Biodegradation of bioplastics in natural environments

Compounding one problem with another? A look at biodegradable microplastics

Environmental concerns about microplastics (MPs) have motivated research of their sources, occurrence, and fate in aquatic and soil ecosystems. To mitigate the environmental impact of MPs, biodegradable plastics are designed to naturally decompose, thus reducing the amount of environmental plastic contamination. However, the environmental fate of biodegradable plastics and the products of their incomplete biodegradation, especially micro-biodegradable plastics (MBPs), remains largely unexplored. This comprehensive review aims to assess the risks of unintended consequences associated with the introduction of biodegradable plastics into the environment, namely, whether the incomplete mineralization of biodegradable plastics could enhance the risk of MBPs formation and thus, exacerbate the problem of their environmental dispersion, representing a potentially additional environmental hazard due to their presumed ecotoxicity. Initial evidence points towards the potential for incomplete mineralization of biodegradable plastics under both controlled and uncontrolled conditions. Rapid degradation of PLA in thermophilic industrial composting contrasts with the degradation below 50 % of other biodegradables, suggesting MBPs released into the environment through compost. Moreover, degradation rates of <60 % in anaerobic digestion for polymers other than PLA and PHAs suggest a heightened risk of MBPs in digestate, risking their spread into soil and water. This could increase MBPs and adsorbed pollutants' mobilization. The exact behavior and impacts of additive leachates from faster-degrading plastics remain largely unknown. Thus, assessing the environmental fate and impacts of MBPs-laden by-products like compost or digestate is crucial. Moreover, the ecotoxicological consequences of shifting from conventional plastics to biodegradable ones are highly uncertain, as there is insufficient evidence to claim that MBPs have a milder effect on ecosystem health. Indeed, literature shows that the impact may be worse depending on the exposed species, polymer type, and the ecosystem complexity.

Degradation efficiency of biodegradable plastics in subtropical open-air and marine environments: Implications for plastic pollution

Bioplastics are increasingly used as a solution to tackle plastic pollution problems. However, their degradability in natural environments is currently under debate. To evaluate their degradation efficiencies, we conducted in-situ degradation experiments in an open-air and two marine environments in Hong Kong. Three groups of biodegradable plastic were tested, namely (1) additive-modified low-density polyethylene (LDPE), labelled as oxo-biodegradable or photodegradable plastics, (2) polylactic acid (PLA), and (3) polyvinyl alcohol (PVA)/starch blends. Most biodegradable plastics fail to completely degrade but remain visually present after six months of exposure. Only PLA is able to demonstrate 100 % disintegration in one to three months in marine settings, suggesting that subtropical marine environments may favor PLA degradation. Biodegradable plastics that are bio-based (PLA and PVA/Starch blends) show notably larger mass losses by 23-100 % than the fossil-based ones (modified-LDPE). Our results reveal higher degradation efficiencies of PLA and PVA/Cassava starch blend in marine than open-air settings (with mass losses larger by 50 %, and by 39-41 %, respectively), potentially via biodegradation and hydrolysis. Meanwhile, modified-LDPE and PVA/Corn starch blends in general show higher degradation efficiencies in open-air than marine settings (with mass losses larger by 2 %, and by 17-33 %, respectively), potentially via abiotic oxidation. Since all tested biodegradable plastics exhibit potential fragmentation signs, further investigation is needed to characterize the behaviours of the microplastics generated. The current labelling on biodegradable bags fails to provide comprehensive information regarding their actual environmental degradation behaviours, especially considering their fragmentation risk and limited degradation exhibited in this study. This highlights the imperative for improved messaging to ensure consumers are better informed about these products.

Microplastics from petroleum-based plastics and their effects: A systematic literature review and science mapping of global bioplastics production

The use of bioplastics is a new strategy for reducing microplastic (MP) waste caused by petroleum-based plastics. This problem has received increased attention worldwide, leading to the development of large-scale bioplastic plants. The large amount of MPs in aquatic and terrestrial environments and the atmosphere has raised global concern. This article delves into the profound environmental impact of the increasing use of petroleum-based plastics, which contribute significantly to plastic waste and, as a consequence, to the increase in MPs. We conducted a comprehensive analysis to identify countries that are at the forefront of efforts to produce bioplastics to reduce MP pollution. In this article, we explain the development, degradation processes, and research trends of bioplastics derived from biological materials such as starch, chitin, chitosan, and polylactic acid (PLA). The findings pinpoint the top 10 countries demonstrating a strong commitment to reducing MP pollution through bioplastics. These nations included the United States, China, Spain, Canada, Italy, India, the United Kingdom, Malaysia, Belgium, and the Netherlands. This study underscores the technical and economic obstacles to large-scale bioplastic production. Integr Environ Assess Manag 2024;00:1-20. © 2024 SETAC.

A progress update on the biological effects of biodegradable microplastics on soil and ocean environment: A perfect substitute or new threat?

Conventional plastics are inherently difficult to degrade, causing serious plastic pollution. With the development of society, biodegradable plastics (BPs) are considered as an alternative to traditional plastics. However, current research indicated that BPs do not undergo complete degradation in natural environments. Instead, they may convert into biodegradable microplastics (BMPs) at an accelerated rate, thereby posing a significant threat to environment. In this paper, the definition, application, distribution, degradation behaviors, bioaccumulation and biomagnification of BPs were reviewed. And the impacts of BMPs on soil and marine ecosystems, in terms of physicochemical property, nutrient cycling, microorganisms, plants and animals were comprehensively summarized. The effects of combined exposure of BMPs with other pollutants, and the mechanism of ecotoxicity induced by BMPs were also addressed. It was found that BMPs reduced pH, increased DOC content, and disrupted the nitrification of nitrogen cycle in soil ecosystem. The shoot dry weight, pod number and root growth of soil plants, and reproduction and body length of soil animals were inhibited by BMPs. Furthermore, the growth of marine plants, and locomotion, body length and survival of marine animals were suppressed by BMPs. Additionally, the ecotoxicity of combined exposure of BMPs with other pollutants has not been uniformly concluded. Exposure to BMPs induced several types of toxicity, including neurotoxicity, gastrointestinal toxicity, reproductive toxicity, immunotoxicity and genotoxicity. The future calls for heightened attention towards the regulation of the degradation of BPs in the environment, and pursuit of interventions aimed at mitigating their ecotoxicity and potential health risks to human.

Toward a Circular Bioeconomy: Designing Microbes and Polymers for Biodegradation

Polymer production is rapidly increasing, but there are no large-scale technologies available to effectively mitigate the massive accumulation of these recalcitrant materials. One potential solution is the development of a carbon-neutral polymer life cycle, where microorganisms convert plant biomass to chemicals, which are used to synthesize biodegradable materials that ultimately contribute to the growth of new plants. Realizing a circular carbon life cycle requires the integration of knowledge across microbiology, bioengineering, materials science, and organic chemistry, which itself has hindered large-scale industrial advances. This review addresses the biodegradation status of common synthetic polymers, identifying novel microbes and enzymes capable of metabolizing these recalcitrant materials and engineering approaches to enhance their biodegradation pathways. Design considerations for the next generation of biodegradable polymers are also reviewed, and finally, opportunities to apply findings from lignocellulosic biodegradation to the design and biodegradation of similarly recalcitrant synthetic polymers are discussed.

Environmental impact of microplastics and potential health hazards

Microscopic plastic (microplastic) pollutants threaten the earth's biodiversity and ecosystems. As a result of the progressive fragmentation of oversized plastic containers and products or manufacturing in small sizes, microplastics (particles of a diameter of 5 mm with no lower limit) are used in medicines, personal care products, and industry. The incidence of microplastics is found everywhere in the air, marine waters, land, and even food that humans and animals consume. One of the greatest concerns is the permanent damage that is created by plastic waste to our fragile ecosystem. The impossibility of the complete removal of all microplastic contamination from the oceans is one of the principal tasks of our governing body, research scientists, and individuals. Implementing the necessary measures to reduce the levels of plastic consumption is the only way to protect our environment. Cutting off the plastic flow is the key remedy to reducing waste and pollution, and such an approach could show immense significance. This review offers a comprehensive exploration of the various aspects of microplastics, encompassing their composition, types, properties, origins, health risks, and environmental impacts. Furthermore, it delves into strategies for comprehending the dynamics of microplastics within oceanic ecosystems, with a focus on averting their integration into every tier of the food chain.

