跟读练习: Bioprocessing Part 1: Fermentation - 通过视频学习英语口语
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we all know something about fermentation it's a process used countless times each day to make a variety of dairy products,
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baked goods, and beverages.
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We sometimes think of it as letting foods go bad, but in a controlled way.
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With a little help, milk becomes yogurt, bread rises, and grains decompose,
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creating alcoholic beverages and alternative fuels.
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But looking at these examples only gives us a clue as to what's really happening,
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and how we can use the power of fermentation to cost -effectively create a broad array of biological products. So, what is fermentation?
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A cell can be thought of as a microfactory.
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These cells can be bacteria, fungi, or specific cells from mammals, plants, or insects.
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In biotechnology, these cells are used to manufacture a product in a process called fermentation.
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For yogurt, buttermilk, and cheese, we use bacteria.
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To make breads and alcoholic beverages, we use yeast, a fungus.
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And the production of some vaccines require the growth of mammalian cells that are infected with a specific virus.
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The product the cells manufacture is usually a chemical the cells contain naturally,
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or a substance that the cells have been genetically altered to create, or even a metabolic waste product of the organism's growth,
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like one of our examples, alcohol.
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There are too many everyday products created by commercial scale fermentation to even list, but some common ones include amino acids,
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biopharmaceuticals, dyes, enzymes, food products, lipids, steroids, and vitamins.
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Fermentation is a reasonably simple process.
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A cell is selected based on its ability to produce the desired product.
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A seed stock of cells is put into a small amount of media.
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Media provides the nutritional products the cell needs to grow.
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When the population of cells has grown and consumed most of the nutrients, it's moved into a larger vessel with more growth media,
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and the process repeats.
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This scaling up is complete when the quantity of cells is large
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and healthy enough to transfer into a production vessel often referred to as a bioreactor
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or fermenter with plenty of fresh media now available
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and under tightly controlled conditions the cells grow and manufacture product
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when the fermentation is complete the product is harvested fermentation is known as an upstream biotechnology process
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it occurs early in the production flow before recovery, purification, formulation, filling, and packaging.
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To better understand the fermentation process, we should first find out a little bit about the cells we use
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and what they may require to reproduce and stay healthy.
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Different cells have different needs.
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Some are aerobic, they need oxygen, while others are anaerobic and do not require oxygen.
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All cells require nutrition.
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A properly formulated media contains the necessary nutrients to allow cells to grow and produce.
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The fermenter mixes the cells evenly throughout the media to suspend the cells and supply the oxygen necessary for growth.
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Effective and efficient fermentation requires rigorous monitoring and control of the environment within the bioreactor.
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Key factors include temperature, pressure, pH, which is a measure of how acidic or alkaline the media is,
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oxygen, usually measured as dissolved oxygen within the media, and nutrient levels.
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Although the environment and the media are tailored to the needs of specific cells, the life cycle of almost all batches follows a predictable pattern.
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The growth pattern has four phases, lag, exponential or log.
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stationary, and death.
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When a cell is first introduced to fresh media, it has to adapt to its new environment.
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This creates a lull or lag in the growth timeline.
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After the organism adapts, the batch takes off.
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The cells begin dividing at a constant rate, an exponential or logarithmic or log increase,
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doubling, then doubling again, and on and on.
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As the nutrients in the media are consumed, toxic metabolic waste products build up, cells begin to die, and growth slows.
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When it reaches the point that just as many cells are dying as are dividing, the batch enters the stationary phase.
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This is the point at which the key nutrients are completely consumed, the fermentation is stopped, and the fermented broth is harvested.
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If the fermentation were allowed to continue, the cells would enter the death phase.
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More cells die than divide.
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And, similar to the exponential phase, the death rate increases logarithmically.
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Now that we have a basic understanding of how fermentation works, let's look at an actual process and see how it all comes together.
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For our sample process, we will look at the production of Green Fluorescent Protein, or GFP.
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GFP is broadly used as a biological marker.
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It's a fluorescent dye that's very well tolerated by most cells and doesn't interfere with normal cellular function.
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In the GFP fermentation process, we'll need to add an antibiotic to protect the purity of the batch, and then, late in the process,
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a biochemical inducer to turn on the GFP gene.
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Our materials for this process will include a bacteria seed stock, in this case E coli,
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that has been genetically enhanced to produce GFP.
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The basic ingredients for a compatible media which include nutrients, stabilizers, an antibiotic, and an anti -foaming agent,
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and IPTG, which is the biochemical inducer that switches on the GFP gene.
