Download 河北交通职业技术学院教案 Lesion 5 Alcoholic Beverages (1) 课题引

河北交通职业技术学院教案
Lesion 5
Alcoholic Beverages (1)
课题引入（时间：5 分钟）：
1、结合食品业中酒精类饮料的现状和发展前景，说明学习酒精类饮料的英
文资料的必要性。
讲授新内容
※※※※
一、前言部分的翻译学习（时间：20 分钟）
前言一般包括对题目研究的意义、研究的状况以及相关研究的评述和目的
等。了解前言内容，即可获知全文涉及的相关内容。
Alcoholic beverages are produced from a range of raw materials but especially
很多未加工的原料都可用于生产酒精饮料，特别包括谷类、水果和糖类作物。
from cereals, fruits and sugar crops. They include non-distilled beverages such as
这些酒精饮料包括非蒸馏饮料，如啤酒、葡萄酒、苹果酒和米酒；
beers, wines, ciders, and sake. Disitlled beverages such as whisky and rum are
还保留蒸馏饮料，如威士忌酒和朗姆酒；这两种分别是从谷类和糖浆发酵而来。
而白兰地酒是从葡萄酒蒸馏生产的。
produced from fermented cereals and molasses, respectively, while brandy is
produced by distillation of wine. Other distilled beverages, such as vodka and gin, are
其他的蒸馏酒饮料，如伏特加酒和杜松子酒，是从发酵的糖浆、谷类、土豆或乳
清中提纯酒精而生产出的。
produced from neutral spirits obtained by distillation of fermented molasses, grain,
potato or whey. A variety of fortified wines are produced by addition of include
多种加酒井的葡萄酒通过附加雪利酒、
波特酒和马德拉酒而生产出的。
sherries, port and Madeira wines.
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二、 正文 Biology of yeast fermentation 部分的翻译（时间：30 分钟）
Biology of yeast fermentation
酵母发酵的生物学
Over 96% of fermentation ethanol is produced using strains of saccharomyces
超过 96%的酒精发酵是采用的菌种都是啤酒酵母或与其相关的酵母，尤其是奶
酒酵母。
河北交通职业技术学院教案
cerevisae or species related to it, particularly saccharomyces uvarum. Ethanol is
奶酒酵母
啤酒酵母
produced by the Embden-Meyerhof-Parnas ( EMP ) parthway. Pyruvate ,produced
EMP 途径是产生酒精的代谢途径。在糖酵解过程中，丙酮酸盐被转化成乙醛和酒精。
全部总反应见下面公式。
during glycolysis is converted to acetaldehyde and ethanol. The overall effect is
summarized as follows.
葡萄糖
Glucose + 2ADP
酒 精
2Ethanol + 2CO2 + 2ATP
Theoretical yield from 1g glucose are 0.51g ethanol and 0.49g CO2. However, in
理论上，1 克葡萄糖可产生 0.51 克酒精和 0.49 克的二氧化碳。
practice, approximately 10% of the glucose is converted to biomass and yield of
然而，实际生产中，近 10%的葡萄糖被转化为生物量，产生的酒精和二氧化碳的
量接近理论值的 90%。
ethanol and CO2 may reach 90% of theoretical values. The ATP formed is used to
supply other cell energy requirements.
形成的 ATP 用于满足其他细胞的能量需要。
The yeast-cell envelope contains a plasma membrane, a periplasmic space and a
酵母细胞的胞膜含一层质膜、周质空间和一个细胞壁；细胞壁主要由大部分多聚
糖和小部分的肽组成。
cell wall consisting mainly of polysaccharides with a small amount of peptide
material. The wall component is a semi-rigid but solute permeable structure which
该细胞壁是一种半硬质，但可溶的有透过性的结构，能够赋予酵母相当的抗压和抗张强度。
provides considerably compressional and tensile strength to yeasts. Carboxyl groups
of cell-wall peptides confer important flocculating characteristics on brewing yeasts,
该壁中肽的羧基基团赋予细胞在发酵过程中重要的絮凝特性，这促进了发酵后期物质的固-液
分离。
facilitating post-fermentation solid-liquid separation. Flocculation is thought to result
该壁中肽的羧基基团赋予细胞在发酵过程中重要的絮凝特性，这促进了发酵后期物质的固-液
分离。
河北交通职业技术学院教案
from salt- bridge formation between calcium ions and these cell-wall carboxyl groups.
