在此阅读中文版文章

We are producing ever greater amounts of plastic – much of which ends up as garbage. What’s more, because plastic does not break down in the same way as other organic materials, it can persist in the environment over hundreds of years. Scientists from the World Agroforestry Centre (ICRAF) and the Kunming Institute of Botany in China have recently identified a fungus which could help deal with our waste problem by using enzymes to rapidly break down plastic materials.

Plastics are ubiquitous in the modern world. From the phone or computer on which you’re reading this article, to the car, bus or bike you use to get around and even in many clothes, plastic plays a big part in your life. However, the tremendous increase in the production and use of various plastics is a huge threat to the environment: plastic waste can choke waterways and soils, release harmful chemicals, and poses a threat to animals which can mistake plastic debris for food.

Due to their xenobiotic nature – meaning that they did not exist before their synthesis by humans – plastic polymers are not easily broken down by the bacteria, fungi and small creatures that feed on other waste matter. There is increasing evidence that, even when they do somewhat degrade, tiny particles of plastic may persist in the environment, threatening human and environmental health. Attempts to deal with plastic waste through burying it in landfill sites, recycling or incineration are either unsustainable, costly, or can result in toxic byproducts, especially in developing countries which often lack the resources to safely dispose of plastics.

However, the authors of a new study titled “Biodegradation of Polyester Polyurethane by Aspergillus tubingensis” believe they may have found an unexpected solution to our growing plastic problem in the form of a humble soil fungus. In the new paper, published in the June 2017 issue of Environmental Pollution, they argue that we urgently need to find new, safer and more effective ways to degrade waste plastic.

“We wanted to identify solutions which already existed in nature, but finding microorganisms which can do the job isn’t easy”, explained Dr Sehroon Khan of the World Agroforestry Centre/Kunming Institute of Biology, and lead author of the study. “We decided to take samples from a rubbish dump in Islamabad, Pakistan, to see if anything was feeding on the plastic in the same way that other organisms feed on dead plant or animal matter”.

Aspergillus tubingensis is a fungus which ordinarily lives in the soil. In laboratory trials, the researchers found that it also grows on the surface of plastics. It secretes enzymes onto the surface of the plastic, and these break the chemical bonds between the plastic molecules, or polymers. Using advanced microscopy and spectroscopy techniques, the team found that the fungus also uses the physical strength of its mycelia – the network of root-like filaments grown by fungi – to help break apart the polymers. Even plastics which would otherwise persist in the environment for years can be broken down by A. tubingensis in a matter of weeks, the scientists say.

The fungus’ performance is affected by a number of environmental factors including pH levels, temperature and the type of culture medium used. The research team say that identifying these could pave the way for large-scale use of the fungus in, for example, waste treatment plants, or for application in soils already contaminated by plastic waste.

The discovery of A. tubingensis’ appetite for plastic joins the growing field of ‘mycoremediation’, which investigates the use of fungi in removing or degrading waste products including plastic, oil and heavy metals. Mycologists estimate that only a small proportion of all fungi species have yet been described, which means that vast numbers of potentially useful species are still to be found. However, the destruction of habitats such as natural forests means that many fungi species are likely being lost before they can be discovered. If this continues, we may come to rely more and more on those species we can find in man-made environments – and more scientists may find themselves doing fieldwork in rubbish dumps rather than rainforests.

“Our team’s next goal is to determine the ideal conditions for fungal growth and plastic degradation, looking at factors such as pH levels, temperature and culture mediums”, said Dr Khan. “This could pave the way for using the fungus in waste treatment plants, or even in soils which are already contaminated by plastic waste.”

Download the article:

http://www.sciencedirect.com/science/article/pii/S0269749117300295

Khan, S., et al., Biodegradation of polyester polyurethane by Aspergillus tubingensis, Environmental Pollution (2017), http://dx.doi.org/10.1016/j.envpol.2017.03.012

Contact:

Sehroon KHAN

sehroon@mail.kib.ac.cn

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科学家在垃圾堆发现以塑料为食的真菌

我们正在生产着愈发大量的塑料 – 其中大部分塑料最终成为垃圾。更为重要的是，因为塑料不会像其他有机材料那样分解，所以它可以在环境中存在很长的时间。中国科学院昆明植物研究所的科学家们最近鉴定出一种真菌，其可以通过使用酶快速分解塑料类材料，从而帮助解决我们的废料问题。

