Plastic waste as a global challenge: are biodegradable plastics the answer to the plastic waste problem?

Rayon fibre rope: A biodegradable alternative for marine use?

Rayon fibres are well-known materials that were primarily utilised as reinforcement in tyres. Today these materials are perceived as a promising substitute for synthetic fibres, exhibiting good mechanical characteristics and biodegradation in many environments. This paper investigates their potential use for marine structures. It first describes the tensile properties of the fibres and their derived yarns and ropes. These properties are then monitored during seawater ageing and the ultimate biodegradation is characterised by respirometry tests. Both material scales demonstrate rapid degradation rates under biotic conditions (90 % strength reduction after 2 weeks for yarns and 6 months for small ropes) and a relative stability in abiotic conditions. Additionally, the fibres show rapid bio-assimilation rates. The rope construction is demonstrated to have a significant impact on the degradation kinetics, suggesting possible strategies to enhance durability. The results indicate that these rayon fibre ropes may offer an attractive alternative to synthetic fibre ropes to reduce impact where there is a high risk of rope loss at sea.

Machine-Learning-Based Design of Metallocene Catalysts for Controlled Olefin Copolymerization

Polyolefins are versatile materials for various purposes, but their functionality should be fine-tuned for target applications including the mitigation of adverse environmental impacts. Producing such polymers with desired properties requires catalysts that can control polymerization at an atomistic level. However, complex reaction mechanisms and very limited experimental data make it difficult to design new efficient catalysts using conventional computational and data-driven approaches. Here, we present a pragmatic strategy based on data-efficient predictive models combined with a genetic algorithm to design new catalysts for controlled ethylene/hexene copolymerization. By deriving the chemically intuitive descriptors from the mechanistic analysis of the polymerization, we achieved the promising predictive models with small data applicable to various core structures and different experimental conditions, respectively. We screened catalysts through a virtual screening scheme combining a genetic algorithm and predictive models using chemically intuitive descriptors and considered their synthesizability through the manual inspections of experts. As a result, we successfully designed nine catalysts with desired comonomer ratios and diverse core structures.

Monitoring Antioxidant Consumption and Build-Up in Polypropylene During Open-Loop and Closed-Loop Mechanical Recycling

Polypropylene (PP), a widely used recyclable plastic in packaging and engineering applications, is prone to thermo-oxidative degradation during reprocessing and molding at high temperatures. Antioxidants (AOs) are essential for stabilizing PP in both its virgin and recycled states. The quantity of AO added is critical: insufficient amounts can lead to poor stabilization, while excessive amounts can cause safety concerns due to build-up. This study presents a modified approach to measure the Oxidation Induction Temperature (OIT) using Differential Scanning Calorimetry (DSC), particularly for recycled PP from waste that contains unpredictable contaminations. This modified approach ensures the safety of the calorimetry cell by limiting the oxidation reaction and preventing the release of volatile compounds during measurements. By performing DSC measurements in inert environments, we obtain the OIT, which can be correlated to residual intact AO levels. This approach to monitoring AO levels is demonstrated in both open- and closed-loop recycling of rigid PP. Although the presence of contamination is known to catalyze thermo-oxidative degradation in PP, our results indicate that recycled PP from open-loop collection still contains sufficient residual AO that allows it to withstand limited thermal reprocessing. However, this tendency of AO retention leads to significant build-up during closed-loop recycling when AOs are added to each cycle, where the PP grade remains fairly homogeneous and the dispersity (Đ) does not significantly increase over multiple recycling loops.

Functionalized recycled polyethylene terephthalate plastic by rare earth oxide for electronic device and housing infrastructure applications

Recycled polyethylene terephthalate (RPET) was doped with Neodymium Oxide (Nd2O3: 0, 1, 2, 4, and 8 wt.%) to investigate its structural, optical, dielectric, and mechanical properties. X-ray diffraction (XRD) analysis revealed that pure RPET exhibited an amorphous structure, while the incorporation ofNd2O3 induced the formation of crystalline phases, with crystallinity increasing as the Nd2O3 concentration increased. Fourier-transform infrared (FTIR) spectroscopy identified chemical interactions between RPET and Nd2O3, evidenced by a new band around 535 cm-1. Optical analysis using diffuse reflectance UV-Vis spectroscopy showed a reduction in the band gap from 3.75 eV for pure RPET to 2.25 eV in 8wt.% doped samples, indicating enhanced optical properties. Dielectric studies revealed that Nd2O3 doping significantly decreased the dielectric constant of RPET, contributing to the thermal stability of the dielectric constant. Furthermore, the dielectric loss and conductivity improved, with enhanced stability observed across varying temperatures. Dynamic mechanical analysis (DMA) revealed that adding 8 wt.% Nd2O3 reduced the storage modulus of RPET from 1.62 GPa to approximately 0.26 GPa at 35 °C, attributed to structural softening. These improvements suggest that Nd2O2-doped RPET is suitable for applications requiring conductive REPT, low storage modulus, thermal stability, and enhanced energy dissipation capabilities.

Enzymes offer a promising avenue for enhancing the competitiveness of biodegradable plastics in environmental restoration and the circular economy

As a promising alternative to traditional plastics, the widespread application of biodegradable plastic (BP) will help solve worsening environmental problems. Enzymes such as cutinase, lipase, protease and esterase produced by bacteria and fungi in the environment play a crucial role in the degradation, recycling and valorization of BP by degrading them into low-molecular-weight oligomers or small monomers. These enzymes offering advantages such as high efficiency, cleanliness, safety and environmental friendliness, making them more competitive in environmental restoration and circular economy. This review describes in detail the occurrence and distribution of enzymes involved in the degradation of BPs (represented by PHB, PLA and PCL). Omics methods (metagenomic and proteomic) combined with high-throughput platforms can screen out BP-degrading enzymes in different environments, and then use protein engineering to optimize the degrading enzymes to improve enzymatic degradation efficiency. Finally, we focus on the methods and strategies for the commercialization of degrading enzymes, future research prospects and challenges are also discussed. This review highlights the importance of BP-degrading enzymes in the bio-cycling of BP, and expected to drive the widespread use of BP.

Differentiating low-carbon waste management strategies for bio-based and biodegradable plastics under various energy decarbonization scenarios

Bio-based and biodegradable (bio-)plastics are heralded as a key solution to mitigate plastic pollution and reduce CO2 emissions. Yet, their end-of-life treatments embodies complex energy and material interactions, potentially leading to emissions through incineration or recycling. This study investigates the cradle-to-grave, emphasizing the waste management stage, carbon footprint for several types of bio-plastics, leveraging both GWP100a and CO2 uptake methods to explore the carbon reduction benefits of recycling over disposal. Our findings indicate that in scenarios characterized by carbon-intensive electricity, using polylactic acid (PLA) as an example, incineration with energy recovery (-1.6316 kg CO2-eq/kg, PLA) yields a more favorable carbon footprint compared to chemical recycling (-1.5317 kg CO2-eq/kg, PLA). In contrast, in environments with a high proportion of renewable energy, chemical recycling is a superior method, and compared to incineration (-1.4087 kg CO2-eq/kg, PLA), the carbon footprint of chemical recycling (-2.0406 kg CO2-eq/kg, PLA) are significantly reduced. While mechanical recycling presents considerable environmental benefits, its applicability is constrained by the waste quality, especially in the case of biodegradable plastics like PLA. In addition, the degradation of biodegradable plastics such as PLA was modeled during compost and anaerobic digestion processes. This enables us to quantify the specific biogenic carbon emissions released during these processing steps, revealing the direct emissions with dynamic degradation. This study highlights the importance of tailoring bio-plastic waste management strategies to support global energy decarbonization while understanding their life-cycle carbon metabolism to effectively tackle plastic pollution and climate change.

