Degradation Of Plastics Research Articles

Progress on Photo-, Electro-, and Photoelectro-Catalytic Conversion of Recalcitrant Polyethylene, Polypropylene, and Polystyrene - A Review.

Recalcitrant waste plastics such a polyethylene, polypropylene, and polystyrene are difficult to recycle and are mostly disposed of in landfills and eventually leached into the environmental as micro- and nano-plastics. This review explores how photo-, electro-, and combined photoelectro-catalyticprocesses can assist in the degradation and upcycling of waste plastic into different chemicals and mitigate their release to the environment. In this work, we discuss how the different reaction mechanisms proceed, explore the current relevant literature, and highlight the developments needed to advance the field.

Application of Polylactic Acid in Clinical Medicine

Polylactic acid (PLA), a bio-based and biodegradable material, shows significant potential in environmental protection and clinical medicine. Derived from renewable resources, PLA's biodegradability reduces long-term environmental pollution by allowing it to decompose rapidly under specific conditions. This review explores PLA's applications in clinical medicine, emphasizing its mechanical properties, biocompatibility, and controlled degradation rates. The study covers PLA's extensive use in drug delivery systems, absorbable sutures, and tissue engineering scaffolds, highlighting its compatibility with human tissues and low immunogenicity. Research methods and designs, including in vitro and in vivo experiments, are discussed to evaluate PLA's efficacy and safety. The challenges of high production costs and specific degradation conditions are also addressed. Future research directions include developing new catalysts to improve synthesis efficiency and exploring renewable raw materials to reduce costs and environmental impact. As global awareness of sustainable development grows, the demand for PLA and other degradable plastics is expected to increase, expanding their applications in various fields. In conclusion, PLA offers substantial advantages in reducing reliance on fossil fuels and mitigating environmental pollution, while providing innovative solutions in the medical field. Technological advancements and increased production are anticipated to lower costs, making PLA more economically competitive and accelerating its application in both environmental protection and clinical medicine.

Degradation of polystyrene plastics by alkane monooxygenase and alcohol dehydrogenase

<p style="text-indent:0.0000pt; text-align:justify"><span style="font-size:10.5pt"><span style="line-height:200%"><span style="font-family:"Times New Roman""><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">The consumption of plastic products has led to the generation of large amounts of plastic waste, which is persistent and difficult to degrade. Polystyrene (PS) is one of the six most important plastics in the world and is difficult to degrade in the environment owing to its high stability. To investigate PS degradation by biological enzymes, two oxidoreductases, alkane hydroxylase (AlkB) and alcohol dehydrogenase (Adh), were selected from the bacterial strain </span></span></span><i><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">Acinetobacter johnsonii</span></span></span></i><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%"> JUN01, which has been proven to be capable of degrading PS. Genetically engineered bacteria capable of expressing AlkB and Adh were constructed using genetic engineering technology, and the degradation activities of AlkB monoenzyme, Adh monoenzyme, and AlkB–Adh composite enzyme were investigated. Thermal field emission scanning electron microscopy </span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">(SEM) </span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">and water contact angle </span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">(WCA) </span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">measurements demonstrated that the investigated enzymes transformed PS from hydrophobic to hydrophilic. Fourier transform infrared </span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">(FTIR)</span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%"> results showed that after enzymatic hydrolysis, the number of hydroxyl groups (–OH) increased, the number of C=C and C=O bonds increased, and the structure of benzene ring was disrupted by degradation using AlkB monoenzyme and AlkB–Adh composite enzyme. X-ray photoelectron spectroscopy </span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">(XPS) </span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">showed that the characteristic C–C bonds of PS decreased, and the number of C–O bonds and C=O bonds increased. The molecular weight of PS changed after digestion, as determined by high-temperature gel chromatography</span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%"> (</span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">GPC)</span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">. Thermogravimetric analysis</span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%"> (TGA)</span></span></span><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%"> was used to demonstrate a decrease in the thermal stability of PS after digestion. These results showed that the AlkB monoenzyme, Adh monoenzyme, and AlkB–Adh composite enzyme all had PS degradation activity, demonstrating that the idea of using a composite enzyme to degrade PS was feasible. In addition, Adh exhibited degradation activity in two different coenzyme reaction systems. Therefore, these results provide a theoretical basis and data support for the future degradation of PS by bioenzymes.</span></span></span></span></span></span></p> <p style="text-indent:0.0000pt; text-align:justify"><span style="font-size:10.5pt"><span style="line-height:200%"><span style="font-family:"Times New Roman""><span style="font-size:12.0000pt"><span style="font-family:'Times New Roman'"><span style="line-height:200%">Keywords: Plastic degrading enzymes; Microplastics; Biodegradation</span></span></span></span></span></span></p>