认为这种絮凝是由于钙离子和细胞壁羧基集团搭建的盐桥而形成的。
三、 正文 Fermentation conditions 部分的翻译（时间：30 分钟）
Fermentation conditions
发酵条件
Fermenting S. cerevisiae brewing yeast cells utilize the sugars, sucrose, fructose,
啤酒酵母利用糖进行发酵时，对蔗糖、果糖、麦芽糖和麦芽三糖有着独特的利
用次序。
maltose and maltotriose in that distinct order. Sucrose is first hydrolyzed by invertase
located in the extracellular periplasmic space. Sugars are transported across the cell
首先在胞外周质空间水解蔗糖；糖类再由诱导型或组成型的透性酶被主动或被
动的进行跨膜转运至胞内。
membrane by either active or passive transport, mediated by inducible or
麦芽糖和麦芽三糖在胞内被 α-葡萄糖苷酶水解。
constitutively-produced permeases. Maltose and maltotroise are hydrolyzed
intracellularly by α-glucosidase. Saccharomyces uvarum (S. carlsbergensis) is
奶酒酵母（卡尔酵母）
taxonomically distinguished from S. cerevisiae in that it can also utilize melibiase.
奶酒酵母（卡尔酵母）因为也可以利用蜜二糖酶，所以其在分类学上区别于啤酒酵母。
Kluyveromyces fragilis and Kluyveromyces lactis, which unlike S. cerevisiae can
脆壁克鲁维酵母
乳酸克鲁维酵母
ferment lactose, contain a lactose permease system for lactose transport into the cell
这两种克鲁维酵母不同于啤酒酵母，它们含有乳糖透性酶系统，可将乳糖转运至细胞内，
从而能够将乳糖水解为葡萄糖和半乳糖而进入糖酵解途径。
where it is hydrolyzed to glucose and galactose which enter glycolysis. With the
酵母菌属中除了糖化酵母之外，其他的不能水解淀粉和胡精。而糖化酵母不适用于酿造。
exception of Saccharomyces diastaticus, which is not suitable for brewing,
河北交通职业技术学院教案
Saccharomyces yeasts are incapable of hydrolyzing starches and dextrins. Use of
starch-based materials for alcoholic fermentations requires addition of exogenous
以淀粉为底物进行发酵需要额外添加酶，如麦芽中的 α-和 β-淀粉酶或者微生物中的 α-淀粉
酶，葡萄糖苷酶（葡萄糖化酶）和支链淀粉酶。
enzymes such as α-and β-amylase of malt or microbial enzymes such as α-amylase,
amyloglucosidase ( glucoamylase) and pullulanase. The major sugars of grape juice
are glucose, any umfermented sugar left in the resulting wine is fructose. In contrast,
葡萄果汁中主要的糖是葡萄糖；在葡萄酒发酵中被剩
下的糖时果糖。相反，白葡萄酒酵母发酵时果糖却比
Sauterne wine yeasts
ferment fructose faster than glucose.
葡萄糖快的多。
河北交通职业技术学院教案
Lesion 5
Alcoholic Beverages (2)
课题引入（时间：5 分钟）：
1、复习上节课的内容，连贯起发酵控制调节部分的翻译学习。
讲授新内容
※※※※
一、正文 Fermentation conditions 部分的翻译（时间：70 分钟）
Brewer’s wort, produced from barley malt contains 19 amino acids and a
从大麦芽产出的酿造麦芽汁，含有 19 种氨基酸和其他大量的营养成分。这些
氨基酸在发酵过程中以不同的速度被利用。
range of other nutrients. These amino acids are assimilated at different rates during
fermentation. A general amino acid permease (GAP) can transport all basic and
常见的氨基酸透性酶可转运除脯氨酸之外的所有的基础型氨基酸和中间型氨基酸。
neutral amino acids except proline. At least 11 other more specific amino acid
transport systems exist in yeast. Proline permease is repressed by other amino acids
至少其他 11 种特定氨基酸转运系统存在于酵母中。
脯氨酸透性酶被其他氨基酸和氨抑制了活性。
and ammonia.
