Enzyme breaks down PET plastic in record time
Dr Christian Sonnendecker and his team discovered an enzyme that breaks down PET plastic at record speed. Credit: Leipzig University / Swen Reichhold

lightweight packaging made of PET plastic becomes a problem if it is not recycled. The scientists at the university have discovered an efficient method of degrading PET. The researchers found the PHL7 in a compost heap, which could make it possible to recycle biological PET much faster. The findings have been published in a scientific journal.

One way in which plants are broken down is bybacteria. It has been known for a long time that some detergents can degrade PET. The team led by Dr. Christian Sonnendecker, an early career researcher, is searching for previously undiscovered examples of these biological helpers. The researchers found the blueprint of the enzyme in a sample from a compost heap, which they used to speed up the process in the laboratory.

Researchers from the Institute of Analytical Chemistry studied seven different enzymes. The results of the seventh candidate, called PHL7, were significantly above average. In the experiments, the researchers added PET to containers with either PHL7 or LCC, the previous leader in PET decomposition. They measured the amount of plastic that was degraded and compared it to the other values.

Within 16 hours, PHL7 caused the PET to break down by 90 percent, and in the same time, LCC only degraded 45 percent. In less than 24 hours, PHL7 broke down a plastic punnet, the kind used for selling grapes in supermarkets. A single building block is responsible for this activity. PHL7 carries a leucine at the site where other previously known hydrolases contain phenylalanine.

Conventional recycling methods rely on thermal processes where the plastic waste is melted down at high temperatures. The quality of the plastic decreases with each recycling cycle. The temperature of 65 to 70 degrees Celsius is what the enzymes need for their work. The fact that they break down the PET into its components can result in a closed cycle because they can reuse the components. The pilot plant in France is the only one that has tested biological recycling.

Professor Wolfgang Zimmermann, who played a key role in establishing research activity into enzyme-based technologies at Leipzig University, says that the discovery of the enzyme in Leipzig can make an important contribution to establishing alternative energy -saving plastic recycling processes. The biocatalyst now developed in Leipzig has been shown to be highly effective in the rapid decomposition of used PET food packaging and is suitable for use in an environmental friendly recycling process in which new plastic can be produced from the decomposition products.

The researchers hope that the discovery of the PHL7 can advance biological recycling in practice and are looking for industrial partners for this purpose. They think the higher speed will reduce recycling costs. They want to create a prototype that will allow them to quantify the economic benefits of their rapid biological recycling process more precisely.

The scientists at the Institute of Analytical Chemistry want to understand the structure and function of the enzymes. They are working on a new method to solve a problem in biological recycling, which is not currently solved by the current method of PET decomposition, which only works for so-called amorphous PET, which is used in things like fruit packaging, but not for plastic bottles with higher crystallinity.

More information: Christian Sonnendecker et al, Low Carbon Footprint Recycling of Post‐Consumer PET Plastic with a Metagenomic Polyester Hydrolase, ChemSusChem (2021). DOI: 10.1002/cssc.202101062 Citation: Enzyme breaks down PET plastic in record time (2022, May 18) retrieved 18 May 2022 from https://phys.org/news/2022-05-enzyme-pet-plastic.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.