Microbial Enzyme Biotechnology to Reach Plastic Waste Circularity: Current Status, Problems and Perspectives

Abstract

The accumulation of synthetic plastic waste in the environment has become a global concern. Microbial enzymes (purified or as whole-cell biocatalysts) represent emerging biotechnological tools for waste circularity; they can depolymerize materials into reusable building blocks, but their contribution must be considered within the context of present waste management practices. This review reports on the prospective of biotechnological tools for plastic bio-recycling within the framework of plastic waste management in Europe. Available biotechnology tools can support polyethylene terephthalate (PET) recycling. However, PET represents only ≈7% of unrecycled plastic waste. Polyurethanes, the principal unrecycled waste fraction, together with other thermosets and more recalcitrant thermoplastics (e.g., polyolefins) are the next plausible target for enzyme-based depolymerization, even if this process is currently effective only on ideal polyester-based polymers. To extend the contribution of biotechnology to plastic circularity, optimization of collection and sorting systems should be considered to feed chemoenzymatic technologies for the treatment of more recalcitrant and mixed polymers. In addition, new bio-based technologies with a lower environmental impact in comparison with the present approaches should be developed to depolymerize (available or new) plastic materials, that should be designed for the required durability and for being susceptible to the action of enzymes.

Strategies for Considering Environmental Justice in the Early-Stage Development of Circular Economy Technologies

“…Enzymatic hydrolysis uses enzymes to depolymerize waste PET into its monomers, ethylene glycol and terephthalic acid, which can then be repolymerized into high quality PET products such as water bottles. 18 As this circular economy solution has been demonstrated at the pilot scale but not widely deployed, 19 we consider it to be at mid TRL.…”

Recent advances on solar-driven valorization of polyethylene terephthalate plastics into value-added chemicals

“…Therefore, crucial to realize PET plastics upgrading is developing an efficient strategy for PET plastics depolymerization. The general approaches, including physical, chemical, and biological methods, were employed to depolymerize PET plastics into monomers or derivatives [47,48]. Among them, grinding PET plastics into powder was applied to PET recycling as a physical method, and other physical methods utilized in the depolymerization of PET plastics include melting and ultrasonic treatment, both which are designed to reduce the crystallinity of PET plastics and to finally break PET plastic down into small fragments [49,50].…”

Recent Progress in Micro- and Nanotechnology-Enabled Sensors for Biomedical and Environmental Challenges

“…The development of micro- and nanotechnology-enabled sensors has been a significant technological advancement that has led to several new applications in the biomedical and environmental fields [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. These devices have enabled the detection and quantification of various analytes with high sensitivity and selectivity, making them ideal for applications such as vital sign monitoring [ 3 , 9 , 10 ], disease diagnosis [ 11 , 12 , 13 ], environmental monitoring [ 5 , 6 , 14 , 15 , 16 ], and food safety [ 17 , 18 , 19 , 20 ].…”