Microbial Degradation of Synthetic Biopolymers Waste

Can the insects Galleria mellonella and Tenebrio molitor be the future of plastic biodegradation?

Plastics have been an integral part of human lives, enhancing the functionality and safety of many everyday products, contributing significantly to our overall well-being. However, petroleum-based plastics can take hundreds or even thousands of years to decompose, resulting in an unprecedented plastic waste accumulation in the environment. Widely used conventional plastic disposal methods as landfilling and incineration are also environmentally harmful, frequently leading to soil/water contamination and the release of microplastics. To overcome these limitations, researchers have been investigating novel sustainable alternatives for plastic waste management, such as the use of microorganisms, microbial-based enzymes, and, more recently, some insect larvae, being Galleria mellonella and Tenebrio molitor the most promising ones. In this review, we explore different methods of plastic waste disposal focusing on recent discoveries regarding biological plastic degradation using insects as alternative methods. We also discuss the plastic degradation mechanisms employed by G. mellonella and T. molitor larvae known so far, as salivary enzymes and the pool of microorganisms in their gut. Finally, this review highlights key challenges in plastic biodegradation, such as standardization and experimental comparability, while proposing innovative perspectives like using insects as bioreactors and exploring unexplored research directions.

Exploring the metabolic potential of Aeromonas to utilise the carbohydrate polymer chitin

Members of the Aeromonas genus are commonly found in natural aquatic ecosystems. However, they are also frequently present in non-chlorinated drinking water distribution systems. High densities of these bacteria indicate favorable conditions for microbial regrowth, which is considered undesirable. Studies have indicated that the presence of Aeromonas is associated with loose deposits and the presence of invertebrates, specifically Asellus aquaticus. Therefore, a potential source of energy in these nutrient poor environments is chitin, the structural shell component in these invertebrates. In this study, we demonstrate the ability of two Aeromonas strains, commonly encountered in drinking water distribution systems, to effectively degrade and utilize chitin as a sole carbon and nitrogen source. We conducted a quantitative proteomics study on the cell biomass and secretome from pure strain cultures when switching the nutrient source from glucose to chitin, uncovering a diverse array of hydrolytic enzymes and metabolic pathways specifically dedicated to the utilization of chitin. Additionally, a genomic analysis of different Aeromonas species suggests the general ability of this genus to degrade and utilize a variety of carbohydrate biopolymers. This study indicates the relation between the utilization of chitin by Aeromonas and their association with invertebrates such as A. aquaticus in loose deposits in drinking water distribution systems.

Selective response of soil bacterial and fungal taxa to biodegradable polymers

Biodegradable mulching films offer an eco-friendly alternative to petroleum-based plastics in agriculture, but their effects on soil parameters are not well understood. A microcosm experiment (20 °C, 75% field capacity) investigated the impact of two doses (0.021% and 1% w/w) of a biodegradable polymer on soil chemical and microbiological properties over a year. The 1% dose significantly (p < 0.05) increased CO2 emissions, water-extractable organic C, and hydrolytic activity. A significant (p < 0.05) effect on microbial alpha- and beta-diversity was noted only during short- and medium-term incubations. In contrast, a taxon-related response was found for both bacterial and fungal taxa affecting the abundance of the genera Aquicella, Cellvibrio, Bacillus, Ramlibacter, and Saccharibacteria genera incertae sedis among bacteria, and Malassezia, Orbilia, and Rhodotorula among fungi (including both yeast and filamentous lifestyles). Microbial functions revealed a greater impact on fungal communities compared to bacterial ones. However, after one year of exposition, only a marginal effect on the abundance of both bacterial and fungal functional groups was found in the microcosms. A significantly higher concentration of tightly bound exopolysaccharides in the presence of 1% biodegradable polymer at the start of the experiment suggested their key role in microbial degradation of bioplastics via biofilm formation.

Hydrocolloid-based bioplastics: Degradation in characterized soils

Three different type of bioplastics were studied. They were made of amylose only, argan proteins only, while the third type contained both polymers at a 1:1 ratio. Their degradation was studied in three different type of soils fully characterized regarding their composition. The rate of degradation was similar for the three type of bioplastics, even though some differences can be observed in relation to the type of soil. Amylose only-based bioplastics are degraded at the same rate in all three different oils, while the Argan-based bioplastics and Amylose-Argan proteins- based one are more resistant to degradation in the calcareous flood soil with a sandy clay loam texture and alkaline pH, namely soil B from the agricultural area of Castel Volturno (Naples, Italy). The soil fertility was also assessed by cultivating garden cress in the soils where the novel bioplastics were left to degrade. Results were compared with a commercial bioplastic, showing a rate of degradation faster than the commercial one. Thus, novel bioplastics can be defined as compostable since obey the definition described by the European label EN 13432.