While alcoholic fermentations are largely anaerobic, some oxygen is needed to
虽然酒精发酵一般都是在厌氧的环境中，但还是需要一些氧气来使酵母合成固醇
和不饱和脂肪酸，组成膜的成分。
enable the yeast to synthesize some sterols and unsaturated fatty acid membrane
components. Brewer’s wort normally contains sub-optimal levels of sterols and
酿造的麦芽汁通常是包含的固醇和不饱和脂肪酸的量不充足，但在培养基中添加
油酸或油酸衍生物，则发酵过程就不需要任何氧气。
unsaturated fatty acids, but if the medium is supplemented with oleic or oleanoic acid,
the requirement for oxygen disappears.
Many strains of S. cerevisiae can attain ethanol concentration of 12-14%. Interest
多数啤酒酵母菌株都可使酒精发酵浓度达到 12-14%。
河北交通职业技术学院教案
has developed in the use of high alcohol production for distillation with a view to
考虑到降低蒸馏成本和增加产量，在高比例酿造过程和酒精蒸馏中，人们对耐酒
精能力强的酵母的利用产生越来越强的兴趣。
increasing plant productivity and decreasing distillation costs. Select strains are able
to produce 18-20% alcohol although fermentation rate is generally greatly reduced as
发酵中虽久久浓度增加，发酵速度一般降低的极快，但人们还是希望选择出可产
生 18-20%酒精的菌株。
ethanol concentration increase. Grape juices with very high sugar and concerntrations
are only fermented by osmophilic yeasts such as Saccharomyces rouxii and
含高糖的葡萄汁仅仅可被耐高渗酵母发酵，例如鲁氏酵母菌和 baili 酵母菌；这两
株菌可高效的发酵果糖。
Saccharomyces bailli which have a high capacity to ferment fructose. Plasma
membrane phospholipid composition is important for ethnal tolerance. Increased
质膜中的磷脂对于细胞耐受酒精具有重要作用。当膜不饱和脂肪酸含量增加时，
细胞耐受酒精的能力也增加。
ethanol tolerance is observed when membrane unsaturated fatty acid content is
increased. Alcohol tolerance may be enhanced by supplementing the growth medium
在培养基中补充不饱和脂肪酸，维生素和蛋白质，可以增强细胞的耐受酒精的能力。
with unsaturated fatty acids, vitamins and proteins. Physiological factors such as the
method of substrate feeding, intracellular ethanol accumulation, osmotic pressure, and
生理学上的那些方法，如添加底物，胞内酒精积累，改变渗透压和温度，都能使
酵母耐受酒精的能力增加。
temperature all contribute to yeast ethanol tolerance. Yeast glycolytic enzyme
hexokinase, gluceraldhydes-3-phosphate dehydrogenase and pryruvate decarboxylase
酵母中分解糖的酶，己糖激酶、甘油醛-3-磷酸脱氢酶和丙酮酸脱羧酶，都对酒精
浓度敏感。
have been shown to be sensitive to ethanol concentration.
For yeasts, pH values between 3 and 6 are most favourable for growth and
河北交通职业技术学院教案
fermentation activity. Fermentation activity is higher at higher pH values and there is
对于酵母来说，pH 值在 3-6 之间，对生长和发酵活性是最适宜的。在此范围内，
pH 高，发酵活性高；但在 3-4 间没有明显变化。
a noticeable lag in fermentation activity at pH 3-4.‖ pH affects formation of
pH 可影响副产物的形成。高 pH 值可增加甘油的产量。葡萄汁的 pH 一定在 3.0-3.9
范围，因为其主要含酒石酸或苹果酸而表现出的高酸度 5-15/l。
by-products. High pH values increase glycerol formation. The pH of grape must is
usually in the range 3.0-3.9 because of its high acid content (5-15/l), mainly tartaric
and malic acids. Since most bacteria, with the exception of acetic acid and lactic acid
bacteria, prefer more neutral pH values the susceptibility of wine musts to infection is
除乙酸和乳酸细菌外，大多数细菌都更适宜中性 pH 值
环境，从而使葡萄汁对细菌污染的敏感性大大降低。
greatly reduced.
