Study of microbes having potentiality for biodegradation of plastics

Microbial degradation of polypropylene microplastics and concomitant polyhydroxybutyrate production: An integrated bioremediation approach with metagenomic insights

The persistence of plastics, particularly polypropylene (PP), and their conversion into microplastics (MPs), specifically PP-MPs, have emerged as serious ecological threats to soil and aquatic environments. In the present study, we aimed to isolate a microbial consortium capable of degrading PP-MPs. The results revealed that three microbial consortia (CPP-KKU1, CPP-KKU2, and CPP-KKU3) exhibited the ability to degrade PP-MPs, achieving weight losses ranging from 11.6 ± 0.2 % to 17.8 ± 0.5 % after 30 days. Fourier transform infrared (FTIR) spectroscopy analysis confirmed the degradation through oxidation, as evidenced by the presence of new functional groups (-OH and -C=O). In particular, CPP-KKU3 showed the highest degradation efficiency, with scanning electron microscopy (SEM) analysis revealing surface cracking after treatment. Additionally, gas chromatography-mass spectrometry (GC-MS) analysis identified various intermediate compounds, including heterocyclic aromatic compounds, phenyl groups, methylthio derivatives, and ethoxycarbonyl derivatives, indicating complex biochemical processes that were likely mediated by microbial enzymes. Furthermore, polyhydroxybutyrate (PHB) production by these consortia was also investigated. The result showed that both CPP-KKU2 and CPP-KKU3 successfully produced PHB, with CPP-KKU3 demonstrating superior performance in terms of PP-MP degradation and PHB production. Metagenomic analysis of CPP-KKU3 revealed abundant carbohydrate-active enzymes (CAZymes), particularly glycosyl transferases and glycoside hydrolases, which are associated with MP digestion. This study presents a promising bioremediation approach that addresses plastic waste degradation and sustainable bioplastic production, offering a potential solution for environmental plastic pollution.

Impact of plastic pollution on ecosystems: a review of adverse effects and sustainable solutions

The primary source of the growing concern regarding marine, aquatic, and land pollution is plastic products, the majority of which are made of synthetic or semi-synthetic organic compounds. These combinations include materials like coal and natural gas that are obtained through petrochemical processes. As these two types of plastic-derived products are produced and disposed of, they have a major impact on the ecosystems. According to recent figures, around 400 million tons of plastic and related products derived from plastic are produced annually, and it became double in the last two decades. Plastic pollutants are introduced into ecosystems by a variety of stakeholders at different points in their daily lives, whether intentionally or accidentally. They have become a major source of adverse effects, toxicity development in natural entities, and problems. The aquatic, marine, and land ecosystems are vital to human existence, which emphasizes how difficult it is to stop pollution from it. This review highlights the adverse impacts of plastics, plastic-based products, and micro-nanoplastics on aquatic, terrestrial, and marine ecosystems while addressing advances in biodegradable plastics, recycling innovations, plastic-degrading enzymes, and sustainable solutions to reduce environmental risks.

Harmful impacts of microplastic pollution on poultry and biodegradation techniques using microorganisms for consumer health protection: A review

Microplastics (MPs) are small plastic particles less than five millimeters in size. Microplastic pollution poses a serious threat to ecosystems, affecting both biotic and abiotic components. Current techniques used to eliminate microplastics include recycling, landfilling, incineration, and biodegradation. Microplastics have been detected in various animal species, including poultry, fish, mammals, and invertebrates, indicating widespread exposure and potential bioaccumulation. In the Middle East, MPs contamination was discovered in chicken purchased from food shops, chain supermarkets, and open markets. The contamination levels ranged from 0.03±0.04 to 1.19±0.72 particles per gram of chicken meat. In poultry, microplastics negatively affect production and harm vital organs such as the kidneys, spleen, and lungs. In humans, exposure to microplastics can lead to inflammation, immune responses, metabolic disturbances, DNA damage, neurological damage, and even cancer upon contact with mucosal membranes or absorption into the body. Several studies have explored the use of microorganisms, including bacteria, fungi, and algae, to degrade microplastics, offering an economical and environmentally friendly solution. Different polymers were cultured with strains of Bacillus spp. (SB-14 and SC-9) and Streptococcus spp. (SC-56) for a duration of 40 days. Degradation rates for LDPE were 11.8 %, 4.8 %, and 9.8 %. The rates of deterioration for HDPE were 11.7 %, 3.8 %, and 13.7 %. Rates for polyester beads were 17.3 %, 9.4 %, and 5.8 %. This review focuses on the effects of microorganisms in removing microplastic pollution, the detrimental impact of microplastics on poultry production, and the connection between microplastic pollution and human health.

Isolation of marine polyethylene (PE)-degrading bacteria and its potential degradation mechanisms

Microbial degradation of polyethylene (PE) offers a promising solution to plastic pollution in the marine environment, but research in this field is limited. In this study, we isolated a novel marine strain of Pseudalkalibacillus sp. MQ-1 that can degrade PE. Scanning electron microscopy and water contact angle results showed that MQ-1 could adhere to PE films and render them hydrophilic. Analyses using X-ray diffraction, fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy showed a decrease in relative crystallinity, the appearance of new functional groups and an increase in the oxygen-to‑carbon ratio of the PE films, making them more susceptible to degradation. The results of gel permeation chromatography and liquid chromatography-mass spectrometry indicated the depolymerization of the long PE chains, with the detection of an intermediate, decanediol. Furthermore, genome sequencing was employed to investigate the underlying mechanisms of PE degradation. The results of genome sequencing analysis identified the genes associated with PE degradation, including cytochrome P450, alcohol dehydrogenase, and aldehyde dehydrogenase involved in the oxidative reaction, monooxygenase related to ester bond formation, and esterase associated with ester bond cleavage. In addition, enzymes involved in fatty acid metabolism and intracellular transport have been identified, collectively providing insights into the metabolic pathway of PE degradation.

Orally Ingested Micro- and Nano-Plastics: A Hidden Driver of Inflammatory Bowel Disease and Colorectal Cancer

Micro- and nano-plastics (MNPLs) can move along the food chain to higher-level organisms including humans. Three significant routes for MNPLs have been reported: ingestion, inhalation, and dermal contact. Accumulating evidence supports the intestinal toxicity of ingested MNPLs and their role as drivers for increased incidence of colorectal cancer (CRC) in high-risk populations such as inflammatory bowel disease (IBD) patients. However, the mechanisms are largely unknown. In this review, by using the leading scientific publication databases (Web of Science, Google Scholar, Scopus, PubMed, and ScienceDirect), we explored the possible effects and related mechanisms of MNPL exposure on the gut epithelium in healthy conditions and IBD patients. The summarized evidence supports the idea that oral MNPL exposure may contribute to intestinal epithelial damage, thus promoting and sustaining the chronic development of intestinal inflammation, mainly in high-risk populations such as IBD patients. Colonic mucus layer disruption may further facilitate MNPL passage into the bloodstream, thus contributing to the toxic effects of MNPLs on different organ systems and platelet activation, which may, in turn, contribute to the chronic development of inflammation and CRC development. Further exploration of this threat to human health is warranted to reduce potential adverse effects and CRC risk.