Improving the behavior of thermoplastic starch with the addition of gum Arabic: Antibacterial, mechanical properties and biodegradability

The incorporation of different amounts of Gum Arabic (GA) in thermoplastic starch (TPS) obtained by extrusion and subsequent thermocompression has been studied. The sheets have been characterized by means of XRD, FTIR, TGA, moisture content, SEM, mechanical properties, antimicrobial activity and biodegradability via composting. The FTIR analysis of the sheets shows the presence of ester groups, while the TGA shows the presence of new processes and a residue much higher than expected is obtained. No changes in crystallinity are observed by XRD. The inclusion of GA confers antimicrobial properties to thermoplastic starch against the Gram + and Gram - bacteria studied even at the smaller concentrations. For a low GA content (0.5 and 1 g GA/100 g TPS) a homogeneous material is observed by SEM, as well as an important increase in tensile strength, modulus and deformation at break, which are very interesting properties facing the applicability of this material in single use plastics which are in contact with food or other consumable goods. At higher contents of GA, hollows and cracks appear in the material, compromising the mechanical properties. In all cases, the inclusion of GA delays the biodegradation process in soil, which can be related to its antibacterial capacity and especially in case of GA concentrations of 2 and 5 g/100 g of TPS with lower humidity of these TPS sheets.

Marine degradation and ecotoxicity of conventional, recycled and compostable plastic bags

Plastic bags are currently a major component of marine litter, causing aesthetical nuisance, and undesirable effects on marine fauna that ingest them or are entangled. Plastic litter also rises concern on the ecotoxicological effects due to the potential toxicity of the chemical additives leached in aquatic environments. Conventional plastic bags are made of polyethylene, either from first use or recycled, but regulations restricting single-use plastics and limiting lightweight carrier bags (<50 μm thickness) have fostered the replacement of thin PE bags by compostable materials advertised as safer for the environment. In this study, we assess the degradation of commercially available plastic bags in marine conditions at two scales: aquariums (60 days) and outdoors flow-through mesocosm (120 days). Strength at break point and other tensile strength parameters were used as ecologically relevant endpoints to track mechanical degradation. Ecotoxicity has been assessed along the incubation period using the sensitive Paracentrotus lividus embryo test. Whereas PE bags did not substantially lose their mechanical properties within the 60 d aquarium exposures, compostable bags showed remarkable weight loss and tensile strength decay, some of them fragmenting in the aquarium after 3-4 weeks. Sediment pore water inoculum promoted a more rapid degradation of compostable bags, while nutrient addition pattern did not affect the degradation rate. Longer-term mesocosms exposures supported these findings, as well as pointed out the influence of the microbial processes on the degradation efficiency of compostable/bioplastic bags. Compostable materials, in contrast toPE, showed moderate toxicity on sea-urchin larvae, partially associated to degradation of these materials, but the environmental implications of these findings remain to be assessed. These methods proved to be useful to classify plastic materials, according to their degradability in marine conditions, in a remarkably shorter time than current standard tests and promote new materials safer for the marine fauna.

Ecotoxicological evaluation of chitosan biopolymer films particles in adult zebrafish (Danio rerio): A comparative study with polystyrene microplastics

To mitigate the environmental impact of microplastics (MPs), the scientific community has innovated sustainable and biodegradable polymers as viable alternatives to traditional plastics. Chitosan, the deacetylated form of chitin, stands as one of the most thoroughly investigated biopolymers and has garnered significant interest due to its versatile applications in both medical and cosmetic fields. Nevertheless, there is still a knowledge gap regarding the impact that chitosan biopolymer films (CBPF) may generate in aquatic organisms. In light of the foregoing, this study aimed to assess and compare the potential effects of CBPF on the gastrointestinal tract, gills, brain, and liver of Danio rerio against those induced by MPs. The findings revealed that both CBPF and MPs induced changes in the levels of oxidative stress biomarkers across all organs. However, it is essential to note that our star plots illustrate a tendency for CBPF to activate antioxidant enzymes and for MPs to produce oxidative damage. Regarding gene expression, our findings indicate that MPs led to an up-regulation in the expression of genes associated with apoptotic response (p53, casp3, cas9, bax, and bcl2) in all fish organs. Meanwhile, CBPF produced the same effect in genes related to antioxidant response (nrf1 and nrf2). Overall, our histological observations substantiated these effects, revealing the presence of plastic particles and tissue alterations in the gills and gastrointestinal tract of fish subjected to MPs. From these results, it can be concluded that CBPF does not represent a risk to fish after long exposure.

Characterization of Ralstonia insidiosa C1 isolated from Alpine regions: Capability in polyhydroxyalkanoates degradation and production

This study ventures into the exploration of potential poly-3-hydroxybutyrate (PHB) degradation in alpine environments. PHB-degrading bacteria were identified in both campus soil, representing a residential area, and Mt. Kurodake soil, an alpine region in Hokkaido, Japan. Next-generation sequencing analysis indicated that the campus soil exhibited higher microbial diversity, while Ralstonia insidiosa C1, isolated from Mt. Kurodake soil, displayed the highest proficiency in PHB degradation. R. insidiosa C1 efficiently degraded up to 3% (w/v) of PHB and various films composed of other biopolymers at 14 °C. This bacterium synthesized homopolymers using substrates such as 3-hydroxybutyric acid, sugars, and acetic acid, while also produced copolymers using a mixture of fatty acids. The analysis results confirmed that the biopolymer synthesized by strain C1 using glucose was PHB, with physical properties comparable to commercial products. The unique capabilities of R. insidiosa C1, encompassing both the production and degradation of bioplastics, highlight its potential to establish a novel material circulation model.

Soil Microplastic Pollution and Microbial Breeding Techniques for Green Degradation: A Review

Microplastics (MPs), found in many places around the world, are thought to be more detrimental than other forms of plastics. At present, physical, chemical, and biological methods are being used to break down MPs. Compared with physical and chemical methods, biodegradation methods have been extensively studied by scholars because of their advantages of greenness and sustainability. There have been numerous reports in recent years summarizing the microorganisms capable of degrading MPs. However, there is a noticeable absence of a systematic summary on the technology for breeding strains that can degrade MPs. This paper summarizes the strain-breeding technology of MP-degrading strains for the first time in a systematic way, which provides a new idea for the breeding of efficient MP-degrading strains. Meanwhile, potential techniques for breeding bacteria that can degrade MPs are proposed, providing a new direction for selecting and breeding MP-degrading bacteria in the future. In addition, this paper reviews the sources and pollution status of soil MPs, discusses the current challenges related to the biodegradation of MPs, and emphasizes the safety of MP biodegradation.

Myco-remediation of plastic pollution: current knowledge and future prospects

To date, enumerable fungi have been reported to participate in the biodegradation of several notorious plastic materials following their isolation from soil of plastic-dumping sites, marine water, waste of mulch films, landfills, plant parts and gut of wax moth. The general mechanism begins with formation of hydrophobin and biofilm proceding to secretion of specific plastic degarding enzymes (peroxidase, hydrolase, protease and urease), penetration of three dimensional substrates and mineralization of plastic polymers into harmless products. As a result, several synthetic polymers including polyethylene, polystyrene, polypropylene, polyvinyl chloride, polyurethane and/or bio-degradable plastics have been validated to deteriorate within months through the action of a wide variety of fungal strains predominantly Ascomycota (Alternaria, Aspergillus, Cladosporium, Fusarium, Penicillium spp.). Understanding the potential and mode of operation of these organisms is thus of prime importance inspiring us to furnish an up to date view on all the presently known fungal strains claimed to mitigate the plastic waste problem. Future research henceforth needs to be directed towards metagenomic approach to distinguish polymer degrading microbial diversity followed by bio-augmentation to build fascinating future of waste disposal.

Room Temperature Phosphorescence from Natural, Organic Emitters and Their Application in Industrially Compostable Programmable Luminescent Tags

Organic semiconductors provide the potential of biodegradable technologies, but prototypes do only rarely exist. Transparent, ultrathin programmable luminescent tags (PLTs) are presented for minimalistic yet efficient information storage that are fully made from biodegradable or at least industrially compostable, ready-to-use materials (bioPLTs). As natural emitters, the quinoline alkaloids show sufficient room temperature phosphorescence when being embedded in polymer matrices with cinchonine exhibiting superior performance. Polylactic acid provides a solution for both the matrix material and the flexible substrate. Room temperature phosphorescence can be locally controlled by the oxygen concentration in the film by using Exceval as additional oxygen blocking layers. These bioPLTs exhibit all function-defining characteristics also found in their regular nonenvironmentally degradable analogs and, additionally, provide a simplified, high-contrast readout under continuous-wave illumination as a consequence of the unique luminescence properties of the natural emitter cinchonine. Limitations for flexible devices arise from limited thermal stability of the polylactic acid foil used as substrate allowing only for one writing cycle and preventing an annealing step during fabrication. Few-cycle reprogramming is possible when using the architecture of the bioPLTs on regular quartz substrates. This work realizes the versatile platform of PLTs with less harmful materials offering more sustainable use in future.

