plastic – Lightsources.org

Revolutionising plastic recycling: a breakthrough in enzyme-based depolymerisation

2025/01/142025/01/21

The accumulation of plastic waste in the environment is an ecological disaster and will require multiple solutions to tackle the problem. Despite recent initiatives to close the plastics loop, only 9% of plastic was recycled in 2019, with the remaining waste either incinerated or accumulating in landfills or natural environments, posing hazards to both living and non-living systems. Bioplastics, derived from renewable sources, have been investigated as green alternatives to conventional fossil-based plastics. However, costly synthetic routes and low recyclability continue to challenge the growth of bioplastics. Poly(lactic acid) (PLA) is the most popular polymer for commercial bioplastics, but its recycling is limited by challenging mechanical recycling and slow biodegradation. A team of researchers from King’s College London has developed a generalisable biocatalysis engineering strategy to enhance the use of enzymes to depolymerise a broad class of plastics, in a publication recently published in Cell Reports Physical Science. This novel approach is 84 times faster than the 12-week-long industrial composting process currently used for recycling bioplastic materials

The problem with plastic waste

The demand for conventional plastics such as Poly(lactic acid) (PLA) or poly(ethylene terephthalate) (PET) is increasing, with 460 million tons produced in 2019; a 230-fold increase from the 2 million tons produced in 1950. Plastic waste is a significant environmental issue, with millions of tons of plastic ending up in natural environments each year. Traditional recycling methods are often inefficient and unable to produce high-quality reusable materials. Bioplastics, derived from biological sources such as corn starch and sugarcane, are seen as a more sustainable alternative. However, current methods of bioplastic production are costly and compete with food-based agriculture for land use. Furthermore, mechanical recycling methods generate CO2 and are incapable of producing high-quality reusable materials, leading many retailers to revert to using oil and fossil-based materials. As an example, it takes up to 84 days at 60°C in industrial composting to recycle PLA, with very little valorisation possible.

An innovative solution

In this publication, the team of researchers developed a new protocol to recycle PLA. This method involves different component to help depolymerise the material.

First, they used ionic liquids to solubilise the plastic. Ionic liquids are salts in a liquid state that have unique properties, such as low volatility and high thermal stability. Ionic liquids have been shown to have the ability to solubilise polymers used in common plastics such as PET and PLA. Secondly, they used a commercially available enzyme, a lipase from Candida antarctica (CaLB) to degrade the plastic.

As the enzyme may not be stable in ionic liquid, the researchers performed some chemical modifications in three different steps to preserve enzyme activity.

Researchers performed circular dichroism at Diamond Light Source on the B23 beamline to ensure that the secondary structure of the enzyme was intact after the chemical modifications. Measurements realised on B23 also showed that the thermostability of the modified protein was higher in ionic liquid (> 80°C) compared to the unmodified protein in aqueous solution. This parameter is important, as heat is required to help depolymerise plastics.

Read more on Diamond website

Image: Graphical abstract of the publication

New enzyme-embedded plastic degrades rapidly

2024/08/012024/08/06

Scientists have developed a biosourced plastic embedded with an enzyme that ensures rapid biodegradation and compostability, overcoming the hurdles of currently used plastics. They used the ESRF to solve the structure of the enzyme. The results are published in Nature.

Plastic production reached a staggering 400 million tons in 2022, with packaging and single-use items making up a significant portion. The resulting waste often ends up in landfills, incinerators, or the environment, contributing to the growing crisis of plastic pollution.

Due to this situation, there is a burgeoning interest in biodegradable and compostable plastics as more sustainable alternatives. Polylactide (PLA) is the most widely used biosourced polymer, however, PLA degrades very slowly in home compost and soil.

Now scientists led by the company Carbios and the Toulouse Biotechnology Institute (TBI), in France, have developed a PLA-based plastic embedded with a specially optimized enzyme that ensures rapid biodegradation and compostability at room temperature through a scalable industrial process.

hey optimised the process used to achieve an engineered enzyme able to withstand the 170°C temperature required to introduce it in molten state PLA during the plastic production process. The new enzyme-embedded material, containing just 0.02% enzyme by weight, fully disintegrated under home compost conditions within 20–24 weeks, meeting all home composting standards. It also helped produce more biomethane, another source of waste recovery.

Part of this research required the structure determination of the enzyme, which the scientists acquired using the ESRF structural biology beamlines. This is the second Nature publication led by Carbios with data from the ESRF. Alain Marty, Chief Scientific Officer of Carbios, explains the long-term collaboration with the ESRF: “Since the early days of Carbios, TBI (Toulouse Biotechnology Institute), IPBS (The Institute of Pharmacology and Structural Biology) and Carbios have collaborated with the ESRF as synchrotron radiation plays an important role in this research. In particular, in this article diffraction data helped us unveil the structure of the enzyme to understand better the relation between the structure of the enzyme and its function. The resulting enzyme engineering work leads to an efficient enzyme that allows the plastic to self-biodegrade at room temperature.”