Polymer material biodegradation in the deep sea. A review

The phenomenon of marine plastic pollution is now well-established, with documented impacts on marine biodiversity and biogeochemical cycles. In order to mitigate this environmental impact, a significant amount of research has been conducted in recent years with the objective of developing biodegradable alternatives to conventional polymers and their composites in marine environments. The findings of this research significantly enhanced our understanding of biodegradation mechanisms and identified promising candidates. However, the majority of these studies have been conducted in coastal marine environments, which represent a minor component of the marine ecosystem. Recent models on the transport of plastic debris in the oceans indicate that deep-sea environments are likely to be the ultimate sink for a significant proportion of plastics entering the oceans. The aim of this review is to provide an overview of the processes of biodegradation of polymers in these deep-sea environments. The diversity and specific characteristics of these environments with respect to degradation mechanisms are discussed. While the majority of deep-sea conditions are not conducive to biodegradation, studies on organic falls (wood and whale carcasses) and a few investigations into materials previously shown to be biodegradable in coastal marine environments demonstrate mechanisms that are similar to those observed in shallow waters. Nevertheless, further research is necessary to reach definitive conclusions. It is essential to extend these studies to a broader range of deep-sea environments. Additionally, new methodologies that integrate microbiology and polymer science are required to accurately assess the process of assimilation of these materials in these environments.

Development of Eco-Friendly Packaging Films from Soyhull Lignocellulose: Towards Valorizing Agro-Industrial Byproducts

Due to their inability to biodegrade, petroleum-based plastics pose significant environmental challenges by disrupting aquatic, marine, and terrestrial ecosystems. Additionally, the widespread presence of microplastics and nanoplastics induces serious health risks for humans and animals. These pressing issues create an urgent need for designing and developing eco-friendly, biodegradable, renewable, and non-toxic plastic alternatives. To this end, agro-industrial byproducts such as soyhulls, which contain 29-50% lignocellulosic residue, are handy. This study extracted lignocellulosic residue from soyhulls using alkali treatment, dissolved it in ZnCl2 solution, and crosslinked it with calcium ions and glycerol to create biodegradable films. The film formulation was optimized using the Box-Behnken design, with response to tensile strength (TS), elongation at break (EB), and water vapor permeability (WVP). The optimized films were further characterized for color, light transmittance, UV-blocking capacity, water absorption, contact angle, and biodegradability. The resulting optimized film demonstrated a tensile strength of 10.4 ± 1.0 MPa, an elongation at break of 9.4 ± 1.8%, and a WVP of 3.5 ± 0.4 × 10-11 g·m-1·s-1·Pa-1. Importantly, 90% of the film degrades within 37 days at 24% soil moisture. This outcome underscores the potential of soyhull-derived films as a sustainable, innovative alternative to plastic packaging, contributing to the circular economy and generating additional income for farmers and allied industries.

Biodegradable films from soyhull cellulosic residue with UV protection and antioxidant properties improve the shelf-life of post-harvested raspberries

Post-harvest loss of fruits and vegetables, and health risks and environmental impact of current plastic packaging warrant new biodegradable packaging. To this end, cellulosic residue from agricultural processing byproducts is suitable due to its renewability and sustainability. Herein, soyhulls cellulosic residue was extracted, solubilized in ZnCl2 solution, and crosslinked with calcium ions and glycerol to prepare biodegradable films. The film combination was optimized using Box Behnken Design and film properties were characterized. The optimized film is translucent and exhibits tensile strength, elongation at break, water vapor permeability, hydrophobicity, and IC50 of 6.3 ± 0.6 MPa, 30.2 ± 0.9%, 0.9 ± 0.3 × 10-10 gm-1 s-1 Pa-1, 72.6°, and 0.11 ± 0.1 g/mL, respectively. The water absorption kinetics follow the Peleg model and biodegrade within 25 days at 24% soil moisture. The film extends the shelf life of raspberries by 6 more days compared to polystyrene film. Overall, the value-added soyhull cellulosic films are advantageous in minimizing post-harvest loss and plastic-related issues, emphasizing the principles of the circular bioeconomy.

Unveiling bisphenol A toxicity: human health impacts and sustainable treatment strategies

INTRODUCTION

The widespread presence of bisphenol-A (BPA) in consumer goods like water bottles and eyeglass frames raises serious concerns about the chemical's ability to accumulate in human tissues. Molecular filtration and activated carbon adsorption are two of the many BPA treatment technologies that have emerged in response to these issues; both are essential in the removal or degradation of BPA from water sources and industrial effluents.

CONTENT

To secure the long-term health and environmental advantages of BPA treatment approaches, sustainable development is essential. Both the efficient elimination or destruction of BPA and the reduction of the treatment operations' impact on the environment are important components of a sustainable approach. Different search engines like Pub-Med, MEDLINE, Google Scholar and Scopus are used for these systematic reviews and analyzed accordingly. This can be accomplished by making treatment facilities more energy efficient and using environmentally friendly materials. Greener ways to deal with BPA pollution are on the horizon, thanks to innovative techniques like bioremediation and improved oxidation processes. Reducing dependence on conventional, resource-intensive procedures can be achieved by investigating the use of bio-based materials and natural adsorbents in treatment processes.

SUMMARY AND OUTLOOK

This review article tackling the health and environmental concerns raised by BPA calls for an integrated strategy that incorporates sustainable development principles and technology progress. We can reduce the negative impacts of BPA contamination, improve environmental stewardship in the long run, and ensure human health by combining cutting-edge treatment technologies with sustainable behaviours.

New model compounds for the efficient colorimetric screening of medium chain length polyhydroxyalkanoate (mcl-PHA) depolymerases reveal mechanism of activity

Plastic pollution presents a significant environmental problem contributing to increased CO2 emissions and persistently accumulation in ecosystems. Biobased polymers, like polyhydroxyalkanoates (PHAs), offer a part of a solution with their biodegradability and reduced carbon footprint. However, effective end-of-life strategies, such as controlled enzymatic depolymerization, are crucial for sustainability, relying on efficient PHA depolymerases (PHAases). Here we describe the synthesis of two new chromogenic compounds derived from polyhydroxyoctanoate (PHO) and their application in a continuous, quantitative spectrophotometric assay for PHO depolymerase and other medium chain lengths PHAase activity within 10 min. These substrates allow activity measurement at temperatures above 45 °C, simplifying the comparison of PHAases and aiding enzymatic degradation progress. The study also explores enzyme specificity and identifies key amino acids involved in PHO recognition by PfPHOase. The 3-hydroxyoctanoyl moieties of both compounds were found to bind specifically to a groove formed by the amino acids Phe96, Phe125, Ile171, and Val230, which are highly conserved in known mcl-PHA depolymerases.

Research progress on degradation of biodegradable micro-nano plastics and its toxic effect mechanism on soil ecosystem

Biodegradable plastics (BPs) are known to decompose into micro-nano plastics (BMNPs) more readily than conventional plastics (CPs). Given the environmental risks posed by BMNPs in soil ecosystems, their impact has garnered increasing attention. However, research focusing on the toxic effects of BMNPs on soils remains relatively limited. The degradation process and duration of BMNPs in soil are influenced by numerous factors, which directly impact the toxic effects of BMNPs. This highlights the urgent need for further research. In this context, this review delineates the classification of BPs, investigates the degradation processes of BPs along with their influencing factors, summarizes the toxic effects on soil ecosystems, and explores the potential mechanisms that underlie these toxic effects. Finally, it provides an outlook on related research concerning BMNPs in soil. The results indicate that specific BMNPs release additives at a faster rate during decomposition, degradation, and aging, with certain compounds exhibiting increased bioavailability. Importantly, a substantial body of research has shown that BMNPs generally manifest more pronounced toxic effects in comparison to conventional micro-nano plastics (CMNPs). The toxic effects associated with BMNPs encompass a decline in soil quality and microbial biomass, disruption of nutrient cycling, inhibition of plant root growth, and negative impacts on invertebrate reproduction, survival, and fertilization rates. The rough and complex surfaces of BMNPs contribute to increased mechanical damage to tested organisms, enhance absorption by microorganisms, and disrupt normal physiological functions. Notably, the toxic effects of BMNPs on soil ecosystems are influenced by factors including concentration, type of BMNPs, exposure conditions, degradation products, and the nature of additives used. Therefore, it is crucial to standardize detection technologies and toxicity testing conditions for BMNPs. In conclusion, this review provides scientific evidence that supports effective prevention and management of BMNP pollution, assessment of its ecological risks, and governance of BMNPs-related products.