Genetic Modifications in Bacteria for the Degradation of Synthetic Polymers: A Review

Synthetic polymers, commonly known as plastics, are currently present in all aspects of our lives. Although they are useful, they present the problem of what to do with them after their lifespan. There are currently mechanical and chemical methods to treat plastics, but these are methods that, among other disadvantages, can be expensive in terms of energy or produce polluting gases. A more environmentally friendly alternative is recycling, although this practice is not widespread. Based on the practice of the so-called circular economy, many studies are focused on the biodegradation of these polymers by enzymes. Using enzymes is a harmless method that can also generate substances with high added value. Novel and enhanced plastic-degrading enzymes have been obtained by modifying the amino acid sequence of existing ones, especially on their active site, using a wide variety of genetic approaches. Currently, many studies focus on the common aim of achieving strains with greater hydrolytic activity toward a different range of plastic polymers. Although in most cases the depolymerization rate is improved, more research is required to develop effective biodegradation strategies for plastic recycling or upcycling. This review focuses on a compilation and discussion of the most important research outcomes carried out on microbial biotechnology to degrade and recycle plastics.

Sustainable struggling: decoding microplastic released from bioplastics-a critical review

This comprehensive review delves into the complex issue of plastic pollution, focusing on the emergence of biodegradable plastics (BDPs) as a potential alternative to traditional plastics. While BDPs seem promising, recent findings reveal that a large number of BDPs do not fully degrade in certain natural conditions, and they often break down into microplastics (MPs) even faster than conventional plastics. Surprisingly, research suggests that biodegradable microplastics (BDMPs) could have more significant and long-lasting effects than petroleum-based MPs in certain environments. Thus, it is crucial to carefully assess the ecological consequences of BDPs before widely adopting them commercially. This review thoroughly examines the formation of MPs from prominent BDPs, their impacts on the environment, and adsorption capacities. Additionally, it explores how BDMPs affect different species, such as plants and animals within a particular ecosystem. Overall, these discussions highlight potential ecological threats posed by BDMPs and emphasize the need for further scientific investigation before considering BDPs as a perfect solution to plastic pollution.

Enzymatic Synthesis and Structural Modeling of Bio-Based Oligoesters as an Approach for the Fast Screening of Marine Biodegradation and Ecotoxicity

Given the widespread use of esters and polyesters in products like cosmetics, fishing nets, lubricants and adhesives, whose specific application(s) may cause their dispersion in open environments, there is a critical need for stringent eco-design criteria based on biodegradability and ecotoxicity evidence. Our approach integrates experimental and computational methods based on short oligomers, offering a screening tool for the rapid identification of sustainable monomers and oligomers, with a special focus on bio-based alternates. We provide insights into the relationships between the chemical structure and properties of bio-based oligomers in terms of biodegradability in marine environments and toxicity in benchmark organisms. The experimental results reveal that the considered aromatic monomers (terephthalic acid and 2,5-furandicarboxylic acid) accumulate under the tested conditions (OECD 306), although some slight biodegradation is observable when the inoculum derives from sites affected by industrial and urban pollution, which suggests that ecosystems adapt to non-natural chemical pollutants. While clean seas are more susceptible to toxic chemical buildup, biotic catalytic activities offer promise for plastic pollution mitigation. Without prejudice to the fact that biodegradability inherently signifies a desirable trait in plastic products, nor that it automatically grants them a sustainable "license", this study is intended to facilitate the rational design of new polymers and materials on the basis of specific uses and applications.

Effects of poly(3-hydroxybutyrate) [P(3HB)] coating on the bacterial communities of artificial structures

The expanding urbanization of coastal areas has led to increased ocean sprawl, which has had both physical and chemical adverse effects on marine and coastal ecosystems. To maintain the health and functionality of these ecosystems, it is imperative to develop effective solutions. One such solution involves the use of biodegradable polymers as bioactive coatings to enhance the bioreceptivity of marine and coastal infrastructures. Our study aimed to explore two main objectives: (1) investigate PHA-degrading bacteria on polymer-coated surfaces and in surrounding seawater, and (2) comparing biofilm colonization between surfaces with and without the polymer coating. We applied poly(3-hydroxybutyrate) [P(3HB)) coatings on concrete surfaces at concentrations of 1% and 6% w/v, with varying numbers of coating cycles (1, 3, and 6). Our findings revealed that the addition of P(3HB) indeed promoted accelerated biofilm growth on the coated surfaces, resulting in an occupied area approximately 50% to 100% larger than that observed in the negative control. This indicates a remarkable enhancement, with the biofilm expanding at a rate roughly 1.5 to 2 times faster than the untreated surfaces. We observed noteworthy distinctions in biofilm growth patterns based on varying concentration and number of coating cycles. Interestingly, treatments with low concentration and high coating cycles exhibited comparable biofilm enhancements to those with high concentrations and low coating cycles. Further investigation into the bacterial communities responsible for the degradation of P(3HB) coatings identified mostly common and widespread strains but found no relation between the concentration and coating cycles. Nevertheless, this microbial degradation process was found to be highly efficient, manifesting noticeable effects within a single month. While these initial findings are promising, it's essential to conduct tests under natural conditions to validate the applicability of this approach. Nonetheless, our study represents a novel and bio-based ecological engineering strategy for enhancing the bioreceptivity of marine and coastal structures.

Exploring the substrate spectrum of phylogenetically distinct bacterial polyesterases

The rapid escalation of plastic waste accumulation presents a significant threat of the modern world, demanding an immediate solution. Over the last years, utilization of the enzymatic machinery of various microorganisms has emerged as an environmentally friendly asset in tackling this pressing global challenge. Thus, various hydrolases have been demonstrated to effectively degrade polyesters. Plastic waste streams often consist of a variety of different polyesters, as impurities, mainly due to wrong disposal practices, rendering recycling process challenging. The elucidation of the selective degradation of polyesters by hydrolases could offer a proper solution to this problem, enhancing the recyclability performance. Towards this, our study focused on the investigation of four bacterial polyesterases, including DaPUase, IsPETase, PfPHOase, and Se1JFR, a novel PETase-like lipase. The enzymes, which were biochemically characterized and structurally analyzed, demonstrated degradation ability of synthetic plastics. While a consistent pattern of polyesters' degradation was observed across all enzymes, Se1JFR stood out in the degradation of PBS, PLA, and polyether PU. Additionally, it exhibited comparable results to IsPETase, a benchmark mesophilic PETase, in the degradation of PCL and semi-crystalline PET. Our results point out the wide substrate spectrum of bacterial hydrolases and underscore the significant potential of PETase-like enzymes in polyesters degradation.

Fungal biodegradation of poly(butylene adipate-co-terephthalate)-polylactic acid-thermoplastic starch based commercial bio-plastic film at ambient conditions

Microbial biodegradation of commercially available poly(butylene adipate-co-terephthalate)-polylactic acid-thermoplastic starch based bio-plastic has been pursued at high temperatures exceeding 55 °C. Herein, we first reported three newly isolated fungal strains from farmland soil samples of Republic of Korea namely, Pyrenochaetopsis sp. strain K2, Staphylotrichum sp. S2-1, and Humicola sp. strain S2-3 were capable of degrading a commercial bio-plastic film with degradation rates of 9.5, 8.6, and 12.2%, respectively after 3 months incubation at ambient conditions. Scanning electron microscopy (SEM) analyses showed that bio-plastic film was extensively fragmented with severe cracking on the surface structure after incubation with isolated fungal strains. X-ray diffraction (XRD) analysis also revealed that high crystallinity of the commercial bio-plastic film was significantly decreased after degradation by fungal strains. Liquid chromatography-mass spectrometry (LC-MS) analyses of the fungal culture supernatants containing the bio-plastic film showed the peaks for adipic acid, terephthalic acid (TPA), and terephthalate-butylene (TB) as major metabolites, suggesting cleavage of ester bonds and accumulation of TPA. Furthermore, a consortium of fungal strain K2 with TPA degrading bacterium Pigmentiphaga sp. strain P3-2 isolated from the same sampling site exhibited faster degradation rate of the bio-plastic film within 1 month of incubation with achieving complete biodegradation of accumulated TPA. We assume that the extracellular lipase activity presented in the fungal cultures could hydrolyze the ester bonds of PBAT component of bio-plastic film. Taken together, the fungal and bacterial consortium investigated herein could be beneficial for efficient biodegradation of the commercial bio-plastic film at ambient conditions.

