Saving Trick for Plastic Recycling by Bacteria
Scientists at the Max Planck Institute in Marburg have developed a more efficient, carbon dioxide-saving way for the bacterial utilization of ethylene glycol, a component of the plastic PET. They equipped the bacterium Pseudomonas putida with a new metabolic pathway discovered in marine microbes, which led to improved growth. Their findings offer new opportunities for the microbial degradation of PET, but also for the further development of sustainable material cycles.
Plastic is everywhere. In 2017, the annual plastic production worldwide was 350 million tons. A significant amount of it ends up in the environment, and plastic pollution threatens the health and livelihoods of all living things and the stability of ecosystems. At the same time, valuable raw materials are lost that could be used in a sustainable way.
One hope of research lies in the possible degradation or recycling of plastic by microorganisms. Since the discovery of the “PET-eating” bacterial species Ideonella sakaiensis in 2016 , much research has focused on PET (polyethylene terephthalate), which is primarily used in the production of water bottles. The basic building block of PET, the C 2molecule ethylene glycol, is also used as an antifreeze or solvent. It can also be generated electrochemically from syngas, making it a key component of future carbon-neutral biotechnologies. Therefore, the development of bacterial strains with improved ethylene glycol conversion is important not only in terms of PET upcycling, but also in the larger context of creating sustainable industrial resource cycles for this ubiquitous chemical.
Scientists at the Max Planck Institute for Terrestrial Microbiology, the Max Planck Institute for Molecular Plant Physiology and the University of Leiden have now taken a dePET (polyethylene terephthalate) is often used for beverage packaging because of its low air and water permeability. Its basic building block, ethylene glycol, is a resource for biotechnology.cisive step towards the sustainable use of valuable materials. By equipping the biotechnologically relevant bacterium Pseudomonas putida with a new metabolic pathway, they increased its capacity to process ethylene glycol.
The research team thus built on earlier work, the discovery of a metabolic pathway in marine microorganisms that converts C 2 molecules particularly efficiently, the beta-hydroxyaspartate cycle (BHAC). Using methods of synthetic biology and directed evolution, they succeeded in incorporating this pathway into the bacterium
“The BHAC is an elegant metabolic cycle in which the carbon in ethylene glycol is recycled without CO 2 release. It is therefore clearly preferable in terms of carbon and energy balance. With it, our newly developed bacterial strain can process the basic building block of PET much more efficiently,” says Lennart Schada von Borzyskowski, one of the main authors and co-initiator of the study. He performed his experiments as part of his postdoctoral research at the Max Planck Institute for Terrestrial Microbiology in Marburg, collaborating with the group of Arren Bar-Even at the Max Planck Institute for Molecular Plant Physiology in Golm.
Helena Schulz-Mirbach, co-author of the study, explains: “First, we used selected E. coli strains to demonstrate that the synthetically modified bacteria are able to form the entire cellular biomass even after incorporating a BHA section. After subsequent incorporation of the entire BHAC, the new P. putida strain was immediately able to grow on ethylene glycol. The incorporation also led to changes in the central carbon metabolism of the host. And third, with targeted laboratory evolution, we were able to create mutations that further improved the growth of the engineered strain on ethylene glycol—by 35% faster growth with a 20% increase in biomass.”
“The development of sustainable material cycles is probably the greatest challenge of our time,” says Tobias Erb, Director at the Max Planck Institute for Terrestrial Microbiology and coordinator of the study. “Microbial plastic degradation without CO 2 release is an important step towards a closed carbon cycle .”
“The study shows the high potential of the BHAC pathway as a ‘plug-and-play’ metabolic module for synthetic biology,” adds Lennart Schada von Borzyskowski, who is now a professor at Leiden University in the Netherlands. “We recently started testing the BHAC in other organisms as well, for example in the model plant Arabidopsis thaliana . Here we were able to show that the BHAC makes plant photosynthesis more efficient by allowing the plant to retain more CO 2 . These results are very promising in terms of research on CO 2 -saving metabolic pathways for biotechnology and agriculture.”
https://www.mpg.de/
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