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- Din, Salah Ud, et al.
(författare)
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The Purification and Characterization of a Cutinase-like Enzyme with Activity on Polyethylene Terephthalate (PET) from a Newly Isolated Bacterium Stenotrophomonas maltophilia PRS8 at a Mesophilic Temperature
- 2023
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- A polyethylene terephthalate (PET)-degrading bacterium identified as Stenotrophomonas maltophilia PRS8 was isolated from the soil of a landfill. The degradation of the PET bottle flakes and the PET prepared as a powder were assessed using live cells, an extracellular medium, or a purified cutinase-like enzyme. These treated polymers were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The depolymerization products, identified using HPLC and LC-MS, were terephthalic acid (TPA), mono(2-hydroxyethyl)-TPA (MHET), and bis(2-hydroxyethyl)-TPA (BHET). Several physicochemical factors were optimized for a better cutinase-like enzyme production by using unique single-factor and multi-factor statistical models (the Plackett–Burman design and the central composite design software). The enzyme was purified for homogeneity through column chromatography using Sephadex G-100 resin. The molecular weight of the enzyme was approximately 58 kDa. The specific activity on para nitrophenyl butyrate was estimated at 450.58 U/mg, with a purification of 6.39 times and a yield of 48.64%. The enzyme was stable at various temperatures (30–40 °C) and pH levels (8.0–10.0). The enzyme activity was significantly improved by the surfactants (Triton X-100 and Tween-40), organic solvent (formaldehyde), and metals (NiCl2 and Na2SO4). The extracellular medium containing the cutinase-type enzyme showed a depolymerization yield of the PET powder comparable to that of Idonella skaiensis IsPETase and significantly higher than that of Humicola insolens thermostable HiCut (HiC) cutinase. This study suggests that S. maltophilia PRS8 is able to degrade PET at a mesophilic temperature and could be further explored for the sustainable management of plastic waste.
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| 2. |
- Mankar, Smita V., et al.
(författare)
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Short-Loop Chemical Recycling via Telechelic Polymers for Biobased Polyesters with Spiroacetal Units
- 2023
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Ingår i: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:13, s. 5135-5146
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Tidskriftsartikel (refereegranskat)abstract
- Spirocyclic acetal structures have recently received growing attention in polymer science due to their dual potential to raise the glass transition temperature (Tg) and enable chemical recycling of biobased polymers. In the present work, a vanillin-based diol with a spirocyclic acetal structure was incorporated in a series of rigid amorphous polyesters based on neopentyl glycol and dimethyl terephthalate (DMT). Up to 50 mol % of spirocyclic diol (with respect to DMT) could be incorporated in the copolyesters, but a reasonably high molecular weight was only achieved when ≤30 mol % of the spirocyclic diol was used. The presence of the spiroacetal units in the polyesters not only enhanced the Tg (up to 103 °C) and thermal stability (T5 ≥ 300 °C) but also the oxygen barrier of solution-cast films. We found that the acetal units in the copolyesters could be selectively hydrolyzed under acidic conditions while virtually retaining all of the ester bonds in the polymer backbone. After acidic hydrolysis, telechelic polymers exclusively terminated by two aldehyde end groups were obtained. In this work, we have demonstrated that these telechelic polyesters can be conveniently converted back into poly(acetal-ester)s via cycloacetalization reactions with pentaerythritol.
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