The highly crystalline <scp>PET</scp> found in plastic water bottles does not support the growth of the <scp>PETase</scp>‐producing bacterium <i>Ideonella sakaiensis</i>

Wallace, Noah E.; Adams, Mary C.; Chafin, Andrew C.; Jones, Diamonte D.; Tsui, Caroline L.; Gruber, Todd D.

doi:10.1111/1758-2229.12878

Cited by 28 publications

(20 citation statements)

References 24 publications

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“…films (e.g. crystallinity 1.9% (Taniguchi et Wallace et al (2020) suggest that 52% to 82% of the plastic in PET water bottles is not amenable to microbial degradation without further treatment, due to the crystalline content of the polymer. PETase enzymes are one of the beststudied enzyme groups in reference to plastic polymer hydrolysis and biotechnological advances provide additional scope for enhanced polymer degradation or the production of high-value compounds from waste PET (Danso et al 2019).…”

Section: Synthesismentioning

confidence: 99%

Microbial abilities to degrade global environmental plastic polymer waste are overstated

Lear

Maday

Gambarini

et al. 2022

Environ. Res. Lett.

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Internationally, the environmental damage caused by the improper disposal of approximately 100 Mt of plastic waste per annum is of growing concern. Attempts to address this issue have generated many hundreds of scientific studies announcing the discovery of novel plastic-degrading microorganisms and their respective enzymes. On closer inspection, however, evidence remains sparse for the microbial degradation of most of the plastic polymers produced globally. We systematically surveyed the international literature to confirm how many microorganisms proposed to degrade plastics (n = 664) cause substantial (i.e.,  20% mass) losses of virgin polymer, rather than losses of plastic additives, filler, and/or shedding of polymer micro-fragments. Additionally, we noted where degradation was only demonstrated for artificially aged polymer since physicochemical ageing procedures increase the abundance of monomers and oligomers such that they may be degraded by microbial activity. Additionally, artificial ageing may introduce functional groups to the polymer backbone, creating more locations susceptible to microbial degradation than would otherwise occur in the environment. We identified multiple studies demonstrating the effective microbial degradation of heterochain plastic polymers such as polylactic acid, polycaprolactone and polyethylene terephthalate (i.e., polymers containing elements other than carbon in the backbone structure). However, in the literature, we find no evidence for the substantial degradation of unadulterated polyethylene, polypropylene, polystyrene or polyvinyl chloride, homochain polymers which represent the overwhelming majority of global plastics production. Current research demonstrates that the pre-treatment of plastics with elevated temperature or UV-light may speed physicochemical plastic degradation, with valuable applications for downstream microbial processing. However, evidence for the microbial degradation of most plastic polymers in current circulation is lacking. We outline simple criteria that should be met before announcing the microbial degradation of plastic polymers. We hope this may help to address largely unsubstantiated expectations that microorganisms can degrade many plastic polymers in situ.

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Section: Synthesismentioning

confidence: 99%

Microbial abilities to degrade global environmental plastic polymer waste are overstated

Lear

Maday

Gambarini

et al. 2022

Environ. Res. Lett.

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“…It follows that mesophilic Is PETase, despite its structural similarities to these cutinases and observed hydrolyzing activities at 30°C, should not be regarded as a PET hydrolase, particularly with respect to application ( Kawai et al, 2020 ). It was also recently demonstrated that while amorphous PET supports growth of I. sakaiensis , high crystallinity PET films and bottles do not (unless hcPET is melted and cooled rapidly to give amorphous plastic) ( Wallace et al, 2020 ). TfH may still be grouped with PET hydrolases as it was the first enzyme reported for efficient PET hydrolysis and it is thermophilic.…”

Section: Challenges and Limitationsmentioning

confidence: 99%

Microbial Polyethylene Terephthalate Hydrolases: Current and Future Perspectives

2020

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Plastic has rapidly transformed our world, with many aspects of human life now relying on a variety of plastic materials. Biological plastic degradation, which employs microorganisms and their degradative enzymes, has emerged as one way to address the unforeseen consequences of the waste streams that have resulted from mass plastic production. The focus of this review is microbial hydrolase enzymes which have been found to act on polyethylene terephthalate (PET) plastic. The best characterized examples are discussed together with the use of genomic and protein engineering technologies to obtain PET hydrolase enzymes for different applications. In addition, the obstacles which are currently limiting the development of efficient PET bioprocessing are presented. By continuing to study the possible mechanisms and the structural elements of key enzymes involved in microbial PET hydrolysis, and by assessing the ability of PET hydrolase enzymes to work under practical conditions, this research will help inform large-scale waste management operations. Finally, the contribution of microbial PET hydrolases in creating a potential circular PET economy will be explored. This review combines the current knowledge on enzymatic PET processing with proposed strategies for optimization and use, to help clarify the next steps in addressing pollution by PET and other plastics.

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“…Low crystallinity results in better degradation. PET degrading I. sakaiensis can degrade amorphous PET but is unable to degrade high crystallinity PET ( Wallace et al, 2020 ). When the crystalline PET was converted to amorphous PET the bacterium again was able to degrade the compound ( Wallace et al, 2020 ).…”

Section: Diversity Of Synthetic Polymersmentioning

confidence: 99%

Toward Microbial Recycling and Upcycling of Plastics: Prospects and Challenges

2022

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Annually, 400 Mt of plastics are produced of which roughly 40% is discarded within a year. Current plastic waste management approaches focus on applying physical, thermal, and chemical treatments of plastic polymers. However, these methods have severe limitations leading to the loss of valuable materials and resources. Another major drawback is the rapid accumulation of plastics into the environment causing one of the biggest environmental threats of the twenty-first century. Therefore, to complement current plastic management approaches novel routes toward plastic degradation and upcycling need to be developed. Enzymatic degradation and conversion of plastics present a promising approach toward sustainable recycling of plastics and plastics building blocks. However, the quest for novel enzymes that efficiently operate in cost-effective, large-scale plastics degradation poses many challenges. To date, a wide range of experimental set-ups has been reported, in many cases lacking a detailed investigation of microbial species exhibiting plastics degrading properties as well as of their corresponding plastics degrading enzymes. The apparent lack of consistent approaches compromises the necessary discovery of a wide range of novel enzymes. In this review, we discuss prospects and possibilities for efficient enzymatic degradation, recycling, and upcycling of plastics, in correlation with their wide diversity and broad utilization. Current methods for the identification and optimization of plastics degrading enzymes are compared and discussed. We present a framework for a standardized workflow, allowing transparent discovery and optimization of novel enzymes for efficient and sustainable plastics degradation in the future.

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The highly crystalline PET found in plastic water bottles does not support the growth of the PETase‐producing bacterium Ideonella sakaiensis

Cited by 28 publications

References 24 publications

Microbial abilities to degrade global environmental plastic polymer waste are overstated

Microbial abilities to degrade global environmental plastic polymer waste are overstated

Microbial Polyethylene Terephthalate Hydrolases: Current and Future Perspectives

Toward Microbial Recycling and Upcycling of Plastics: Prospects and Challenges

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