Temperature optima are distinctly different for yeast fermentation, yeast
对酵母的发酵、呼吸和发酵来说，都有不同的适宜的温度。
respiration and cell growth. Fermentation rate generally increase with temperature in
the range 15-35℃ and glycerol, acetone, butane-2-3-diol, acetaldehyde, pyruvate and
在 15-35℃范围内，发酵速度一般随温度增加；甘油、丙酮、2-3-丁烷二醇、乙缩醛乙
二醇、丙酮酸盐和戊酮二磷酸盐的含量也增加。高级醇形成也依赖高温。
2-ketoglutarate levels increase in the fermentation broth. Formation of higher alcohols
is also temperature-dependent. With white wines, lower fermentation temperatures
produce fresher and more fruity wines, and the risk of bacterial infection and resultant
对白葡萄酒来说，发家温度低，产生的酒更新鲜和果味更浓；也增加了细菌污染的机
会，导致挥发性酸量降低。
volatile acid production is reduced. Higher temperatures of 22-30℃ are used for
production of red wines, fermented on the skins, leading to increased colour
河北交通职业技术学院教案
extraction and production of a rich aroma.
22-30℃范围的发酵高温情况下，通过表面发酵，
生产的红葡萄酒，导致就颜色增加且富有香气。
河北交通职业技术学院教案
Lesion 6 Amino Acids (1)
课题引入（时间：5 分钟）：
1、结合营养学上氨基酸的知识，说明氨基酸类英文资料的必要性。
讲授新内容
※※※※
一、例文中第一部分的翻译学习（时间：20 分钟）
Amino acids are produced using a range of technologies including direct
氨基酸的生产有很多途径，包括直接发酵法、用细胞或酶合成前提的方法、蛋
白水解物抽提法和化学合成法。
fermentation, biotransformation of precursors using cells or enzymes, extraction of
protein hydrolysates and chemical synthesis. They have a variety of uses as nutrients
在食品和饲料工业中，氨基酸具有诸如作为营养素和提高风味的多种用途。
and flavours in the food and feed industries. Table 1 indicates the annual demand,
表 1 指在食品工业中，生产氨基酸的每年的产量、方法和应用目的。
production methods and applications of amino acids in the food industry. Important
amino acids with non-food applications include L-arginine, L-gludtamine, L-histidine,
L-leucine, L-phenylalanine, L-tyrosine and L-valine.
重要的非食品用氨基酸包含 L-精氨酸、L-谷氨酰胺、 L-组氨酸、 L-亮氨酸、
L-苯丙氨酸、 L-酪氨酸和 L-缬氨酸。
※※※※
二、例文中第二部分的翻译学习（时间：10 分钟）
While fermentation or biotransformation processes have been developed for
在发酵或生物合成的生产过程中，现已经可以生产除甘氨酸、L-半胱氨酸和胱
氨酸之外所有的氨基酸了，但并不是所有的生产方法都可进行商业生产。
production of all amino acids except glycine, L-cysteine and L-cystine, not all of
these processes are commercially viable. L-asparagine, L-leucine, L-tyrosine,
L-天冬酰胺、L-亮氨酸、L-酪氨酸、L-半胱氨酸和 L-胱氨酸的生产是对蛋白水
解物的提纯方法。
L-cysteine, and L-cystine are produced by purification of protein hydrolysates.
河北交通职业技术学院教案
Chemical synthesis is more economical for production of optically-inactive racemic
化学合成方法更适宜生产不旋光的外消旋混合物 D-和 L-异构体，如 D、L-蛋
氨酸，D、L-色氨酸和甘氨酸。
mixtures of D- and L-isomers, and D, L-Methionine, D, L-tryptophan and glycine are
produced in this way. Processing involving amino acylase enzymes may be used to
在上述生产中，可以使用氨基转移酶
来解决消除外消旋混合物的产生。
resolve these racemic mixtures.