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The equipment that we'll be using includes a 300 -liter bioreactor, a UV -Vis spectrophotometer to monitor the optical density,
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which is a measure of the concentration of cells in the bioreactor, a glucose analyzer to measure glucose,
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a key nutrient, an offline pH meter to help track the acid -base balance and adjust online measurements if needed,
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and a broth tank for our final product.
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The bioreactor is equipped with a water jacket around the vessel to regulate temperature and integrated sensors to monitor key environmental factors,
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including dissolved oxygen, pH, internal temperature, water jacket temperature, and vessel pressure.
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The reactor also has an agitator, dedicated ports for adding seed stock and media ingredients,
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separate ports for acid and base supplement, air filters for supply and exhaust,
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and valves for drawing samples and for harvesting.
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Most fermentation and monitoring functions can be managed from the bioreactor's dedicated process controller.
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Before the fermentation process can begin, the area must be prepared.
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Preparation includes removing equipment and material that won't be used in the process, cleaning and sanitizing the area and equipment,
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and sterilizing equipment as required by the SOPs, Standard Operating Procedures.
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Sterilization is used to eliminate unwanted microorganisms, which can grow naturally in the fermentation media and process equipment.
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Also, all required materials and documentation should be gathered and prepared.
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And all process control software should be loaded and verified.
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The fermentation batch process will be guided and documented with the BPR, Batch Process Record.
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The batch record leads the operator through the process, step by step, with each step requiring a sign -off and separate verification.
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This record also includes spaces for documenting key times, activities, and instrument readings.
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The GFP fermentation process really begins with the expansion of our bacteria seed stock.
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After removing the specially modified E coli from the freezer and thawing it,
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it's used to inoculate a small amount of fresh media in a shaker flask.
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After the number of cells has reached the target amount, the thriving cells are ready for fermentation.
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Meanwhile, in the fermentation area, operators begin with a complete check of all critical equipment.
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Valves, caps, and lines are checked.
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Hoses are tightened.
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Probes are verified and calibrated.
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and 10 kilograms of HPW is added to the vessel.
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The bioreactor is brought up to normal process pressure and held there in order to check for leaks.
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The pressure is monitored over a 30 -minute period.
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If a leak is detected, the problem is corrected and the test is run again.
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Once the reactor passes the test, we are ready to mix the media in the vessel.
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The agitator is turned on, and the ingredients are added.
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Yeast extract, triptych soy broth,
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ammonium chloride, sodium biphosphate, monopotassium phosphate,
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and an anti -foam compound.
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Once all the initial ingredients are in, another 10 kilograms of high -purity water is added.
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All ports and valves are closed.
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All condensate valves are opened.
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And the bioreactor begins an SIP, sterilize -in -place cycle.
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The target for sterilization is 121 degrees Celsius for 30 minutes.
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As soon as the temperature climbs to the targeted temperature, the condensate valves are closed, and the SIP cycle completes automatically.
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Both the vessel and the media are now sterile, and we're ready to add the final ingredients to our media.
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The glucose hose is attached to the vessel, the connection is steamed to sterilize it,
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and the separately sterilized glucose antibiotic solution is pumped into the vessel.
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Then a manual pH reading of the media is taken and the bioreactor is set up for its fermentation cycle.
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After the inoculation hose is connected to the reactor and steamed for 20 minutes,
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the expanded seed stock is pumped into the reactor containing the media.
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Fermentation now begins.
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The operator takes zero -hour readings and begins to regularly monitor batch temperature,
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agitator RPMs, dissolved oxygen levels, pH, vessel pressure, optical density,
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airflow rate, and glucose concentrations.
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Optical densities and glucose concentrations are of particular interest, so they're graphed as well as documented.
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When the targeted levels of glucose and optical density are achieved, it's time to add IPTG to the vessel to activate
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or turn on the expression of the green fluorescent protein in the cells.
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After allowing enough time for the cells to produce green fluorescent protein usually five hours more final readings are taken
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and a sample is drawn to check the percentage of cell
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solids the product is now referred to as broth the broth
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which contains spent media and cells is complete
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when the key nutrient glucose is mostly consumed and the batch has reached the desired concentration.
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The batch is then cooled down, pumped into a broth tank, and labeled with the batch number, volume, time, and date.
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The fermentation process is now complete.
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The harvested broth will now move downstream to the recovery process, where the cells will be ruptured to free the green fluorescent protein,
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and the protein will be separated from the other broth components.