Does short-span chemical oxidation induce more weathering than prolonged thermal aging on polypropylene microplastics? Its consequence during the interaction with cadmium

Weathering and degradation of plastics in the environment are evident in almost all conditions. However, the difference is the changes in the polymer properties, which varies with the aging mechanism, polymer type, and other prevailing environmental conditions. Aging is an essential factor that further determines the fate and transportation of smaller plastics. Apart from UV radiation for microplastics (MPs) aging, other mechanisms also play a crucial role in changing the physicochemical properties of polymers in natural environments. Other aging mechanisms, such as chemical and thermal oxidation, were used in this study. Also, thermally stable and chemical resistant polypropylene MP is used in this study to understand the oxidation mechanisms and to know the breakpoint where it becomes susceptible to the reactions. From the results, the aged MPs showed roughness, pore formation, and cracks on the surface; more specifically, PP MPs were more weathered during thermal oxidation, revealed in both physicochemical characterizations of MPs. However, the chemical oxidation reached almost half the aging of the thermal process within a short period. The additives in the PP MPs make it resistant to the treatment, where it takes time to break during the thermal treatment, which was contradictory with Fenton aging. Further, the adsorption study was conducted to determine its interaction with Cd2+ and which aged MPs adsorb more. It can be concluded that PP MPs are more vulnerable towards chemical aging within a short duration, but it takes time to stimulate weathering under increased temperature.

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: synergistic effects of nitrogen vacancies and Fe

The introduction of nitrogen vacancies (VN) and iron (Fe) single atoms sites significantly enhances the visible light absorption and charge transfer ability of carbon nitride (CN) catalysts. This paper presents the successful synthesis of a VN-rich, Fe single atoms incorporated CN, a catalyst that demonstrates exceptional degradation performance and cycling stability. The 2-mercaptobenzothiazole (MBT) removal rate by 20Fe-CN reached 99.51% within just 11min under visible light, and the catalyst maintained superior photocatalytic performance upon repeated use. Additionally, the 20Fe-CN/Photo/High-temperature system effectively converted polystyrene (PS) to benzoic acid (BA), achieving a BA yield of 19.73% after 48hours. Under visible light irradiation, the VN sites captured electrons and facilitated their rapid transfer to neighboring Fe sites, enhancing the photocatalytic redox processes. This study also identified ·O2- as the primary active species in the photocatalytic process. This research supports the development of diverse single-atom modified carbon nitride photocatalysts, holding significant potential for wastewater treatment and plastic resource recycling, and providing valuable insights for future photocatalysts in environmental remediation.

Tuning the performance of a TphR-based terephthalate biosensor with a design of experiments approach

Transcription factor-based biosensors are genetic tools that aim to predictability link the presence of a specific input stimuli to a tailored gene expression output. The performance characteristics of a biosensor fundamentally determines its potential applications. However, current methods to engineer and optimise tailored biosensor responses are highly nonintuitive, and struggle to investigate multidimensional sequence/design space efficiently. In this study we employ a design of experiments (DoE) approach to build a framework for efficiently engineering activator-based biosensors with tailored performances, and we apply the framework for the development of biosensors for the polyethylene terephthalate (PET) plastic degradation monomer terephthalate (TPA). We simultaneously engineer the core promoter and operator regions of the responsive promoter, and by employing a dual refactoring approach, we were able to explore an enhanced biosensor design space and assign their causative performance effects. The approach employed here serves as a foundational framework for engineering transcriptional biosensors and enabled development of tailored biosensors with enhanced dynamic range and diverse signal output, sensitivity, and steepness. We further demonstrate its applicability on the development of tailored biosensors for primary screening of PET hydrolases and enzyme condition screening, demonstrating the potential of statistical modelling in optimizing biosensors for tailored industrial and environmental applications.