Soil burial-induced degradation of cellulose films in a moisture-controlled environment

In this study, the biodegradability of cellulose films was evaluated in controlled-moisture soil environments. The films were prepared from low-quality cotton fibers through dissolution in DMAc/LiCl, casting, regeneration, glycerol plasticization, and hot-pressing. Two soil burial degradation experiments were conducted in August 2020 (11th August to 13th October) and March 2021 (24th March to 24th July) under controlled moisture conditions to assess the biodegradation behavior of cellulose films. The films were retrieved from soil beds at seven-day intervals, and morphological and physicochemical changes in the films were investigated. The results indicated that the cellulose films exhibited gradual changes starting on Day 7 and major changes after Day 35. Stereomicroscopy images showed the growth and development of fungal mycelia on the surface of the films, and FTIR spectroscopy confirmed the presence of biomolecules originating from microorganisms. The tensile strength and elongation of cellulose films were significantly reduced by 64% and 96% in the first experiment and by 40% and 94% in the second experiment, respectively, during the degradation period. Degradation also significantly impacted the thermal stability (14% and 16.5% reduction, respectively, in the first and second studies) of the films. The cellulose-based films completely degraded within 63 days in late summer and 112 days in spring. This study demonstrates that, unlike synthetic plastics, films prepared from low-quality cotton fibers can easily degrade in the natural environment.

Deterioration of single-use biodegradable plastics in high-humidity air and freshwaters over one year: Significant disparities in surface physicochemical characteristics and degradation rates

More single-use plastics are accumulating in the environment, and likewise biodegradable plastics (BPs), which are being vigorously promoted, cannot escape the fate. Currently, studies on the actual degradation of BPs in open-air and freshwaters are underrepresented despite they are potentially headmost leakage and contamination sites for disposable BPs. Herein, we compared the degradation behavior of six BP materials and non-degradable polypropylene (PP) plastics over a 1-year in situ suspension in the high-humidity air, a eutrophic river, and an oligotrophic lake. Moreover, a 3-months laboratory incubation was performed to detect the release of dissolved organic carbon (DOC) from BPs. In both air and freshwaters, poly(p-dioxanone) (PPDO) degraded significantly while PP and polylactic acid (PLA) showed no signs of degradation. The average degradation rates of three poly(butylene adipate-co-terephthalate) (PBAT)-based films varied: 100% in river, 55% in lake, and 10% in air. In addition to PLA, surface chemical groups, hydrophilicity, and thermal stability of BPs changed, and microplastics were found on their surfaces. Correspondingly, BPs with faster degradation rates released relatively higher amounts of DOC. Environmental microbial and chemical characteristics may contribute to differences in BP degradation besides polymer specificity. Altogether, our results indicate the need for appropriate monitoring of BPs.

Sustainable degradation of synthetic plastics: A solution to rising environmental concerns

Plastics have a significant role in various sectors of the global economy since they are widely utilized in agriculture, architecture, and construction, as well as health and consumer goods. They play a crucial role in several industries as they are utilized in the production of diverse things such as defense materials, sanitary wares, tiles, plastic bottles, artificial leather, and various other household goods. Plastics are utilized in the packaging of food items, medications, detergents, and cosmetics. The overconsumption of plastics presents a significant peril to both the ecosystem and human existence on Earth. The accumulation of plastics on land and in the sea has sparked interest in finding ways to breakdown these polymers. It is necessary to employ suitable biodegradable techniques to decrease the accumulation of plastics in the environment. To address the environmental issues related to plastics, it is crucial to have a comprehensive understanding of the interaction between microorganisms and polymers. A wide range of creatures, particularly microbes, have developed techniques to survive and break down plastics. This review specifically examines the categorization of plastics based on their thermal and biodegradable properties, as well as the many types of degradation and biodegradation. It also discusses the various types of degradable plastics, the characterization of biodegradation, and the factors that influence the process of biodegradation. The plastic breakdown and bioremediation capabilities of these microbes make them ideal for green chemistry applications aimed at removing hazardous polymers from the ecosystem.

Organic waste-to-bioplastics: Conversion with eco-friendly technologies and approaches for sustainable environment

Petrochemical-based synthetic plastics poses a threat to humans, wildlife, marine life and the environment. Given the magnitude of eventual depletion of petrochemical sources and global environmental pollution caused by the manufacturing of synthetic plastics such as polyethylene (PET) and polypropylene (PP), it is essential to develop and adopt biopolymers as an environment friendly and cost-effective alternative to synthetic plastics. Research into bioplastics has been gaining traction as a way to create a more sustainable and eco-friendlier environment with a reduced environmental impact. Biodegradable bioplastics can have the same characteristics as traditional plastics while also offering additional benefits due to their low carbon footprint. Therefore, using organic waste from biological origin for bioplastic production not only reduces our reliance on edible feedstock but can also effectively assist with solid waste management. This review aims at providing an in-depth overview on recent developments in bioplastic-producing microorganisms, production procedures from various organic wastes using either pure or mixed microbial cultures (MMCs), microalgae, and chemical extraction methods. Low production yield and production costs are still the major bottlenecks to their deployment at industrial and commercial scale. However, their production and commercialization pose a significant challenge despite such potential. The major constraints are their production in small quantity, poor mechanical strength, lack of facilities and costly feed for industrial-scale production. This review further explores several methods for producing bioplastics with the aim of encouraging researchers and investors to explore ways to utilize these renewable resources in order to commercialize degradable bioplastics. Challenges, future prospects and Life cycle assessment of bioplastics are also highlighted. Utilizing a variety of bioplastics obtained from renewable and cost-effective sources (e.g., organic waste, agro-industrial waste, or microalgae) and determining the pertinent end-of-life option (e.g., composting or anaerobic digestion) may lead towards the right direction that assures the sustainable production of bioplastics.

PHA is not just a bioplastic!

Polyhydroxyalkanoates (PHA) have evolved into versatile biopolymers, transcending their origins as mere bioplastics. This extensive review delves into the multifaceted landscape of PHA applications, shedding light on the diverse industries that have harnessed their potential. PHA has proven to be an invaluable eco-conscious option for packaging materials, finding use in films foams, paper coatings and even straws. In the textile industry, PHA offers a sustainable alternative, while its application as a carbon source for denitrification in wastewater treatment showcases its versatility in environmental remediation. In addition, PHA has made notable contributions to the medical and consumer sectors, with various roles ranging from 3D printing, tissue engineering implants, and cell growth matrices to drug delivery carriers, and cosmetic products. Through metabolic engineering efforts, PHA can be fine-tuned to align with the specific requirements of each industry, enabling the customization of material properties such as ductility, elasticity, thermal conductivity, and transparency. To unleash PHA's full potential, bridging the gap between research and commercial viability is paramount. Successful PHA production scale-up hinges on establishing direct supply chains to specific application domains, including packaging, food and beverage materials, medical devices, and agriculture. This review underscores that PHA's future rests on ongoing exploration across these industries and more, paving the way for PHA to supplant conventional plastics and foster a circular economy.

Revealing the environmental hazard posed by biodegradable microplastics in aquatic ecosystems: An investigation of polylactic acid's effects on Microcystis aeruginosa

The influence of petroleum-based microplastics (MPs) on phytoplankton has been extensively studied, while research on the impact of biodegradable MPs, derived from alternative plastics to contest the environmental crisis, remains limited. This study performed a 63 days co-incubation experiment to assess the effect of polylactic acid MPs (PLA-MPs) on the growth, physiology, and carbon utilization of M. aeruginosa and the change in PLA-MPs surface properties. The results showed that despite PLA-MPs induced oxidative stress and caused membrane damage in M. aeruginosa, the presence of PLA-MPs (10, 50, and 200 mg/L) triggered significant increases (p < 0.05) in the density of M. aeruginosa after 63 days. Specifically, the algal densities upon 50 and 200 mg/L PLA-MPs exposure were increased by 20.91% and 36.31% relative to the control, respectively. Meanhwhile, the reduced C/O ratio on PLA-MPs surface and change in PLA-MPs morphological characterization, which is responsible for substantially increase in the aquatic dissolved inorganic carbon concentration during the co-incubation, implying the degradation of PLA-MPs; thus, provided sufficient carbon resources that M. aeruginosa could assimilate. This was in line with the declined intracellular carbonic anhydrase content in M. aeruginosa. This study is the first attempt to uncover the interaction between PLA-MPs and M. aeruginosa, and the finding that their interaction promotes the degrading of PLA-MPs meanwhile favoring M. aeruginosa growth will help elucidate the potential risk of biodegradable MPs in aquatic environment.

