雇用了一个“老的”酵母组员,用比旧的生化途径 — — 酒精发酵 — — 制造乙醇。 酒精发酵是一个生物化学过程,在这个过程中,甘蔗、浮糖和苏克罗斯等糖被转化成少量的ATP,生产乙醇和二氧化碳。

    lesson content
    Ethanol provides up to 85% of the energy needs of new “flex-fuel” cars. Although its energy efficiency is still controversial, ethanol from corn or cellulose appears to be more “renewable” than fossil fuels.

    Many people consider renewable biofuels such as ethanol a partial solution to the declining availability of nonrenewable fossil fuels . Although controversy still surrounds the true efficiency of producing fuel from corn, ethanol is creeping into the world fuel resource picture. Many countries have implemented policies promoting the blending of ethanol with petrol.
    ::许多人认为乙醇等可再生生物燃料是不可再生化石燃料供应量下降的部分解决办法。 尽管从玉米生产燃料的真正效率仍存在争议,但乙醇正在逐渐进入世界燃料资源状况。 许多国家已经实施了促进乙醇与汽油混合的政策。

    Ethanol fuel
    Ethanol from corn or cellulose is produced by yeasts through alcoholic fermentation – an anaerobic type of respiration.

    You are probably most familiar with the term fermentation in terms of alcoholic beverages. You may not have considered that the process is actually a chemical reaction certain bacteria and yeasts use to make ATP. Like lactic acid fermentation , alcoholic fermentation, which is also referred to as ethanol fermentation , processes pyruvate one step further in order to regenerate NAD + so that can continue to make ATP, even in low-oxygen environments. In this form of , pyruvate is broken down into ethyl alcohol (C 2 H 6 O) and carbon dioxide.
    ::您可能最熟悉酒精饮料发酵这一术语。 您可能并不认为该过程实际上是一种化学反应, 某些细菌和酵母用来制造ATP。 和乙醇发酵一样, 酒精发酵, 也被称为乙醇发酵, 加工过程更进一步, 以便再生NAD+, 从而即使在低氧环境下也能继续生成ATP。 在这种形式下, pruvate 被分解为乙醇( C2H6O) 和二氧化碳。

    C 3 H 3 O 3 (pyruvate) + NADH → C 2 H 5 OH (ethyl alcohol) + CO 2 + NAD +
    ::+ NADH + C2H5HH(乙醇)+ CO2+ NAD+ NAD+ NADH + C2H5OH(乙醇)+ CO2+ NAD+

    lesson content
    Alcoholic fermentation produces ethanol and NAD+. The NAD+ allows glycolysis to continue making ATP.

    Fermentation by Yeast
    ::动物发酵

    We have domesticated yeast ( Figure  and Figure  ) to carry out this type of anaerobic respiration for many commercial purposes. Some yeasts, such as the baker's yeast Saccharomyces cerevisiae, actually prefer fermentation over aerobic respiration . These yeasts will produce ethanol even under aerobic conditions. When you make bread, you employ the yeast to make the bread “rise” by producing bubbles of carbon dioxide gas. Ethanol is also produced. Why do you suppose that eating bread does not intoxicate you?
    ::我们已经将酵母(图和图)驯化为多种商业用途的此类厌氧呼吸。有些酵母,例如面包师的酵母沙迦罗梅斯蛋白,实际上更喜欢发酵而不是有氧呼吸。这些酵母即使在有氧呼吸条件下也会生产乙醇。当你做面包时,你用酵母制造面包“起” , 生产二氧化碳气泡。伊森诺也生产。你为什么认为吃面包不会使你中毒?

    Bread is not intoxicating because the bread fermentation process takes a short amount of time, only allowing for a small amount of alcohol to be produced, most of which will evaporate during the baking process. A study was reported to the American Chemical Society suggesting that after collecting samples from bakeries and household ovens, they found that the alcohol content varied from 0.04% to 1.9%. The alcohol content of bread varies with the kind of yeast used, the time it sets, and the temperature of baking. 
    ::面包不令人陶醉,因为面包发酵过程需要很短的时间,只允许少量的酒精生产,其中多数会在烘烤过程中蒸发。 向美国化学学会报告的一项研究显示,在从面包房和家用烤箱采集样品后,他们发现酒精含量从0.04%到1.9%不等。 面包的酒精含量随使用的酵母种类、设定的时间和烘烤温度而不同。

    lesson content
    Yeasts (A) are facultative anaerobes, which means that in the absence of oxygen, they use alcoholic fermentation to produce ethyl alcohol and carbon dioxide. Both products are important commercially. Recall that yeasts are single-celled eukaryotic organisms that reproduce asexually (B).
    lesson content
    We employ yeasts to use their anaerobic talents to help bread rise (via bubbles of CO2) and grapes ferment (adding ethanol).