Microbial production of adipic acid from 6-hydroxyhexanoic acid for biocatalytic upcycling of polycaprolactone

To valorize waste polycaprolactone (PCL), one of the most widely used biodegradable plastics, into a value-added chemical, we upcycled 6-hydroxyhexanoic acid (6-HHA), the sole monomer of PCL, into adipic acid (AA) using a microbial method. Recombinant Escherichia coli strains expressing chnD (6-HHA dehydrogenase) and chnE (6-oxohexanoic acid dehydrogenase) genes from three bacteria were constructed, and all these strains successfully produced AA from 6-HHA. Among these, the E. coli strain harboring ChnDE genes from Acinetobacter strain SE19 (E. coli [pKK-AcChn]) showed the highest AA-producing ability. To increase the AA production titer, we optimized the culture temperature of this strain in flask culture and performed fed-batch fermentation in a 5 L bioreactor. After the fed-batch fermentation, the AA production titer increased to 15.6 g/L. As 6-HHA is a monomer of PCL, our results provide the groundwork for the development of a biocatalytic upcycling method of PCL.

Recent Advances in Degradable Biomedical Polymers for Prevention, Diagnosis and Treatment of Diseases

Biomedical polymers play a key role in preventing, diagnosing, and treating diseases, showcasing a wide range of applications. Their unique advantages, such as rich source, good biocompatibility, and excellent modifiability, make them ideal biomaterials for drug delivery, biomedical imaging, and tissue engineering. However, conventional biomedical polymers suffer from poor degradation in vivo, increasing the risks of bioaccumulation and potential toxicity. To address these issues, degradable biomedical polymers can serve as an alternative strategy in biomedicine. Degradable biomedical polymers can efficiently relieve bioaccumulation in vivo and effectively reduce patient burden in disease management. This review comprehensively introduces the classification and properties of biomedical polymers and the recent research progress of degradable biomedical polymers in various diseases. Through an in-depth analysis of their classification, properties, and applications, we aim to provide strong guidance for promoting basic research and clinical translation of degradable biomedical polymers.

Chemical toxicity of leachates from synthetic and natural-based spat collectors on the embryo-larval development of the pearl oyster, Pinctada margaritifera

In French Polynesia, the pearl farming industry relies entirely on collecting natural spat using a shade-mesh collector, which is reported to contribute to both plastic pollution and the release of toxic chemicals. With the aim of identifying more environment-friendly collectors, this study investigates the chemical toxicity of shade-mesh (SM) and alternative materials, including reusable plates (P), a newly developed biomaterial (BioM) and Coconut coir geotextile (Coco), on the embryo-larval development of Pinctada margaritifera. Embryos were exposed during 48 h to four concentrations (0, 0.1, 10 and 100 g L-1) of leachates produced from materials. Chemical screening of raw materials and leachates was performed to assess potential relationships with the toxicity observed on D-larvae development. Compared to the other tested materials, results demonstrated lower levels of chemical pollutants in BioM and no toxic effects of its leachates at 10 g L-1. No toxicity was observed at the lowest tested concentration (0.1 g L-1). These findings offer valuable insights for promoting safer spat collector alternatives such as BioM and contribute to the sustainable development of pearl farming.

Insights into the biodegradation of polyhydroxyalkanoates by the tropical marine isolate, Nocardiopsis dassonvillei NCIM 5124

In the current study, the ability of an indigenous marine Actinomycete Nocardiopsis dassonvillei (NCIM 5124) to degrade poly(3-hydroxybutyrate)-PHB was examined. From the whole genome sequencing data of the organism, information regarding the PHB depolymerase gene and amino acid sequence (Accession number: MCK9871921.1) was retrieved. In silico studies indicated the presence of a signal peptide characteristic of extracellular enzymes. ProtParam tool predicted that the protein had a molecular mass of 42.46 kDa with an isoelectric point of 4.51. Aliphatic and instability index values suggested that the protein was stable and the observed GARVY value indicated its hydrophilic nature. 3D structure prediction and multiple sequence alignments revealed the presence of Type I catalytic domain [including the oxyanion histidine towards the N terminal, the catalytic triad with serine (as a part of GLSAG pentapeptide), aspartate and histidine], substrate binding and linker domain. The organism was able to grow on PHB in solid and liquid media and effectively degrade it. Maximum enzyme activity (1.8 U/mL/min) was observed after 5 d of incubation in Bushnell Hass Medium containing 0.1% PHB, 1.5% sodium chloride, at 30 °C, pH 7.5 with agitation at 130 rpm. Application of the organism in disintegrating films of PHB and its copolymers was successfully demonstrated on the basis of weight loss and scanning electron microscope analysis. To the best of our knowledge, this is the first report on production of PHB depolymerase with high efficiency by N. dassonvillei, an organism that holds promise in degrading PHB-derived waste material.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04079-3.

Corncob-derived biodegradable packaging films: A sustainable solution for raspberry post-harvest preservation

Plastic food packaging, with its harmful migration of microplastics and nanoplastics into food, presents significant ecological imbalance and human health risks. In this regard, using food and agricultural byproducts as packaging materials reduces environmental and economic concerns and supports their sustainable management. Herein, cellulosic residue from corncob was employed as a renewable source for developing biodegradable packaging films. It was solubilized in ZnCl2 solution, crosslinked with Ca2+ ions, and plasticized with sorbitol to form films and used to improve the shelf-life of raspberries. The optimized film possesses water vapor permeability, tensile strength, and elongation at break of 1.8(4) x10-10 g-1 s-1 Pa-1, 4.7(1) MPa, and 15.4(7)%, respectively. It displays UV-blocking and antioxidant properties and biodegrades within 29 days at 24% soil moisture. It preserves raspberries for 7 and 5 more days at room temperature and refrigeration conditions, respectively, compared to polystyrene film. Overall, more value addition could be envisioned from agricultural residues to minimize post-harvest losses and food waste through biodegradable packaging, which also aids in mitigating plastic perils.

Biofilm mitigation in hybrid chemical-biological upcycling of waste polymers

Introduction: Accumulation of plastic waste in the environment is a serious global issue. To deal with this, there is a need for improved and more efficient methods for plastic waste recycling. One approach is to depolymerize plastic using pyrolysis or chemical deconstruction followed by microbial-upcycling of the monomers into more valuable products. Microbial consortia may be able to increase stability in response to process perturbations and adapt to diverse carbon sources, but may be more likely to form biofilms that foul process equipment, increasing the challenge of harvesting the cell biomass. Methods: To better understand the relationship between bioprocess conditions, biofilm formation, and ecology within the bioreactor, in this study a previously-enriched microbial consortium (LS1_Calumet) was grown on (1) ammonium hydroxide-depolymerized polyethylene terephthalate (PET) monomers and (2) the pyrolysis products of polyethylene (PE) and polypropylene (PP). Bioreactor temperature, pH, agitation speed, and aeration were varied to determine the conditions that led to the highest production of planktonic biomass and minimal formation of biofilm. The community makeup and diversity in the planktonic and biofilm states were evaluated using 16S rRNA gene amplicon sequencing. Results: Results showed that there was very little microbial growth on the liquid product from pyrolysis under all fermentation conditions. When grown on the chemically-deconstructed PET the highest cell density (0.69 g/L) with minimal biofilm formation was produced at 30°C, pH 7, 100 rpm agitation, and 10 sL/hr airflow. Results from 16S rRNAsequencing showed that the planktonic phase had higher observed diversity than the biofilm, and that Rhodococcus, Paracoccus, and Chelatococcus were the most abundant genera for all process conditions. Biofilm formation by Rhodococcus sp. And Paracoccus sp. Isolates was typically lower than the full microbial community and varied based on the carbon source. Discussion: Ultimately, the results indicate that biofilm formation within the bioreactor can be significantly reduced by optimizing process conditions and using pure cultures or a less diverse community, while maintaining high biomass productivity. The results of this study provide insight into methods for upcycling plastic waste and how process conditions can be used to control the formation of biofilm in bioreactors.

