Biotechnology Revision for IGCSE CIE Biology | IGCSE CIE 生物技术考点精讲

📚 Biotechnology Revision for IGCSE CIE Biology | IGCSE CIE 生物技术考点精讲

Biotechnology uses living organisms or their enzymes to manufacture useful products on a large scale. In IGCSE Biology, you need to understand the principles of fermentation, the design of industrial fermenters, the role of enzymes, and examples such as yoghurt production, bread making, penicillin production, biogas generation, and genetic modification. This article covers all key points with paired English-Chinese explanations to support your revision.

生物技术利用生物体或其酶大规模制造有用产品。在 IGCSE 生物学中，你需要理解发酵的原理、工业发酵罐的设计、酶的作用以及酸奶制作、面包制作、青霉素生产、沼气生成和基因改造等实例。本文涵盖所有重点，提供中英对照讲解，助力复习备考。

1. What Is Biotechnology? | 什么是生物技术？

Biotechnology is the industrial use of living organisms, such as bacteria, fungi, or yeast, or their enzymes, to produce food, medicines, and fuels. Traditional biotechnology includes processes like bread making and cheese production that people have used for thousands of years. Modern biotechnology involves genetic engineering, where we directly modify an organism’s DNA.

生物技术是利用细菌、真菌或酵母等生物体或其酶来工业化生产食品、药品和燃料。传统生物技术包括数千年来人们使用的面包制作和奶酪生产等工艺。现代生物技术则涉及基因工程，即直接修改生物的 DNA。

Many biotechnological processes rely on microorganisms’ metabolism, particularly respiration. Fermentation is a form of anaerobic respiration in which sugars are broken down without oxygen to produce useful end-products. The two main types you must know for IGCSE are alcoholic fermentation (by yeast) and lactic acid fermentation (by bacteria).

许多生物技术过程依赖微生物的代谢，特别是呼吸作用。发酵是一种无氧呼吸形式，在不消耗氧气的情况下降解糖类，产生有用的终产物。IGCSE 考试中你必须掌握的两种主要类型是：酵母的酒精发酵和细菌的乳酸发酵。

2. Alcoholic Fermentation by Yeast | 酵母的酒精发酵

Yeast is a single-celled fungus that respires anaerobically to carry out alcoholic fermentation. The word equation is:

酵母是一种单细胞真菌，在无氧条件下进行酒精发酵。文字方程式如下：

glucose → ethanol + carbon dioxide (+ energy)

葡萄糖 → 乙醇 + 二氧化碳 (+ 能量)

Using chemical symbols, the balanced equation is:

用化学符号表示的方程式为：

C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂

In bread making, the carbon dioxide produced makes the dough rise, creating a light and spongy texture. The ethanol evaporates during baking. Bakers mix flour, water, sugar, and yeast, then leave the dough in a warm place to allow fermentation.

在面包制作中，产生的二氧化碳使面团膨胀，产生松软的海绵状质地。乙醇在烘烤过程中蒸发。面包师将面粉、水、糖和酵母混合，然后将面团放在温暖处发酵。

For beer brewing, barley grains are allowed to germinate to produce maltose-rich malt. This is mixed with hot water to extract sugars (mashing), and then boiled with hops for flavour. Yeast is added to the cooled liquid (wort) and ferments in the absence of air, producing ethanol. The alcohol concentration usually reaches around 4-6%.

酿造啤酒时，让大麦谷物发芽以产生富含麦芽糖的麦芽。将其与热水混合提取糖分（糖化），然后与啤酒花一起煮沸以增加风味。冷却后的液体（麦芽汁）中加入酵母，在无氧条件下发酵产生乙醇。酒精浓度通常达到约 4-6%。

Wine is produced by fermenting crushed grapes with their natural sugars in the absence of air. Yeast naturally present on grape skins can be used, or selected strains are added. The CO₂ escapes or is captured for sparkling wines.

葡萄酒通过将压碎的葡萄与其天然糖分在无氧条件下发酵生产。葡萄皮上天然存在的酵母即可使用，也可添加筛选的菌株。产生的二氧化碳逸出，或对起泡酒进行收集。

3. Lactic Acid Fermentation by Bacteria | 细菌的乳酸发酵

Certain bacteria, such as Lactobacillus and Streptococcus species, carry out lactic acid fermentation when oxygen is limited. The simplified equation is:

某些细菌，如乳酸杆菌和链球菌属，在氧气有限时进行乳酸发酵。简化方程式为：

glucose → lactic acid (+ energy)

葡萄糖 → 乳酸 (+ 能量)

Or using chemical formulas:

或使用化学式：

C₆H₁₂O₆ → 2 C₃H₆O₃

In yoghurt production, milk is first pasteurised by heating to kill any harmful microbes. It is then cooled and inoculated with a starter culture of Lactobacillus bulgaricus and Streptococcus thermophilus. The mixture is kept warm at around 40-45°C for several hours. The bacteria ferment lactose (milk sugar) into lactic acid, which lowers the pH to around 4.5. This acidity coagulates milk proteins, creating the thick, tangy texture of yoghurt.