Biodegradable microplastics induce profound changes in lettuce (Lactuca sativa) defense mechanisms and to some extent deteriorate growth traits

The development of agricultural technologies has intensified the use of plastic in this sector. Products of plastic degradation, such as microplastics (MPs), potentially threaten living organisms, biodiversity and agricultural ecosystem functioning. Thus, biodegradable plastic materials have been introduced to agriculture. However, the effects of biodegradable plastic substitutes on soil ecosystems are even less known than those of traditional ones. Here, we studied the effects of environmentally relevant concentrations of MPs prepared from a biodegradable plastic (a starch-polybutylene adipate terephthalate blend, PBAT-BD-MPs) on the growth and defense mechanisms of lettuce (Lactuca sativa) in CLIMECS system (CLImatic Manipulation of ECosystem Samples). PBAT-BD-MPs in the highest concentrations negatively affected some traits of growth, i.e., dry weight percentage, specific leaf area, and both C and N contents. We observed more profound changes in plant physiology and biochemistry, as PBAT-BD-MPs decreased chlorophyll content and triggered a concerted response of plant defense mechanisms against oxidative stress. In conclusion, exposure to PBAT-BD-MPs induced plant oxidative stress and activated plant defense mechanisms, leading to oxidative homeostasis that sustained plant growth and functioning. Our study highlights the need for in-depth understanding of the effect of bioplastics on plants.

Upcycling CO2 and bio-derived furan into degradable plastic monomer via coupling of photocatalysis and thermocatalysis

Coupling of CO2 with biomass-derived molecules into degradable plastic monomer provides a promising strategy to address the increasing problems of carbon recycle and carbon neutrality. Herein, we develop a sustainable route to produce 6-hydroxycaproate (6-HMC) by coupling photocatalytic carboxylation of biomass-derived furfuryl alcohol with CO2 to 2-furanacetic acid (FA), and the thermocatalytic hydrogenolysis of methyl 2-tetrahydrofuranyl acetate (MTFA) derived from FA, wherein Pd/CeO2 exhibit the highest productivity of 6-HMC (505 mmol6-HMC mmol-1metal h−1), much higher than its counterparts of precious- and non-precious-metal catalysts. Moreover, Pd/CeO2 also presents good stability for 6 recycles without remarkable decrease in 6-HMC yield. Systematic experiments and computational studies suggest that higher concentration of oxygen vacancies and strong metal-support interactions account for enhanced catalytic performance of Pd/CeO2. The work employs CO2 and lignocellulosic-derived platform molecule as feedstocks to produce valuable degradable plastic monomer, providing a promising route to access pure-CO2 originated high-carbon oxygen-containing compounds.

Status and Enhancement Techniques of Plastic Waste Degradation in the Environment: A Review

Plastic waste has been gradually accumulating in the environment due to rapid population growth and increasing consumer demand, posing threats to both the environment and human health. In this overview, we provide a comprehensive understanding of the degradation of plastics in real environments, such as soil, aquatic environment, landfill, and compost. Both conventional and biodegradable plastics exhibit limited degradation in real environments, except for biodegradable plastics during industrial composting with high thermophilic temperatures. Meanwhile, we also review techniques for enhanced degradation of plastics such as physical technologies (e.g., photocatalysis, mechanical degradation, and pyrolysis), chemical technologies (e.g., hydrolysis, alcoholysis, ammonia, strong oxidation, and supercritical fluids), and biotechnologies (e.g., microorganisms, microfauna, and microalgae). The future research directions for the enhancement of plastic degradation are also discussed, such as the establishment of equivalency standards, adoption of internal control techniques, the control of precise recycling of plastic products, and the ecotoxicology of their degradation products. Therefore, this review comprehensively summarizes the state of plastic degradation in real environments and proposes methods to improve plastic degradation, providing a theoretical basis for the future control and disposal of plastics.

Enhancing PET degradation efficiency through fusing carbohydrate-binding modules in LCC-ICCG

Polyethylene terephthalate (PET) is a largely-produced polymer worldwide. However, its extensive waste generation and resistance to degradation pose significant environmental concerns. Consequently, there is considerable interest in researching enzymatic degradation of PET. Relevant studies have shown that the addition of a carbohydrate binding module (CBM) can increase the affinity between the enzyme and the substrate, enhancing the enzyme's degradation ability. In order to develop more efficient PET hydrolytic enzymes, this study introduced carbohydrate binding domains (CBMs) from different families with different substrate affinities into the PET-degrading enzyme LCC-ICCG. High crystallinity PET powder and amorphous PET film were used as substrates to characterize the degradation efficiency of the modified enzymes, aiming to explore the enzyme with the optimal degradation ability. The results showed that the fusion of type B CBM reduced the degradation rate and Tm value of the enzyme towards PET, while the introduction of type A and type C CBMs significantly improved the degradation rate of the enzyme towards the film-like substrate. The degradation rate and Tm value of PET were also enhanced, especially with the fusion enzyme LCC-ICCG-CBM9-2, which showed an over 10-fold increase in the degradation rate compared to the original enzyme LCC-ICCG. Therefore, this study demonstrates that by introducing type A and type C CBMs, the degradation rate and thermal stability of LCC-ICCG towards film-like PET can be improved, addressing the issue of its low activity and enabling more effective PET degradation. This research provides support for plastic degradation technology and contributes to environmental conservation efforts.