Read more on ESRF website

Image: The encapsulated enzyme CARBIOS Active, in granule form, when integrated directly into PLA-based packaging or products at the production phase, enables compostability at room temperature.

Credit: Carbios.

Plastic from Wood

2020/02/272020/02/27

X-ray analysis points the way to lignin-based components made to measure

The biopolymer lignin is a by-product of papermaking and a promising raw material for manufacturing sustainable plastic materials. However, the quality of this naturally occurring product is not as uniform as that of petroleum-based plastics. An X-ray analysis carried out at DESY reveals for the first time how the internal molecular structure of different lignin products is related to the macroscopic properties of the respective materials. The study, which has been published in the journal Applied Polymer Materials, provides an approach for a systematic understanding of lignin as a raw material to allow for production of lignin-based bioplastics with different properties, depending on the specific application.

Image: Lignin is a promising raw material (left) for thermoplast (right) production.
Credit: KTH Stockholm, Marcus Jawerth

“Molecular scissors” for plastic waste

2019/04/122019/04/12

A research team from the University of Greifswald and Helmholtz-Zentrum-Berlin (HZB) has solved the molecular structure of the important enzyme MHETase at BESSY II.

MHETase was discovered in bacteria and together with a second enzyme – PETase – is able to break down the widely used plastic PET into its basic building blocks. This 3D structure already allowed the researchers to produce a MHETase variant with optimized activity in order to use it, together with PETase, for a sustainable recycling of PET. The results have been published in the research journal Nature Communications.

Plastics are excellent materials: extremely versatile and almost eternally durable. But this is also exactly the problem, because after only about 100 years of producing plastics, plastic particles are now found everywhere – in groundwater, in the oceans, in the air, and in the food chain. Around 50 million tonnes of the industrially important polymer PET are produced every year. Just a tiny fraction of plastics is currently recycled at all by expensive and energy-consuming processes which yield either downgraded products or depend in turn on adding ‘fresh’ crude oil.

Image: At the MX-Beamlines at BESSY II, Gottfried Palm, Gert Weber and Manfred Weiss could solve the 3D structure of MHETase.
Credit: F. K./HZB

Analysing the structure of biopolymers for the food industry

2018/10/302018/10/31

A research group from the Institute of Agrochemistry and Food Technology (IATA-CSIC) in Valencia is using scattering techniques at the ALBA Synchrotron to develop new packaging systems made of biopolymers, an environmentally friendly solution for the food industry.

Plastic is the packaging material of most of the food we consume nowadays. This results in a severe problem as common plastics are made of petroleum – a limited resource with highly variable price – and supposes a huge environmental impact – most plastic wastes need more than 400 years to decompose.

Researchers from the Food Safety and Preservation department of the Institute of Agrochemistry and Food Technology (IATA-CSIC), located in Paterna (Valencia), are looking for more sustainable ways of producing food packaging with appropriate mechanical and chemical properties. They are investigating biopolymers that can be made from biomass such as algae.
“We need to look for alternative sources which do not compete with food. This is why marine resources such as algae and microalgae are very interesting. They proliferate very quickly, grow in a wide variety of environments and do not interfere with food production”, according to Ámparo López-Rubio, researcher at the IATA-CSIC.

>Read more on the ALBA website

Image: At the left, Juan Carlos Martínez, scientist from the ALBA Synchrotron with users Amparo López Rubio and Marta Martínez Sanz from IATA-CSIC at the NCD-SWEET experimental hutch.

Solution to plastic pollution on the horizon

2018/04/162018/04/18

Engineering a unique plastic-degrading enzyme

The inner workings of a recently discovered bacterium with a fascinating ability to use plastic as an energy source have been recently revealed in PNAS. The world’s unique Long-Wavelength Macromolecular Crystallography (MX) beamline here at Diamond Light Source was used to successfully solve the structure of the bacterial enzyme responsible for chopping up the plastic. This newly evolved enzyme could be the key to tackling the worldwide problem of plastic waste.

Plastic pollution is a global threat that desperately needs addressing. Plastics are rarely biodegradable and they can remain in the environment for centuries. One of the most abundant plastics that contributes hugely to this dire situation is poly(ethylene terephthalate) (PET).

PET is used largely in textiles, where it is commonly referred to as polyester, but it is also used as packaging for liquids and foodstuffs. In fact, PET’s excellent water-repellent properties led to it being the plastic of choice for soft drink bottles. However, once plastic bottles are discarded in the environment the water resistance of PET means that they are highly resistant to natural biodegradation. PET bottles can linger for hundreds of years and plastic waste like this will accumulate over time unless a solution is found to degrade them.

A recent breakthrough came in the discovery of a unique bacterium, Ideonella sakaiensis 201-F6, which was found feeding on waste from an industrial PET recycling facility. PET has only been widely used since the 1970s, so the bacterium had evolved at breakneck speed to be able to take advantage of the new food source.

The bacterium had the amazing ability to degrade PET and use it to provide carbon for energy. Central to this ability was the production of a PET-digesting enzyme, known as PETase.