塑料可被用于制造出各种惊人的材料：从你正在用着的阅读这篇文章的手机或电脑，再到汽车、公交车和自行车这些你用来到达目的地的交通工具，还有甚至是在许多衣物中，塑料都是现代世界里普遍存在的。然而，巨量增长的各种人造塑料生产与使用已经造成了对环境的巨大威胁：塑料废弃物可以阻塞水路和土壤，释放有害物质，甚至对动物造成威胁，这些动物会把塑料碎片误认为食物。塑料聚合物需要很多年才可分解，因为它们的外源生物性质 – 意味着在人类合成它们前这些物质是不存在的 – 它们不容易被细菌、真菌和其他废物上的小生物所分解。即使是它们有些降解了，塑料的微小颗粒可能会在环境里持续存在，对人类与环境的健康造成未知的后果。然而，一项题为“通过塔宾曲霉菌Aspergillus tubingensis生物降解聚氨基甲酸酯”的研究的作者认为，他们或许已经发现了一个意想不到的解决方案，以一种不起眼的土壤真菌的形式来解决我们不断增长的塑料问题。

通过掩埋、回收或焚化来处理塑料废材的尝试是不可尝试的，这些方法成本高昂，并且可能导致生成对人类健康有害的有毒副产品。最近的这篇文章作者们，发表其在杂志环境污染Environmental Pollution上，因而认为我们迫切需要找到新的更安全且更有效的的降解塑料的方法。昆明生物研究所的Sehroon Khan博士是此研究的主要作者，他说：“我们所知的可行的的方式是寻找已经在自然界里存在的解决方案，但是发现可以胜任这项工作的微生物并不容易。”最终，研究团队发现了他们的以塑料为食的真菌适宜生活场所：一个地处巴基斯坦伊斯兰堡的垃圾处理厂。在乌鸦和秃鹫的注视之下，研究人员们取出了各种土壤和垃圾的样品，希望得以找出一种生物体，可以和其他以死亡的动植物遗体为食的真菌一样，以相同的方式吸收掉塑料废材的生物体。

塔宾曲霉菌Aspergillus tubingensis是一类通常生活在土壤里的真菌。在实验室试验中，研究人员发现它也在塑料表面生长。它将酶分泌在塑料表面，而后这些酶破坏塑料分子间或聚合物间的化学键。该团队使用先进的显微镜和光谱技术，发现真菌还利用了其菌丝的物理强度，由真菌生长的根状细丝网络，以帮助其掰开聚合物。科学家们说，多年来一直存在于环境中的塑料，可能会在几个星期之内被塔宾曲霉菌分解。

真菌的性能受到多种环境因素影响，包括酸碱度pH，温度和所使用的培养基类型。据Khan博士说，“我们团队的下一个目标是确定真菌生长和塑料降解的理想条件”。这可能为大规模的利用真菌铺平道路，例如，废物处理厂，或是应用于已被塑料废材污染的土壤中。塔宾曲霉菌塑料食性的发现加入了“真菌修复”的增长领域，此项目调查使用真菌去除或降解包括塑料、油和重金属在内的废物。真菌学家估计，只有小部分真菌物种被描述，这意味着仍有大量潜在有用的物种可被发现。然而，诸如天然林一类的栖息地被破坏，意味着许多真菌物种在被发现之前就消失了，更别说对其进行用途测试了。如果继续这么下去，我们可能会越来越依赖在人造环境里寻找那些物种，更多的科学家可能会发现自己是在垃圾处理厂进行实地调查而不是在热带雨林之中。

文章下载地址

http://www.sciencedirect.com/science/article/pii/S0269749117300295

Khan, S., et al., Biodegradation of polyester polyurethane by Aspergillus tubingensis, Environmental Pollution (2017), http://dx.doi.org/10.1016/j.envpol.2017.03.012

联系方式：

Sehroon KHAN

昆明植物研究所

sehroon@mail.kib.ac.cn

贡献机构

a 中国科学院昆明植物研究所经济植物与生物技术重点实验室；昆明650201，中国云南

b 东亚和中亚世界农林中心，昆明市兰黑路132号650201，中国云南

c 巴基斯坦伊斯兰堡奎德伊兹兰大学生物科学学院微生物系

d 本努科学与技术大学科学院化学系，开博尔-普士图省，28100 本努，巴基斯坦

e 云南农业大学水稻研究所，黑龙潭，昆明650201，中国云南

f COMSATS信息技术研究所，化学系，阿伯塔巴德-22060，巴基斯坦

g 巴基斯坦伊斯兰堡奎德伊兹兰大学生物科学学院生物技术系

h 云南农业大学植物保护学院，昆明650201，中国云南