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三、例文中第二部分的翻译学习（时间：40 分钟）
棒状杆菌属
短杆菌属
Microbial strains from the genera Croynebacterium and Brevibacterium have
人们已经认识到，发酵生产氨基酸中重要的菌株来源于棒状杆菌和短杆菌属。
assumed major importance in the production of amino acids by fermentation. Natural
自然界分离的这些野生菌株就能够分泌大量的谷氨酸。
isolates of these strains can excrete large quantities of glutamic acid. Because of cell
metabolic regulatory mechanisms, particularly end-prodcut repression and inhibition,
由于细胞有代谢调节机制，特别是终产物的抑制作用，野生的种群很少分泌大
量水平的氨基酸。
substantial levels of amino acids are rarely excreted by wild-type isolates. Production
of commercial quantities of the amino acids has been dependent on the successful
商业上生产氨基酸的产量就决定于能否成功应用可分泌大量氨基酸的菌株突变体。
development of deregulated mutants. The two most important methods involve use of
auxotrophic and regulatory mutants or a combination of the two. Auxotrophic mutants,
有两种重要的方法可获得营养缺陷体和调控突变株，或者两者同时缺陷的突变体。
which lack the enzyme needed to form the regulatory effector metabolite (often the
end-product), many accumulate and excrete the metabolic intermediate which is the
河北交通职业技术学院教案
substrate for the eliminated enzyme. A lysine auxotroph, for example, lacks an
营养缺陷突变体就是缺少某种酶，可调控代谢受体的形成（一般是终产物）
；积累
或分泌需要的代谢中产物可作为消除该酶抑制反应。
enzyme in the pathway necessary for lysine synthesis and requires lysine, or a
例如，赖氨酸缺陷体，缺少赖氨酸合成途径中的一个酶，必需添加赖氨酸或者其
代谢前提才能转化成赖氨酸来满足生长需求。
metabolic precursor which can be converted to lysine, for growth. End-product
inhibition by the amino acid product of an unbranched biosynthetic pathway may be
avoided
by
the
development
of
regulatory
mutants,
having
an
altered
没有支路得生物合成途径生产的氨基酸终产物的抑制作用也许可以通过调控突变体的发展而
避免，该调控突变体具有对反馈抑制不敏感的关键酶，从而可以积累某些特殊的氨基酸。
feedback-insensitive key enzyme, thus allowing accumulation of the particular amino
acid. Analogues of the end-product, which are also capable of inhibition of the
终产物类似物也能对抑制敏感的关键酶产生抑制作用；这时可以选择抗类似物的或可调节类似
物作用的突变体，来屏蔽此种抑制作用。
sensitive key enzyme, may be used in screening methods for selection of
analogue-resistant or regulatory mutants. Revertants may be selected from
auxotrophic mutants (apparently lacking the key regulatory enzyme) which produce a
没有支路得生物合成途径生产的氨基酸终产物的抑制作用也许可以通过调控突变体的发展而
从营养缺陷突变体（显然缺失关键调节酶）中筛选回复子，其可意产生一种能更好解除抑
避免，该调控突变体具有对反馈抑制不敏感的关键酶，从而可以积累某些特殊的氨基酸。
制的酶。
modified deregulated enzyme.
河北交通职业技术学院教案
Lesion 6 Amino Acids (2)
—— Glutamic Acid Production
课题引入（时间：5 分钟）：
1、结合上节课学习的内容和营养学上氨基酸的知识，说明氨基酸类英文资
料的必要性。
讲授新内容
※※※※
一、例文中第一段的翻译学习（时间：10 分钟）
The flavour-enhancing properties of sodium glutamate were discovered in
在 20 世纪初谷氨酸钠的鲜味增强作用在日本被发现，
Japan at the start of the twentieth century and a fermentation process for its
目前通过谷氨酸钠棒状杆菌发酵来生产，
每年世界市场有 400000 吨。
production by Corynebacterium glutamicum currently supplies and annual world
market of about 400 000t.
※※※※
二、例文中第二段的翻译学习（时间：15 分钟）
Molasses or starch hydrolysates are generally used for commercial production of
糖蜜或者淀粉水解物通常被用来进行谷氨酸棒状杆菌和相关菌系的谷氨酸商品生产
glutamic acid by C. glutamicum and related strains. An ample supply of a suitable
nitrogen source such as ammonium salts is essential, since NH3 is incorporated into
适当氮源，例如铵盐的充足补充是非常必要的，因为 NH 是氨基酸分子的组成部分。
the amino acid molecule. Glutamic acid producing bacteria can also utilize urea as
谷氨酸生产菌也能利用尿素作为氮源。
nitrogen source. The concertration of ammonium ion must be maintained at a low
铵离子浓度必须在介质中维持较低的水平，因为较高浓度对细胞生长和产物形成是有害的。
level in the medium as higher concentrations are detrimental to cell growth and
product formation. The pH of medium tends to drop due to cell glutamate excretion
河北交通职业技术学院教案
and ammonium ion assimilation, and gaseous ammonia is used as a means of
介质中的 pH 是逐渐降低的，这是由于细胞谷氨酸的释放和铵离子的消耗。
simultaneously medium nitrogen level and a fermentation pH optimum of 7.0-8.0.