The potential impact of nano- and microplastics on human health: Understanding human health risks

Plastics are used all over the world. Unfortunately, due to limited biodegradation, plastics cause a significant level of environmental pollution. The smallest recognized to date are termed nanoplastics (1 nm [nm] up to 1 μm [μm]) and microplastics (1 μm-5 mm). These nano- and microplastics can enter the human body through the respiratory system via inhalation, the digestive tract via consumption of contaminated food and water, or penetration through the skin via cosmetics and clothes contact. Bioaccumulation of plastics in the human body can potentially lead to a range of health issues, including respiratory disorders like lung cancer, asthma and hypersensitivity pneumonitis, neurological symptoms such as fatigue and dizziness, inflammatory bowel disease and even disturbances in gut microbiota. Most studies to date have confirmed that nano- and microplastics can induce apoptosis in cells and have genotoxic and cytotoxic effects. Understanding the cellular and molecular mechanisms of plastics' actions may help extrapolate the risks to humans. The article provides a comprehensive review of articles in databases regarding the impact of nano- and microplastics on human health. The review included retrospective studies and case reports of people exposed to nanoplastics and microplastics. This research highlights the need for further research to fully understand the extent of the impact of plastics on human health.

A screening method for plastic-degrading fungi

The growing amount of plastic waste requires new ways of disposal or recycling. Research into the biodegradation of recalcitrant plastic polymers is gathering pace. Despite some progress, these efforts have not yet led to technologically and economically viable applications. In this study, we show that respirometric screening of environmental fungal isolates in combination with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy can be used to identify new strains with the potential for the degradation of plastic polymers. We screened 146 fungal strains, 71 isolated from car repair shops, an environment rich in long-chain hydrocarbons, and 75 isolated from hypersaline water capable of growing at high concentrations of NaCl. When grown in a minimal medium with no carbon source, some strains produced significantly more CO2 when a pure plastic polymer was added to the medium, some only at high salinity. A selection of these strains was shown by FTIR and Raman spectroscopy to alter the properties of plastic polymers: Cladosporium sp. EXF-13502 on polyamide, Rhodotorula dairenensis EXF-13500 on polypropylene, Rhodotorula sp. EXF-10630 on low-density polyethylene and Wickerhamomyces anomalus EXF-6848 on polyethylene terephthalate. Respirometry in combination with specific spectroscopic methods is an efficient method for screening microorganisms capable of at least partial plastic degradation and can be used to expand the repertoire of potential plastic degraders. This is of particular importance as our results also show that individual strains are only active against certain polymers and under certain conditions. Therefore, efficient biodegradation of plastics is likely to depend on a collection of specialized microorganisms rather than a single universal plastic degrader.

Recycling and reusing potential of disposable low-density polyethylene plastic waste for flexible paver tile construction for outdoor application

Plastic waste disposal has escalated into a serious global concern due to the non-biodegradable nature of plastics, which are composed of high-molecular-mass organic polymers along with other ingredients. Therefore, this study focuses on reusing and recycling LDPE plastic waste as a binding agent in paver tile production. This aligns with global sustainability goals by promoting resource efficiency and reducing waste generation. The investigation aims to address the environmental impact of plastic waste by finding sustainable solutions for its management. This includes exploring the feasibility and viability of using LDPE plastic waste in paver tile production as a means of recycling and reusing locally collected waste. The LDPE waste plastic collection, identification, milling, and melting at 170 °C. Subsequently, the sampled sand, sieved to a size of ≤0.75 mm, was blended with molten plastic in a specified proportion and then molded to create paving tiles using a hydraulic press machine. The researchers utilized response surface methodology (RSM) combined with Box-Benken designs (BBD) to optimize three key experimental parameters (plastic-to-sand ratio: 10 %, 25 %, 40 %; time: 2, 5, 8 min, pressure: 1, 3, 5 MPa) influencing mechanical properties of paver tiles, including water absorption (WA), flexural strength (FS), and compressive strength (CS). The result revealed that the optimal combination of 25 % waste plastic, 5 min, and 3 MPa of pressure resulted in a maximum flexural strength (FS) of 3.689 MPa and compressive strength (CS) of 4.141 MPa, with an average water absorption (WA) of 0.322 %. Therefore, the mechanical properties of the developed tiles met the desired standard. In conclusion, the mechanical qualities of the tiles were promising, indicating that reusing waste LDPE plastic to create paver tiles presents an appealing option for plastic waste disposal. The composite paver tiles exhibited promising attributes for outdoor applications, such as park pavement and outdoor public spaces, owing to their favorable mechanical properties and low water absorption.

TidyTron: Reducing lab waste using validated wash-and-reuse protocols for common plasticware in Opentrons OT-2 lab robots

Every year biotechnology labs generate a combined total of ∼5.5 million tons of plastic waste. As the global bioeconomy expands, biofoundries will inevitably increase plastic consumption in-step with synthetic biology scaling. Decontamination and reuse of single-use plastics could increase sustainability and reduce recurring costs of biological research. However, throughput and variable cleaning quality make manual decontamination impractical in most instances. Automating single-use plastic cleaning with liquid handling robots makes decontamination more practical by offering higher throughput and consistent cleaning quality. However, open-source, validated protocols using low-cost lab robotics for effective decontamination of plasticware-facilitating safe reuse-have not yet been developed. Here we introduce and validate TidyTron: a library of protocols for cleaning micropipette tips and microtiter plates that are contaminated with DNA, E. coli, and S. cerevisiae. We tested a variety of cleaning solutions, contact times, and agitation methods with the aim of minimizing time and cost, while maximizing cleaning stringency and sustainability. We tested and validated these cleaning procedures by comparing fresh (first-time usage) versus cleaned tips and plates for contamination with cells, DNA, or cleaning solutions. We assessed contamination by measuring colony forming units by plating, PCR efficiency and DNA concentration by qPCR, and event counts and debris by flow cytometry. Open source cleaning protocols are available at https://github.com/PlantSynBioLab/TidyTron and hosted on a graphical user interface at https://jbryantvt.github.io/TidyTron/.

Critical review on airborne microplastics: An indoor air contaminant of emerging concern

Airborne Microplastics (MPs), an emerging environmental issue, have gained recent attention due to their newfound presence in indoor environments. Utilizing the Web of Science database for literature collection, the paper presents a comprehensive review of airborne MPs including emission sources, assessment methods, exposure risks, and mitigation strategies. This review delves into the diverse sources and mechanisms influencing indoor airborne MP pollution, underscoring the complex interplay between human activities, ventilation systems, and the characteristics of indoor environments. Major sources include the abrasion of synthetic textiles and the deterioration of flooring materials, with factors like carpeting, airflow, and ventilation significantly impacting MP levels. Human activities, such as increased movement in indoor spaces and the intensive use of plastic-based personal protective equipment (PPE) post-pandemic, notably elevate indoor MP concentrations. The potential health impacts of airborne MPs are increasingly concerning, with evidence suggesting their role in respiratory, immune, and nervous system diseases. Despite this, there is a scarcity of information on MPs in diverse indoor environments and the inhalation risks associated with the frequent use of PPE. This review also stresses the importance of developing effective strategies to reduce MP emissions, such as employing HEPA-filtered vacuums, minimizing the use of synthetic textiles, and enhancing indoor ventilation. Several future research directions were proposed, including detailed temporal analyses of indoor MP levels, interactions of MP with other atmospheric pollutants, the transport dynamics of inhalable MPs (≤10 μm), and comprehensive human exposure risk assessments.

