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1.
J Biotechnol ; 341: 76-85, 2021 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-34534594

RESUMO

The environmental impact arising from poly(ethylene terephthalate) (PET) waste is notable worldwide. Enzymatic PET hydrolysis can provide chemicals that serve as intermediates for value-added product synthesis and savings in the resources. In the present work, some reaction parameters were evaluated on the hydrolysis of post-consumer PET (PC-PET) using a cutinase from Humicola insolens (HiC). The increase in PC-PET specific area leads to an 8.5-fold increase of the initial enzymatic hydrolysis rate (from 0.2 to 1.7 mmol L-1 h-1), showing that this parameter plays a crucial role in PET hydrolysis reaction. The effect of HiC concentration was investigated, and the enzymatic PC-PET hydrolysis kinetic parameters were estimated based on three different mathematical models describing heterogeneous biocatalysis. The model that best fits the experimental data (R2 = 0.981) indicated 1.68 mgprotein mL-1 as a maximum value of the enzyme concentration to optimize the reaction rate. The HiC thermal stability was evaluated, considering that it is a key parameter for its efficient use in PET degradation. The enzyme half-life was shown to be 110 h at 70 ºC and pH 7.0, which outperforms most of the known enzymes displaying PET hydrolysis activity. The results evidence that HiC is a very promising biocatalyst for efficient PET depolymerization.


Assuntos
Modelos Teóricos , Polietilenotereftalatos , Biocatálise , Etilenos , Gênero de Fungos Humicola , Hidrólise , Ácidos Ftálicos , Polietilenotereftalatos/metabolismo
2.
Bioprocess Biosyst Eng ; 44(3): 507-516, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33111179

RESUMO

Massive plastics production has raised concerns about low recycling rates and disposal of these materials in nature, causing environmental and economic impacts. Poly(ethylene terephthalate) (PET) is one of main polymers used for manufacture of plastic packaging (e.g. bottles, trays). Enzymatic recycling of PET has been a route of increasing study aiming at to recover its monomers (terephthalic acid and ethylene glycol), resulting in a circular production chain. In this study, investigation of pH control and fractionation of enzyme feeding were explored in post-consumed PET (PC-PET) hydrolysis reactions catalyzed by Humicola insolens cutinase (HiC) in stirred reactors. It was found that the unbuffered reaction provided of pH control by 0.5 M NaOH addition showed 2.39-fold improvement in the released monomers (to a total of 26.3 mM), comparatively to the Tris-HCl-buffered reaction. In addition, it was observed a possibility of reducing the enzyme loading used in the process by half, leading to an increase of 2.41-fold in the specific terephthalic acid concentration released per protein amount, whilst maintaining a high products concentration (97 mM). A simplified cost analysis of reaction consumables was performed, and the data reported here demonstrates that these alternative process strategies contribute to costs reduction on the enzymatic depolymerization reactions of PET.


Assuntos
Biocatálise , Hidrolases de Éster Carboxílico/química , Gênero de Fungos Humicola/enzimologia , Proteínas Fúngicas/química , Polietilenotereftalatos/química
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