酸奶生产中，牛奶先通过加热巴氏消毒以杀灭有害微生物，然后冷却并接种保加利亚乳杆菌和嗜热链球菌的发酵剂。混合物在约 40-45°C 保温数小时。细菌将乳糖发酵为乳酸，使 pH 降至约 4.5。这种酸度使牛奶蛋白凝固，形成酸奶浓稠、略带酸味的质地。

For cheese, lactic acid bacteria are also used, but a clotting enzyme called rennet is added to speed up the separation of solid curds from liquid whey. The type of bacteria and additional steps such as pressing, salting, and ripening determine the cheese variety.

制作奶酪也使用乳酸菌，但会添加一种称为凝乳酶的凝固酶，以加速固态凝乳与液态乳清的分离。使用的细菌种类以及压榨、加盐和成熟等额外步骤决定了奶酪的品种。

4. Fermenter Design and Controlled Conditions | 发酵罐设计与条件控制

Large-scale fermenters (bioreactors) are vessels used to grow microorganisms under tightly controlled conditions. A typical industrial fermenter is made of stainless steel, which is resistant to corrosion and easy to sterilise. It includes:

大规模发酵罐（生物反应器）是在严格控制条件下培养微生物的容器。典型的工业发酵罐由不锈钢制造，耐腐蚀且易于灭菌。它包括：

An air inlet with a filter – to supply sterile air for aerobic organisms and prevent contamination.

带过滤器的进气口 – 为好氧生物提供无菌空气，防止污染。

A stirrer (impeller) – to distribute nutrients, oxygen, and heat evenly throughout the culture.

搅拌器（叶轮） – 使营养物质、氧气和热量在培养物中均匀分布。

A cooling jacket or water jacket – to remove excess heat generated by microbial respiration and control temperature.

冷却夹套或水套 – 带走微生物呼吸产生的多余热量并控制温度。

Probes for pH and temperature monitor conditions continuously.

pH 和温度探头持续监测条件。

A sampling port – to withdraw small amounts of culture for testing without introducing contaminants.

取样口 – 取出少量培养物进行检测，而不会引入污染物。

Controlling these conditions is critical because enzymes inside microorganisms work best within specific ranges. For most fermentations, temperature is kept at the optimum for the organism’s enzymes (e.g., 25-30°C for yeast, 23-28°C for Penicillium). pH is regulated by adding acid or alkali. In aerobic fermentations, oxygen supply must be sufficient to meet the high demand. Sterile conditions are maintained to prevent competition from unwanted bacteria and fungi.

控制这些条件至关重要，因为微生物体内的酶在特定范围内活性最高。对大多数发酵过程而言，温度需保持在微生物酶的最适范围（如酵母 25-30°C，青霉菌 23-28°C）。通过添加酸或碱调节 pH。在好氧发酵中，氧气供应必须满足高需求。无菌条件的维持可防止杂菌污染。

5. Use of Enzymes in Biotechnology | 酶在生物技术中的应用

Enzymes isolated from microorganisms are widely used because they are specific, work at moderate temperatures, and are biodegradable. Biological washing powders contain proteases, lipases, and sometimes amylases. Proteases break down protein stains like blood and egg; lipases digest fatty stains such as grease; amylases remove starch-based residues. Using these enzymes allows effective cleaning at lower temperatures (30-40°C), saving energy and protecting fabrics.

从微生物中分离的酶应用广泛，因为它们专一性强、在温和温度下工作且可生物降解。生物洗衣粉含有蛋白酶、脂肪酶，有时还有淀粉酶。蛋白酶分解血液、蛋液等蛋白质污渍；脂肪酶消化油脂类污渍；淀粉酶去除淀粉类残留物。这些酶的使用可在较低温度（30-40°C）下有效清洁，节省能源并保护织物。

Pectinase is an enzyme added during fruit juice extraction. It breaks down pectin, a polysaccharide that holds plant cell walls together. As pectin breaks down, the fruit pulp releases more juice, yields increase, and the juice becomes clearer. Likewise, lactase converts lactose into glucose and galactose, producing lactose-free milk for people who are lactose intolerant.

果胶酶是果汁提取过程中添加的酶。它分解果胶（一种将植物细胞壁连接在一起的多糖）。随着果胶分解，果肉释放更多果汁，产量提高，果汁变得更清澈。同样，乳糖酶将乳糖转化为葡萄糖和半乳糖，为乳糖不耐受者生产无乳糖牛奶。

In many industrial processes, enzymes are immobilised by trapping them in alginate beads or attaching them to inert supports. This allows enzymes to be reused, makes product purification easier, and lowers costs.

