Science:日本发现能吃塑料的细菌

全世界每年消费超过3亿吨塑料，这其中包括5000万吨的对苯二甲酸乙二醇酯（PET），PET主要用于塑料瓶，各式各样的塑料包装。但是PET几乎不可生物降解，人们发现塑料废弃物在自然界中进过几十年，并没有发生降解，而是变成塑料微粒，被鱼类，鸟类等生物误食，一部分甚至进入人类的食物链。

日本京都工艺纤维大学研究人员Shosuke Yoshida研究人员已经发现了一类只用2种酶就能分解塑胶的细菌。聚对苯二甲酸乙二酯--或PET是用于制造塑胶的一种多聚物，它有很强的抵抗生物降解的能力。全世界仅在2013年就生产了约5600万吨的PET，而在全球各地， PET在生态系统中的积累问题正变得日益严重。到目前为止，能分解PET的真菌种类十分稀少。

Fig. 1微生物在PET上生长

Yoshida等人为此收集了250个PET碎片样本，并对其进行筛检，寻找以PET膜作为主要碳来源从而得以生长的候选细菌。他们发现了一种新型细菌并将其命名为Ideonella sakaiensis 201-F6，在30度的温度时，这种细菌几乎能在6周后完全降解PET薄膜。进一步的研究发现了一种叫做ISF6_4831的酶，它能与水一起令PET降解成一种中间产物，后者接着会被第二种叫做ISF6_0224的酶进一步降解。仅这两种酶就能将PET分解成其更简单的分子结构。

值得注意的是，这些酶与其它细菌的已知酶相比具有独特的功能性，从而产生一个疑问——这些吃塑料垃圾的细菌是如何进化的。庆应义塾大学生物科学和信息学系Shosuke Yoshida说：“PET是全球广泛采用的塑料制品，PET在环境中形成的垃圾已成为一个全球问题。”目前，这项最新研究报告发表在《科学》杂志上。

摘要速递：

A bacterium that degrades and assimilates poly(ethylene terephthalate)

Science

DOI: 10.1126/science.aad6359

11 Mar 2016

Some bacteria think plastic is fantastic

Bacteria isolated from outside a bottle-recycling facility can break down and metabolize plastic. The proliferation of plastics in consumer products, from bottles to clothing, has resulted in the release of countless tons of plastics into the environment. Yoshida et al. show how the biodegradation of plastics by specialized bacteria could be a viable bioremediation strategy (see the Perspective by Bornscheuer). The new species, Ideonella sakaiensis, breaks down the plastic by using two enzymes to hydrolyze PET and a primary reaction intermediate, eventually yielding basic building blocks for growth.

Science, this issue p. 1196; see also p. 1154

Abstract

Poly(ethylene terephthalate) (PET) is used extensively worldwide in plastic products, and its accumulation in the environment has become a global concern. Because the ability to enzymatically degrade PET has been thought to be limited to a few fungal species, biodegradation is not yet a viable remediation or recycling strategy. By screening natural microbial communities exposed to PET in the environment, we isolated a novel bacterium, Ideonella sakaiensis 201-F6, that is able to use PET as its major energy and carbon source. When grown on PET, this strain produces two enzymes capable of hydrolyzing PET and the reaction intermediate, mono(2-hydroxyethyl) terephthalic acid. Both enzymes are required to enzymatically convert PET efficiently into its two environmentally benign monomers, terephthalic acid and ethylene glycol.

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