气态氨通常被用来作为监测介质中实时氮水平的指标。发酵的最适 pH 是 7.0-8.0。
Glutamate biosynthesis is an aerobic process requiring oxygen throughout the
谷氨酸盐的生物合成是一个需氧过程，需要通过发酵来获得氧气。
fermentation.
※※※※
三、例文中第三段的翻译学习（时间：20 分钟）
Glutamate-producing bacteria require biotin for growth but accumulation of the
谷氨酸盐生产菌的生长需要生物素，在生物素浓度为 0.5μg/g 细胞（干重）时
amino acid is maximum at a critical biotin concentration of 0.5μg/g cells (dry),
氨基酸的积累量达到最大值。但该条件不是达到菌最大生长值的条件。
which is sub-optimal for maximum growth. Excess biotin, while supporting abundant
growth, impairs glutamate accumulation. Addition of C16-C18 saturated fatty acids
过量的生物素在维持足够的生长时，会消弱谷氨酸盐的积累。在生长过程中添加 C16-C18
during growth also permits accumulation of glutamate even in presence of high biotin
饱和脂肪酸甚至在高浓度生物素存在的条件下也能促进谷氨酸盐的积累。
concentrations. This is because accumulation of the amino acid id primarily controlled
by its rate of excretion rather than by its rate of biosynthesis. Biotin is a co-factor of
这是因为氨基酸的积累主要受它释放速率而不是生物合成速率的影响。
acetyl CoA carboxylase(羧化酶), the first enzyme in the pathway for biosynthesis of
生物素是乙酰辅酶 A 羧化酶的协同因子，乙酰辅酶 A 羧化酶是油酸（不饱和的，C18：1）
oleic acid (unsaturated, C18:1 ) and its subsequent incorporation into phospholipids.
生物合成通路的第一个酶，随后它又掺入磷脂。
C16-C18 saturated fatty acid repress acety CoA carboxylase. Phospholipids appear to
C16-C18 饱和脂肪酸抑制乙酰辅酶 A 羧化酶活性。
河北交通职业技术学院教案
regulate the permeability of the cell to glutamate and sub-optimal biotin
磷脂看来具有调节细胞中谷氨酸盐、不适生物素浓度或 C16-C18 饱和脂肪酸渗透的功能，
concentrations or C16-C18 saturated fatty acids to decrease the concentration of
因此降低细胞中磷脂的浓度，能增加细胞谷氨酸的渗透。
phospholipids in the cell, thereby increasing cell permeability to glutamate.
※※※※
四、例文中第四段的翻译学习（时间：10 分钟）
Even in the presence of excess biotin, glutamic acid producing bacteria, grown in
在青霉素存在下的谷氨酸生产菌，在过量生物素存在的条件下也能积累大量的谷氨酸盐。
the presence of penicillin, can accumulate large amounts of glutamate. Penicillin
inhibits bacterial cell-wall synthesis and the enhanced accumulation of glutamate is
thought to result from the formation of swollen cells with weakened cell walls,
青霉素抑制细菌细胞壁的合成，导致了肿胀细胞的形成，消弱了细胞壁，破坏了细胞
resulting in damage to the permeability barrier of the cell membrane.