在许多工业过程中，通过将酶包埋在海藻酸盐珠中或固定在惰性支撑物上实现酶的固定化。这样酶可重复使用，产品纯化更简单，成本降低。

6. Production of the Antibiotic Penicillin | 抗生素青霉素的生产

Penicillin is produced by the filamentous fungus Penicillium chrysogenum in aerobic, submerged fermentation. The fungal culture requires a nutrient-rich medium containing corn steep liquor, lactose or glucose, mineral salts, and a nitrogen source. Sterile air is continuously supplied because the fungus is strictly aerobic.

青霉素由丝状真菌产黄青霉在好氧深层发酵中产生。真菌培养需要富含营养的培养基，包含玉米浆、乳糖或葡萄糖、矿物盐和氮源。由于真菌严格好氧，需持续供给无菌空气。

The fermenter is maintained at a temperature of 23 to 28°C and pH around 6.5, as these are the optimum conditions for Penicillium growth and penicillin production. After about 5–7 days, the fungus secretes penicillin into the broth. The antibiotic is then extracted, purified, and crystallised. Sterile technique throughout is vital to prevent contamination, which could introduce competing organisms or β-lactamase producers that destroy penicillin.

发酵罐保持在 23 至 28°C 的温度和约 6.5 的 pH，这是产黄青霉生长和青霉素产生的最适条件。约 5-7 天后，真菌将青霉素分泌到发酵液中。随后提取、纯化并结晶抗生素。全程无菌技术至关重要，以防止污染引入竞争生物或产生破坏青霉素的β-内酰胺酶的菌株。

7. Biogas Production: Anaerobic Digestion | 沼气生产：厌氧消化

Biogas is a mixture of mainly methane (CH₄, about 60-70%) and carbon dioxide (CO₂, about 30-40%), with traces of other gases. It is produced when organic matter such as animal manure, crop residues, or food waste is broken down by bacteria in the absence of oxygen inside a digester. The simplified overall conversion is:

沼气是主要由甲烷（CH₄，约 60-70%）和二氧化碳（CO₂，约 30-40%）组成的混合气体，并含有痕量其他气体。当动物粪便、作物残渣或厨余垃圾等有机物在消化器内无氧条件下被细菌分解时，就产生沼气。简化的总转化可表示为：

organic matter → CH₄ + CO₂ + other products

有机物 → CH₄ + CO₂ + 其他产物

The process involves several groups of bacteria working sequentially. Hydrolytic bacteria break down complex polymers into simpler molecules; acidogenic bacteria convert these into organic acids; acetogenic bacteria produce acetate and hydrogen; and methanogenic archaea finally produce methane. The digester must be sealed and maintained at a suitable temperature – either mesophilic (around 35°C) or thermophilic (around 55°C) – for optimal microbial activity.

该过程涉及多组细菌依次工作。水解菌将复杂聚合物分解为简单分子；产酸菌将其转化为有机酸；产乙酸菌生成乙酸盐和氢气；最后产甲烷古菌产生甲烷。消化器必须密封，并维持在适宜温度——中温（约 35°C）或高温（约 55°C）——以获得最佳微生物活性。

The methane produced can be burned directly for cooking, heating, or to generate electricity. Biogas is a renewable energy source that also reduces methane release from waste, as the burning process converts methane into less potent CO₂.

产生的甲烷可直接燃烧用于烹饪、取暖或发电。沼气是一种可再生能源，同时还能减少废弃物中甲烷的释放，因为燃烧过程将甲烷转化为温室效应较弱的二氧化碳。

8. Genetic Engineering: Making Human Insulin | 基因工程：制造人胰岛素

Genetic engineering modifies an organism’s DNA to give it new characteristics. One of the first and most important applications was the production of human insulin using the bacterium Escherichia coli. Before this, diabetics were treated with insulin extracted from pigs or cattle, which could cause allergic reactions. Recombinant human insulin is identical to the human version and is now the standard treatment.

基因工程修改生物的 DNA 以赋予其新性状。最早且最重要的应用之一是利用大肠杆菌生产人胰岛素。在此之前，糖尿病患者使用从猪或牛提取的胰岛素，可能引起过敏反应。重组人胰岛素与人体自身的胰岛素完全相同，现已成为标准治疗。

The process involves several steps: The human insulin gene is isolated and cut out using a restriction enzyme. The same restriction enzyme is used to cut open a small circular DNA molecule called a plasmid inside the bacterial cell, creating sticky ends. DNA ligase then joins the insulin gene into the plasmid to form recombinant DNA. The plasmid is inserted into E. coli cells, which are then grown in large fermenters. As the bacteria multiply, they follow the instructions in the human gene to produce insulin protein. The insulin is extracted and purified for medical use.