    Brewers of beer and wine use yeast to add alcohol to beverages. Traditional varieties of yeast not only make but also limit the quantity of alcohol in these beverages, because, above 18% by volume, alcohol becomes toxic to the yeast itself. Wine is produced by fermentation of the natural sugars present in grapes and other kinds of fruit . Beer, whiskey, and vodka are produced by fermentation of grain starches that have been converted to sugar by the amylase , and rum is produced by fermentation of sugarcane. In each of these fermentations, sugars are converted into small amounts of ATP, using and regenerating NAD + in the process, and producing ethanol and carbon dioxide. Scientists have recently developed new strains of yeast which can tolerate up to 25% alcohol by volume. These are used primarily in the production of ethanol fuel.
    ::啤酒和葡萄酒的酿酒者用酵母来增加饮料中的酒精; 传统的酵母品种不仅制造而且限制这些饮料中的酒精数量,因为酒精量超过18%,对酵母本身产生毒性; 葡萄酒是通过葡萄和其他水果中天然糖的发酵产生的; 啤酒、威士忌和伏特加是用氨酸盐转化为糖的谷物淀粉的发酵产生的; 朗姆酒是通过甘蔗的发酵产生的; 在每一种发酵过程中,糖被转化成少量的ATP,在过程中使用和再产生NAD+,生产乙醇和二氧化碳; 科学家最近研制出新的酵母菌菌株,可以容容量高达25%的酒精; 这些主要用于生产乙醇燃料。

    Human use of alcoholic fermentation depends on the chemical energy remaining in pyruvate after glycolysis. Transforming pyruvate does not add ATP to that produced in glycolysis, and for anaerobic organisms , this is the end of the ATP-producing line. All types of anaerobic respiration yield only 2 ATP per glucose.
    ::人类使用酒精发酵取决于在水晶解析后在气压中残留的化学能量。 转化气压除去在水晶解析中产生的化学能量之外,不会增加ATP,对于厌氧生物来说,这是ATP生产线的终点。 所有类型的厌氧呼吸都只能产生2ATP/每根葡萄糖。

    Summary
    ::摘要

    • Both alcoholic and lactic acid fermentation pathways change pyruvate in order to continue producing ATP by glycolysis.
      ::酒精和杀菌酸发酵途径都变化了药效,以便通过水解继续生产ATP。
    • Alcoholic fermentation is a type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to ethanol and carbon dioxide and the regeneration of NAD + from NADH.
      ::酒精发酵是一种厌氧呼吸类型,包括液解,随后将丙酸转化为乙醇和二氧化碳,并从国家人权组织中恢复NAD+。

    Review
    ::回顾

    1. Human cells cannot carry out alcoholic fermentation, yet we use it for many purposes. Analyze its importance to human life.
      ::人类细胞不能进行酒精发酵,但我们却为了许多目的使用酒精发酵,分析酒精发酵对人类生命的重要性。
    2. Indicate the maximum alcohol content of wine and beer, and explain the reason for this limit.
      ::指出葡萄酒和啤酒的最大酒精含量,并解释这一限制的理由。
    3. Outline the process used to produce fuel from corn and explain why some consider this fuel “renewable” and preferable to fossil fuels. Research the pros and cons of this fuel.
      ::概述从玉米生产燃料的过程,并解释为什么有些人认为这种燃料“可再生”,比化石燃料更可取。 研究这种燃料的利弊。
    4. Explain how fermentation is used to make bread.
      ::解释发酵是如何用来做面包的。
    5. Explain why both alcoholic and lactic acid fermentation must change pyruvic acid, even though no energy is gained in this conversion.
      ::解释为什么酒精和乳酸发酵必须改变丙酸,即使这种转化没有获得能量。