Evaluation of bioplastics biodegradation under simulated landfill conditions

Bioplastics that are generated from renewable sources have been regarded as an alternative to conventional plastics. Polylactic acid (PLA) is one of the mostly produced bioplastics because of its long shelf life for various applications. Even though bioplastics have drawn attention recently, their ultimate fate in landfills is still unknown. In this study, a standardized laboratory-scale lysimeter experiment was performed for the simulation of landfill conditions in order to evaluate the biodegradability of PLA during municipal solid waste stabilization. The reactors were loaded with municipal solid waste (MSW) taken from an operating landfill, certified PLA cups, and seed sludge. Various phases of landfill stabilization were simulated; hence, the reactors were operated under aerobic, semi-aerobic, and anaerobic conditions, respectively. Throughout the operation, both leachate and biogas generation in the reactors were regularly monitored. At the end of each phase, bioplastic cups were removed from the reactors, gently cleaned, weighed, and examined under a scanning electron microscope (SEM). The experimental results indicated that bioplastics did not undergo significant biodegradation during the first two stabilization phases (aerobic and semi-aerobic). On the other hand, it was observed that the cups were much softer and whiter at the end of the anaerobic phase. The weight of cups decreased by 12.8% on average, and their surfaces were prominently damaged after the completion of the last phase indicating the potential signs of biodegradation.

An investigation of the environmental implications of bioplastics: Recent advancements on the development of environmentally friendly bioplastics solutions

The production and utilization of plastics may prove beneficial, but the environmental impact suggests the opposite. The single-use plastics (SUP) and conventional plastics are harmful to the environment and need prompt disposal. Bioplastics are increasingly being considered as a viable alternative to conventional plastics due to their potential to alleviate environmental concerns such as greenhouse gas emissions and pollution. However, the previous reviews revealed a lack of consistency in the methodologies used in the Life Cycle Assessments (LCAs), making it difficult to compare the results across studies. The current study provides a systematic review of LCAs that assess the environmental impact of bioplastics. The different mechanical characteristics of bio plastics, like tensile strength, Young's modulus, flexural modulus, and elongation at break are reviewed which suggest that bio plastics are comparatively much better than synthetic plastics. Bioplastics have more efficient mechanical properties compared to synthetic plastics which signifies that bioplastics are more sustainable and reliable than synthetic plastics. The key challenges in bioplastic adoption and production include competition with food production for feedstock, high production costs, uncertainty in end-of-life management, limited biodegradability, lack of standardization, and technical performance limitations. Addressing these challenges requires collaboration among stakeholders to drive innovation, reduce costs, improve end-of-life management, and promote awareness and education. Overall, the study suggests that while bioplastics have the potential to reduce environmental impact, further research is needed to better understand their life cycle and optimize their end-of-life (EoL) management and production to maximize their environmental benefits.

Sustainable papaya plant waste and green tea residue composite films integrated with starch and gelatin for active food packaging applications

This study explores the sustainable utilization of wastes from a papaya plant (papaya peels (PP), papaya seeds (PS), leaf-stem (PL)) and dried green tea residues (GTR) for the synthesis of bioplastics. The dried GTR were individually blended with each papaya waste extract and then boiled in water to get three composite papaya plant waste-green tea supernatants. Potato starch and gelatin-based functional films were prepared by integrating each with the composite papaya waste-green tea supernatant liquid. This work introduces a dissolved organic matter (DOM) study to the field of bioplastics, with the goal of identifying the organic components and macromolecules inherent in the PW supernatants. When compared with the films prepared solely from papaya waste (PW) supernatants, PW-GTR composite supernatant films prevent UV light transmission with superior antioxidant and mechanical properties. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and atomic force microscopy (AFM) were utilized to characterize the starch and gelatin PW-GTR films. Owing to the exceptional antioxidant, UV barrier, and remarkable biodegradable properties of the starch/PW/GTR and gelatin/PW/GTR composite films, make them ideal for use in food packaging applications.

Unraveling the threat: Microplastics and nano-plastics' impact on reproductive viability across ecosystems

Plastic pollution pervades both marine and terrestrial ecosystems, fragmenting over time into microplastics (MPs) and nano-plastics (NPs). These particles infiltrate organisms via ingestion, inhalation, and dermal absorption, predominantly through the trophic interactions. This review elucidated the impacts of MPs/NPs on the reproductive viability of various species. MPs/NPs lead to reduced reproduction rates, abnormal larval development and increased mortality in aquatic invertebrates. Microplastics cause hormone secretion disorders and gonadal tissue damage in fish. In addition, the fertilization rate of eggs is reduced, and the larval deformity rate and mortality rate are increased. Male mammals exposed to MPs/NPs exhibit testicular anomalies, compromised sperm health, endocrine disturbances, oxidative stress, inflammation, and granulocyte apoptosis. In female mammals, including humans, exposure culminates in ovarian and uterine deformities, endocrine imbalances, oxidative stress, inflammation, granulosa cell apoptosis, and tissue fibrogenesis. Rodent offspring exposed to MPs experience increased mortality rates, while survivors display metabolic perturbations, reproductive anomalies, and weakened immunity. These challenges are intrinsically linked to the transgenerational conveyance of MPs. The ubiquity of MPs/NPs threatens biodiversity and, crucially, jeopardizes human reproductive health. The current findings underscore the exigency for comprehensive research and proactive interventions to ameliorate the implications of these pollutants.

Biodegradation of plastics in the pelagic environment of the coastal zone - Proposed test method under controlled laboratory conditions

The increasing quantities of plastic litter accumulated in the oceans, including microplastics, represent a serious environmental threat. Despite the recent legislative actions, the plastic littering problem will not disappear in a short time. It may, however be ameliorated by replacing conventional non-degradable plastics with bio-based materials biodegradable in marine environment (targeting the non-recycled or mismanaged plastic waste). Although priority is set to prevention of plastic litter by means of the circular economy principles, biodegradability is a means of controlling unintentional plastic pollution. In this effort, the development of reliable test methods that would be used along with standard specifications for determining the biodegradability of novel polymeric materials or plastics in marine environments, is a necessary complementary component of the whole strategy to control the marine plastic litter and micro-, nano-plastics threat. The present work focuses on identifying gaps and improving available laboratory test methods for measuring the aerobic biodegradation of plastics in the seawater column within the coastal zone (pelagic environment). The research work followed a methodology that is based on recommendations of ASTM D6691:2017 concerning biodegradation of plastics in the seawater and the similar ISO 23977-1:2020. Three different implementation schemes of the test method were applied using different experimental setups and measuring techniques for monitoring the evolved CO2. The effect of critical parameters affecting nutrient adequacy (concentration in inoculum) and oxygen adequacy (bioreactor size, sample size, frequency of aeration) on the biodegradation of four tested materials was explored, and optimal values are proposed. The results allowed for the refinement of the proposed test method to improve reliability and reproducibility.

Biobased, biodegradable and compostable plastics: chemical nature, biodegradation pathways and environmental strategy

Increasing pollution of plastic waste is one of the major global environmental threats, deteriorating our land, water and air. The shift towards biobased, biodegradable and compostable plastics is considered a green alternative to petroleum-based plastic due to its renewable source or biodegradability. However, there is a misconception about biodegradable plastics and their degradability and behaviour after service life. Biobased, biodegradable and compostable plastics offer various benefits such as less carbon footprint, energy efficiency, independence and eco-safety. On the other hand, there are some disadvantages such as higher cost, limited recycling, misuse of terms and lack of legislation. Also, there is an urgent need for comparable international standard methods to define these materials as biodegradable material, or biocompostable material. There are some standards currently available, however, an in-depth detail and explanation of these standards is still missing. This review outlines the basic definition and chemical structure of biobased, biodegradable and compostable plastics; describes the degradation pathways of biodegradable and compostable plastics; and summarises current key applications of these materials together with possible future applications in different industries. Finally, strategies are developed for minimising the environmental impacts and the need for future research is proposed.

Zinc oxide nanoparticle-reinforced pectin/starch functionalized films: A sustainable solution for biodegradable packaging

Environmental pollution caused by non-biodegradable plastic pollutants adversely affects various ecosystems. This study proposes the development of novel functional and biodegradable films based on corn starch (CST) and pectin (PEC) containing zinc oxide nanoparticles (ZnONPs) from the casting method. The films exhibited processability, transparency, low water vapor permeation, and desirable mechanical properties for food packaging and coating applications. The ZnONPs acted as a plasticizer, enhancing the film elongation at the break, increasing the pec25-1 (PEC 25 wt% and ZnONPs 1 wt%) elongation from 79.85 to 162.32 %. The improved film elasticity supported by ZnONPs reduced the material stiffness. However, the films still demonstrated an average tensile strength (0.69 MPa) 17-fold higher than the tensile strength (0.04 MPa) of the non-biodegradable commercial film based on poly(vinyl chloride). Furthermore, the ZnONPs enhanced the UV-blocking capabilities of the films, leading to wettable materials with water contact angles lower than 90°. The films showed high biodegradation rates under natural disposal conditions. The results indicated that the pec25-1/ZnONPs film is a promising eco-friendly coating in food preservation due to its biodegradability, suitable mechanical properties, low water vapor permeability, and UV-blocking properties.

