Major challenges in searches for plastics-active enzymes
One of the major challenges will be the identification of novel enzymes
for polymers for which none are currently known 11,52.
Thus, we urgently need enzymes acting on PE, PP, PVC, but also on
polymeric PA and PU ether bonds. Further we realized the lack of a
common PET or PUR model substrate, which would allow the direct
comparison of the kinetic parameters of different plastics-active
enzymes. In contrast, kinetic analysis is generally performed for
typical esterase substrates such as pNP-caproate. This data, however,
does not allow a reliable prediction of the actual plastics activity.
The few enzymes that have been characterized using polymers were tested
on different polymer types, and pre-treatment was used to enable better
degradation (see Table 1 for references). In addition, all
kinetic data was recorded using single point measurements, thus the
hydrolysis of the polymer could not be separated from the attachment of
the enzyme to the polymer surface or from the hydrolysis of the
resulting oligomers. Within this framework, a characterization of
surface area and a control of surface properties such as crystallinity
would be favourable to obtain better and more reliable kinetic data on
the actual polymer.
The accumulation of verified plastics-active enzymes in databases with a
reliable structure-function analysis will allow more predictive searches
to rapidly and reliably identify novel and more active enzymes. Thereby
it will allow to foster the search and development of novel pathways to
create designer bugs using to solve the plastics problem.