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本课的词汇与口语要点
这节口语课以视频“Bioprocessing Part 1: Fermentation”为素材。 视频中反复出现的词有：cell, fermentation, process, product, vessel。 这段视频共有 128 个句子、1692 个单词可供跟读。 讲话部分时长为 14:32。 说话人语速平稳，每分钟约 116 个词，很适合跟读。 只有 72% 的单词属于英语最常用的 3,000 词，词汇难度较高。
视频中的重点词汇
视频中 15 个值得学习的单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| vessel 名词 | /ˈvɛsəl/ | 船隻 /船只, 船 |
| batch 名词 | /bæt͡ʃ/ | 批次, 批 |
| nutrient 名词 | /ˈnuː.tɹi.ənt/ | 養分 /养分, 營養素 /营养素 |
| oxygen 名词 | /ˈɑksɪd͡ʒən/ | 氧 |
| monitor 名词 | /ˈmɑ.nɪ.tɚ/ | 顯示器 /显示器 |
| valve 名词 | /ˈvælv/ | 閥門 /阀门 |
| ingredient 名词 | /ɪnˈɡɹiːdi.ənt/ | 成份, 材料 |
| density 名词 | /ˈdɛn.sə.ti/ | 密度 |
| concentration 名词 | /ˌkɑn.sənˈtɹeɪ.ʃən/ | 專注力 /专注力 |
| harvest 名词 | /ˈhɑɹ.vəst/ | 收穫 /收获 |
| consume 动词 | /kənˈsum/ | 耗費 /耗费, 消耗 |
| reactor 名词 | /ɹiˈæktɚ/ | 反應器 /反应器 |
| acid 名词 | /ˈæsɪd/ | 酸 |
| operator 名词 | /ˈɑpəˌɹeɪtɚ/ | 話務員 /话务员, 接線員 /接线员 |
| pump 名词 | /pʌmp/ | 泵, 唧筒 |
视频中出现的短语动词
| 单词 | 发音 | 释义 |
|---|---|---|
| come together 动词 | /ˈkʌm tʊˈɡɛðɚ/ | 集合, 联合 |
| cool down 动词 | /kuːl ˈdaʊn/ | 冷卻 /冷却 |
| find out 动词 | 找出, 查明 | |
| take off 动词 | 脫 /脱 |
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | can be thought · are infected · have been genetically altered |
| 现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事 | have been · has grown · has been |
| 定语从句 who / which + 从句 — 补充说明人或事物 | IPTG, which is · microorganisms, which can |
需要注意的发音
说话人用了 6 次缩略和弱读形式，例如 we'll, doesn't, they're。请按听到的简短形式来说。
- “th” 音: gather /ˈɡæðɚ/, thrive /θɹajv/, broth /bɹɔθ/
- “sh” 和 “zh” 音: concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, stationary /ˈsteɪʃəˌnɛɹi/, efficient /ɪˈfɪʃənt/, preparation /ˌpɹɛpəˈɹeɪʃ(ə)n/, nutrition /njuːˈtɹɪʃ.ən/
- 长单词——注意重音位置: ingredient /ɪnˈɡɹiːdi.ənt/, concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, operator /ˈɑpəˌɹeɪtɚ/, antibiotic /ˌæn.taɪ.baɪˈɑ.tɪk/, naturally /ˈnæt͡ʃ.(ə.)ɹə.li/
中文母语者容易读错的音：
- /v/ — 不要读成 /w/，上齿轻触下唇: vessel /ˈvɛsəl/, valve /ˈvælv/, harvest /ˈhɑɹ.vəst/, divide /dɪˈvaɪd/, beverage /ˈbɛv(ə)ɹɪd͡ʒ/
- 词尾辅音 — 要读清楚，后面不要加元音: batch /bæt͡ʃ/, glucose /ˈɡluː.kəʊz/, nutrient /ˈnuː.tɹi.ənt/, valve /ˈvælv/, ingredient /ɪnˈɡɹiːdi.ənt/
- /r/ 和 /l/ 的区别: naturally /ˈnæt͡ʃ.(ə.)ɹə.li/, controller /kənˈtɹoʊlɚ/, separately /ˈsɛp.ɹət.li/, alter /ˈɔl.təɹ/, reasonably /ˈɹiː.zən.ə.bli/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 用正常速度逐句跟读，每句重复到你的节奏与说话人一致为止。
- 录下自己的声音并与原声对比，特别注意 vessel, batch, nutrient 这类单词。
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。