Microbial decomposition of biodegradable plastics on the deep-sea floor

Microbes can decompose biodegradable plastics on land, rivers and seashore. However, it is unclear whether deep-sea microbes can degrade biodegradable plastics in the extreme environmental conditions of the seafloor. Here, we report microbial decomposition of representative biodegradable plastics (polyhydroxyalkanoates, biodegradable polyesters, and polysaccharide esters) at diverse deep-sea floor locations ranging in depth from 757 to 5552 m. The degradation of samples was evaluated in terms of weight loss, reduction in material thickness, and surface morphological changes. Poly(L-lactic acid) did not degrade at either shore or deep-sea sites, while other biodegradable polyesters, polyhydroxyalkanoates, and polysaccharide esters were degraded. The rate of degradation slowed with water depth. We analysed the plastic-associated microbial communities by 16S rRNA gene amplicon sequencing and metagenomics. Several dominant microorganisms carried genes potentially encoding plastic-degrading enzymes such as polyhydroxyalkanoate depolymerases and cutinases/polyesterases. Analysis of available metagenomic datasets indicated that these microorganisms are present in other deep-sea locations. Our results confirm that biodegradable plastics can be degraded by the action of microorganisms on the deep-sea floor, although with much less efficiency than in coastal settings.

Development of Antibacterial Thermoplastic Starch with Natural Oils and Extracts: Structural, Mechanical and Thermal Properties

In this study, the influence of the incorporation of eucalyptus (EO), tea tree (TT) and rosemary (RO) essential oils and Chiriyuyo extract (CE) on the structure and properties of thermoplastic starch (TPS) obtained from potato starch, glycerin and water was evaluated. All oils and the extract were used at a concentration of 0.5 g/100 g of TPS, while for TT, the effect of the concentration was also studied. The mixtures obtained were processed by extrusion and thermocompression molding. The sheets were characterized by XRD, FTIR, TGA, SEM and analyses of their mechanical properties, antimicrobial characteristics and biodegradability. The results show that the use of small concentrations of the oils in 70TPS does not induce changes in the TPS structure according to the results of XRD, FTIR and TGA, with each essential oil and CE affecting the mechanical properties unevenly, although in all cases, antimicrobial activity was obtained, and the biodegradability of TPS in soil was not modified. An increase in the concentration of TT in 60TPS causes marked changes in the crystallinity of TPS, providing a greater modulus with a higher concentration of TT. Regardless of the amount of TT, all sheets maintain antimicrobial characteristics, and their biodegradation in soil is delayed with a higher oil content.

From Fundamental Amyloid Protein Self-Assembly to Development of Bioplastics

Proteins can self-assemble into a range of nanostructures as a result of molecular interactions. Amyloid nanofibrils, as one of them, were first discovered with regard to the relevance of neurodegenerative diseases but now have been exploited as building blocks to generate multiscale materials with designed functions for versatile applications. This review interconnects the mechanism of amyloid fibrillation, the current approaches to synthesizing amyloid protein-based materials, and the application in bioplastic development. We focus on the fundamental structures of self-assembled amyloid fibrils and how external factors can affect protein aggregation to optimize the process. Protein self-assembly is essentially the autonomous congregation of smaller protein units into larger, organized structures. Since the properties of the self-assembly can be manipulated by changing intrinsic factors and external conditions, protein self-assembly serves as an excellent building block for bioplastic development. Building on these principles, general processing methods and pathways from raw protein sources to mature state materials are proposed, providing a guide for the development of large-scale production. Additionally, this review discusses the diverse properties of protein-based amyloid nanofibrils and how they can be utilized as bioplastics. The economic feasibility of the protein bioplastics is also compared to conventional plastics in large-scale production scenarios, supporting their potential as sustainable bioplastics for future applications.

Microplastic pollution in terrestrial ecosystems: Global implications and sustainable solutions

Microplastic (MPs) pollution has become a global environmental concern with significant impacts on ecosystems and human health. Although MPs have been widely detected in aquatic environments, their presence in terrestrial ecosystems remains largely unexplored. This review examines the multifaceted issues of MPs pollution in terrestrial ecosystem, covering various aspects from additives in plastics to global legislation and sustainable solutions. The study explores the widespread distribution of MPs worldwide and their potential antagonistic interactions with co-occurring contaminants, emphasizing the need for a holistic understanding of their environmental implications. The influence of MPs on soil and plants is discussed, shedding light on the potential consequences for terrestrial ecosystems and agricultural productivity. The aging mechanisms of MPs, including photo and thermal aging, are elucidated, along with the factors influencing their aging process. Furthermore, the review provides an overview of global legislation addressing plastic waste, including bans on specific plastic items and levies on single-use plastics. Sustainable solutions for MPs pollution are proposed, encompassing upstream approaches such as bioplastics, improved waste management practices, and wastewater treatment technologies, as well as downstream methods like physical and biological removal of MPs. The importance of international collaboration, comprehensive legislation, and global agreements is underscored as crucial in tackling this pervasive environmental challenge. This review may serve as a valuable resource for researchers, policymakers, and stakeholders, providing a comprehensive assessment of the environmental impact and potential risks associated with MPs.

Nanoscale Pickering emulsion food preservative films/coatings: Compositions, preparations, influencing factors, and applications

Pickering emulsion (PE) technology effectively addresses the issues of poor compatibility and low retention of hydrophobic active ingredients in food packaging. Nonetheless, it is important to recognize that each stage of the preparation process for PE films/coatings (PEFCs) can significantly influence their functional properties. With the fundamental considerations of environmental friendliness and human safety, this review extensively explores the potential of raw materials for PEFC and introduces the preparation methods of nanoparticles, emulsification technology, and film-forming techniques. The critical factors that impact the performance of PEFC during the preparation process are analyzed to enhance food preservation effectiveness. Moreover, the latest advancements in PE packaging across diverse food applications are summarized, along with prospects for innovative food packaging materials. Finally, the preservation mechanism and application safety have been systematically elucidated. The study revealed that the PEFCs provide structural flexibility, where designable nanoparticles offer unique functional properties for intelligent control over active ingredient release. The selection of the dispersed and continuous phases, along with component proportions, can be customized for specific food characteristics and storage conditions. By employing suitable preparation and emulsification techniques, the stability of the emulsion can be improved, thereby enhancing the effectiveness of the films/coatings in preserving food. Including additional substances broadens the functionality of degradable materials. The PE packaging technology provides a safe and innovative solution for extending the shelf life and enhancing the quality of food products by protecting and releasing active components.

Bioconversion of glycerol into polyhydroxyalkanoates through an atypical metabolism shift using Priestia megaterium during fermentation processes: A statistical analysis of carbon and nitrogen source concentrations

Polyhydroxyalkanoates (PHA) are bioplastics which are well known as intracellular energy storage compounds and are produced in a large number of prokaryotic species. These bio-based inclusions are biodegradable, biocompatible and environmental friendly. Industrial production of, short chain and medium chain length PHA, involves the use of microorganisms and their enzymes. Priestia megaterium previously known as Bacillus megaterium is a well-recognized bacterium for producing short chain length PHA. This study focuses to characterize this bacterium for the production of medium chain length PHA, and a novel blend of both types of monomers having enhanced properties and versatile applications. Statistical analyses and simulations were used to demonstrate that cell dry weight can be derived as a function of OD600 and PHA content. Optimization of growth conditions resulted in the maximum PHA production as: 0. 05 g. g-x. H-1, where the rate of PHA production was 0.28 g L-1. H-1 and PHA concentration was 4.94 g. L-1. This study also demonstrated FTIR to be a semi quantitative tool for PHA production. Moreover, conversion of scl-PHA to mcl-PHA with reference to time intermissions using GC-FID are shown.

