(ORDO NEWS) — An international team of scientists has discovered and described a new enzyme that takes one step closer to sustainable and complete recycling of plastic waste. In addition, the research will help develop biological systems that turn plastic waste into valuable reusable products.
More than 400 million tons of plastic waste is produced annually in the world, the vast majority of which ends up in landfills. The other part accumulates in places that are completely not intended for this, for example, in the Pacific Ocean.
The accumulation of anthropogenic debris (mostly plastic) in the northern part of the Pacific Ocean is widely known – the Great Pacific Garbage Patch , with an area of \u200b\u200bup to one and a half million square kilometers (33 times the area of \u200b\u200bthe Moscow Region).
Strategies for the bioconversion (recycling using biological processes) of plastic have become important components of the circular economy of synthetic plastics, especially those that have chemical similarities to natural compounds such as polyesters.
The new study, published in the journal PNAS, was conducted by an international team of scientists led by Professor Jennifer DuBois from the University of Montana (USA) and Professor John McGeehan from the University of Portsmouth (UK). McGeehan previously led an international team that discovered a natural enzyme that can break down PET plastic.
PET plastic is used in the production of disposable plastic bottles, clothing, packaging, automotive parts, medical products and many other everyday items.
Previously discovered by Professor McGeehan’s team, the enzymes PETase and MGETase sequentially break down the polymer polyethylene terephthalate (PET) into the chemical building blocks of ethylene glycol (EG) and terephthalate (TPA). A new study takes this idea further and describes an enzyme for processing TFA, terephthalate dioxygenase (TPADO).
A pathway for the enzymatic conversion of terephthalate (TFA or TPA) to protocatechuate (PCA or PCA). (A) Organization of the genes encoding the necessary enzymes. (B) The TPADO enzyme (orange) uses molecular oxygen to dehydroxylate TPA, and the reducing equivalents are supplied by reductase (yellow). The product (DCD) is converted to protocatechuate by Zn dependent dehydrogenase (blue). And the enzymes for further processing of PCA are generally already known
“While EG is a chemical that can be used for many things like the antifreeze you put in your car TFA doesn’t have a wide range of uses outside of PET. At the same time, most bacteria cannot even digest it,” Professor Dubois comments on the work.
“However, the Portsmouth team found that an enzyme from PET-consuming bacteria recognizes TPA like a gloved hand (that is, the enzyme recognizes the TPA molecule well and catalyzes its transformation – ed .). Our group at Montana State University then demonstrated that this enzyme, called TPADO, breaks down TFA and almost only TFA with amazing efficiency.”
Visualization of the 3D structure of the TPADO enzyme. The mechanism of TPA binding is also shown
The study was conducted as part of the BOTTLE (Bio-Optimized Technologies to Prevent Thermoplastics from Landfills and the Environment) Consortium, an international collaboration between the US and the UK. It brings together researchers from a wide range of scientific fields to solve the problem of plastic recycling and recycling.
“Over the past few years, incredible progress has been made in the development of enzymes to break down PET plastic into building blocks.
This work goes even further and considers the first enzyme in the cascade that can break down these building blocks into simpler molecules that bacteria can then use to create environmentally friendly chemicals and materials needed to produce valuable products from plastic waste,” McGeehan concluded.
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