Page 44 - Plastics News September 2022

TECHNOLOGY

platform; “The accumulation of plastic
New Engineering Platform Takes Commercial Enzymatic in the environment is a major global
Plastic Recycling A Step Forward challenge. For this reason, we were keen

to use our enzyme evolution capabilities
to enhance the properties of plastic de-
grading enzymes to help alleviate some
of these problems. We are hopeful that
in the future our scalable platform will
allow us to quickly develop new and
specific enzymes are suitable for use in
large-scale plastic recycling processes.”
To test their platform, they went on
to develop a new enzyme, HotPETase,
through the directed evolution of Is-
PETase. IsPETase is a recently discov-
ered enzyme produced by the bacte-
rium Ideonella sakaiensis, which can
use PET as a carbon and energy source.

esearchers from the Manches- plastic recycling to be used widely While IsPETase has the natural ability
Rter Institute of Biotechnol- on a commercial scale, MIB says. to degrade some semi-crystalline forms
ogy (MIB) have developed a new One challenge is that natural en- of PET, the enzyme is unstable at tem-
enzyme engineering platform aimed zymes with the ability to break down peratures above 40°C, far below desira-
at improving plastic degrading en- plastics typically are less effective and ble process conditions. This low stabil-
zymes through directed evolution. are unstable under the conditions ity means that reactions must be run at
temperatures below the glass transition
To illustrate the utility of their platform, needed for an industrial-scale process. temperature of PET (~65°C), which
they have engineered an enzyme that To address these limitations, in a paper leads to low depolymerisation rates.
can successfully degrade poly(ethylene) released in Nature Catalysis, research-
terephthalate (PET), the plastic ers from The University of Manches- To address this limitation, the team de-
commonly used in plastic bottles. ter have reported a new enzyme en- veloped a thermostable enzyme, Hot-
PETase, which is active at 70°C, which
MIB says that, in recent years, the enzy- gineering platform that can quickly is above the glass transition temperature
matic recycling of plastics has emerged improve the properties of plastic de- of PET. This enzyme can depolymerise
as “an attractive and environmentally grading enzymes to help make them semi-crystalline PET more rapidly than
friendly strategy to help alleviate the more suitable for plastic recycling at previously reported enzymes and can
problems associated with plastic waste”. large scales. Their integrated and au- selectively deconstruct the PET com-
Although there are a number of ex- tomated platform can successfully as- ponent of a laminated packaging ma-
isting methods for recycling plas- sess the plastic degradation ability of terial, highlighting the selectivity that
tics, enzymes could potentially around 1000 enzyme variants per day. can be achieved by enzymatic recycling.
offer a more “cost-effective and The accumulation of plastic in the Professor Anthony Green, Lecturer
energy efficient alternative”, MIB says. environment is a major global chal- in Organic Chemistry, said: “The de-
It also says they could be used to se- lenge. For this reason, we were keen velopment of HotPETase nicely illus-
lectively breakdown specific compo- to use our enzyme evolution capa- trates the capabilities of our enzyme
nents of mixed plastic waste streams bilities to enhance the properties of engineering platform. We are now
that are currently difficult to re- plastic degrading enzymes to help excited to work with process engi-
cycle using existing technologies. alleviate some of these problems. neers and polymer scientists to test

There are considerable hurdles that Dr Elizabeth Bell, who led the experi- our enzyme in real world applications.
need to be overcome for enzymatic mental work at the MIB, says of the

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