Characterization of the dynamic aging and leached dissolved organic carbon from biodegradable and conventional plastics under photooxidation

Biodegradable plastics have been regarded as promising candidates in the struggle against plastic pollution. However, the aging and dynamic leaching process of biodegradable and conventional plastics under photooxidation is still unclear. Herein, three types of non-biodegradable plastics (polypropylene, polyethylene, and polyethylene terephthalate), and two types of biodegradable plastics (polylactic acid and cornstarch-based plastics) were treated with 21 days of photooxidation followed by 13 days of dark conditions. Scanning electron microscopy was applied to display the morphological changes. Also, the carbonyl index, oxygen-to-carbon ratio, and contact angle were utilized to characterize the aging degree of the plastic surface. Unexpectedly, biodegradable plastics did not always display a greater aging degree than non-biodegradable plastics. Moreover, the dissolved organic carbon during the leaching process was identified using excitation-emission matrix fluorescence spectroscopy. The findings suggested that biodegradable plastics showed the potential to release more dissolved organic carbon. Particularly, the polylactic acid plastic displayed higher concentrations and more types of dissolved organic carbon release than that of conventional plastics in our experiment. This research highlights the necessity for monitoring the aging process of both biodegradable and non-biodegradable plastics and the non-negligible ecological risk of leached organic pollutants due to plastic degradation.

Engineered Geobacillus lipolytic enzymes - Attractive polyesterases that degrade polycaprolactones and simultaneously produce esters

Plastic pollution is one of the biggest environmental problems plaguing the modern world. Polyester-based plastics contribute significantly to this ecological safety concern. In this study, lipolytic biocatalysts GD-95RM and GDEst-lip developed based on lipase/esterase produced by Geobacillus sp. 95 strain were applied for the degradation of polycaprolactone films (Mn 45.000 (PCL45000) and Mn 80.000 (PCL80000)). The degradation efficiency was significantly enhanced by the addition of short chain alcohols. Lipase GD-95RM (1 mg) can depolymerize 264.0 mg and 280.7 mg of PCL45000 and PCL80000, films respectively, in a 24 h period at 30 °C, while the fused enzyme GDEst-lip (1 mg) is capable of degrading 145.5 mg PCL45000 and 134.0 mg of PCL80000 films in 24 h. The addition of ethanol (25 %) improves the degradation efficiency ~2.5 fold in the case of GD-95RM. In the case of GDEst-lip, 50 % methanol was found to be the optimal alcohol solution and the degradation efficiency was increased by ~3.25 times. The addition of alcohols not only increased degradation speeds but also allowed for simultaneous synthesis of industrially valuable 6-hydroxyhexonic acid esters. The suggested system is an attractive approach for removing of plastic waste and supports the principles of bioeconomics.

Assessment of biodegradation of lignocellulosic fiber-based composites - A systematic review

Lignocellulosic fiber-reinforced polymer composites are the most extensively used modern-day materials with low density and better specific strength specifically developed to render better physical, mechanical, and thermal properties. Synthetic fiber-reinforced composites face some serious issues like low biodegradability, non-environmentally friendly, and low disposability. Lignocellulosic or natural fiber-reinforced composites, which are developed from various plant-based fibers and animal-based fibers are considered potential substitutes for synthetic fiber composites because they are characterized by lightweight, better biodegradability, and are available at low cost. It is very much essential to study end-of-life (EoL) conditions like biodegradability for the biocomposites which occur commonly after their service life. During biodegradation, the physicochemical arrangement of the natural fibers, the environmental conditions, and the microbial populations, to which the natural fiber composites are exposed, play the most influential factors. The current review focuses on a comprehensive discussion of the standards and assessment methods of biodegradation in aerobic and anaerobic conditions on a laboratory scale. This review is expected to serve the materialists and technologists who work on the EoL behaviour of various materials, particularly in natural fiber-reinforced polymer composites to apply these standards and test methods to various classes of biocomposites for developing sustainable materials.

Activities of cellulose acetate and microcrystalline cellulose on the thermal and morphomechanical performances of a biobased hybrid composite made polybutylene succinate

Microcrystalline cellulose (MCC-30 wt%) was extruded with a blend of polybutylene succinate (PBS) and cellulose acetate (CADS=2.5-20 wt%) to produce two grades of binary (PBS/CA, PBS/MCC) and ternary (PBS/CA/MCC) specimens by injection into a mold previously thermostated at 22 °C and 78 °C. The structure-property relationships of neat PBS (n-PBS) and PBS-based blends were investigated by Fourier transform infrared (FTIR) spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electron microscopy (SEM), rheology, differential scanning calorimetry (DSC), thermogravimetry, and mechanical (tensile, bending) tests. FTIR/DRIFT outcomes revealed physical interactions between the ingredients through hydrogen bonds. Rheology and SEM evidenced the presence of entanglements and micro-voids absent in n-PBS. Non-isothermal DSC showed that 22 °C-molded formulations displayed crystalline degrees higher than 78 °C-specimens, except for PBS/MCC. DSC-isothermal analysis showed a hindrance effect of CA on PBS/CA crystallinity and a nucleating impact of MCC on PBS/MCC. Tensile and bending moduli increased for both material grades while the elongation at break decreased. Entanglements and micro-voids had detrimental effects on stress levels because the maximum tensile strength decreased when each or both biofillers were added to PBS. These structural configurations were beneficial for bending strengths since all blends' stiffness relatively increased regardless of material grade.

Synthesis and commercialization of bioplastics: Organic waste as a sustainable feedstock

Substituting synthetic plastics with bioplastics, primarily due to their inherent biodegradable properties, represents a highly effective strategy to address the current global issue of plastic waste accumulation in the environment. Advances in bioplastic research have led to the development of materials with improved properties, enabling their use in a wide range of applications in major commercial sectors. Bioplastics are derived from various natural sources such as plants, animals, and microorganisms. Polyhydroxyalkanoate (PHA), a biopolymer synthesized by bacteria through microbial fermentation, exhibits physicochemical and mechanical characteristics comparable to those of synthetic plastics. In response to the growing demand for these environmentally friendly plastics, researchers are actively investigating various cleaner production methods, including modification or derivatization of existing molecules for enhanced properties and new-generation applications to expand their market share in the coming decades. By 2026, the commercial manufacturing capacity of bioplastics is projected to reach 7.6 million tonnes, with Europe currently holding a significant market share of 43.5 %. Bioplastics are predominantly utilized in the packaging industry, indicating a strong focus of their application in the sector. With the anticipated rise in bioplastic waste volume over the next few decades, it is crucial to comprehend their fate in various environments to evaluate the overall environmental impact. Ensuring their complete biodegradation involves optimizing waste management strategies and appropriate disposal within these facilities. Future research efforts should prioritize exploration of their end-of-life management and toxicity assessment of degradation products. These efforts are crucial to ensure the economic viability and environmental sustainability of bioplastics as alternatives to synthetic plastics.

Prevalence of pharmaceuticals and personal care products, microplastics and co-infecting microbes in the post-COVID-19 era and its implications on antimicrobial resistance and potential endocrine disruptive effects

The COVID-19 (coronavirus disease 2019) pandemic's steady condition coupled with predominance of emerging contaminants in the environment and its synergistic implications in recent times has stoked interest in combating medical emergencies in this dynamic environment. In this context, high concentrations of pharmaceutical and personal care products (PPCPs), microplastics (MPs), antimicrobial resistance (AMR), and soaring coinfecting microbes, tied with potential endocrine disruptive (ED) are critical environmental concerns that requires a detailed documentation and analysis. During the pandemic, the identification, enumeration, and assessment of potential hazards of PPCPs and MPs and (used as anti-COVID-19 agents/applications) in aquatic habitats have been attempted globally. Albeit receding threats in the magnitude of COVID-19 infections, both these pollutants have still posed serious consequences to aquatic ecosystems and the very health and hygiene of the population in the vicinity. The surge in the contaminants post-COVID also renders them to be potent vectors to harbor and amplify AMR. Pertinently, the present work attempts to critically review such instances to understand the underlying mechanism, interactions swaying the current health of our environment during this post-COVID-19 era. During this juncture, although prevention of diseases, patient care, and self-hygiene have taken precedence, nevertheless antimicrobial stewardship (AMS) efforts have been overlooked. Unnecessary usage of PPCPs and plastics during the pandemic has resulted in increased emerging contaminants (i.e., active pharmaceutical ingredients and MPs) in various environmental matrices. It was also noticed that among COVID-19 patients, while the bacterial co-infection prevalence was 0.2-51%, the fungi, viral, protozoan and helminth were 0.3-49, 1-22, 2-15, 0.4-15% respectively, rendering them resistant to residual PPCPs. There are inevitable chances of ED effects from PPCPs and MPs applied previously, that could pose far-reaching health concerns. Furthermore, clinical and other experimental evidence for many newer compounds is very scarce and demands further research. Pro-active measures targeting effective waste management, evolved environmental policies aiding strict regulatory measures, and scientific research would be crucial in minimizing the impact and creating better preparedness towards such events among the masses fostering sustainability.

