ENVIRONMENT
Enzymes herald naturebased clean-up
Scientists who helped pioneer the use of enzymes to digest plastic have taken an important next step in developing nature-based solutions to the global plastics waste crisis .
They have characterised an enzyme that has the capacity to help break down terephthalate ( TPA ), one of the chemical building blocks of PET plastic . PET plastic is used to make single-use drink bottles , clothing and synthetic carpets .
The latest research has been co-led by Professor Jennifer DuBois , Montana State University ( MSU ), and Professor John McGeehan , inaugral Director of the University of Portsmouth ’ s Centre for Enzyme Innovation .
It was Professor McGeehan who in 2018 led the international team that engineered a natural enzyme that could break down PET plastic . The enzymes – PETase and MHETase – break the PET polymer into the chemical building blocks , TPA and ethylene glycol ( EG ).
Now researchers have found an enzyme , called TPADO , that can break down TPA – further strengthening the potential for natural agents to biodegrade some of the most problematic plastics .
Professor DuBois explains the TPA / EG / PET relationship : “ While EG is a chemical with many uses – it ’ s part of the antifreeze you put into your car , for example – TPA does not have many uses outside of PET .
“ However , the Portsmouth team revealed that one of the PET-consuming enzymes , called TPADO , recognises the TPA chemical .
“ Our group at MSU then demonstrated that this enzyme breaks down TPA and pretty much only TPA , with amazing efficiency .”
3D structure of the TPADO enzyme .
Natural chemicals resource
It is anticipated that this research will open the way to the development of biological systems that can convert waste plastic into potentially useful by-products or natural chemicals with which new fully recyclable plastics can be made .
Researchers at the Centre for Enyme Innovation say the past few years have seen incredible advances in the engineering of enzymes to break down PET plastic into its building blocks :
“ Our new work goes a stage further and looks at the first enzyme in a cascade that can deconstruct those building blocks into simpler molecules . These can then be utilised by bacteria to generate sustainable chemicals and materials , potentially making valuable products out of plastic waste .”
Using powerful X-ray technology at the Diamond Light Source – the UK ’ s national synchrotron science facility in Oxfordshire – Portsmouth ’ s team was able to generate a detailed 3D structure of the TPADO enzyme .
From this structure , the researchers can better understand how TPADO can break down the TPA molecules , and it has given researchers a blueprint for engineering faster and more efficient versions of this complex enzyme .
ILLUSTRATION : RITA CLARE , MONTANA STATE UNIVERSITY
36 REVOLUTION PLASTICS / 2023