scholarly journals An Efficient Protein Evolution Workflow for the Improvement of Bacterial PET Hydrolyzing Enzymes

2021 ◽  
Vol 23 (1) ◽  
pp. 264
Author(s):  
Valentina Pirillo ◽  
Marco Orlando ◽  
Davide Tessaro ◽  
Loredano Pollegioni ◽  
Gianluca Molla

Enzymatic degradation is a promising green approach to bioremediation and recycling of the polymer poly(ethylene terephthalate) (PET). In the past few years, several PET-hydrolysing enzymes (PHEs) have been discovered, and new variants have been evolved by protein engineering. Here, we report on a straightforward workflow employing semi-rational protein engineering combined to a high-throughput screening of variant libraries for their activity on PET nanoparticles. Using this approach, starting from the double variant W159H/S238F of Ideonella sakaiensis 201-F6 PETase, the W159H/F238A-ΔIsPET variant, possessing a higher hydrolytic activity on PET, was identified. This variant was stabilized by introducing two additional known substitutions (S121E and D186H) generating the TS-ΔIsPET variant. By using 0.1 mg mL−1 of TS-ΔIsPET, ~10.6 mM of degradation products were produced in 2 days from 9 mg mL−1 PET microparticles (~26% depolymerization yield). Indeed, TS-ΔIsPET allowed a massive degradation of PET nanoparticles (>80% depolymerization yield) in 1.5 h using only 20 μg of enzyme mL−1. The rationale underlying the effect on the catalytic parameters due to the F238A substitution was studied by enzymatic investigation and molecular dynamics/docking analysis. The present workflow is a well-suited protocol for the evolution of PHEs to help generate an efficient enzymatic toolbox for polyester degradation.

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Maurizio Canetti ◽  
Fabio Bertini

AbstractPoly(ethylene terephthalate) (PET) has been compounded with lignin (L) by a single-screw extruder. The influence of L presence and its content on the thermal stability of PET has been studied by using thermogravimetric analysis. The experiments carried out in oxidative conditions evidenced the barrier effect of L that interferes to the diffusion of the volatile degradation products to the gas phase and at the same time to the diffusion of the oxygen from the gas phase to the PET matrix. The influence of L on the melting behaviour of PET has been investigated on samples submitted to subsequent annealing steps procedure. X-ray techniques were employed to investigate crystallinity and crystal dimensions of pure PET and PET/L composites. Considering the supermolecular and crystal structure of the annealed samples, their melting behaviour was explained assuming small changes in the melting entropy.


2021 ◽  
Author(s):  
Wojciech Rejmer

Abstract: The aim of these research is to investigate the air content on aging of poly(ethylene terephthalate) (PET) preforms. Three air pressures were selected and in each pressure 5 samples were aged during 21 days in 80oC. Three samples were selected to cut and measure their density with the use of hydrostatic method. Sample mass, Young modulus and surface roughness were measured for each sample before and after aging and differences between those parameters were presented as results. The changes of parameters may lead to a conclusion that mechanism of polymeric chain oxidation is dominant during thermal aging of PET. However the aging is not the fastest in atmospheric pressure but in lower air contents. This effect may be caused by greater evaporation of small molecule degradation products and shifting of reaction equilibrium in the direction of further decomposition.


Engineering ◽  
2018 ◽  
Vol 4 (6) ◽  
pp. 888-893 ◽  
Author(s):  
Yuan Ma ◽  
Mingdong Yao ◽  
Bingzhi Li ◽  
Mingzhu Ding ◽  
Bo He ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document