Biodegradation of PHB/PBAT films and isolation of novel PBAT biodegraders from soil microbiomes

Polyhydroxyalkanoates (PHAs) are important candidates for replacing petroleum-based plastics. This transition is urgent for the development of a biobased economy and to protect human health and natural ecosystems. PHAs are biobased and biodegradable polyesters that when blended with other polymers, such as poly(butylene adipate-co-terephthalate) (PBAT), acquire remarkable improvements in their properties, which allow them to comply with the requirements of packaging applications. However, the biodegradation of such blends should be tested to evaluate the impact of those polymers in the environment. For instance, PBAT is a compostable aliphatic-aromatic copolyester, and its biodegradation in natural environments, such as soil, is poorly studied. In this work, we evaluated the biodegradation of a bilayer film composed of PHB and PBAT, by a soil microbiome. The bilayer film reached 47 ± 1 % mineralization in 180 days and PHB was no longer detected after this period. The increased crystallinity of the PBAT residue was a clear sign of biodegradation, indicating that the amorphous regions were preferentially biodegraded. Seven microorganisms were isolated, from which 4 were closely related to microorganisms already known as PHB degraders, but the other 3 species, closely related to Streptomyces coelicoflavus, Clonostachys rosea and Aspergillus insuetus, were found for the first time as PHB degraders. Most remarkably, two fungi closely related to Purpureocillium lilacinum and Aspergillus pseudodeflectus (99.83 % and 100 % identity by ITS sequencing) were isolated and identified as PBAT degraders. This is very interesting due to the rarity of isolating PBAT-degrading microorganisms. These results show that the bilayer film can be biodegraded in soil, at mesophilic temperatures, showing its potential to replace synthetic plastics in food packaging.

Eco-friendly approaches for mitigating plastic pollution: advancements and implications for a greener future

Plastic pollution has become a global problem since the extensive use of plastic in industries such as packaging, electronics, manufacturing and construction, healthcare, transportation, and others. This has resulted in an environmental burden that is continually growing, which has inspired many scientists as well as environmentalists to come up with creative solutions to deal with this problem. Numerous studies have been reviewed to determine practical, affordable, and environmentally friendly solutions to regulate plastic waste by leveraging microbes' innate abilities to naturally decompose polymers. Enzymatic breakdown of plastics has been proposed to serve this goal since the discovery of enzymes from microbial sources that truly interact with plastic in its naturalistic environment and because it is a much faster and more effective method than others. The scope of diverse microbes and associated enzymes in polymer breakdown is highlighted in the current review. The use of co-cultures or microbial consortium-based techniques for the improved breakdown of plastic products and the generation of high-value end products that may be utilized as prototypes of bioenergy sources is highlighted. The review also offers a thorough overview of the developments in the microbiological and enzymatic biological degradation of plastics, as well as several elements that impact this process for the survival of our planet.

Microplastics and nanoplastics: Source, behavior, remediation, and multi-level environmental impact

Plastics introduced into the natural environment persist, degrade, and fragment into smaller particles due to various environmental factors. Microplastics (MPs) (ranging from 1 μm to 5 mm) and nanoplastics (NPs) (less than 1 μm) have emerged as pollutants posing a significant threat to all life forms on Earth. Easily ingested by living organisms, they lead to ongoing bioaccumulation and biomagnification. This review summarizes existing studies on the sources of MPs and NPs in various environments, highlighting their widespread presence in air, water, and soil. It primarily focuses on the sources, fate, degradation, fragmentation, transport, and ecotoxicity of MPs and NPs. The aim is to elucidate their harmful effects on marine organisms, soil biota, plants, mammals, and humans, thereby enhancing the understanding of the complex impacts of plastic particles on the environment. Additionally, this review highlights remediation technologies and global legislative and institutional measures for managing waste associated with MPs and NPs. It also shows that effectively combating plastic pollution requires the synergization of diverse management, monitoring strategies, and regulatory measures into a comprehensive policy framework.

Are we underestimating stormwater? Stormwater as a significant source of microplastics in surface waters

Stormwater represent a critical pathway for transporting microplastics (MPs) to surface waters. Due to complex dynamics of MPs in stormwater, its dispersion, weathering, risk, and transport are poorly understood. This review bridges those gaps by summarizing the latest findings on sources, abundance, characteristics, and dynamics involved in stormwater MP pollution. Weathering starts before or after MPs enter stormwater and is more pronounced on land due to continuous heat and mechanical stress. Land use patterns, rainfall intensity, MPs size and density, and drainage characteristics influence the transport of MPs in stormwater. Tire and road wear particles (TRWPs), littering, and road dust are major sources of MPs in stormwater. The concentrations of MPs varies from 0.38-197,000 particles/L globally. Further MP concentrations showed regional variations, highlighting the importance of local monitoring efforts needed to understand local pollution sources. We observed unique signatures associated with the shape and color of MPs. Fibers and fragments were widely reported, with transparent and black being the predominant colors. We conclude that the contribution of stormwater to MP pollution in surface waters is significantly greater than wastewater treatment plant effluents and demands immediate attention. Field and lab scale studies are needed to understand its behavior in stormwater and the risk posed to the downstream water bodies.

Molecular docking and metagenomics assisted mitigation of microplastic pollution

Microplastics, tiny, flimsy, and direct progenitors of principal and subsidiary plastics, cause environmental degradation in aquatic and terrestrial entities. Contamination concerns include irrevocable impacts, potential cytotoxicity, and negative health effects on mortals. The detection, recovery, and degradation strategies of these pollutants in various biota and ecosystems, as well as their impact on plants, animals, and humans, have been a topic of significant interest. But the natural environment is infested with several types of plastics, all having different chemical makeup, structure, shape, and origin. Plastic trash acts as a substrate for microbial growth, creating biofilms on the plastisphere surface. This colonizing microbial diversity can be glimpsed with meta-genomics, a culture-independent approach. Owing to its comprehensive description of microbial communities, genealogical evidence on unconventional biocatalysts or enzymes, genomic correlations, evolutionary profile, and function, it is being touted as one of the promising tools in identifying novel enzymes for the degradation of polymers. Additionally, computational tools such as molecular docking can predict the binding of these novel enzymes to the polymer substrate, which can be validated through in vitro conditions for its environmentally feasible applications. This review mainly deals with the exploration of metagenomics along with computational tools to provide a clearer perspective into the microbial potential in the biodegradation of microplastics. The computational tools due to their polymathic nature will be quintessential in identifying the enzyme structure, binding affinities of the prospective enzymes to the substrates, and foretelling of degradation pathways involved which can be quite instrumental in the furtherance of the plastic degradation studies.