Concentration analysis of metal-labeled nanoplastics in different water samples using electrochemistry

Despite the threats posed by nanoplastics to the environment and human health, little was known about the occurrence, formation, migration, and environmental impacts of nanoplastics due to the lack of quantitative and sensitive detection techniques. In this work, an electrochemical strategy for the detection of nanoplastics based on Ag labeling was proposed. Positively charged silver ions were attached to negatively charged polystyrene nanoplastics (PSNPs), and then the silver ions on the surface of PSNPs were reduced to Ag by sodium borohydride. Subsequently, the concentration of PSNPs was determined by identifying the signal of Ag by differential pulse voltammetry. The method showed different sensitivity for PSNPs of different sizes (100, 367, 500 nm). For tap water samples, the reason for the change in Ag electrochemical signal was discussed. The sensitivity of the method to PSNPs in tap water was investigated. The feasibility of the method for environmental water samples was verified using spiked lake water and spiked seawater, and satisfactory recoveries (93-112 %) were obtained for PSNPs of different sizes and concentrations. This study provided a sensitive, low-cost, and simple method without complex instrumentation, which was important for the determination of PSNPs in environmental water samples.

Reprocessing Possibilities of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-Hemp Fiber Composites Regarding the Material and Product Quality

An important issue addressed in research on the assessment of the quality of polymer products is the quality of the polymer material itself and, in accordance with the idea of waste-free management, the impact of its repeated processing on its properties and the quality of the products. In this work, a biocomposite, based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with short hemp fibers, was obtained and repeatedly processed, which is a continuation of the research undertaken by the team in the field of this type of biocomposites. After subsequent stages of processing, the selected mechanical, processing and functional properties of the products were assessed. For this purpose, microscopic tests were carried out, mechanical properties were tested in static tensile and impact tests, viscosity curves were determined after subsequent processing cycles and changes in plastic pressure in the mold cavity were determined directly during processing. The results of the presented research confirm only a slight decrease in the mechanical properties of the produced type of biocomposite, even after it has been reprocessed five times, which gives extra weight to arguments for its commercialization as a substitute for petrochemical-based plastics. No significant changes were found in the used parameters and processing properties with the stages of processing, which allows for a predictable and stable manufacturing process using, for example, the injection molding process.

Force-Induced Alignment of Nanofibrillated Bacterial Cellulose for the Enhancement of Cellulose Composite Macrofibers

Bacterial cellulose, as an important renewable bioresource, exhibits excellent mechanical properties along with intrinsic biodegradability. It is expected to replace non-degradable plastics and reduce severe environmental pollution. In this study, using dry jet-wet spinning and stretching methods, we fabricate cellulose composite macrofibers using nanofibrillated bacterial cellulose (BCNFs) which were obtained by agitated fermentation. Ionic liquid (IL) was used as a solvent to perform wet spinning. In this process, force-induced alignment of BCNFs was applied to enhance the mechanical properties of the macrofibers. The results of scanning electron microscopy revealed the well-aligned structure of BCNF along the fiber axis. The fiber prepared with an extrusion rate of 30 m min-1 and a stretching ratio of 46% exhibited a strength of 174 MPa and a Young's modulus of 13.7 GPa. In addition, we investigated the co-spinning of carboxymethyl cellulose-containing BCNF with chitosan using IL as a "container", which indicated the compatibility of BCNFs with other polysaccharides. Recycling of the ionic liquid was also verified to validate the sustainability of our strategy. This study provides a scalable method to fabricate bacterial cellulose composite fibers, which can be applied in the textile or biomaterial industries with further functionalization.

Enzyme selection, optimization, and production toward biodegradation of post-consumer poly(ethylene terephthalate) at scale

Poly(ethylene terephthalate) (PET) is one of the world's most widely used polyester plastics. Due to its chemical stability, PET is extremely difficult to hydrolyze in a natural environment. Recent discoveries in new polyester hydrolases and breakthroughs in enzyme engineering strategies have inspired enormous research on biorecycling of PET. This study summarizes our research efforts toward large-scale, efficient, and economical biodegradation of post-consumer waste PET, including PET hydrolase selection and optimization, high-yield enzyme production, and high-capacity enzymatic degradation of post-consumer waste PET. First, genes encoding PETase and MHETase from Ideonella sakaiensis and the ICCG variant of leaf-branch compost cutinase (LCCICCG ) were codon-optimized and expressed in Escherichia coli BL21(DE3) for high-yield production. To further lower the enzyme production cost, a pelB leader sequence was fused to LCCICCG so that the enzyme can be secreted into the medium to facilitate recovery. To help bind the enzyme on the hydrophobic surface of PET, a substrate-binding module in a polyhydroxyalkanoate depolymerase from Alcaligenes faecalis (PBM) was fused to the C-terminus of LCCICCG . The resulting four different LCCICCG variants (LCC, PelB-LCC, LCC-PBM, and PelB-LCC-PBM), together with PETase and MHETase, were compared for PET degradation efficiency. A fed-batch fermentation process was developed to produce the target enzymes up to 1.2 g L-1 . Finally, the best enzyme, PelB-LCC, was selected and used for the efficient degradation of 200 g L-1 recycled PET in a well-controlled, stirred-tank reactor. The results will help develop an economical and scalable biorecycling process toward a circular PET economy.

A review on takeaway packaging waste: Types, ecological impact, and disposal route

Rapid economic growth and urbanization have led to significant changes in the world's consumption patterns. Accelerated urbanization, the spread of the mobile Internet, and the increasing pace of work globally have all contributed to the demand for the food takeaway industry. The rapid development of the takeaway industry inevitably brings convenience to life, and with it comes great environmental pressure from waste packaging materials. While maintaining the convenience of people's lives, further reducing the environmental pollution caused by takeaway packaging materials and promoting the recycling and reuse of takeaway packaging waste need to attract the attention and concern of the whole society. This review systematically and comprehensively introduces common takeaway food types and commonly used packaging materials, analyzes the impacts of discarded takeaway packaging materials on human health and the ecological environment, summarizes the formulation and implementation of relevant policies and regulations, proposes treatment methods and resourceful reuse pathways for discarded takeaway packaging, and also provides an outlook on the development of green takeaway packaging. Currently, only 20% of waste packaging materials are recycled worldwide, and there is still a need to develop more green takeaway packaging materials and continuously improve relevant policies and regulations to promote the sustainable development of the takeaway industry. The review is conducive to further optimizing the takeaway packaging management system, alleviating the environmental pollution problem, and providing feasible solutions and technical guidance for further optimizing takeaway food packaging materials and comprehensive utilization of resources.

Are biodegradable mulch films a sustainable solution to microplastic mulch film pollution? A biogeochemical perspective

Mulch film residue contributes significantly to global plastic pollution, and consequently biodegradable mulch films (BDMs) are being adopted as a solution. BDMs decompose relatively quickly, but their complete biodegradation requires suitable conditions that are difficult to achieve in nature, causing biodegradable microplastics (bio-MPs) to be more likely to accumulate in soil than traditional microplastics (MPs). If BDMs are to be considered as a sustainable solution, long-term and in-depth studies to investigate the impact of bio-MPs on the biogeochemical processes are vital to agroecosystems operation and ecosystem services supply. Although bio-MP-derived carbon can potentially convert into biomass during decomposition, its contribution to soil carbon stocks is insignificant. Instead, given their biodegradability, bio-MPs can result in greater alterations of soil biodiversity and community composition. Their high carbon-nitrogen ratios may also significantly regulate various processes involved in the natural decomposition and transformation of soil organic matter, including the reduction of nutrient availability and increase in greenhouse gas emissions. Soil ecosystems are complex organic entities interconnected by disturbance-feedback mechanisms. Given the prevailing knowledge gaps regarding the impact of bio-MPs on soil biogeochemical cycles and ecosystem balance, this study emphasized the safety and sustainability assessment of bio-MPs and the prevailing comprehensive challenges.

