Non-Hydrolyzable Plastics – An Interdisciplinary Look at Plastic Bio-Oxidation

Inderthal, Hedda; Tai, Siew Leng; Harrison, Susan T.L.

doi:10.1016/j.tibtech.2020.05.004

Cited by 109 publications

(83 citation statements)

References 84 publications

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“…These enzymes primarily belong to carboxylic ester hydrolases (EC 3.1.1) family, such as cutinases (EC 3.1.1.74), lipases (EC 3.1.1.3), and carboxylesterases (EC 3.1.1.1) [23,95,111]. As for non-hydrolyzable plastics, they are extremely resistant to biological cleavage, and thus only limited reports on the enzymes to degrade them are available [112].…”

Section: Glossarymentioning

confidence: 99%

Enzyme discovery and engineering for sustainable plastic recycling

Zhu

Wang

Wei

2022

Trends in Biotechnology

180

114

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The drastically increasing amount of plastic waste is causing an environmental crisis that requires innovative technologies for recycling post-consumer plastics to achieve waste valorization while meeting environmental quality goals. Biocatalytic depolymerization mediated by enzymes has emerged as an efficient and sustainable alternative for plastic treatment and recycling. A variety of plasticdegrading enzymes have been discovered from microbial sources. Meanwhile, protein engineering has been exploited to modify and optimize plastic-degrading enzymes. This review highlights the recent trends and up-to-date advances in mining novel plastic-degrading enzymes through state-of-the-art omics-based techniques and improving the enzyme catalytic efficiency and stability via various protein engineering strategies. Future research prospects and challenges are also discussed. Biocatalysis as an Emerging Solution for the Global Plastic Waste ChallengePlastic materials play a revolutionary role in the modern world, although the enormous manufacture and extensive use of plastic commodities inevitably generate an extraordinary amount of post-consumer plastic waste. Around 12 000 million metric tons of plastic waste are predicted to accumulate in landfills and the natural environment by 2050 [1]. Improper handling of plastic waste has caused a grand environmental challenge. The debris of plastic waste, especially microplastics (see Glossary), can impose hazardous effects on various organisms and eventually threaten human well-being [2-5]. In addition, the degradation resistance of plastics further escalates their adverse environmental impacts [6]. Therefore, it is urgent to develop innovative technologies for treatment and recycling of post-consumer plastics, to achieve both waste valorization and environmental protection.Enzymatic biocatalysis has gained increasing attention as an eco-friendly alternative to conventional plastic treatment and recycling methods (Box 1) [7]. To date, various microbial plastic-degrading enzymes have been discovered, representing promising biocatalyst candidates for plastic depolymerization. Considering the ubiquity of plastics in different ecosystems and the tremendous metabolic and genetic diversity of microorganisms, microbial communities in various habitats have likely evolved capabilities in plastic decomposition and utilization. The plastic-degrading enzymes identified so far might only account for a small portion of the enzymes relevant to plastic depolymerization in the environment. Therefore, it is of ever-growing interest to explore diverse environments to discover new plastic-degrading enzymes with desirable properties and functionalities. However, naturally occurring plasticdegrading enzymes are not well suited for synthetic plastic degradation in industrial applications due to poor thermostability and low catalytic activity. Particularly, synthetic plastic materials usually possess distinct physical and chemical properties (e.g., high crystallinity) that render them more resistant to...

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Section: Glossarymentioning

confidence: 99%

Enzyme discovery and engineering for sustainable plastic recycling

Zhu

Wang

Wei

2022

Trends in Biotechnology

180

114

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“…Several studies described the ability of microorganisms and enzymes to degrade these plastics [33][34][35][36][37][38][39][40][41][42][43][44][45][46]. Typical enzymes are cutinases, lipases, and carboxylesterases [47]. The main challenge of enzymatic degradation is the fraction of plastic polymers based on persistent and robust chemical groups, which resist hydrolysis with common biological enzymes that are highly recalcitrant even under conditions favouring microbial processes.…”

Section: Microbial and Enzymatic Plastics Biotransformationmentioning

confidence: 99%

“…These polymers (e.g., PE, PP, PS, PVC) obtained by chain polymerization comprise the major part of the plastic waste market and are generally considered non-biodegradable. The polymers possess extensive inert C-C backbone structures, are completely devoid of functional groups and might be only degraded by highenergy redox reactions [47]. Only a few enzymes have been reported to reduce the molar mass of PE and PS.…”

Section: Microbial and Enzymatic Plastics Biotransformationmentioning

confidence: 99%

“…Only a few enzymes have been reported to reduce the molar mass of PE and PS. Alkane hydroxylase AlkB, a hydroquinone peroxidase, laccases, and a laccase mediator system demonstrated C-C-bond cleavage via autooxidation mediated by putative radical mechanisms thought to occur randomly, generating a large diversity of short-chain scission products [4,[47][48][49][50][51][52][53][54]. In addition to the description of enzymatic activities towards PE and PS, several reports described their mineralization to CO 2 by insect larvae and their enteric microbiome.…”

Section: Microbial and Enzymatic Plastics Biotransformationmentioning

confidence: 99%

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MIXed Plastics Biodegradation and UPcycling Using Microbial Communities: The EU Horizon 2020 Project MIX-UP

Ballerstedt

Tiso

Wierckx

et al. 2021

Preprint

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This article introduces the EU Horizon 2020 research project MIX-UP, “Mixed plastics biodegradation and upcycling using microbial communities”. The project focuses on the ambitious vision to change the traditional linear value chain of plastics to a sustainable, biodegradable based one. In MIX-UP, plastic mixtures containing five of the top six fossil-based recalcitrant plastics (PE, PUR, PP, PET, and PS), along with upcoming biobased and biodegradable plastics (bioplastics) such as PHA and PLA, will be used as feedstock for microbial transformations. The generated new workflow increases recycling quotas and adds value to present poorly recycled plastic waste streams. Consecutive controlled enzymatic and microbial degradation of mechanically pre-treated plastics waste combined with subsequent microbial conversion to polymers and value-added chemicals by mixed cultures. Through optimization of known plastic-degrading enzymes by integrated protein engineering, high specific binding capacities, stability, and catalytic efficacy towards a broad spectrum of plastic polymers under high salt content and temperature conditions will be achieved. Another focus lies in the search and isolation of novel enzymes active on recalcitrant polymers. MIX-UP will also enhance the production of enzymes and formulate enzyme cocktails tailored to specific waste streams. In vivo and in vitro application of these cocktails enables stable, self-sustaining microbiomes to convert the released plastic monomers selectively into value-added products, key building blocks, and biomass. Any of the remaining material recalcitrant to the enzymatic activity will be recirculated into the process by physicochemical treatment. The Chinese-European MIX-UP is a multidisciplinary and industry-participating consortium to address the market need for novel sustainable routes to valorize plastic waste streams. MIX-UP realizes a circular (bio) plastic economy and will contribute where mechanical and chemical plastic recycling show limits.

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“…Some applications are being commercialized while others are at earlier stages of research (Taning et al, 2020a ). The Editors believe that applications of HIGS and SIGS can make major contributions to sustainable and integrated crop protection and support “Green” systems for intensification of agricultural production as advocated in UN Sustainability Development Goals and by FAO, EU, and many national governments (Mezzetti et al, 2020 ; Taning et al, 2020b ). The editors would like to acknowledge the opportunity provided by Frontiers for publishing these papers and thank the authors for their contributions.…”

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confidence: 99%