Electrospun PCL Filtration Membranes Enhanced with an Electrosprayed Lignin Coating to Control Wettability and Anti-Bacterial Properties

This study reports on the two-step manufacturing process of a filtration media obtained by first electrospinning a layer of polycaprolactone (PCL) non-woven fibers onto a paper filter backing and subsequently coating it by electrospraying with a second layer made of pure acidolysis lignin. The manufacturing of pure lignin coatings by solution electrospraying represents a novel development that requires fine control of the underlying electrodynamic processing. The effect of increasing deposition time on the lignin coating was investigated for electrospray time from 2.5 min to 120 min. Microstructural and physical characterization included SEM, surface roughness analysis, porosity tests, permeability tests by a Gurley densometer, ATR-FTIR analysis, and contact angle measurements vs. both water and oil. The results indicate that, from a functional viewpoint, such a natural coating endowed the membrane with an amphiphilic behavior that enabled modulating the nature of the bare PCL non-woven substrate. Accordingly, the intrinsic hydrophobic behavior of bare PCL electrospun fibers could be reduced, with a marked decrease already for a thin coating of less than 50 nm. Instead, the wettability of PCL vs. apolar liquids was altered in a less predictable manner, i.e., producing an initial increase of the oil contact angles (OCA) for thin lignin coating, followed by a steady decrease in OCA for higher densities of deposited lignin. To highlight the effect of the lignin type on the results, two grades of oak (AL-OA) of the Quercus cerris L. species and eucalyptus (AL-EU) of the Eucalyptus camaldulensis Dehnh species were compared throughout the investigation. All grades of lignin yielded coatings with measurable antibacterial properties, which were investigated against Staphylococcus aureus and Escherichia coli, yielding superior results for AL-EU. Remarkably, the lignin coatings did not change overall porosity but smoothed the surface roughness and allowed modulating air permeability, which is relevant for filtration applications. The findings are relevant for applications of this abundant biopolymer not only for filtration but also in biotechnology, health, packaging, and circular economy applications in general, where the reuse of such natural byproducts also brings a fundamental demanufacturing advantage.

Insight on recently discovered PET polyester-degrading enzymes, thermostability and activity analyses

The flexibility and the low production costs offered by plastics have made them crucial to society. Unfortunately, due to their resistance to biological degradation, plastics remain in the environment for an extended period of time, posing a growing risk to life on earth. Synthetic treatments of plastic waste damage the environment and may cause damage to human health. Bacterial and fungal isolates have been reported to degrade plastic polymers in a logistic safe approach with the help of their microbial cell enzymes. Recently, the bacterial strain Ideonella sakaiensis (201-F6) was discovered to break down and assimilate polyethylene terephthalate (PET) plastic via metabolic processes at 30 °C to 37 °C. PETase and MHETase enzymes help the bacterium to accomplish such tremendous action at lower temperatures than previously discovered enzymes. In addition to functioning at low temperatures, the noble bacterium's enzymes have amazing qualities over pH and PET plastic degradation, including a shorter period of degradation. It has been proven that using the enzyme PETase, this bacterium hydrolyzes the ester linkages of PET plastic, resulting in production of terephthalic acid (TPA), nontoxic compound and mono-2-hydroxyethyl (MHET), along with further depolymerization of MHET to release ethylene glycogen (EG) and terephthalic acid (TPA) by the second enzyme MHETase. Enzymatic plastic degradation has been proposed as an environmentally friendly and long-term solution to plastic waste in the environment. As a result, this review focuses on the enzymes involved in hydrolyzing PET plastic polymers, as well as some of the other microorganisms involved in plastic degradation.

Assessing biodegradation of roadway particles via complementary mass spectrometry and NMR analyses

Roadway particles (RP) that can be collected with on-vehicle system, consist of a mixture of Tire and road wear particles (TRWP) with other traffic-derived particles (exhaust or non-exhaust) and/or biogenic compounds and represent a significant source of xenobiotics, susceptible to reach the different environmental compartments. The study of the RP fate is thus a major challenge to tackle in order to understand their degradation and impact. They offer a variety of carbon sources potentially usable by microorganisms, ranging from the tire-derived plasticizers, vulcanizing agents, protective agents and their transformation products, to other traffic, road and environmental-derived contaminants. A multi-analytical approach was implemented to characterize RP and study their biodegradation. Kinetics of RP extractions were monitored during 21 days in water, methanol, acetone and chloroform to identify leaching and extractable compounds and monitor the particle composition. The results confirmed that hundreds of readily leachable chemicals can be extracted from RP directly into water according to a dynamic process with time while additional poorly soluble compounds remain in the particles. Mass spectrometry (LC-HRMS and GC-MS) allowed us to propose 296 putative compounds using an extensive rubber database. The capacity of 6 bacterial strains, belonging to Rhodococcus, Pseudomonas and Streptomyces genera, to biodegrade RP was then evaluated over 14 days of incubation. The selected strains were able to grow on RP using various substrates. Elastomer monitoring by 1H NMR revealed a significant 12 % decrease of the extractable SBR fraction when the particles were incubated with Rhodococcus ruber. After incubation, the biodegradation of 171 compounds among leachable and extractable compounds was evaluated. Fatty acids and alkanes from rubber plasticizers and paraffin waxes were the most degraded putative compounds by the six strains tested, reaching 75 % of biodegradation for some of them.

The Other Side of Plastics: Bioplastic-Based Nanoparticles for Drug Delivery Systems in the Brain

Plastics have changed human lives, finding a broad range of applications from packaging to medical devices. However, plastics can degrade into microscopic forms known as micro- and nanoplastics, which have raised concerns about their accumulation in the environment but mainly about the potential risk to human health. Recently, biodegradable plastic materials have been introduced on the market. These polymers are biodegradable but also bioresorbable and, indeed, are fundamental tools for drug formulations, thanks to their transient ability to pass through biological barriers and concentrate in specific tissues. However, this "other side" of bioplastics raises concerns about their toxic potential, in the form of micro- and nanoparticles, due to easier and faster tissue accumulation, with unknown long-term biological effects. This review aims to provide an update on bioplastic-based particles by analyzing the advantages and drawbacks of their potential use as components of innovative formulations for brain diseases. However, a critical analysis of the literature indicates the need for further studies to assess the safety of bioplastic micro- and nanoparticles despite they appear as promising tools for several nanomedicine applications.

Sources, Degradation, Ingestion and Effects of Microplastics on Humans: A Review

Celluloid, the predecessor to plastic, was synthesized in 1869, and due to technological advancements, plastic products appear to be ubiquitous in daily life. The massive production, rampant usage, and inadequate disposal of plastic products have led to severe environmental pollution. Consequently, reducing the employment of plastic has emerged as a pressing concern for governments globally. This review explores microplastics, including their origins, absorption, and harmful effects on the environment and humans. Several methods exist for breaking down plastics, including thermal, mechanical, light, catalytic, and biological processes. Despite these methods, microplastics (MPs, between 1 and 5 mm in size) continue to be produced during degradation. Acknowledging the significant threat that MPs pose to the environment and human health is imperative. This form of pollution is pervasive in the air and food and infiltrates our bodies through ingestion, inhalation, or skin contact. It is essential to assess the potential hazards that MPs can introduce. There is evidence suggesting that MPs may have negative impacts on different areas of human health. These include the respiratory, gastrointestinal, immune, nervous, and reproductive systems, the liver and organs, the skin, and even the placenta and placental barrier. It is encouraging to see that most of the countries have taken steps to regulate plastic particles. These measures aim to reduce plastic usage, which is essential today. At the same time, this review summarizes the degradation mechanism of plastics, their impact on human health, and plastic reduction policies worldwide. It provides valuable information for future research on MPs and regulatory development.