Transcriptomic analysis of oxidative stress mechanisms induced by acute nanoplastic exposure in Sepia esculenta larvae

Nanoplastics (NPs), as a new type of pollutant with a size small than 1 μm, are ubiquitous and harmful to organisms. There has been an increasing amount of research concerning the effects of NPs on organisms over recent years, especially on aquatic animals. However, there is a limited study on the impact of NPs on mollusk cephalopods. In this research, Sepia esculenta, belonging to Cephalopoda, Coleoidea, Sepioidea, was selected to explore the effects caused by NPs exposure. The S. esculenta larvae were exposed to polystyrene NPs (PS-NPs) with diameter 50 nm (100 mg/L) for 4 h. The detection of oxidative stress biomarkers displayed an obvious increase in SOD (superoxide dismutase) activity and MDA (malondialdehyde) level. Then, RNA-Seq was performed to explore the oxidative stress response at mRNA level. The transcriptome analysis demonstrated that the expression of 2,570 genes was affected by PS-NPs. Besides, the signaling pathways of ribosome, ribosome biogenesis in eukaryotes, proteasome, and MAPK were enriched. This study not only provides novel references for understanding the mechanisms of oxidative stress response induced by NPs, but also reminds us to follow with interest the influence of acute exposure to NPs.

Discovery of a polyesterase from Deinococcus maricopensis and comparison to the benchmark LCCICCG suggests high potential for semi-crystalline post-consumer PET degradation

Plastic pollution remains a significant environmental challenge, with conventional waste management strategies proving insufficient in addressing the problem. Enzymatic degradation has emerged as a promising alternative, with LCCICCG, an engineered metagenome-derived cutinase, being the most effective in degrading polyethylene terephthalate (PET), the most commonly produced and discarded polyester. However, more efficient PET-hydrolases are needed for the upscaling of a PET-waste biorefinery. In this regard, the study reports the characterization of a novel, phylogenetically distinct, thermophilic polyesterase from Deinococcus maricopensis (DmPETase) and its comparison to LCCICCG. DmPETase is capable of degrading various synthetic polymers, including PET, polyurethane, as well as four semi-crystalline aliphatic polyesters. DmPETase was found to be comparable to LCCICCG at 50 °C in degrading semi-crystalline sections of post-consumer PET bottles, but it appeared to be less sensitive to crystallinity degree increase. This property makes DmPETase a new template for protein engineering endeavors to create an efficient biocatalyst to be integrated into the bio-recycling process of PET waste, without the need for amorphization of the materials.

Biological Degradation of Plastics and Microplastics: A Recent Perspective on Associated Mechanisms and Influencing Factors

Plastic and microplastic pollution has caused a great deal of ecological problems because of its persistence and potential adverse effects on human health. The degradation of plastics through biological processes is of great significance for ecological health, therefore, the feasibility of plastic degradation by microorganisms has attracted a lot of attention. This study comprises a preliminary discussion on the biodegradation mechanism and the advantages and roles of different bacterial enzymes, such as PET hydrolase and PCL-cutinase, in the degradation of different polymers, such as PET and PCL, respectively. With a particular focus on their modes of action and potential enzymatic mechanisms, this review sums up studies on the biological degradation of plastics and microplastics related to mechanisms and influencing factors, along with their enzymes in enhancing the degradation of synthetic plastics in the process. In addition, biodegradation of plastic is also affected by plastic additives and plasticizers. Plasticizers and additives in the composition of plastics can cause harmful impacts. To further improve the degradation efficiency of polymers, various pretreatments to improve the efficiency of biodegradation, which can cause a significant reduction in toxic plastic pollution, were also preliminarily discussed here. The existing research and data show a large number of microorganisms involved in plastic biodegradation, though their specific mechanisms have not been thoroughly explored yet. Therefore, there is a significant potential for employing various bacterial strains for efficient degradation of plastics to improve human health and safety.

Discovery of plastic-degrading microbial strains isolated from the alpine and Arctic terrestrial plastisphere

Increasing plastic production and the release of some plastic in to the environment highlight the need for circular plastic economy. Microorganisms have a great potential to enable a more sustainable plastic economy by biodegradation and enzymatic recycling of polymers. Temperature is a crucial parameter affecting biodegradation rates, but so far microbial plastic degradation has mostly been studied at temperatures above 20°C. Here, we isolated 34 cold-adapted microbial strains from the plastisphere using plastics buried in alpine and Arctic soils during laboratory incubations as well as plastics collected directly from Arctic terrestrial environments. We tested their ability to degrade, at 15°C, conventional polyethylene (PE) and the biodegradable plastics polyester-polyurethane (PUR; Impranil®); ecovio® and BI-OPL, two commercial plastic films made of polybutylene adipate-co-terephthalate (PBAT) and polylactic acid (PLA); pure PBAT; and pure PLA. Agar clearing tests indicated that 19 strains had the ability to degrade the dispersed PUR. Weight-loss analysis showed degradation of the polyester plastic films ecovio® and BI-OPL by 12 and 5 strains, respectively, whereas no strain was able to break down PE. NMR analysis revealed significant mass reduction of the PBAT and PLA components in the biodegradable plastic films by 8 and 7 strains, respectively. Co-hydrolysis experiments with a polymer-embedded fluorogenic probe revealed the potential of many strains to depolymerize PBAT. Neodevriesia and Lachnellula strains were able to degrade all the tested biodegradable plastic materials, making these strains especially promising for future applications. Further, the composition of the culturing medium strongly affected the microbial plastic degradation, with different strains having different optimal conditions. In our study we discovered many novel microbial taxa with the ability to break down biodegradable plastic films, dispersed PUR, and PBAT, providing a strong foundation to underline the role of biodegradable polymers in a circular plastic economy.

Tailoring the HHx monomer content of P(HB-co-HHx) by flexible substrate compositions: scale-up from deep-well-plates to laboratory bioreactor cultivations

The enhanced material properties exhibited by the microbially synthetized polyhydroxyalkanoate (PHA) copolymer poly(hydroxybutyrate-co-hydroxyhexanoate) [P(HB-co-HHx)] evidence that this naturally biodegrading biopolymer could replace various functionalities of established petrochemical plastics. In fact, the thermal processability, toughness and degradation rate of P(HB-co-HHx) can be tuned by modulating its HHx molar content enabling to manufacture polymers à-la-carte. We have developed a simple batch strategy to precisely control the HHx content of P(HB-co-HHx) to obtain tailor-made PHAs with defined properties. By adjusting the ratio of fructose to canola oil as substrates for the cultivation of recombinant Ralstonia eutropha Re2058/pCB113, the molar fraction of HHx in P(HB-co-HHx) could be adjusted within a range of 2-17 mol% without compromising polymer yields. The chosen strategy proved to be robust from the mL-scale in deep-well-plates to 1-L batch bioreactor cultivations.

