Disposable water bottles are commonly made of poly(ethylene terephthalate), and the bacterium <i>Ideonella sakaiensis</i> is known to be able to grow on this type of plastic using the specialized enzymes PETase and MHETase. We discovered that the crystallinity of the plastic substrate affects growth; specifically, <i>Ideonella</i> is not able to grow on highly crystalline plastic, whereas it grows on amorphous plastic. We find this in both model plastic film as well as post-consumer plastics such as water bottles and clam-shell style PET containers. Further, highly crystalline plastic can be converted to a growth source via melting a highly crystalline substrate and reforming as an amorphous substrate. We also found that amorphous portions of plastic water bottles (namely the threading at the top and the center of the bottom) support growth of the bacteria, whereas the highly crystalline portions do not. These amorphous portions represent less than half the mass of the plastic, suggesting challenges for biodegradation of plastic water bottles. Further, using fluorescent substrates, we have screened for bacterial variants with altered capacity for degradation, searching for both improved plastic degradation as well as altered metabolic capacity to degrade plastic under different circumstances.

Studies on a poly(ethylene terephthalate) plastic-degrading microorganism: Role of crystallinity and screening for variants

ACS Spring 2022

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