Making Persistent Plastics Degradable

The vastness of the scale of the plastic waste problem will require a variety of strategies and technologies to move toward sustainable and circular materials. One of these strategies to address the challenge of persistent fossil-based plastics is new catalytic processes that are being developed to convert recalcitrant waste such as polyethylene to produce propylene, which can be an important precursor of high-performance polymers that can be designed to biodegrade or to degrade on demand. Remarkably, this process also enables the production of biodegradable polymers using renewable raw materials. In this Perspective, current catalyst systems and strategies that enable the catalytic degradation of polyethylene to propylene are presented. In addition, concepts for using "green" propylene as a raw material to produce compostable polymers is also discussed.

Biodegradation of Plastics Induced by Marine Organisms: Future Perspectives for Bioremediation Approaches

Plastic pollution is a distinctive element of the globalized world. In fact, since the 1970s the expansion and use of plastics, particularly in the consumer and commercial sectors, has given this material a permanent place in our lives. The increasing use of plastic products and the wrong management of end-of-life plastic products have contributed to increasing environmental pollution, with negative impacts on our ecosystems and the ecological functions of natural habitats. Nowadays, plastic pollution is pervasive in all environmental compartments. As aquatic environments are the dumping points for poorly managed plastics, biofouling and biodegradation have been proposed as promising approaches for plastic bioremediation. Known for the high stability of plastics in the marine environment, this represents a very important issue to preserve marine biodiversity. In this review, we have summarized the main cases reported in the literature on the degradation of plastics by bacteria, fungi, and microalgae and the degradation mechanisms involved, to highlight the potential of bioremediation approaches to reduce macro and microplastic pollution.

Bacterial degradation kinetics of poly(Ɛ-caprolactone) (PCL) film by Aquabacterium sp. CY2-9 isolated from plastic-contaminated landfill

Despite the identification of numerous bioplastic-degrading bacteria, the inconsistent rate of bioplastic degradation under differing cultivation conditions limits the intercomparison of results on biodegradation kinetics. In this study, we isolated a poly (Ɛ-caprolactone) (PCL)-degrading bacterium from a plastic-contaminated landfill and determined the principle-based biodegradation kinetics in a confined model system of varying cultivation conditions. Bacterial degradation of PCL films synthesized by different polymer number average molecular weights (M_n) and concentrations (% w/v) was investigated using both solid and liquid media at various temperatures. As a result, the most active gram-negative bacterial strain at ambient temperature (28 °C), designated CY2-9, was identified as Aquabacterium sp. Based on 16 S rRNA gene analysis. A clear zone around the bacterial colony was apparently exhibited during solid cultivation, and the diameter sizes increased with incubation time. During biodegradation processes in the PCL film, the thermal stability declined (determined by TGA; weight changes at critical temperature), whereas the crystalline proportion increased (determined by DSC; phase transition with temperature increment), implying preferential degradation of the amorphous region in the polymer structure. The surface morphologies (determined by SEM; electron optical system) were gradually hydrolyzed, creating destruction patterns as well as alterations in functional groups on film surfaces (determined by FT-IR; infrared spectrum of absorption or emission). In the kinetic study based on the weight loss of the PCL film (4.5 × 10⁴ Da, 1% w/v), ∼1.5 (>±0.1) × 10^-1 day^-1 was obtained from linear regression for both solid and liquid media cultivation at 28 °C. The biodegradation efficiencies increased proportionally by a factor of 2.6-7.9, depending on the lower polymer number average molecular weight and lower concentration. Overall, our results are useful for measuring and/or predicting the degradation rates of PCL films by microorganisms in natural environments.

Settling behaviors of microplastic disks in water

Microplastic (MP) disks have not been studied for settling behaviors in aquatic environments, which affects the transport and fate of MPs. Therefore, settling experiments were conducted on MP disks of three shapes and four common-seen materials. Lighter MP disks (with density ρ_s = 1.038 g/cm³ and length l ≤ 5 mm) followed rectilinear vertical trajectories, while heavier MP disks (ρ_s = 1.161-1.343 g/cm³ and l = 5 mm) followed zigzag trajectories with oscillations and rotations. The mean terminal settling velocities of MP disks were 19.6-48.8 mm/s. Instantaneous settling velocities of heavier MP disks fluctuated. Existing formulas could not accurately predict the settling velocity of MP disks; thus, a new model was proposed with an error of 15.5 %. Finally, the Re_d - I* diagram (Re_d is the disk Reynolds number and I* is the dimensionless moment of inertia) was extended for MP disks to predict settling trajectories.

Biotechnological methods to remove microplastics: a review

Microplastics pollution is major threat to ecosystems and is impacting abiotic and biotic components. Microplastics are diverse and highly complex contaminants that transport other contaminants and microbes. Current methods to remove microplastics include biodegradation, incineration, landfilling, and recycling. Here we review microplastics with focus on sources, toxicity, and biodegradation. We discuss the role of algae, fungi, bacteria in the biodegradation, and we present biotechnological methods to enhance degradation, e.g., gene editing tools and bioinformatics.

In vivo degradation of polyethylene terephthalate using microbial isolates from plastic polluted environment

Accumulation of plastics alarms a risk to the environment worldwide. As polyethylene pterephthalate (PET) degrades slowly and produces hazardous substances, therefore, it is now essential to eliminate plastic wastes from the environment. Given that, the current study is concerned with PET degradation potential of naturally occurring microbial strains isolated from plastic waste dumping sites, Sarcina aurantiaca (TB3), Bacillus subtilis (TB8), Aspergillus flavus (STF1), Aspergillus niger (STF2). To test the biodegradability of PET films, the films were incubated for 60 days at 37 °C with the microorganisms designated as TB3, TB8, STF1, STF2 and the microbial consortium (TB3+TB8+STF1+STF2) in Minimal Salt Medium and Bushnell Hass Broth. Hydrophobicity, viability, and total protein content of isolates were investigated. Using Field Emission Scanning Electron Microscopy and Fourier Transform Infrared Spectrophotometry to measure variations in functional groups and carbonyl index on PET surface, biodegradation process was affirmed by fissures and modified surfaces. Results revealed that the microbial consortium (S. aurantiaca + B. subtilis + A. flavus + A. niger) that the weight loss of PET films was 28.78%. The microbial consortium could be used to treat PET waste, posing no health or environmental risks. The developed microbial consortium has the potential to degrade PET, hence can be employed for eliminating PET in plastic contaminated sites.

Marine-Derived Actinomycetes: Biodegradation of Plastics and Formation of PHA Bioplastics-A Circular Bioeconomy Approach

Plastics are present in the majority of daily-use products worldwide. Due to society's production and consumption patterns, plastics are accumulating in the environment, causing global pollution issues and intergenerational impacts. Our work aims to contribute to the development of solutions and sustainable methods to mitigate this pressing problem, focusing on the ability of marine-derived actinomycetes to accelerate plastics biodegradation and produce polyhydroxyalkanoates (PHAs), which are biodegradable bioplastics. The thin plastic films' biodegradation was monitored by weight loss, changes in the surface chemical structure (Infra-Red spectroscopy FTIR-ATR), and by mechanical properties (tensile strength tests). Thirty-six marine-derived actinomycete strains were screened for their plastic biodegradability potential. Among these, Streptomyces gougerotti, Micromonospora matsumotoense, and Nocardiopsis prasina revealed ability to degrade plastic films-low-density polyethylene (LDPE), polystyrene (PS) and polylactic acid (PLA) in varying conditions, namely upon the addition of yeast extract to the culture media and the use of UV pre-treated thin plastic films. Enhanced biodegradation by these bacteria was observed in both cases. S. gougerotti degraded 0.56% of LDPE films treated with UV radiation and 0.67% of PS films when inoculated with yeast extract. Additionally, N. prasina degraded 1.27% of PLA films when these were treated with UV radiation, and yeast extract was added to the culture medium. The main and most frequent differences observed in FTIR-ATR spectra during biodegradation occurred at 1740 cm^-1, indicating the formation of carbonyl groups and an increase in the intensity of the bands, which indicates oxidation. Young Modulus decreased by 30% on average. In addition, S. gougerotti and M. matsumotoense, besides biodegrading conventional plastics (LDPE and PS), were also able to use these as a carbon source to produce degradable PHA bioplastics in a circular economy concept.