Aquatic plastisphere: Interactions between plastics and biofilms

Because of the high production rates, low recycling rates, and poor waste management of plastics, an increasing amount of plastic is entering the aquatic environment, where it can provide new ecological niches for microbial communities and form a so-called plastisphere. Recent studies have focused on the one-way impact of plastic substrata or biofilm communities. However, our understanding of the two-way interactions between plastics and biofilms is still limited. This review first summarizes the formation process and the co-occurrence network analysis of the aquatic plastisphere to comprehensively illustrate the succession pattern of biofilm communities and the potential consistency between keystone taxa and specific environmental behavior of the plastisphere. Furthermore, this review sheds light on mutual interactions between plastics and biofilms. Plastic properties, environmental conditions, and colonization time affect biofilm development. Meanwhile, the biofilm communities, in turn, influence the environmental behaviors of plastics, including transport, contaminant accumulation, and especially the fragmentation and degradation of plastics. Based on a systematic literature review and cross-referencing from these disciplines, the current research focus, and future challenges in exploring aquatic plastisphere development and biofilm-plastic interactions are proposed.

Selective isolation and genomic characterization of biopolymer producer-a novel feature of halophile Brachybacterium paraconglomeratum MTCC 13074

BACKGROUND

Biopolymers like polyhydroxyalkanoates (PHA) are the best natural macromolecules to use as alternative to the synthetic polymers. Many prokaryotes accumulate PHA as cytoplasmic intracellular granules and their accumulation is triggered by starving conditions. The PHAs are ecofriendly and used to create biodegradable plastics. The microbial synthesized PHA had acquired global importance in industrial and biomedical sectors.

RESULTS

Ten different bacterial strains were isolated for the screening of PHA producers from the estuarine region of the Bay of Bengal, Suryalanka in Bapatla. A yellowish slimy circular colony known as M4 is actively growing on selective minimal media and was screened for polymeric granules in its cytoplasm using Sudan Black B and confirmed with the fluorescent dye Nile blue A. All of the isolates were biochemically tested and isolate M4 is the most capable of growing at high NaCl concentrations (3.2 percent) and tests positive for catalase, methyl red. The M4 strain revealed clear hydrolysis of gelatin, starch, and casein. The 16S rRNA sequencing revealed that M4 is 99.72% of identity to Brachybacterium paraconglomeratum LMG 19861(T) in BLAST and the obtained strain was assigned with accession no. MTCC 13074 and deposited in NCBI with accession no. MW899045. The chief cellular fatty acids found in M4 were C14:0, C15:0, C16:0, C18:1cis-9, C18:0, iso-C15: 0, iso-C14: 0, anteiso-C17: 0 and C18:1-7. Crotonic acid formation from M4-PHB extract was detected at 235nm in a UV spectrophotometer. Methanolysis was done, and derivatives of polyhydroxybutyric acid (PHB) in the extract were analyzed using GC-MS. Increasing viscosity was seen in the extracts which confirms the presence of polymer in the extracts. Thermogravimetric analysis was studied to determine the thermal profile of the PHB in the extract of M4.

CONCLUSION

In the study, the selective screening and extraction of ecofriendly PHB from M4 strain was highlighted. Brachybacterium paraconglomeratum is a novel strain showed its uniqueness by producing few monomeric derivatives of PHB. The strain was reporting for the first time as PHA producer. B. paraconglomeratum has promising characteristics according to its metabolic profile. In addition, this study also helps to understand the diversity of bacteria isolated from marine sources.

Effect of Chain Extending Cross-Linkers on the Disintegration Behavior of Composted PBAT/PLA Blown Films

A biodegradable blend of PBAT-poly(butylene adipate-co-terephthalate)-and PLA-poly(lactic acid)-for blown film extrusion was modified with four multi-functional chain extending cross-linkers (CECL). The anisotropic morphology introduced during film blowing affects the degradation processes. Given that two CECL increased the melt flow rate (MFR) of tris(2,4-di-tert-butylphenyl)phosphite (V1) and 1,3-phenylenebisoxazoline (V2) and the other two reduced it (aromatic polycarbodiimide (V3) and poly(4,4-dicyclohexylmethanecarbodiimide) (V4)), their compost (bio-)disintegration behavior was investigated. It was significantly altered with respect to the unmodified reference blend (REF). The disintegration behavior at 30 and 60 °C was investigated by determining changes in mass, Young's moduli, tensile strengths, elongations at break and thermal properties. In order to quantify the disintegration behavior, the hole areas of blown films were evaluated after compost storage at 60 °C to calculate the kinetics of the time dependent degrees of disintegration. The kinetic model of disintegration provides two parameters: initiation time and disintegration time. They quantify the effects of the CECL on the disintegration behavior of the PBAT/PLA compound. Differential scanning calorimetry (DSC) revealed a pronounced annealing effect during storage in compost at 30 °C, as well as the occurrence of an additional step-like increase in the heat flow at 75 °C after storage at 60 °C. The disintegration consists of processes which affect amorphous and crystalline phase of PBAT in different manner that cannot be understood by a hydrolytic chain degradation only. Furthermore, gel permeation chromatography (GPC) revealed molecular degradation only at 60 °C for the REF and V1 after 7 days of compost storage. The observed losses of mass and cross-sectional area seem to be attributed more to mechanical decay than to molecular degradation for the given compost storage times.

Optimization of Whey Protein-Based Films Incorporating Foeniculum vulgare Mill. Essential Oil

Petroleum-based plastics used in food packaging are not biodegradable. They accumulate in the environment in large amounts, causing a decrease in soil fertility, jeopardizing marine habitats, and causing serious problems to human health. Whey protein has been studied for applications in food packaging, either because of its abundant availability or because it confers transparency, flexibility, and good barrier properties to packaging materials. Taking advantage of whey protein to produce new food packaging materials is a clear example of the so-called circular economy. The present work focuses on optimizing the formulation of whey protein concentrate-based films to enhance their general mechanical properties applying the Box-Behnken experimental design. Foeniculum vulgare Mill. (fennel) essential oil (EO) was incorporated into the optimized films, which were then further characterized. The incorporation of fennel EO in the films leads to a significant increase (p < 0.05) in peak elongation (from 14.03 to 31.61%) and tensile index (from 0.40 to 0.50 N.m/g). The optimized whey protein films were yellowish and very transparent (>90%). The results of the bioactive activities of the optimized films showed their ability to be applied as active materials for food packaging to improve the shelf-life of food products and also to prevent foodborne diseases associated with the growth of pathogenic microorganisms.

Characterization of Biodegradable Films Made from Taro Peel (Colocasia esculenta) Starch

Studies of renewable polymers have highlighted starch’s role to replace petroleum-based components to produce biodegradable films with plastic-like qualities. In this study, the novelty of taro peel starch (TPS) to produce such films using the casting technique is reported for the first time. A response surface method (RSM) approach was employed to optimize different concentrations of TPS (2.5−3.5%, w/w) and glycerol (25−35%, w/w) and investigate their effects on the physico-mechanical and water barrier properties of TPS films. TPS films showed a positive linear effect (p < 0.05) for thickness (0.058−0.088 mm), opacity (1.95−2.67), water vapor permeability (0.06−0.09 g∙m/m2∙kPa∙h), and cubic effect (p < 0.05) for moisture content (0.58−1.57%), which were linked to high starch concentrations when plasticized with glycerol. X-ray diffraction analysis of TPS films depicted “amorphous”-type crystalline structure peaks at 19.88°, while the thermogravimetric analysis of the film samples exhibited 75−80% of the weight loss of TPS film in the second phase between temperatures of 300 °C to 400 °C. All films exhibited homogenous, transparent surfaces with flexibility, and completely degraded in 5 days in simulated river water and composting soil environments, which confirmed TPS as a promising film polymer in food packaging.

A systematic review on plastic waste conversion for a circular economy: recent trends and emerging technologies

Our biosphere has been adversely affected by plastic waste pollution, especially non-biodegradables in landfills, which induces hazardous chemical leaching and toxic gas emissions on burning into the atmosphere.