Accepting the decay of plastic artifacts in museums: pasts and futures surfacing in a life preserver from sunken MS Estonia

ABSTRACT This is a case study of a deformed life preserver originating from the ferryboat MS Estonia that sank in the Baltic Sea in 1994. In this post qualitatively positioned research article, I argue that transformed plastic is an active agent of both the decision-making and interpretation of a museum object made of plastic. This article contributes in a new way to the discussion of how museums of cultural history could manage deteriorating plastic objects. So far, a scientific materialist approach, guided by research in conservation science, has emphasised the need for special conditions to safeguard rapidly deteriorating plastic artefacts for future generations. However, the agency of deteriorating plastic does not only call for conserving the plastic material ‘forever’, but it also requires letting go of the ideal of minimising the further degradation of plastic.

ATR-FTIR characterisation of daily-use plastics mycodegradation

Synthetic polymers, such as plastics, have permeated all aspects of modern life, and nowadays plastic pollution is a major environmental problem. Mycodegradation of these polymers could represent part of the solution to this problem since it calls on a broad toolbox of enzymes and applies non-enzymatic mechanisms to degrade and deteriorate recalcitrant materials. However, not enough is known about this ability for most of the representatives of the fungal kingdom. Another bottleneck is the harmonisation of technologies to analyse plastic degradation. This work involved the design of a biodegradation experiment, where the potential of four fungi representative of Dikarya and Penicillia (Funalia floccosa, Trametes versicolor, Pycnoporus cinnabarinus and Penicillium oxalicum) were tested on their ability to deteriorate the six most used plastics based on gravimetry and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The following correlation between changes in the band signals and the loss of mass after treatment was determined using polyethylene terephthalate, polypropylene, polyethylene, poly vinyl chloride, high density polyethylene, low density polyethylene and nylon. After treatment, the decrease in absorbance of the characteristic bands of the plastics was taken as an indication of the degradation of the corresponding bonds/functionalities. The four fungi used could transform CH, CH2, CH3, CO, CO, CN, NH and CCl bonds. The best result was obtained using the fungus F. floccosa with 90-day treatments for high density polyethylene (∼ 62.0 %), low density polyethylene (∼ 23.6 %) and nylon (∼ 35.6 %). Therefore, mycodegradation could open up new doors in the fight against plastic pollution.

Upconversion Phosphor-Driven Photodegradation of Plastics.

Plastic waste poses a profound threat to ecosystems and human health, necessitating novel strategies for effective degradation in nature. Here, we present a novel approach utilizing upconversion phosphors as additives to significantly accelerate plastic photodegradation in nature via enhancing ultraviolet (UV) radiation. Pr-doped Li2CaGeO4 (LCGO:Pr) upconversion phosphors readily converting blue light into deep-UV radiation, dramatically improve photodegradation rates for polyethylene (PE) and polyethylene terephthalate (PET) microplastics. In situ spectroscopic studies show that upconversion fluorescence initiates the photophysical cleavage of C-C and C-O bonds in the backbones of PE and PET, resulting in plastic degradation. Moreover, incorporating LCGO:Pr into polypropylene (PP) sheets realizes markedly enhanced photodamage, with the cracking area increasing by nearly 38-fold under simulated sunlight for 10 days. This underscores the potential of employing this approach for the construction of light-driven destructible polymers. Further optimization and exploration of material compatibility hold promise for developing sustainable photodegradable plastics.

Omic-driven strategies to unveil microbiome potential for biodegradation of plastics: a review.