Microbial remediation of plastic pollutants generated from discarded and abandoned marine fishing nets

A wide range of plastic debris dumped into the ocean has recently gained concern of the marine ecosystems. Discarded and abandoned fishing nets, also known as ghost nets, are lost in the marine water and has no commercial significance. Additionally these fishing gear left out in the aquatic environment pose a severe risk to marine environment. Fishing nets, made up of synthetic plastic materials, are a major source of marine pollutants and act as a vector for transporting other toxic chemical pollutants. Approximately 10% of total marine plastic pollutants come from commercial fishing nets, and each year up to 1 million tons of fishing gear are discarded into the marine ecosystem. It can be estimated that by 2050 the amount will be doubled, adding 15-20 million metric tons of discarded lost fishing gears into ocean. The gradual and increased deposition of plastic pollutants in aquatic habitat also affects the whole food chain. Recently, microbial degradation of marine plastics has focussed the eyes of researchers and a lot of investigations on potential microbial degraders are under process. Microorganisms have developed the ability to grow under plastic stress condition and adapt to alter metabolic pathways by which they can directly feed upon marine plastic pollutants as sole carbon source. The present review compiles information on marine plastic pollution from discarded and abandoned fishing nets, their effect on aquatic ecosystems, marine animals and food chain and discusses microbial remediation strategies to control this pollution, especially and their implications in the marine ecosystems.

Bioinspired Electropun Fibrous Materials Based on Poly-3-Hydroxybutyrate and Hemin: Preparation, Physicochemical Properties, and Weathering

The development of innovative fibrous materials with valuable multifunctional properties based on biodegradable polymers and modifying additives presents a challenging direction for modern materials science and environmental safety. In this work, high-performance composite fibrous materials based on semicrystalline biodegradable poly-3-hydroxybutyrate (PHB) and natural iron-containing porphyrin, hemin (Hmi) were prepared by electrospinning. The addition of Hmi to the feed PHB mixture (at concentrations above 3 wt.%) is shown to facilitate the electrospinning process and improve the quality of the electrospun PHB/Hmi materials: the fibers become uniform, their average diameter decreases down to 1.77 µm, and porosity increases to 94%. Structural morphology, phase composition, and physicochemical properties of the Hmi/PHB fibrous materials were studied by diverse physicochemical methods, including electronic paramagnetic resonance, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, elemental analysis, differential scanning calorimetry, Fourier-transformed infrared spectroscopy, mechanical analysis, etc. The proposed nonwoven Hmi/PHB composites with high porosity, good mechanical properties, and retarded biodegradation due to high antibacterial potential can be used as high-performance and robust materials for biomedical applications, including breathable materials for wound disinfection and accelerated healing, scaffolds for regenerative medicine and tissue engineering.

Spatial and seasonal distribution of microplastic in surface water of Bueng Boraphet Wetland-a Ramsar wetland in Thailand

This study sought to assess microplastic contamination in the surface water of the inland freshwater wetland, Bueng Boraphet Wetland, Thailand, which is a lentic system with various land-use patterns, including community areas, agricultural areas, and natural resource conservation areas. In 2019, water samples were collected during the wet and dry periods from the three land-use zones at depths of 0-30 cm using a plankton net with 333 µm in mesh size. The water samples were digested via a wet peroxide oxidation process prior to the identification of microplastic morphology using a stereomicroscope. The polymer types of microplastic were analyzed using Fourier transform infrared spectrophotometry. Microplastic was found to range from 0.00 to 4.61 particles/m² (0.34 ± 0.81 particles/m²) or 0.0 to 19.57 particles/m³ (1.44 ± 3.4 particles/m³). Furthermore, significantly high amounts of microplastics were found in samples from the community area. No microplastic was detected in the sample from the natural resource conservation area. The quantity of microplastic did not significantly differ between the sampling periods. Polymer types, including polyester, polypropylene, and polyethylene terephthalate, were identified in this study. The microplastics were predominantly small and were colored black or red. Microplastic with a fiber shape (93.8%) was observed. Besides the specific gravity of the microplastic and hydrological characteristics, the high concentration of microplastics found in samples from the community area (0.62 ± 0.79 particles/m² or 2.63 ± 3.36 particles/m³) is likely related to the high human pressure. As microplastic contamination can impact aquatic animals and wetland ecosystems, appropriate control measures for human activities and plastic waste management are required.

Global qualitative and quantitative distribution of micropollutants in the deep sea

Micropollutants (MPs) include a wide range of biological disruptors that can be toxic to wildlife and humans at very low concentrations (<1 μg/L). These mainly anthropogenic pollutants have been widely detected in different areas of the planet, including the deep sea, and have impacts on marine life. Because of this potential toxicity, the global distribution, quantity, incidence, and potential impacts of deep-sea MPs were investigated in a systematic review of the literature. The results showed that MPs have reached different zones of the ocean and are more frequently reported in the Northern Hemisphere, where higher concentrations are found. MPs are also concentrated in depths up to 3000 m, where they are also more frequently studied, but also extend deeper than 10,000 m. Potentially toxic metals (PTMs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), organotins, and polycyclic aromatic hydrocarbons (PAHs) were identified as the most prevalent and widely distributed MPs at ≥200 m depth. PTMs are widely distributed in the deep sea in high concentrations; aluminum is the most prevalent up to 3000 m depth, followed by zinc and copper. PCBs, organotins, hexachlorocyclohexanes (HCHs), PAHs, and phenols were detected accumulated in both organisms and environmental samples above legislated thresholds or known toxicity levels. Our assessment indicated that the deep sea can be considered a sink for MPs.

