They can be tight, flared, ripped at the knee. Jeans come in all styles and colours these days, but one hue will always be synonymous with the world’s favourite garment: indigo blue.
如今，牛仔褲有各種款式和顏色，款式有緊身的、喇叭式的、露膝蓋的。但是有一種顏色一直是世界上最受歡迎的服裝的代名詞：靛藍色。
To satisfy the world’s seemingly insatiable demand for blue denim, more than 45,000 tonnes of indigo dye are produced every year, with much of the waste making its way into rivers and streams, conservationists say.
環保主義者稱，爲滿足世界對藍色牛仔布無盡的需求,每年要生產45000多噸靛藍染料，同時造成大量的廢物流入河流和小溪。
On Monday, scientists announced they had developed a greener method to produce the coveted tint -- using lab-grown bacteria.
週一, 科學家們宣佈他們已經開發出一種更加綠色環保的方法，生產人們一直渴望的色調——利用實驗室培育的細菌。
While not yet commercially viable, the technique holds promise for a "much-needed to the historic, but unsustainable, indigo dyeing process," researchers wrote in the journal Nature Chemical Biology.
研究人員在《自然化學生物學》雜誌上撰文稱，這項技術雖然還沒有商業可行性, 但是有望改良“歷史上亟需更新的但不能長期保持色澤的靛藍染色工藝。”
"Demand for the dye is higher than ever before, making its ecological consequences unsustainable," they warned.
他們警告說：“人們對染料的需求比以往任何時候都要大，這樣會造成生態的不可持續。”
Originally extracted from plants, indigo is one of the oldest dyes, with evidence of its use in textile colouring going back some 6,000 years.
靛藍染料最初是從植物中提取的, 是最古老的染料之一。有證據表明靛藍染料用於紡織品着色的歷史可以追溯到大約6000年前。
It is prized for being vibrant and long-lasting, and was an important cash crop until humans started making synthetic indigo in the early 1900s.
靛藍染料的價值在於它的鮮豔色澤和持久性，它是一種重要的經濟作物，到了20世紀早期人類開始生產人造靛藍染料。
Indigo crystals cling easily to the cotton fibres used in jeans and are resistant to laundry detergents, yet flake off slightly with wear-and-tear to yield the sought-after worn-in look.
靛藍水晶容易附着在用於製作牛仔褲的棉纖維上，而且經得住洗衣液的洗滌，但卻會隨着磨損而脫落，從而產生人們追求的磨損效果。
Some four billion denim garments are produced every year, the vast majority indigo-tinted, said the study authors, and warned of "a serious sustainability problem".
研究報告的作者們說，每年生產的牛仔服裝大約有40億件，絕大多數都是靛藍色的.。他們還警告說“這是一個嚴重的持續性問題”。
The first danger: producing indigo dye requires the use of toxic chemicals such as formaldehyde and hydrogen cyanide.
第一個危險: 生產靛藍染料需要使用甲醛和氰化氫等有毒的化學物質。
Furthermore, synthesised indigo is insoluble in water, meaning chemicals are needed to make it suitable for dyeing.
另外，合成靛藍不溶於水，這就意味着需要化學物質使其適合染色。
Not currently feasible
目前不可行
One such chemical is sodium dithionite, which decomposes into sulfate and sulfite which can corrode equipment and pipes in dye mills and wastewater treatment plants.
這樣的一種化學物質是連二亞硫酸鈉, 可以分解成硫酸鹽和亞硫酸鹽，會腐蝕染料廠和污水處理廠的設備和管道。
"Many dye mills avoid the additional cost of wastewater treatment by dumping the spent dye materials into rivers, where they have negative ecological impacts," said the research team.
研究小組說：“許多染料廠通過將廢染料傾倒到河水裏避免污水處理的額外費用，從而對河水產生不良的生態影響。”
The new method mimics the workings of the Japanese plant Persicaria tinctoria.
這種新的方法就是模仿日本蓼藍植物的工作原理。
Instead of a plant, "we engineered a common lab strain of Escherichia coli, a bacteria found in our gut, to be a chemical factory for the production of indigo dye," study co-author John Dueber of the University of California’s bioengineering department told AFP.
新方法並不是一種植物。加利福尼亞大學生物工程系的合著者約翰·杜伯告訴法新社說：“我們設計了一種常見的大腸桿菌實驗室菌株，這是一種在我們腸道里發現的細菌, 可以成爲一個化學工廠，用於生產靛藍染料。”
Like the plant, the bacteria produces a compound called indoxyl, which is insoluble and cannot be used as a dye. By adding a sugar molecule, the indoxyl is turned into indican -- a precursor of indigo.
像植物一樣, 細菌產生的化合物稱爲吲哚酚，它不溶於水，不能用作染料。加入糖分子, 吲哚酚就會轉化成糖苷——靛藍前驅體。
Indican can be stored and transformed into indigo direcly on the cloth when dyeing, by adding an enzyme to the mix.
糖苷可以存儲，染色時，可以在混合物中加入一種酶，這樣糖苷就可以直接在布料上轉化成靛藍色。
The lab is working to make the process commercially feasible, Dueber said.
杜伯稱，實驗室正在努力使這一過程實現商業化。
For now, producing five grammes of indigo to colour one pair of jeans would require "several litres of bacteria," he said, and would be more expensive.
現在, 生產五克靛藍色染料來染一條牛仔褲，就需要“數升的細菌”，他說, 牛仔褲以後會更貴。