膜的渗透障碍，提高谷氨酸盐的积累。
※※※※
五、例文中第五段的翻译学习（时间：25 分钟）
Under optimized conditions for glutamate production from hexose, the
对己糖生产谷氨酸进行优化条件，控制 EMP 途径是最关键的；其是连接糖
转化成三羧酸的桥梁。
Embden-Meyerhof-Parnas pathway predominates, channeling carbon precusors into
the tricarboxylic acid. The NADPH + H+ formed in the oxidative decarboxylation(氧
化脱羧) of isocitrate (异柠檬酸盐) to α-ketoglutarate provides the reduced co-factor
在异柠檬酸盐氧化脱羧转化为α酮戊二酸时形成的 NADPH+H+提供了减少与 NH3
which together with NH3 is required for conversion of α-ketoglutarate to glutamate
共同协同作用的协同因子，这些对α酮戊二酸通过谷氨酸盐脱氢酶转化为谷氨酸盐是必须的。
河北交通职业技术学院教案
by glutamate dehydrogenase. Commercial glutamic acid-producing strains lack the
商品化的谷氨酸生产菌缺乏三羧酸循环酶α酮戊二酸脱氢酶，因此在缺乏 NH4+
tricarboxylic acid cycle enzyme α-ketoglutarate dehydrogenase and consequently, in
the absence of NH4+ ions but with sufficient oxygen, α-ketoglutarate acid
但是有充足的氧时，α酮戊二酸积累。
accumulates. Krebs cycle (克雷布斯循环，即三羧酸循环)intermediates, required for
replenishment of oxaloacetate needed for the citrate synthase condensation reaction
and other cell reactions, are supplied by efficient anaplerotic reaction and other cell
三羧酸循环高效的补偿反应需要补充草酰乙酸盐，在柠檬酸合成酶的作用
下，进行缩合反应和其他的细胞反应。
reactions, are supplied by efficient anaplerotic reactions. Phosphoenolpyruvate
回补反应;补给反应;补偿反应
carboxylase plays an important role in the carboxylation of phosphoenolpyruate to
磷酸烯醇丙酮酸羧化酶对磷酸烯醇丙酮酸转化形成草酰乙酸乙酸起到重要作用。
form oxaloacetate. Alternatively, the Krebs cycle intermediates may be replenished by
还有一条途径，通过乙醛酸循环的代谢也可以补充三羧酸循环的中间产物。
the operation of the glyoxylate cycle. Stoichiometrically 1mole of glutamate is
化学计算
produced from 1.4 mole glucose when the glyoxylate cycle is involved whereas the
化学计算出，通过乙醛酸循环，1.4 摩尔葡萄糖可转化成 1 摩尔谷氨酸；但该途
径通过固定二氧化碳时，每摩尔葡萄糖可产生 2 摩尔谷氨酸。
pathway involving carbon dioxide fixation by producing 2 moles glutamate per mole
of glucose. In order to increase the efficiency of conversion, some mutants have been
为了增加谷氨酸的转化效率，人们通过采用一些可降低柠檬酸裂解酶的水平的突变体。
introduced which have decreased levels of the glyoxylate cycle enzyme, isocitrate
lyase. The metabolic pathway for production of glutamate from glucose is
河北交通职业技术学院教案
summarized in Fig.1.
从葡萄糖生产谷氨酸的代谢途径图总结于图 1 中。
河北交通职业技术学院教案
Lesion 6 yogurt fermentation (1)
课题引入（时间：5 分钟）：
1、结合食品业中酸奶发酵的现状和发展前景，说明学习酸奶发酵类的英文
资料的必要性。
讲授新内容
※※※※
一、第一段的翻译学习（时间：20 分钟）
Yogurt is another well-known fermented dairy product that forms an important
酸奶是一种众所周知的发酵乳制品，世界上很多地方已经成为人类食物重要的一
部分。
part of the human diet in many parts of the world. In the United States alone, 1979
仅在美国 1979 年，酸奶消费数据表明已经大大超过了 565 百万磅。
sales figures indicated that more than 565 million pounds of this fermented dairy
product were sold. Depending on the system of manufacture and the nature of the
根据生产工艺和产品凝固的特性，酸奶分为凝固型和搅拌型。
coagulum, yogurts may be classified as being of two main types, set or stirred. Tow
lactose-fermenting bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus,
保加利亚乳杆菌
嗜热链球菌
are used as the starter culture to make yogurt. Equal numbers of L. bulgaricus and S.
发酵剂
乳杆菌
thermophilus are desirable for flavor and texture production. The lactobacilli grow
乳糖发酵细菌，保加利亚乳杆菌和嗜热链球菌被用来作制作酸奶的发酵剂。并且，
两种菌等量使用可以得到最佳的风味产品。
first, liberating the amino acids glycine and histidine and stimulating the growth of
乳杆菌先生长，释放甘氨酸和组氨酸，并能够刺激链球菌的生长。
streptococci. The production of the characteristic flavor by the aforementioned culture
is a function of time as well as the sugar content of the starting yogurt material.