Microbial Communities of Seawater and Coastal Soil of Russian Arctic Region and Their Potential for Bioremediation from Hydrocarbon Pollutants

The development of Arctic regions leads to pollution of marine and coastal environments with oil and petroleum products. The purpose of this work was to determine the diversity of microbial communities in seawater, as well as in littoral and coastal soil, and the potential ability of their members to degrade hydrocarbons degradation and to isolate oil-degrading bacteria. Using high-throughput sequencing of the V4 region of the 16S rRNA gene, the dominance of bacteria in polar communities was shown, the proportion of archaea did not exceed 2% (of the total number of sequences in the libraries). Archaea inhabiting the seawater belonged to the genera Nitrosopumilus and Nitrosoarchaeum and to the Nitrososphaeraceae family. In the polluted samples, members of the Gammaproteobacteria, Alphaproteobacteria, and Actinomycetes classes predominated; bacteria of the classes Bacteroidia, Clostridia, Acidimicrobiia, Planctomycetia, and Deltaproteobacteria were less represented. Using the iVikodak program and KEGG database, the potential functional characteristics of the studied prokaryotic communities were predicted. Bacteria were potentially involved in nitrogen and sulfur cycles, in degradation of benzoate, terephthalate, fatty acids, and alkanes. A total of 19 strains of bacteria of the genera Pseudomonas, Aeromonas, Oceanisphaera, Shewanella, Paeniglutamicibacter, and Rhodococcus were isolated from the studied samples. Among them were psychrotolerant and psychrophilic bacteria growing in seawater and utilizing crude oil, diesel fuel, and motor oils. The data obtained suggest that the studied microbial communities could participate in the removal of hydrocarbons from arctic seawater and coastal soils and suggested the possibility of the application of the isolates for the bioaugmentation of oil-contaminated polar environments.

Micrococcus luteus strain CGK112 isolated from cow dung demonstrated efficient biofilm-forming ability and degradation potential toward high-density polyethylene (HDPE)

Biodegradation is the most promising environmentally sustainable method that offers a significant opportunity with minimal negative environmental consequences while searching for solutions to this global problem of plastic pollution that has now spread to almost everywhere in the entire world. In the present work, HDPE-degrading bacterial strain CGK112 was isolated from the fecal matter of a cow. The bacterial strain was identified as Micrococcus luteus CGK112 by 16S rRNA sequence coding analysis. Significant weight loss, i.e., 3.85% was recorded in the HDPE film treated with strain CGK112 for 90 days. The surface micromorphology was examined using FE-SEM, which revealed spectacular bacterial colonization as well as structural deformation. Furthermore, the EDX study indicated a significant decrease in the atomic percentage of carbon content, whereas FTIR analysis confirmed functional groups alternation as well as an increase in the carbonyl index which can be attributed to the metabolic activity of biofilm. Our findings provide insight into the capacity of our strain CGK112 to colonize and utilize HDPE as a single carbon source, thus promoting its degradation.

A Coupled Ketoreductase-Diaphorase Assay for the Detection of Polyethylene Terephthalate-Hydrolyzing Activity

In the last two decades, several PET-degrading enzymes from already known microorganisms or metagenomic sources have been discovered to face the growing environmental concern of polyethylene terephthalate (PET) accumulation. However, there is a limited number of high-throughput screening protocols for PET-hydrolyzing activity that avoid the use of surrogate substrates. Herein, a microplate fluorescence screening assay was described. It was based on the coupled activity of ketoreductases (KREDs) and diaphorase to release resorufin in the presence of the products of PET degradation. Six KREDs were identified in a commercial panel that were able to use the PET building block, ethylene glycol, as substrate. The most efficient KRED, KRED61, was combined with the diaphorase from Clostridium kluyveri to monitor the PET degradation reaction catalyzed by the thermostable variant of the cutinase-type polyesterase from Saccharomonospora viridis AHK190. The PET degradation products were measured both fluorimetrically and by HPLC, with excellent correlation between both methods.

Recent advances in plastic degradation - From microbial consortia-based methods to data sciences and computational biology driven approaches

The conventional methods of plastic waste management such as mechanical and chemical recycling, landfill complemented by incineration and pyrosis have limited scope. Thus, microbiological-based approaches by the application of microbial consortia or cocultures are appropriate, cost-effective, and eco-friendly to manage plastic wastes. Screening of novel plastic degrading microorganisms, the formulation of microbial consortia, and utilisation of their enzymes probably play a role in plastic waste management. The by-products of microbial degradation of plastic waste can be used as bio-energy sources, that aids in the development of cost-effective bio-digesters. The recent advancements in computational biology and bioinformatics play a vital role in understanding the molecular basis of enzymatic degradation of plastic polymers by microorganisms. Understanding the three-dimensional structures of plastic degrading enzymes and their metabolic pathways play a vital role in studying the microbial degradation of plastics. The present review highlights the scope of various microorganisms and their enzymes in plastic degradation. The review emphasizes the applications of co-cultures or microbial consortia-based approaches for the enhanced degradation of plastic polymers and the production of value-added end products that can be used as the prototypes of bioenergy sources. The review also provides a comprehensive outlook on the applications of data sciences, computational biology, and bioinformatics resources, and web-based tools towards the study of microbial degradation of plastic polymers.

Key knowledge gaps for One Health approach to mitigate nanoplastic risks

There are increasing concerns over the threat of nanoplastics to environmental and human health. However, multidisciplinary barriers persist between the communities assessing the risks to environmental and human health. As a result, the hazards and risks of nanoplastics remain uncertain. Here, we identify key knowledge gaps by evaluating the exposure of nanoplastics in the environment, assessing their bio-nano interactions, and examining their potential risks to humans and the environment. We suggest considering nanoplastics a complex and dynamic mixture of polymers, additives, and contaminants, with interconnected risks to environmental and human health. We call for comprehensive integration of One Health approach to produce robust multidisciplinary evidence to nanoplastics threats at the planetary level. Although there are many challenges, this holistic approach incorporates the relevance of environmental exposure and multi-sectoral responses, which provide the opportunity to identify the risk mitigation strategies of nanoplastics to build resilient health systems.

Screening for polystyrene nanoparticle toxicity on kidneys of adult male albino rats using histopathological, biochemical, and molecular examination results

Polystyrene Nanoparticles (PS-NPs) used for packaging foam, disposable cups, and food containers. Therefore, this study aimed to evaluate PS- NPs toxic effects on kidney of adult male albino rats. A total of 30 rats divided into three groups (n = 10): group I negative control group; group II orally administered 3% PS-NPs (3 mg/kg body weight/day) and group III orally administered 3% PS-NPs (10 mg/kg body weight/day) for 35 days. Blood and kidney samples collected and processed for biochemical, histopathological, and immunohistochemical examinations. Results showed that low and high doses PS-NPs had significantly increased serum blood urea nitrogen (BUN), creatinine, malondialdehyde, significantly further reduced glutathione, downregulation of nuclear factor erythroid 2–related factor 2 and glutathione peroxidase, upregulation of caspase-3 and Cytochrome-c. Histopathological examination revealed several alterations. Low dose of PS-NPs exhibited dilated glomerular capillaries, hypotrophy of some renal corpuscles significantly decreases their diameter to 62 μm. Some proximal convoluted tubules and distal convoluted tubules showed loss of cellular architecture with pyknotic nuclei. Hyalinization and vacuolation in renal medulla. In high dose PS-NPs, alterations increased in severity. A significant increase in percentage area of cyclooxygenase-2 in low and high-doses. In conclusion, PS-NPs are a nephrotoxic causing renal dysfunction.