Plastic waste accumulation has lately been identified as the leading and pervasive environmental concern, harming all living beings, natural habitats, and the global market. Given this issue, developing ecologically friendly solutions, such as biodegradation instead of standard disposal, is critical. To effectively address and develop better strategies, it is critical to understand the inter-relationship between microorganisms and plastic, the role of genes and enzymes involved in this process. However, the complex nature of microbial communities and the diverse mechanisms involved in plastic biodegradation have hindered the development of efficient plastic waste degradation strategies. Omics-driven approaches, encompassing genomics, transcriptomics and proteomics have revolutionized our understanding of microbial ecology and biotechnology. Therefore, this review explores the application of omics technologies in plastic degradation studies and discusses the key findings, challenges, and future prospects of omics-based approaches in identifying novel plastic-degrading microorganisms, enzymes, and metabolic pathways. The integration of omics technologies with advanced molecular technologies such as the recombinant DNA technology and synthetic biology would guide in the optimization of microbial consortia and engineering the microbial systems for enhanced plastic biodegradation under various environmental conditions.

Effects of biological filtration by ascidians on microplastic composition in the water column

Plastic pollution, a widespread environmental challenge, significantly impacts marine ecosystems. The degradation of plastic under environmental conditions results in the generation of microplastic (MP; <5 mm) fragments, frequently ingested by marine life, including filter-feeders such as ascidians (Chordata, Ascidiacea). These organisms are integral to benthic-pelagic coupling, transporting MP from the water column through marine food web.Here, we explored the effect of filtration and digestion by the solitary ascidian Styela plicata on the composition of MP in the water column and on the sinking rates of faecal matter, focusing on differences between two distinct plastics, polystyrene (PS) and the biodegradable polylactic acid (PLA). The ascidians efficiently removed 2–5 μm particles within 2 h of filtration. Following digestion and secretion process, PS concentrations in water increased while PLA concentration remained stable. Some particles were egested into the water column repackaged inside faecal pellets, which significantly increased the pellets' drag force and sinking velocity. Raman spectral analysis of digested MP revealed distinct spectrum alterations due to coating by organic substances. These findings highlight the role of ascidians — and other filter-feeders— in modifying the structure of MP in their environment. Research into such modifications is crucial for understanding the MP cycle and its consequences in marine environments.

Anaerobic Degradation of Aromatic and Aliphatic Biodegradable Plastics: Potential Mechanisms and Pathways.

Biodegradable plastics (BDPs) have been widely used as substitutes for traditional plastics, and their environmental fate is a subject of intense research interest. Compared with the aerobic degradation of BDPs, their biodegradability under anaerobic conditions in environmental engineering systems remains poorly understood. This study aimed to investigate the degradability of BDPs composed of poly(butylene adipate-co-terephthalate) (PBAT), poly(lactide acid) (PLA), and their blends, and explore the mechanism underlying their microbial degradation under conditions of anaerobic digestion (AD). The BDPs readily depolymerized under thermophilic conditions but were hydrolyzed at a slow rate under conditions of mesophilic AD. After 45 days of thermophilic AD, a decrease in the molecular weight and significant increase in the production of methane and carbon dioxide production were observed. Network and metagenomics analyses identified AD as reservoirs of plastic-degrading bacteria that produce multiple plastic-degrading enzymes. PETase was identified as the most abundant plastic-degrading enzyme. A potential pathway for the anaerobic biodegradation of BDPs was proposed herein. The polymers of high molecular weight were subjected to abiotic hydrolysis to form oligomers and monomers, enabling subsequent microbial hydrolysis and acetogenesis. Ultimately, complete degradation was achieved predominantly via the pathway involved in the conversion of acetic acid to methane. These findings provide novel insight into the mechanism underlying the anaerobic degradation of BDPs and the microbial resources crucial for the efficient degradation of BDPs.

Microplastic levels in the indoor air of buildings based on plastic waste recycling in Indonesia

Introduction: Microplastics are a new type of contamination in the environment caused by plastic fragmentation and degradation. The generation of plastic waste increases every year, therefore efforts are made to recycle it into building materials. It is unclear how building use resulting from recycling plastic waste affects the development of microplastics in the atmosphere. The purpose of this study is to determine the airborne concentrations of microplastics in buildings constructed from recycled plastic waste. Materials and methods: The study measured microplastic levels in the air for 30 days in a miniature building made from plastic waste. Samples taken during the dry season in Indonesia in 2023. Air sampling is carried out by passive method. Visual observation of the shape, and amount of microplastics using a microscope. Results: Microplastics are found in the air of building spaces made from recycled plastic waste with varying levels every day. The average level of microplasty in the air for 30 days was 30,8 particles/m2/day. Maximum microplastic rate of 63 particles/m2/day, and minimum rate of 18 particles/m2/ day. The average air temperature when sampling is 25,48 ºC, air humidity is 68,37 % and ultraviolet intensity is 860 mwatt/cm2. Conclusions: Microplastic levels in the air of building spaces made from recycled plastic waste that can not be identified can be identified whether they are still within safe limits or not. This is because there is no regulation in Indonesia even in the world that regulates the safe limit of microplastic levels in the environment.

