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研究人员设计微生物来解决聚酯塑料污染

16 人参与  2021年10月15日 14:54  分类 : 化学  评论
by National Renewable Energy Laboratory NREL and ORNL researchers have developed a method to upcycle PET into performance-advantaged nylon, a precursor to other valuable products such as waterproof clothing, stick-free cookware coatings, and heat-resistant machine parts

Credit: National Renewable Energy Laboratory From overflowing landfills to floating garbage islands in the oceans to microplastics in remote wilderness areas, billions of tons of discarded plastic have created a global pollution crisis

Although plastics are essential to our everyday lives, they are durable materials that do not naturally biodegrade, taking decades or even centuries to decompose in landfills or the natural environment

More than 82 million metric tons of polyethylene terephthalate (PET) is produced globally each year to make single-use beverage bottles, packaging, clothing, and carpets, and it is one of the largest sources of plastic waste

Scientists from the U

S

Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL) are making progress on a possible solution to PET waste

A collaborative research team is combining chemistry and biology to turn PET into a nylon material with better properties that can be used to create a more versatile range of new products

In conjunction with the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium, NREL researchers and partners from Oak Ridge National Laboratory (ORNL) engineered a bacterium to convert deconstructed PET into building blocks for a superior nylon product

As described in "Tandem chemical deconstruction and biological upcycling of poly(ethylene terephthalate) to β-ketoadipic acid by Pseudomonas putida KT2440," recently published in Metabolic Engineering, these high-performance monomers can then be recycled into higher-value plastic materials and products, a process known as upcycling

"This biological conversion step is one important part of the equation that makes PET upcycling possible, creating the opportunity to turn polluting plastic bottles into prized manufacturing materials, ultimately moving us closer to a circular economy at scale," said NREL scientist and journal article first author Allison Werner

A circular economy can extend the functional lifespan of the molecules to make virgin plastics, while reducing waste, conserving resources, and boosting efficiency

This can help deliver supplies that are manufactured using less raw material and energy and stay out of landfills

BOTTLE researchers are exploring how a range of chemical and biological processes can be used to deconstruct plastic wastes and upcycle them to higher-value, recyclable materials

The recent BOTTLE project deconstructed PET using a chemo-catalytic process and engineered the bacterium Pseudomonas putida KT2440 to convert the PET into the chemical β-ketoadipic acid (βKA), a building block for performance-advantaged nylon

NREL and ORNL collaborated in engineering the bacteria

ORNL engineered the bacteria to utilize a key intermediate in PET breakdown, which enabled the NREL team to build a complete platform for bioconversion

Dealing with problem PET Each type of plastic has its own molecular properties that potentially require different methods to deconstruct

PET can be deconstructed to monomers using several different chemical processes

However, the mechanical methods used for the majority of PET recycling today can result in poor quality and less profitable products, leading to low recycling rates

Various sources show that currently only 15% to 35% of all PET bottles find a second life

The biological transformations engineered by NREL and ORNL scientists into P

putida, paired with a chemo-catalytic glycolysis process, can create a more valuable product from PET and ultimately incentivize higher reclamation rates—eventually translating into fewer discarded plastic bottles polluting ocean waters and mountain wilderness areas

The material extracted through this tandem catalytic deconstruction and biological conversion technique offers better properties than the common types of nylon it is intended to replace, including lower water permeability, higher melt temperature, and higher glass transition temperature

These performance advantages expand the ways the material can be used, including for automotive parts that need to withstand high temperatures

Increased value of the recycled material could incentivize industry to recycle more plastic, leading to plastic recovery on a much larger scale

Refusing to roll over on plastic pollution While this initial breakthrough already promises to expand opportunities for PET upcycling, researchers continue to refine the approach

In addition to optimizing the chemistry-biology interface, the team is evaluating a wide range of other factors

Postconsumer PET waste streams can contain additives that P

putida may be unable to catabolize

Characterization of these streams to identify the chemicals present and engineering metabolic pathways to enable consumption of these compounds as well will be needed to maximize efficiency of the bioconversion process, increase yields, and comprehensively deal with the plastic waste

The future success of any tandem deconstruction and upcycling approach for PET will ultimately be determined by its combined technical feasibility, economic viability, and environmental impact

The NREL team plans to perform techno-economic analysis and life cycle assessment to build a better understanding of the process energy requirements and greenhouse gas emissions

"Plastics have revolutionized modern life, but, until recently, plastic manufacturing has followed a strictly linear economy and is carbon-intensive," said NREL Senior Research Fellow, BOTTLE Consortium Lead, and journal article senior author Gregg Beckham

"Circular approaches to this problem can reduce our reliance on fossil-based carbon and thus reduce greenhouse gas emissions

With annual plastic production expected at nearly 600 million tons by 2050, the time to act is now

" The efforts of NREL and the BOTTLE Consortium, including these new chemical deconstruction and biological upcycling techniques, will be vital tactics in combatting the plastic pollution crisis and the environmental and energy challenges associated with climate change

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