发酵的时间也和开始发酵时蔗糖含量一样都决定了
前述发酵的产品风味特征。
※※※※
二、 第二段的翻译（时间：30 分钟）
河北交通职业技术学院教案
Commercially, yogurt is made from a mix of whole, partially defatted milk;
市售商品化的酸奶有多种形式，包括有全部或部分的脱脂牛奶，炼乳脱脂奶，奶
酪和脱脂奶粉发酵而成的。
condensed skim milk; cream; and nonfat dry milk. Milk fat levels in such preparations
脱脂乳
奶脂肪含量一般范围在 1.0%-3.25%之间。
range from 1.0% to 3.25%. Only products containing a minimum of 3.25% milk fat
are labeled yogurt. Those with 0.5% to 2.0% or less than 0.5% milk fat are labeled
只有产品脂肪含量在 3.25%以上才可标明是酸奶。那些脂肪含量在 0.5-2.0%之间或者
低于 0.5%的，只能分别被标识是低脂和脱脂酸奶。
low-fat and nonfat yogurts, respectively. In addition to milk fat, other milk ingredients
are found in yogurt. These include casein, sodium and calcium caseinates, whey, and
除了乳脂肪外，酸奶里还含有其它乳成分；包括酪蛋白、酪酸钙和钠、乳清和乳清
蛋白。
whey protein concentrates. Additives of several kinds are also permitted in
commercially produced yogurt, such as nutritive carbohydrate sweeteners, coloring,
几种添加剂允许在商品化的酸奶中使用，例如碳水化合物营养甜味剂、色素、稳定
剂（使组织结构光滑细腻及延长货架寿命）， 以及增加酸奶风味的水果。
stabilizers ( for smooth texture and longer shelf life), and fruit preparations for
flavoring. Fruit preparations for blending in yogurt are specially designed to meet the
调入水果的目的，特别是为了满足市场上不同人群的口味需求。
marketing requirements for different types of yogurt. The types most commonly
marketed include the sundae style (fruit preserves are layered on the bottom of
containers) and the Swiss style (fruit preparations are thoroughly blended in yogurt
大多数市售类型包括圣代风格（水果分层加在容器底）和瑞士风格（水果被充分的
混合在酸奶中）
。
after culturing).
※※※※
三、 第三段的翻译（时间：25 分钟）
河北交通职业技术学院教案
The product is prepared either by reducing the water content of either whole or
skim milk by at least one fourth (may be done in a vacuum pan following sterilization
产品制备有两种方式，其一是通过降低全脂或脱脂乳四分之一的水分含量（可在真
空锅内灭菌）
；其二是通过增加至约 5%的牛奶固形物（用冷凝法处理使水分降低）。
of milk), or by adding about 5% milk solids followed by water reduction (condensing).
牛奶固形物
The concentrated milk is then heated to 82-93℃ for 30-60minutes and cooled to
炼乳然后被加热到 82-93℃，保持 30-60 分钟，然后冷却到约 45℃。
around 45℃. The yogurt starter is now added at a level of around 2% by volume and
酸奶发酵剂
incubated at 45℃ for 3-5 hours followed by cooling to 5 ℃. The titratable acidity of a
现今酸奶发酵剂使用量约为容器的 2%，在 45℃ 下培养 3-5 小时，然
后冷却至 5 ℃。
good finished product is around 0.85-0.9%, and to get this amount of acidity the
fermenting product should be removed from 45 ℃ when the titratable acidity is
好的发酵终产品的滴定酸度约 0.85-0.9%；如果酸度达到 0.65-0.7%时，发
酵产物应被立即在 45℃终止。
around 0.65-0.7%. Good yogurt keeps well at the rod, so that after around 3 hours, the
numbers of the two organisms should be approximately equal. Higher amounts of
发酵好的酸奶很好的保持杆菌，因为 3 小时后，那两种菌的数量约相等。
acidity, such as 4%, can be achieved by allowing the product to ferment longer, with
the effect that the rods will exceed the cocci in number. The streptococci tend to be
延长发酵时间可以增加酸度，诸如能达到 4%，此时在杆菌的作用下，其数
量将超过球菌。
inhibited at pH values of 4.2-4.4, whereas the lactobacilli can tolerate pH values in the
球菌在 pH 值 4.2-4.4 范围内被抑制，而乳酸杆菌则可以耐受到 pH3.5-3.8 的范围。
3.5-3.8 range.
※※※※
四、 第四段的翻译（时间：5 分钟）
河北交通职业技术学院教案
Yogurt and other cultured dairy foods are excellent sources of high-quality
酸奶和其他发酵奶制品都具有极好的高蛋白和 B 组维生素与矿物质。
protein and certain B-complex vitamins and minerals. In addition to the nutritional
importance of yogurt, it has been found to be of value in maintaining a balance in the
intestinal microbial flora.
酸奶除营养价值外，它也被发现具有保持肠内微生态
平衡的功能。