Environmental impact assessment of plastic waste during the outbreak of COVID-19 and integrated strategies for its control and mitigation

During the COVID-19 pandemic, many positive shifts have been observed in the ecosystem, with a significant decrease in the greenhouse gas emissions and air pollution. On the other hand, there were unavoidable negative shifts due to a surge in demand for plastic products such as food and groceries' delivery packaging, single-use plastics, medical and personal protective equipment to prevent transmission of COVID-19. Plastic pollution can be considered as a key environmental issue in world due to the huge footprints of plastics on natural ecosystems and public health. Herein, we presented an overview on the rise of plastic pollution during the COVID-19 pandemic. The potential sources of plastic waste during COVID-19 with its negative effects on the environment such as marine ecosystems and the global economics are highlighted. We also suggested some strategies and recommendations to tackle plastic leakages by applying feedstock recycling, sterilization, and with the use of biodegradable plastics that have become a sustainable alternative to fossil fuel plastics. Also, the importance of elevating public awareness and some recommendations to mitigate plastic generated during the pandemic has been addressed as well.

Novel Production Methods of Polyhydroxyalkanoates and Their Innovative Uses in Biomedicine and Industry

Polyhydroxyalkanoate (PHA), a biodegradable polymer obtained from microorganisms and plants, have been widely used in biomedical applications and devices, such as sutures, cardiac valves, bone scaffold, and drug delivery of compounds with pharmaceutical interests, as well as in food packaging. This review focuses on the use of polyhydroxyalkanoates beyond the most common uses, aiming to inform about the potential uses of the biopolymer as a biosensor, cosmetics, drug delivery, flame retardancy, and electrospinning, among other interesting uses. The novel applications are based on the production and composition of the polymer, which can be modified by genetic engineering, a semi-synthetic approach, by changing feeding carbon sources and/or supplement addition, among others. The future of PHA is promising, and despite its production costs being higher than petroleum-based plastics, tools given by synthetic biology, bioinformatics, and machine learning, among others, have allowed for great production yields, monomer and polymer functionalization, stability, and versatility, a key feature to increase the uses of this interesting family of polymers.

Petroleum-based and biodegradable microplastics alter tissue structure and fecundity in the eastern mudsnail (Ilyanassa obsoleta)

Microplastics are hazardous to aquatic life. Most experiments focus on the effects of a single type of microbead, while in the environment, organisms are exposed to irregularly shaped fragments belonging to several chemical groups. The effects of biodegradable plastics are unknown. We tested the effects of mixed-source (MS) petroleum-based and biodegradable (polylactic acid, PLA) microplastics on the intertidal eastern mudsnail, Ilyanassa obsoleta (Say, 1822), a benthic grazer. MS plastics were collected from local coastal areas (polystyrene, polyethylene, polypropylene, polyvinyl chloride and polyethylene terephthalate, combined) and were tested at three exposures, including one similar to concentrations found locally (2250 particles/kg sediment). Plastics were milled to be similar in size to the biofilm–sediment mix provided to the snails as food (32.94 µm2 for sediment, 137.99 µm2 for MS, and 31.16 µm2 for PLA). Locally relevant exposures of MS microplastics disrupted digestive gland histology, while extreme exposures additionally increased the number of hemocytes and reduced fecundity. Effects of PLA were similar to those of MS microplastics, at the extreme exposure tested here. These results indicate that both petroleum-based and biodegradable microplastics disrupt the structure of the digestive gland and that environmentally relevant exposures induce “hidden” tissue-level changes that are invisible without specialized techniques.

Recovery of value-added products from biowaste: A review

This review provides an update on the state-of-the art technologies for the valorization of solid waste and its mechanism to generate various bio-products. The organic content of these wastes can be easily utilized by the microbes and produce value-added compounds. Microbial fermentation techniques can be utilized for developing waste biorefinery processes. The utilization of lignocellulosic and plastics wastes for the generation of carbon sources for microbial utilization after pre-processing steps will make the process a multi-product biorefinery. The C1 and C2 gases generated from different industries could also be utilized by various microbes, and this will help to control global warming. The review seeks to expand expertise about the potential application through several perspectives, factors influencing remediation, issues, and prospects.

A polyesterase from the Antarctic bacterium Moraxella sp. degrades highly crystalline synthetic polymers

The uncontrolled release of plastics in the environment has rendered them ubiquitous around the planet, threatening the wildlife and human health. Biodegradation and valorization of plastics has emerged as an eco-friendly alternative to conventional management techniques. Discovery of novel polymer-degrading enzymes with diversified properties is hence an important task in order to explore different operational conditions for plastic-waste upcycling. In the present study, a barely studied psychrophilic enzyme (MoPE) from the Antractic bacterium Moraxella sp. was heterologously expressed, characterized and its potential in polymer degradation was further investigated. Based on its amino acid composition and structure, MoPE resembled PET-degrading enzymes, sharing features from both mesophilic and thermophilic homologues. MoPE hydrolyzes non-biodegradable plastics, such as polyethylene terephthalate and polyurethane, as well as biodegradable synthetic polyesters, such as polycaprolactone, polyhydroxy butyrate, polybutylene succinate and polylactic acid. The mass fraction crystallinity of the aliphatic polymers tested ranged from 11% to 64% highlighting the potential of the enzyme to hydrolyze highly crystalline plastics. MoPE was able to degrade different types of amorphous and semi-crystalline PET, releasing water-soluble monomers and showed synergy with a feruloyl esterase of the tannase family for the release of terephthalic acid. Based on the above, MoPE was characterized as a versatile psychrophilic polyesterase demonstrating a broad-range plastics degradation potential.

Quantitative and sensitive analysis of polystyrene nanoplastics down to 50 nm by surface-enhanced Raman spectroscopy in water

Despite being an emerging risk to the environment and human health, little is known about the occurrence, formation, transport, and environmental impact of nanoplastics owing to the lack of quantitative and sensitive sensing techniques. Herein, a surface-enhanced Raman spectroscopy (SERS) method was developed for quantitative sensitive nanoplastics analysis, in which KI was added to Ag nanoparticles as a coagulant and cleaner to remove surface impurities. Polystyrene (PS) nanoplastics with four sizes (50, 100, 200, and 500 nm) were used to evaluate the proposed method, which exhibited high sensitivity (detection limit of 6.25 μg/mL for 100 nm PS nanoplastics), interference resistance, good repeatability, and quantitative analysis ability (R² > 0.970). The feasibility of extending the proposed method to real-world water samples was verified using spiked lake water, and satisfactory recovery rates (87.5-110%) were obtained for nanoplastics with different sizes and concentrations. Thus, this study serves as a solid step in the quantitative analysis of nanoplastics, and the findings can be applied to other areas of research on nanoplastics.

Recent Advances in Biological Recycling of Polyethylene Terephthalate (PET) Plastic Wastes

Polyethylene terephthalate (PET) is one of the most commonly used polyester plastics worldwide but is extremely difficult to be hydrolyzed in a natural environment. PET plastic is an inexpensive, lightweight, and durable material, which can readily be molded into an assortment of products that are used in a broad range of applications. Most PET is used for single-use packaging materials, such as disposable consumer items and packaging. Although PET plastics are a valuable resource in many aspects, the proliferation of plastic products in the last several decades have resulted in a negative environmental footprint. The long-term risk of released PET waste in the environment poses a serious threat to ecosystems, food safety, and even human health in modern society. Recycling is one of the most important actions currently available to reduce these impacts. Current clean-up strategies have attempted to alleviate the adverse impacts of PET pollution but are unable to compete with the increasing quantities of PET waste exposed to the environment. In this review paper, current PET recycling methods to improve life cycle and waste management are discussed, which can be further implemented to reduce plastics pollution and its impacts on health and environment. Compared with conventional mechanical and chemical recycling processes, the biotechnological recycling of PET involves enzymatic degradation of the waste PET and the followed bioconversion of degraded PET monomers into value-added chemicals. This approach creates a circular PET economy by recycling waste PET or upcycling it into more valuable products with minimal environmental footprint.