Biotechnological Aspects and Mathematical Modeling of the Biodegradation of Plastics under Controlled Conditions

The strong environmental impact caused by plastic pollution has led research to address studies from different perspectives. The mathematical modeling of the biodegradation kinetics of solid materials is a major challenge since there are many influential variables in the process and there is interdependence of microorganisms with internal and external factors. In addition, as solid substrates that are highly hydrophobic, mass transfer limitations condition degradation rates. Some mathematical models have been postulated in order to understand the biodegradation of plastics in natural environments such as oceans. However, if tangible and optimizable solutions are to be found, it is necessary to study the biodegradation process under controlled conditions, such as using bioreactors and composting systems. This review summarizes the biochemical fundamentals of the main plastics (both petrochemical and biological origins) involved in biodegradation processes and combines them with the main mathematical equations and models proposed to date. The different biodegradation studies of plastics under controlled conditions are addressed, analyzing the influencing factors, assumptions, model developments, and correlations with laboratory-scale results. It is hoped that this review will provide a comprehensive overview of the process and will serve as a reference for future studies, combining practical experimental work and bioprocess modeling systems.

Environmental Impacts of Microplastics and Nanoplastics: A Current Overview

The increasing distribution of miniaturized plastic particles, viz. microplastics (100 nm–5 mm) and nanoplastics (less than 100 nm), across the various ecosystems is currently a subject of major environmental concern. Exacerbating these concerns is the fact that microplastics and nanoplastics (MNPs) display different properties from their corresponding bulk materials; thus, not much is understood about their full biological and ecological implications. Currently, there is evidence to prove that these miniaturized plastic particles release toxic plastic additives and can adsorb various chemicals, thereby serving as sinks for various poisonous compounds, enhancing their bioavailability, toxicity, and transportation. Furthermore, there is a potential danger for the trophic transfer of MNPs to humans and other higher animals, after being ingested by lower organisms. Thus, this paper critically analyzes our current knowledge with regard to the environmental impacts of MNPs. In this regard, the properties, sources, and damaging effects of MNPs on different habitats, particularly on the biotic components, were elucidated. Similarly, the consequent detrimental effects of these particles on humans as well as the current and future efforts at mitigating these detrimental effects were discussed. Finally, the self-cleaning efforts of the planet via a range of saprophytic organisms on these synthetic particles were also highlighted.

Biodegradation of microplastics: Better late than never

Plastics use is growing due to its applications in the economy, human health and aesthetics. The major plastic particles in the form of microplastics (MPs) released into the environment are made up of polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), and polyethylene terephthalate (PET). Tremendous usage and continuous accumulation of MPs in the environment pose a global threat to ecosystems and human health. The current knowledge of biotechnological, aerobic and aerobic biodegradation approaches emphasizes the microbial culture's potential towards MPs removal. This review selectively provides recent biotechnological advances such as biostimulation, bioaugmentation and enzymatic biodegradation that can be applied for MPs removal by biodegradation and bioaccumulation. This review summarizes the knowledge and the research exploration on the biodegradation of synthetic organic MPs with different biodegradability. However, further research is still needed to understand the underlying mechanism of MPs biodegradation in soil and water systems, leading to the development of an effective method for MPs removal.

Current Advances in the Biodegradation and Bioconversion of Polyethylene Terephthalate

Polyethylene terephthalate (PET) is a widely used plastic that is polymerized by terephthalic acid (TPA) and ethylene glycol (EG). In recent years, PET biodegradation and bioconversion have become important in solving environmental plastic pollution. More and more PET hydrolases have been discovered and modified, which mainly act on and degrade the ester bond of PET. The monomers, TPA and EG, can be further utilized by microorganisms, entering the tricarboxylic acid cycle (TCA cycle) or being converted into high value chemicals, and finally realizing the biodegradation and bioconversion of PET. Based on synthetic biology and metabolic engineering strategies, this review summarizes the current advances in the modified PET hydrolases, engineered microbial chassis in degrading PET, bioconversion pathways of PET monomers, and artificial microbial consortia in PET biodegradation and bioconversion. Artificial microbial consortium provides novel ideas for the biodegradation and bioconversion of PET or other complex polymers. It is helpful to realize the one-step bioconversion of PET into high value chemicals.

Microplastic pollution in aquatic environments with special emphasis on riverine systems: Current understanding and way forward

Microplastics (MPs) are emerging as a severe threat in our environment. Their diverse existence in marine environments is being researched globally and thus a widely known fact; however, their presence in the freshwater counterpart has gained attention lately only. Riverine systems, the most critical freshwater resources serve as an essential link between terrestrial and marine environments and their contamination with MPs is going to create severe environmental issues. Because of their small size and unique morphology, these polymers can exhibit variable toxicity to the interacting biota and alter their habitat properties; thus, causing serious impacts on the environment and health of living beings, including humans. These microplastics can also interact with pollutants like heavy metals and organic pollutants, which further augment their harming potential. Inefficient and poor plastic waste disposal practices play an important role in the generation of microplastic pollutants. In the present COVID 19 pandemics, the excessive use of plastic to contain the spread of infection has further added the plastic load in the environment which will eventually lead to the generation of microplastic particles. Also, a significant amount of microplastic pollutants in riverine systems are delivered through wastewater treatment plant effluents. These trade-offs create a distress situation in the environment. The present study connects these key issues for a better understanding of the diverse existence of microplastic pollutants, their sources, and fate, with a special emphasis on riverine systems. A critical appraisal of the knowledge gaps and proposal of suitable solutions through this review might open up avenues for further research and effective management of the microplastics in aquatic environments.

A Comparative Taxonomic Profile of Microbial Polyethylene and Hydrocarbon-Degrading Communities in Diverse Environments

Background

Polyethylene (PE) is one of the most abundant plastic wastes which accumulates in marine and terrestrial environments. As microbial degradation has been a promising approach for the bioremediation of polluted environments, identification of the microbial community profile where these pollutants accumulate, has recently been in focus.

Objective

We have investigated the taxonomic and functional characteristics of polyethylene- degrading microorganisms in a plastic waste recycling site in Tehran, Iran.

Materials and Methods

We have analyzed and compared a 16S rRNA dataset from this study with 15 datasets from 4 diverse plastic and oil polluted habitats to identify and evaluate bacterial communities involved in bioremediation.

Results

Our findings reveal that Proteobacteria, Actinobacteria, Acidobacteria and Cloroflexi were the dominant phyla and Actinobacteria, Alphaproteobacteria, Gammaproteobacteria and Acidimicrobia were dominant classes in these samples. The most dominant Kegg Orthology associated with PE bioremediation in these samples are related to peroxidases, alcohol dehydrogenases, monooxygenases and dioxygenases.

Conclusions

Long-term presence of contaminants in soil could lead to changes in bacterial phyla abundance, resulting in metabolic adaptations to optimize biological activity and waste management in a diverse group of bacteria.

A marine bacterial community capable of degrading poly(ethylene terephthalate) and polyethylene

Plastic wastes are becoming the most common form of marine debris and present a growing global pollution problem. Here, we used a screening approach on hundreds of plastic waste-associated samples and discovered a marine bacterial community capable of efficiently colonizing and degrading both poly(ethylene terephthalate) (PET) and polyethylene (PE). Using absolute quantitative 16S rRNA sequencing and cultivation methods, we obtained corresponding abundance and purified cultures of three bacterial strains that mediated plastic degradation. We further performed numerous techniques to characterize the efficient degradation of PET and PE by the reconstituted bacterial community containing these three bacteria. Additionally, we used liquid chromatography-mass spectrometry to further demonstrate the degradation of PET and PE films by the reconstituted bacterial community. We conducted transcriptomic methods to investigate the plastic degradation process and potential degradation mechanisms mediated by our reconstituted bacterial community. Lastly, we overexpressed PE degradation enzymes based on transcriptomic results and verified their significant degradation effects on the PE films. Overall, our study establishes a stable marine bacterial community that efficiently degrades PET and PE and provides insights into plastic degradation pathways and their associated biological and mechanistic processes-paving the way for developing microbial products against plastic wastes.

