The smallest solution to one of our biggest problems - Tierney Thys & Christian Sardet

譯者: Camila Lin 審譯者: Helen Chang

At this very moment, almost everything around you is being eaten.

此刻，你周遭的一切幾乎都在被啃食。

Invisible to the naked eye, organisms called microbes swarm every surface.

肉眼看不見的微生物 遍佈所有物體表面。

Hordes of bacteria, archaea, and fungi have evolved to produce powerful enzymes

大量的細菌、古菌和真菌， 已經進化到能產出強大的酵素，

that break down tough organic material into digestible nutrients.

可分解結實的有機物， 將其轉化為可被消化的營養。

But there’s one particularly widespread type of material

但幾乎沒有微生物可生物分解 某種隨處可見的物質：

that almost no microbes can biodegrade:

plastics.

塑膠。

To make most plastics, molecules from oil, gas and coal are refined

為了製造大部分的塑膠， 我們提煉石油、天然氣和煤炭的分子，

將其重新排列，製成 又長又重複的連結，稱為聚合物。

and turned into long, repeating chains called polymers.

This process often requires temperatures above 100˚C, incredibly high pressure,

這個過程通常需要攝氏 100 度以上的溫度、驚人的高壓，

and various chemical modifications.

以及各種化學改質。

The resulting man-made polymers are quite different

這種人工製造的聚合物，

和天然聚合物相當不同。

from the polymers found in nature.

And since they’ve only been around since the 1950s,

因為它們在 1950 年代才出現，

most microbes haven’t had time to evolve enzymes to digest them.

大多數的微生物還沒有足夠的時間， 進化出可分解塑膠的酵素。

Making matters even more difficult,

讓事態更難以收拾的是，

breaking most plastics’ chemical bonds requires high temperatures

想分解塑膠的化學鍵，

需要和製造塑膠時差不多的高溫，

comparable to those used to create them—

and such heat is deadly to most microbes.

而絕大多數的微生物， 都無法在這種溫度下生存。

This means that most plastics never biologically degrade—

意味著大多數的塑膠 都不可能被生物分解，

they just turn into countless, tiny, indigestible pieces.

只能成為無數細小、不可分解的碎片。

And pieces from the most common plastics like Polyethylene, Polypropylene,

而最常見的塑膠製品， 如聚乙烯、聚丙烯，

and Polyester-terephthalate have been piling up for decades.

和聚酯-對苯二甲酸酯的碎片， 已經堆積了數十年。

Each year humanity produces roughly 400 million more tons of plastic,

我們每年約會製造四億多噸的塑膠，

80% of which is discarded as trash.

其中有 80% 都被當成垃圾丟棄。

Of that plastic waste, only 10% is recycled.

只有一成的塑膠垃圾會被回收。

60% gets incinerated or goes into the landfills,

六成的垃圾會被焚燒或掩埋，

and 30% leaks out into the environment

三成則會流入環境，

where it will pollute natural ecosystems for centuries.

汙染自然生態系統長達數百年。

An estimated 10 million tons of plastic waste end up in the ocean each year,

據估計，每年約有一千萬噸的 塑膠垃圾流入海洋，

mostly in the form of microplastic fragments that pollute the food chain.

大多數都成了汙染食物鏈的塑膠微粒。

Fortunately, there are microbes that may be able

幸運的是，我們現在已發現

也許能將日益嚴重的 塑膠危機分解的微生物。

to take a bite out of this growing problem.

In 2016, a team of Japanese researchers sampling sludge

2016 年，一支日本研究團隊，

至寶特瓶回收工廠取樣汙泥時，

at a plastic-bottle recycling plant discovered

發現了大阪堺菌 201-F6。

Ideonella sakaiensis 201-F6.

This never-before-identified bacterium contained two enzymes

這個首次被發現的細菌含有兩種酵素，

capable of slowly breaking down PET polymers

可在相對低溫的環境中， 緩慢分解 PET 塑膠聚合物。

at relatively low temperatures.