Tandem microplastic degradation and hydrogen production by hierarchical carbon nitride-supported single-atom iron catalysts

Microplastic pollution, an emerging environmental issue, poses significant threats to aquatic ecosystems and human health. In tackling microplastic pollution and advancing green hydrogen production, this study reveals a tandem catalytic microplastic degradation-hydrogen evolution reaction (MPD-HER) process using hierarchical porous carbon nitride-supported single-atom iron catalysts (FeSA-hCN). Through hydrothermal-assisted Fenton-like reactions, we accomplish near-total ultrahigh-molecular-weight-polyethylene degradation into C3-C20 organics with 64% selectivity of carboxylic acid under neutral pH, a leap beyond current capabilities in efficiency, selectivity, eco-friendliness, and stability over six cycles. The system demonstrates versatility by degrading various daily-use plastics across different aquatic settings. The mixture of FeSA-hCN and plastic degradation products further achieves a hydrogen evolution of 42 μmol h‒1 under illumination, outperforming most existing plastic photoreforming methods. This tandem MPD-HER process not only provides a scalable and economically feasible strategy to combat plastic pollution but also contributes to the hydrogen economy, with far-reaching implications for global sustainability initiatives.

Genome-Centric Metagenomics Insights into the Plastisphere-Driven Natural Degradation Characteristics and Mechanism of Biodegradable Plastics in Aquatic Environments.

Biodegradable plastics (BPs) are pervasively available as alternatives to traditional plastics, but their natural degradation characteristics and microbial-driven degradation mechanisms are poorly understood, especially in aquatic environments, the primary sink of plastic debris. Herein, the three-month dynamic degradation process of BPs (the copolymer of poly(butylene adipate-co-terephthalate) and polylactic acid (PLA) (PBAT/PLA) and single PLA) in a natural aquatic environment was investigated, with nonbiodegradable plastics polyvinyl chloride, polypropylene, and polystyrene as controls. PBAT/PLA showed the weight loss of 47.4% at 50 days and severe fragmentation within two months, but no significant decay for other plastics. The significant increase in the specific surface area and roughness and the weakening of hydrophobicity within the first month promoted microbial attachment to the PBAT/PLA surface. Then, a complete microbial succession occurred, including biofilm formation, maturation, and dispersion. Metagenomic analysis indicated that plastispheres selectively enriched degraders. Based on the functional genes involved in BPs degradation, a total of 16 high-quality metagenome-assembled genomes of degraders (mainly Burkholderiaceae) were recovered from the PBAT/PLA plastisphere. These microbes showed the greatest degrading potential at the biofilm maturation stage and executed the functions by PLA_depolymerase, polyesterase, hydrolase, and esterase. These findings will enhance understanding of BPs' environmental behavior and microbial roles on plastic degradation.

Microplastics and Nanoplastics as Environmental Contaminants of Emerging Concern: Potential Hazards for Human Health

With nearly 40% of the total plastics produced being used for packaging, up to five trillion plastic bags are consumed in the world annually. The inadequate disposal of plastic waste and its persistence has become a serious challenge/risk to the environment, health, and well-being of living creatures, including humans. The natural degradation of plastics is extremely slow; large pieces of plastic may break down into microplastics (MPs) (1 μm–5 mm) or nanoplastics (NPs) (&lt;1000 nm) after protracted physical, chemical, and/or biological degradations. A brief overview of the transport of micro- and nanoplastics in the aquatic, terrestrial, and atmospheric environments is presented. Details are provided on the exposure routes for these waste materials and their entry into humans and other biota through ingestion, inhalation, and dermal contact. The greatest concern is the cumulative impact of the heterogeneous secondary MPs and NPs on planetary and human health. Inhaled MPs and NPs have been shown to affect the upper respiratory tract, lower respiratory tract, and alveoli; prolonged exposure can lead to chronic inflammatory changes and systemic disease. These can also lead to autoimmune diseases and other chronic health conditions, including atherosclerosis and malignancy. Sustainable mitigation strategies to reduce the impact of MPs/NPs include source reduction, material substitution, filtration and purification, transformation of plastic waste into value-added materials, technological innovations, etc. Multidisciplinary collaborations across the fields of medicine, public health, environmental science, economics, and policy are required to help limit the detrimental effects of widespread MPs and NPs in the environment.