Development and evaluation of quercetin enriched bentonite-reinforced starch-gelatin based bioplastic with antimicrobial property

Nowadays novel bio-based materials have been widely employed in food and pharmaceutical industry because of their wide acceptability by the consumers rather than the synthetic materials nevertheless, they possess poor mechanical properties. Reinforcement of biopolymers with intercalation of mineral clays can improve their physicochemical properties; so that such biocomposites possess superior barrier and mechanical properties as well as stability and drug loading efficacy. Thus, this research aimed at formulating quercetin loaded bentonite-reinforced starch-gelatin based novel bioplastic with diverse applicability. The methodology of the study included Box Behnken optimization as well as physical, structural, mechanical and antimicrobial properties evaluation of the proposed reinforced bioplastics. Amount of starch, bentonite and glycerin were the independent variables while the tensile strength, swelling index and elongation percentage were studied as dependent variables. The optimized bioplastic film showed excellent physicochemical and morphological characteristics and also for efficient percentage drug content. The antimicrobial activity showed the highest activity against Escherichia coli followed by Pseudomonas aeruginosa and Staphylococcus aureus. Scanning electron microscopy (SEM) revealed the non-homogenous nature of the film. Generally, the results revealed that quercetin loaded bentonite-reinforced starch-gelatin based could be used as ecological friendly active food packaging as well as pharmaceutical application with significant antimicrobial properties.

Effects of polycaprolactone degradation products on the water flea, Daphnia magna: Carbodiimide additives have acute and chronic toxicity

Plastics have benefited our lives in many ways, but their long persistence in the environment causes serious problems. Rapid decomposition and detoxification of plastics after use are significant challenges. As a possible solution, biodegradable plastics have attracted attention, and for environmental risk assessment research on polymer toxicity, use of indicator organisms, like water fleas and fish, has increased globally. However, such research often focuses on standardized substances without considering changes in toxicity due to plastic degradation products. Additionally, tests generally focus on acute toxicity, while long-term effects on organismal reproduction and lifespan are largely unknown. Understanding the impact of degraded polymers on biological activities is crucial for accurate risk assessment. In this study, we investigated the biological toxicity of substances generated during degradation of polycaprolactone (PCL), a common biodegradable plastic, using the indicator organism, Daphnia magna. We examined PCL, oligocaprolactones (OCLs), and monomers resulting from polymer cleavage, as well as carbodiimides, added during polyester synthesis. As a result, PCL, which is insoluble in water, reduced individual survival and total number of offspring at an exposure concentration of 100 mg/L, while no toxicity was observed for water-soluble degradation products, OCLs, and monomers. Furthermore, carbodiimides, which are expected to be released during PCL degradation, showed strong toxicity, significantly reducing individual survival and total number of offspring at 0.1-10 mg/L. These findings suggest that changes in physical properties due to polymer degradation and release of additives can significantly alter their toxicity.

Microplastic ingestion affects hydrogen production and microbiomes in the gut of the terrestrial isopod Porcellio scaber

Microplastic (MP) is an environmental burden and enters food webs via ingestion by macrofauna, including isopods (Porcellio scaber) in terrestrial ecosystems. Isopods represent ubiquitously abundant, ecologically important detritivores. However, MP-polymer specific effects on the host and its gut microbiota are unknown. We tested the hypothesis that biodegradable (polylactic acid [PLA]) and non-biodegradable (polyethylene terephthalate [PET]; polystyrene [PS]) MPs have contrasting effects on P. scaber mediated by changes of the gut microbiota. The isopod fitness after an 8-week MP-exposure was generally unaffected, although the isopods showed avoidance behaviour to PS-food. MP-polymer specific effects on gut microbes were detected, including a stimulation of microbial activity by PLA compared with MP-free controls. PLA stimulated hydrogen emission from isopod guts, while PET and PS were inhibitory. We roughly estimated 107  kg year-1 hydrogen emitted from the isopods globally and identified their guts as anoxic, significant mobile sources of reductant for soil microbes despite the absence of classical obligate anaerobes, likely due to Enterobacteriaceae-related fermentation activities that were stimulated by lactate generated during PLA-degradation. The findings suggest negative effects of PET and PS on gut fermentation, modulation of important isopod hydrogen emissions by MP pollution and the potential of MP to affect terrestrial food webs.

Designing biodegradable alternatives to commodity polymers

The development and widespread adoption of commodity polymers changed societal landscapes on a global scale. Without the everyday materials used in packaging, textiles, construction and medicine, our lives would be unrecognisable. Through decades of use, however, the environmental impact of waste plastics has become grimly apparent, leading to sustained pressure from environmentalists, consumers and scientists to deliver replacement materials. The need to reduce the environmental impact of commodity polymers is beyond question, yet the reality of replacing these ubiquitous materials with sustainable alternatives is complex. In this tutorial review, we will explore the concepts of sustainable design and biodegradability, as applied to the design of synthetic polymers intended for use at scale. We will provide an overview of the potential biodegradation pathways available to polymers in different environments, and highlight the importance of considering these pathways when designing new materials. We will identify gaps in our collective understanding of the production, use and fate of biodegradable polymers: from identifying appropriate feedstock materials, to considering changes needed to production and recycling practices, and to improving our understanding of the environmental fate of the materials we produce. We will discuss the current standard methods for the determination of biodegradability, where lengthy experimental timescales often frustrate the development of new materials, and highlight the need to develop better tools and models to assess the degradation rate of polymers in different environments.

Valorization of Agricultural Waste Lignocellulosic Fibers for Poly(3-Hydroxybutyrate-Co-Valerate)-Based Composites in Short Shelf-Life Applications

Biocircularity could play a key role in the circular economy, particularly in applications where organic recycling (composting) has the potential to become a preferred waste management option, such as food packaging. The development of fully biobased and biodegradable composites could help reduce plastic waste and valorize agro-based residues. In this study, extruded films made of composites of polyhydroxybutyrate-co-valerate (PHBV) and lignocellulosic fibers, namely almond shell (AS) and Oryzite® (OR), a polymer hybrid composite precursor, have been investigated. Scanning electron microscopy (SEM) analysis revealed a weak fiber-matrix interfacial interaction, although OR composites present a better distribution of the fiber and a virtually lower presence of "pull-out". Thermogravimetric analysis showed that the presence of fibers reduced the onset and maximum degradation temperatures of PHBV, with a greater reduction observed with higher fiber content. The addition of fibers also affected the melting behavior and crystallinity of PHBV, particularly with OR addition, showing a decrease in crystallinity, melting, and crystallization temperatures as fiber content increased. The mechanical behavior of composites varied with fiber type and concentration. While the incorporation of AS results in a reduction in all mechanical parameters, the addition of OR leads to a slight improvement in elongation at break. The addition of fibers improved the thermoformability of PHBV. In the case of AS, the improvement in the processing window was achieved at lower fiber contents, while in the case of OR, the improvement was observed at a fiber content of 20%. Biodisintegration tests showed that the presence of fibers promoted the degradation of the composites, with higher fiber concentrations leading to faster degradation. Indeed, the time of complete biodisintegration was reduced by approximately 30% in the composites with 20% and 30% AS.

Nutrient enrichment mediates the effect of biodegradable and conventional microplastics on macroinvertebrate communities

There is growing concern regarding the lack of evidence on the effects bioplastics may have on natural ecosystems, whilst their production continues to increase as they are considered as a greener alternative to conventional plastics. Most research is limited to investigations of the response of individual taxa under laboratory conditions, with few experiments undertaken at the community or ecosystem scale, either investigating microplastics independently or in combination with other pollutants, such as nutrient enrichment. The aim of this study is to experimentally compare the effects of oil-based (high density polyethylene - HDPE) with those of bio-based biodegradable (polylactic acid - PLA) microplastics and their interaction with nutrient enrichment on freshwater macroinvertebrate communities under seminatural conditions. There were no significant differences in total abundance, alpha and beta diversities, or community composition attributable to the type of microplastics, their concentration, or nutrient enrichment compared with the control. However, there was a significant difference in macroinvertebrate alpha diversity between high concentrations of both microplastic types under ambient nutrient conditions, with lower diversity in communities exposed to HDPE compared with PLA. Nutrient enrichment mediated the effect of microplastic type, such that the diversity of macroinvertebrate communities exposed to HDPE were similar to those communities exposed to PLA. These findings suggest that the effects of microplastic pollution on macroinvertebrate communities are very weak at large-scale settings under seminatural conditions and that these effects might be mediated by the nutrient status of freshwater ecosystems. More research under large-scale, long-term, seminatural settings are needed in order to elucidate the impact of both conventional plastics and bioplastics on natural environments and their interactive effect with other occurring stressors and pollutants.