The impact of microplastic-microbe interactions on animal health and biogeochemical cycles: A mini-review

Microplastic (MP) pollution has attracted global attention due to the extensive use of plastic products. The hydrophobic MP surface provides a habitat for multiple microorganisms. Although there have been several studies on the impact of plastic particles on microbial communities, there are few reviews that have systematically summarized the interaction between MPs and microbes and their effects on human health and biochemical circulation. The discussions in this review will take place under the following topics: (1) MPs prompt colonization, biofilm generation, and transfer of environmental microbes; (2) the microbial communities can cause the morphological alterations and biodegradation of MPs; (3) MP-microbe combinations can induce the alteration of intestinal flora and hazard animal health; (4) the biogeochemical cycles affected by MP-microbe interactions. This review will highlight the close interactions between MPs and microorganisms, and provide suggestions for future studies.

Weathering Plastics as a Planetary Boundary Threat: Exposure, Fate, and Hazards

We described in 2017 how weathering plastic litter in the marine environment fulfils two of three criteria to impose a planetary boundary threat related to "chemical pollution and the release of novel entities": (1) planetary-scale exposure, which (2) is not readily reversible. Whether marine plastics meet the third criterion, (3) eliciting a disruptive impact on vital earth system processes, was uncertain. Since then, several important discoveries have been made to motivate a re-evaluation. A key issue is if weathering macroplastics, microplastics, nanoplastics, and their leachates have an inherently higher potential to elicit adverse effects than natural particles of the same size. We summarize novel findings related to weathering plastic in the context of the planetary boundary threat criteria that demonstrate (1) increasing exposure, (2) fate processes leading to poorly reversible pollution, and (3) (eco)toxicological hazards and their thresholds. We provide evidence that the third criterion could be fulfilled for weathering plastics in sensitive environments and therefore conclude that weathering plastics pose a planetary boundary threat. We suggest future research priorities to better understand (eco)toxicological hazards modulated by increasing exposure and continuous weathering processes, to better parametrize the planetary boundary threshold for plastic pollution.

An ecotoxicological approach to microplastics on terrestrial and aquatic organisms: A systematic review in assessment, monitoring and biological impact

Marine and land plastic debris biodegrades at micro- and nanoscales through progressive fragmentation. Oceanographic model studies confirm the presence of up to ∼2.41 million tons of microplastics across the Atlantic, Pacific, and Indian subtropical gyres. Microplastics distribute from primary (e.g., exfoliating cleansers) and secondary (e.g., chemical deterioration) sources in the environment. This anthropogenic phenomenon poses a threat to the flora and fauna of terrestrial and aquatic ecosystems as ingestion and entanglement cases increase over time. This review focuses on the impact of microplastics across taxa at suggested environmentally relevant concentrations, and advances the groundwork for future ecotoxicological-based research on microplastics including the main points: (i) adhesion of chemical pollutants (e.g., PCBs); (ii) biological effects (e.g., bioaccumulation, biomagnification, biotransportation) in terrestrial and aquatic organisms; (iii) physico-chemical properties (e.g., polybrominated diphenyl ethers) and biodegradation pathways in the environment (e.g., chemical stress, heat stress); and (iv) an ecotoxicological prospect for optimized impact assessments.

Micro- and Nanosized Substances Cause Different Autophagy-Related Responses

With rapid industrialization, humans produce an increasing number of products. The composition of these products is usually decomposed. However, some substances are not easily broken down and gradually become environmental pollutants. In addition, these substances may cause bioaccumulation, since the substances can be fragmented into micro- and nanoparticles. These particles or their interactions with other toxic matter circulate in humans via the food chain or air. Whether these micro- and nanoparticles interfere with extracellular vesicles (EVs) due to their similar sizes is unclear. Micro- and nanoparticles (MSs and NSs) induce several cell responses and are engulfed by cells depending on their size, for example, particulate matter with a diameter ≤2.5 μm (PM2.5). Autophagy is a mechanism by which pathogens are destroyed in cells. Some artificial materials are not easily decomposed in organisms. How do these cells or tissues respond? In addition, autophagy operates through two pathways (increasing cell death or cell survival) in tumorigenesis. Many MSs and NSs have been found that induce autophagy in various cells and tissues. As a result, this review focuses on how these particles interfere with cells and tissues. Here, we review MSs, NSs, and PM2.5, which result in different autophagy-related responses in various tissues or cells.

Source, distribution and emerging threat of micro- and nanoplastics to marine organism and human health: Socio-economic impact and management strategies

The nature of micro- and nanoplastics and their harmful consequences has drawn significant attention in recent years in the context of environmental protection. Therefore, this paper aims to provide an overview of the existing literature related to this evolving subject, focusing on the documented human health and marine environment impacts of micro- and nanoplastics and including a discussion of the economic challenges and strategies to mitigate this waste problem. The study highlights the micro- and nanoplastics distribution across various trophic levels of the food web, and in different organs in infected animals which is possible due to their reduced size and their lightweight, multi-coloured and abundant features. Consequently, micro- and nanoplastics pose significant risks to marine organisms and human health in the form of cytotoxicity, acute reactions, and undesirable immune responses. They affect several sectors including aquaculture, agriculture, fisheries, transportation, industrial sectors, power generation, tourism, and local authorities causing considerable economic losses. This can be minimised by identifying key sources of environmental plastic contamination and educating the public, thus reducing the transfer of micro- and nanoplastics into the environment. Furthermore, the exploitation of the potential of microorganisms, particularly those from marine origins that can degrade plastics, could offer an enhanced and environmentally sound approach to mitigate micro- and nanoplastics pollution.

The fate of plastic in the ocean environment - a minireview

The presence of plastics in the marine environment poses a threat to ocean life and has received much scientific and public attention in recent years. Plastics were introduced to the market in the 1950s and since then, global production figures and ocean plastic littering have increased exponentially. Of the 359 million tonnes (Mt) produced in 2018, an estimated 14.5 Mt has entered the ocean. In particular smaller plastic particles can be ingested by marine biota causing hazardous effects. Plastic marine debris (PMD) is exposed to physical, chemical and biological stressors. These cause macro and microplastic to break down into smaller fragments, including sub micrometre sized nanoplastic particles, which may account for an important but so far unevaluated fraction of the ocean plastic budget. Physicochemical and biological deterioration of PMD also leads to the release of more volatile compounds and the terminal oxidation of PMD, which most likely accounts for an important but also unevaluated fraction in the ocean plastic budget. This minireview provides an overview on (1) the quantity of plastic production and waste, pathways for plastics to enter the marine realm, the inventory of PMD and the negative effects of PMD to ocean life. (2) We discuss plastic degradation mechanisms in the ocean, expanding on the processes of photodegradation and biodegradation. (3) This review also highlights the emerging topic of nanoplastics in the sea and provides an overview on their specific physical and chemical properties, potential harm to ocean life, and nanoplastic detection techniques.