Process strategies to improve biocatalytic depolymerization of post-consumer PET packages in bioreactors, and investigat
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RESEARCH PAPER
Process strategies to improve biocatalytic depolymerization of post‑consumer PET packages in bioreactors, and investigation on consumables cost reduction Adriano Carniel1,3 · Absai da Conceição Gomes2 · Maria Alice Zarur Coelho3 · Aline Machado de Castro2 Received: 14 July 2020 / Accepted: 7 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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. Keywords Poly(ethylene terephthalate) · Terephthalic acid · PET recycling · Enzymatic depolymerization · Humicola insolens · Cutinase
Introduction Since the development and industrial production of polymeric materials in the 1950s, their demand has grown exponentially over the years [1]. Plastic production reached 396 million metric tons only in 2016 and it is estimated to increase 40% until 2030 [2]. Food and beverage plastic packages have been a major target of concern, since these materials are generally for single use and then readily discarded * Aline Machado de Castro [email protected] 1
Falcão Bauer, R. Aquinos, 111. Água Branca, São Paulo 05036‑070, Brazil
2
Biotechnology Division, Research and Development Center, PETROBRAS, Av. Horácio Macedo, 950, Ilha do Fundão, Rio de Janeiro 21941‑915, Brazil
3
Department of Biochemical Engineering, Escola de Química, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro 21949‑900, Brazil
after consumption [2, 3]. Due to low recycling rates, the majority of these residues are disposed in landfills or directly leaked into terrestrial and marine ecosystems, causing environmental impacts and economic loss due to waste of monomers present in these packages [4]. Poly(ethyl
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