Researchers isolated the genes coding for these plastic-digesting enzymes,

研究者將製造這種 酵素的基因編碼分離，

allowing other bioengineers to combine and improve the pair—

讓其他生物工程師結合、 增強這兩種酵素，

creating super-enzymes that could break down PET up to 6 times faster.

創造出能以六倍速 分解塑膠的超級酵素。

Even with this boost,

雖然已經過改良，

these lab-grown enzymes still took weeks to degrade a thin film of PET,

這些實驗室培養的超級酵素

仍需花費數週才能分解一片 PET 薄膜，

and they operated best at temperatures below 40˚C.

且在低於攝氏 40 度時表現最佳。

However, another group of scientists in Japan had been researching

然而，另一個日本科學家團隊，

長期研究細菌酵素 對高溫環境的適應力，

bacterial enzymes adapted to high temperature environments

like compost piles.

例如堆肥。

And within one particularly warm pile of rotting leaves and branches,

而在特別溫熱的一堆腐葉和樹枝中，

they found gene sequences for powerful degrading enzymes

他們發現了一組能製造 強大分解酵素的基因序列，

known as Leaf Branch Compost Cutinases.

也就是「葉枝堆肥角質酶」。

Using fast-growing microorganisms,

利用快速生長的微生物，

other researchers were able to genetically engineer

其他研究者也能利用基因工程，

high quantities of these enzymes.

培養出大量這種酵素。

They then enhanced and selected special variants of the Cutinases

接著，他們增強、選擇 一種特定的角質酶變體，

that could degrade PET plastic in environments reaching 70˚C—

它能在攝氏 70 度下 分解 PET 塑膠，

a high temperature that can weaken PET polymers and make them digestible.

這種溫度可軟化 PET 塑膠， 讓它們更易分解。

With the help of these and other tiny diehards,

有了這些細菌的幫助，

the future of PET recycling looks promising.

回收 PET 塑膠看似前景可期。

But PET is just one type of plastic.

但 PET 只是一種塑膠。

We still need ways to biologically degrade all the other types,

我們仍需要找到能夠生物分解 其他的塑膠的方法，

including abundant PEs and PPs

其中包含大量的聚苯醚碸和聚苯硫醚，

which only begin breaking down at temperatures well above 130˚C.

它們要在攝氏 130 度 以上才能被分解。

Researchers don’t currently know of any microbes or enzymes

研究者現在仍未發現任何

tough enough to tolerate such temperatures.

能忍受這種高溫的微生物或酵素。

So for now, the main way we deal with these plastics

所以，我們現在處理 這些塑膠的主要方法，

is through energy-intensive physical and chemical processes.

是高能量的物理和化學過程。

Today only a small fraction of plasticwaste

今天，只有一小部分的塑膠垃圾，

can be biologically degraded by microbes.

可被微生物生物分解。

Researchers are looking for more heat-tolerant plastivores

研究者還在地球最惡劣的環境中，

in the planet’s most hostile environments

尋找更多能耐高熱、 可分解塑膠的微生物，

and engineering better plastivorous enzymes in the lab.

並在實驗室中，以基因改造做出 更優秀的塑膠分解酵素。

But we can’t rely solely on these tiny helpers to clean up our enormous mess.

但我們不能只靠這些小幫手 清理我們製造出的巨量垃圾。

We need to completely rethink our relationship with plastics,

我們必須從頭反省我們和塑膠的關係，

make better use of existing plastics,

更完善地利用已存的塑膠產品，

and stopproducing more of the same.

並不再製造更多塑膠產品。

And we urgently need to design more environmentally friendly types of polymers

我們也需要快點設計出 對環境更友善的聚合物，

that our growing entourage of plastivores can easily break down.

讓不停增長的塑膠分解微生物， 可輕易將它們分解。