Page 64 - Plastics News May 2026
P. 64
PRODUCT NEWS
HEAT-STABLE ENZYME ADVANCES
PET RECYCLING
esearchers from Tokyo University of Sci- flexibility at the active site. This combination is
ence have characterized a thermophilic typically difficult to achieve.
Rcutinase enzyme to better understand
how biocatalysts can operate under conditions Thermophilic enzyme model and analytical
relevant to polyethylene terephthalate (PET) re- approach
cycling. The study examines how structural sta- The research team analyzed a cutinase de-
bility and local flexibility are balanced to main- rived from the fungus Chaetomium thermophi-
tain catalytic activity at elevated temperatures. lum. Both the native enzyme (CtCutWT) and a
mutant variant (CtCutS136A) were examined.
Structural characterization and thermal stability
measurements were conducted using differen-
tial scanning calorimetry across a temperature
range from 30 °C to 100 °C.
Rigid core and flexible lid loop
The enzyme adopts an α/β-hydrolase fold, pro-
viding a stable structural framework. A mobile
lid loop covers the active site and regulates sub-
The cutinase enzyme combines a rigid α/β- strate access. Structural observations indicate
hydrolase core with a flexible lid loop near the that this loop undergoes conformational chang-
active site. Structural comparison suggests that es during ligand binding, enabling catalytic func-
the lid loop undergoes conformational changes tion without compromising overall stability.
more readily than the rigid core.Copyright: Pro-
fessor Tatsuya Nishino from Tokyo University of A chloride ion detected near the active site sug-
Science, Japan. gests the presence of a positively charged mi-
croenvironment. This may support substrate
Biorecycling context and temperature con- interaction even in the absence of bound mol-
straints ecules.
Enzymatic recycling approaches target polymer Stepwise thermal unfolding
bonds in PET, commonly used in packaging and
textiles. Efficient depolymerization occurs near Thermal analysis identified a two-stage unfold-
70 C, where the polymer becomes more ac- ing process, with initial structural changes be-
0
cessible. Under these conditions, enzymes must ginning at approximately 60 °C and a second
retain global structural integrity while preserving transition occurring between 65 °C and 70 °C.
These findings indicate that different regions of
66 PLASTICS NEWS May 2026
