Two-Step Chemo-Microbial Degradation of Post-Consumer Polyethylene Terephthalate (PET) Plastic Enabled by a Biomass-Waste Catalyst

Polyethylene terephthalate (PET) pollution has significant environmental consequences; thus, new degradation methods must be explored to mitigate this problem. We previously demonstrated that a consortium of three Pseudomonas and two Bacillus species can synergistically degrade PET in culture. The c...

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Bibliographic Details
Published in:Bioengineering (Basel) 2023-10, Vol.10 (11), p.1253
Main Authors: Shingwekar, Deepika, Laster, Helen, Kemp, Hannah, Mellies, Jay L
Format: Article
Language:English
Subjects:
Bacteria
biocatalyst
Biocompatibility
Biodegradation
Bioengineering
Biopolymers
Cancer
Catalysts
Chemical reactions
Chemotherapy
Consortia
Crystals
Culture media
Depolymerization
Enzymes
Ethylene glycol
Glycolysis
Inoculation
Microorganisms
Molecular weight
Monomers
NMR
Nuclear magnetic resonance
PET plastic
Pollution
Polyethylene terephthalate
Polymers
Reaction products
Recycling (Waste, etc.)
Software
Spectrum analysis
Structure
Terephthalic acid
Transesterification
Waste management
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Summary:Polyethylene terephthalate (PET) pollution has significant environmental consequences; thus, new degradation methods must be explored to mitigate this problem. We previously demonstrated that a consortium of three Pseudomonas and two Bacillus species can synergistically degrade PET in culture. The consortium more readily consumes bis(2-hydroxyethyl) terephthalate (BHET), a byproduct created in PET depolymerization, compared to PET, and can fully convert BHET into metabolically usable monomers, namely terephthalic acid (TPA) and ethylene glycol (EG). Because of its crystalline structure, the main limitation of the biodegradation of post-consumer PET is the initial transesterification from PET to BHET, depicting the need for a transesterification step in the degradation process. Additionally, there have been numerous studies done on the depolymerization reaction of PET to BHET, yet few have tested the biocompatibility of this product with a bacterial consortium. In this work, a two-step process is implemented for sustainable PET biodegradation, where PET is first depolymerized to form BHET using an orange peel ash (OPA)-catalyzed glycolysis reaction, followed by the complete degradation of the BHET glycolysis product by the bacterial consortium. Results show that OPA-catalyzed glycolysis reactions can fully depolymerize PET, with an average BHET yield of 92% (w/w), and that the reaction product is biocompatible with the bacterial consortium. After inoculation with the consortium, 19% degradation of the glycolysis product was observed in 2 weeks, for a total degradation percentage of 17% when taking both steps into account. Furthermore, the 10-week total BHET degradation rate was 35%, demonstrating that the glycolysis products are biocompatible with the consortium for longer periods of time, for a total two-step degradation rate of 33% over 10 weeks. While we predict that complete degradation is achievable using this method, further experimentation with the consortium can allow for a circular recycling process, where TPA can be recovered from culture media and reused to create new materials.
ISSN:2306-5354
2306-5354
DOI:10.3390/bioengineering10111253