该过程包括几个步骤：分离人胰岛素基因并用限制酶切出。同种限制酶用于切开细菌细胞内称为质粒的小环状 DNA 分子，形成黏性末端。然后 DNA 连接酶将胰岛素基因插入质粒，形成重组 DNA。将质粒导入大肠杆菌细胞，随后在大发酵罐中培养。细菌繁殖时，会按照人类基因的指令生产胰岛素蛋白。提取并纯化胰岛素供医疗使用。

The main advantages are: larger quantities of insulin can be produced at lower cost; the product is pure human insulin, reducing allergic reactions; and it avoids ethical or religious concerns linked to animal-derived insulin.

主要优点是：能以较低成本大量生产胰岛素；产品是纯人胰岛素，减少过敏反应；且避免了与动物源性胰岛素相关的伦理或宗教问题。

9. Genetically Modified Crops | 转基因作物

Genetically modified (GM) crops have had specific genes inserted to improve desirable traits. Common examples tested in the IGCSE syllabus include:

转基因（GM）作物插入了特定基因以改良优良性状。IGCSE 大纲中常考的实例包括：

Herbicide-resistant soybean: a bacterial gene allows the crop to survive when sprayed with a broad-spectrum herbicide (e.g., glyphosate). Weeds are killed while the crop remains undamaged.

抗除草剂大豆：一种细菌基因使作物在喷洒广谱除草剂（如草甘膦）时能够存活。杂草被杀死而作物不受损害。

Bt maize/cotton: a gene from Bacillus thuringiensis bacterium produces a protein toxic to insect larvae. These plants produce their own insecticide, reducing the need for chemical spraying.

Bt 玉米/棉花：来自苏云金芽孢杆菌的基因产生一种对昆虫幼虫有毒的蛋白质。这些植物自身产生杀虫剂，减少化学喷施的需要。

Golden Rice: enriched with beta-carotene (provitamin A) to combat vitamin A deficiency, a major cause of childhood blindness in developing countries.

黄金大米：富含β-胡萝卜素（维生素 A 原），以对抗维生素 A 缺乏症——发展中国家儿童失明的主要原因之一。

Potential benefits of GM crops are increased yields, reduced pesticide use, enhanced nutritional content, and the ability to grow crops in harsh conditions. However, possible risks include the spread of herbicide-resistance genes to wild plants, unintended harm to beneficial insects such as pollinators, unknown long-term health effects, and ethical objections to manipulating nature.

转基因作物的潜在好处包括：提高产量、减少农药使用、增强营养成分以及能够在恶劣环境中种植作物。然而，可能的风险包括：除草剂抗性基因向野生植物扩散、对益虫（如传粉昆虫）的无意伤害、未知的长期健康影响以及因操纵自然而产生的伦理反对。

10. Benefits and Risks of Biotechnology | 生物技术的优点与风险

Biotechnology offers significant advantages across medicine, agriculture, and industry. It enables the mass production of life-saving drugs like insulin and antibiotics, improves food quality through fermentation and enzyme use, provides renewable fuels such as biogas, and helps clean up the environment through bioremediation. GM crops can contribute to food security and reduce reliance on chemical inputs.

生物技术在医药、农业和工业领域提供了显著优势。它能够大规模生产胰岛素和抗生素等救命药物，通过发酵和酶的使用改善食品品质，提供沼气等可再生燃料，并通过生物修复帮助清洁环境。转基因作物有助于粮食安全并减少对化学投入品的依赖。

Nevertheless, there are important risks and ethical concerns. Industrial fermentations can be contaminated, leading to economic losses and potential hazards. The release of GM organisms into the environment might disrupt ecosystems or transfer antibiotic resistance genes to pathogens. Some people argue that genetic modification is ‘playing God’, and consumers demand clear labelling of GM products. Therefore, regulatory bodies enforce strict safety assessments and require risk evaluation before any new biotechnological product is approved.

然而，也存在重要风险和伦理关切。工业发酵可能发生污染，导致经济损失和潜在危害。转基因生物释放到环境中可能破坏生态系统或将抗生素抗性基因转移给病原体。有人认为基因改造是‘扮演上帝’，消费者要求转基因产品明确标注。因此，监管机构强制执行严格的安全评估，并要求在批准任何新的生物技术产品之前进行风险评估。

For IGCSE, you should be able to discuss both sides of the argument using scientific reasoning and real-world examples. Understanding the controlled conditions in fermenters, the principles of genetic modification, and the ecological and ethical dimensions will help you score top marks.

对 IGCSE 而言，你应该能够运用科学推理和现实案例讨论正反两面。理解发酵罐的控制条件、基因改造的原理以及生态与伦理维度，将有助于你取得高分。

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Biotechnology Revision for IGCSE CIE Biology | IGCSE CIE 生物技术考点精讲