Improving a plastic-degrading enzyme for better recycling | March 5, 2018 Issue - Vol. 96 Issue 10 | Chemical & Engineering News
Volume 96 Issue 10 | p. 7 | Concentrates
Issue Date: March 5, 2018

Improving a plastic-degrading enzyme for better recycling

Adding sugars to a cutinase enzyme makes it more effective at breaking down polyethylene terephthalate
Department: Science & Technology
Keywords: Biochemistry, polymers, PET, polyethylene terephthalate, enzymatic degradation, plastic, cutinase
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Glycosylating three asparagine residues (purple) in a bacterial cutinase enzyme makes it more difficult for the enzyme to form inactive clumps.
Credit: Biochemistry
Illustration of cutinase enzyme with the active site and three glycosylated asparagine residues at positions 197, 239, and 266 marked.
 
Glycosylating three asparagine residues (purple) in a bacterial cutinase enzyme makes it more difficult for the enzyme to form inactive clumps.
Credit: Biochemistry

Stabilizing a bacterial enzyme by strategically decorating it with sugars could help it recycle polyethylene terephthalate (PET), the polymer widely used to make plastic water and shampoo bottles (Biochemistry 2018, DOI: 10.1021/acs.biochem.7b01189). The enzyme, called cutinase, breaks down PET into ethylene glycol and terephthalic acid, which can be recovered to make new bottles. But at the optimal PET processing temperature of 75 °C, cutinase begins to unfold and form clumps. To prevent formation of these inactive clumps, Richard A. Gross of Rensselaer Polytechnic Institute and colleagues genetically engineered yeast to produce a cutinase originally isolated from microbes found in leaf and branch compost. The yeast cells naturally glycosylated the enzyme at three sites, adding short strings of sugars. The glycosylated cutinase formed fewer clumps and degraded more PET than the nonglycosylated protein. The improved stability and activity marks a big step toward optimizing the enzyme for commercial recycling of PET, Gross says.

 
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