Review of the Synthesis and Degradation Mechanisms of Some Biodegradable Polymers in Natural Environments

The escalating demand for sustainable materials has been fueling the rapid proliferation of the biopolymer market. Biodegradable polymers within natural habitats predominantly undergo degradation mediated by microorganisms. These microorganisms secrete enzymes that cleave long-chain polymers into smaller fragments for metabolic assimilation. This review is centered around dissecting the degradation mechanisms of specific biodegradable polymers, namely PLA, starch-based polymers, and plant fiber-based polymers. Recent investigations have unveiled that PLA exhibits augmented biocompatibility when combined with HA, and its degradation is subject to the influence of enzymatic and abiotic determinants. In the case of starch-based polymers, chemical or physical modifications can modulate their degradation kinetics, as evidenced by Wang et al.'s superhydrophobic starch-based nanocomposite cryogel. For plant fiber-based polymers, the effects of temperature, humidity, and cellulose degradation on their properties, along with the implications of various treatments and additives, are probed, as exemplified by Liu et al.'s study on jute/SiO2/PP composites. Specifically, with respect to PLA, the polymerization process and the role of catalysts such as SnCl2 in governing the structure and biodegradability are expounded in detail. The degradation of PLA in SBF and its interaction with β-TCP particles constitute crucial aspects. For starch-based polymers, the enzymatic degradation catalyzed by amylase and glucosidase and the environmental impacts of temperature and humidity, in addition to the structural ramifications of amylose and amylopectin, are further elucidated. In plant fiber-based polymers, the biodegradation of cellulose and the effects of plasma treatment, electron beam irradiation, nanoparticles, and crosslinking agents on water resistance and stability are explicated with experimental substantiation. This manuscript also delineates technological accomplishments. PLA incorporated with HA demonstrates enhanced biocompatibility and finds utility in drug delivery systems. Starch-based polymers can be engineered for tailored degradation. Plant fiber-based polymers acquire water resistance and durability through specific treatments or the addition of nanoparticles, thereby widening their application spectrum. Synthetic and surface modification methodologies can be harnessed to optimize these materials. This paper also consolidates reaction conditions, research techniques, their merits, and demerits and delves into the biodegradation reaction mechanisms of these polymers. A comprehensive understanding of these degradation mechanisms is conducive to their application and progression in the context of sustainable development and environmental conservation.

Characterization and Evaluation of Zero-Order Release System Comprising Glycero-(9,10-trioxolane)-trialeate and PLA: Opportunity for Packaging and Biomedicine Applications

Glycerol-(9,10-trioxolane) trioleate (OTOA) is a promising material that combines good plasticizing properties for PLA with profound antimicrobial activity, which makes it suitable for application in state-of-the-art biomedical and packaging materials with added functionality. On the other hand, application of OTOA in PLA-based antibacterial materials is hindered by a lack of knowledge on kinetics of the OTOA release. In this work, the release of glycero-(9,10-trioxolane) trioleate (OTOA) from PLA films with 50% OTOA content was studied during incubation in normal saline solution, and for the first time, the kinetics of OTOA release from PLA film was evaluated. Morphological, thermal, structural and mechanical properties of the PLA + 50% OTOA films were studied during incubation in normal saline and corresponding OTOA release using differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy and mechanical tests. It was confirmed by DSC and XRD that incubation in the saline solution and corresponding OTOA release from PLA film does not lead to significant changes in the structure of the polymer matrix. Thus, the formation of more disturbed α' crystalline phase of PLA due to partial hydrolysis of amorphous zones and/or most unstable crystallites in the PLA/OTOA semi-crystalline structure was observed. The degree of crystallinity of PLA + OTOA film was also slightly increased at the prolonged stages of OTOA release. PLA + 50% OTOA film retained its strength properties after incubation in normal saline, with a slight increase in the elastic modulus and tensile strength, accompanied by a significant decrease in relative elongation at break. The obtained results showed that PLA + 50% OTOA film could be characterized by sustained OTOA release with the amount of released OTOA exceeding 50% of the initial content in the PLA film. The OTOA release profile was close to zero-order kinetics, which is beneficial in order to provide stable drug release pattern. Developed PLA + 50% OTOA films showed a strong and stable antibacterial effect against Raoultella terrigena and Escherichia coli, bacterial strains with multidrug resistance behavior. The resulting PLA + OTOA films could be used in a variety of biomedical and packaging applications, including wound dressings and antibacterial food packaging.

Bibliometric study and potential applications in the development of starch films with nanocellulose: A perspective from 2019 to 2023

This study aimed to perform a bibliometric analysis of starch films with nanocellulose, using the Scopus database and VOSviewer and Bibliometrix software. A total of 258 documents were identified between 2019 and 2023, reflecting a growing interest in research, particularly in journals such as the International Journal of Biological Macromolecules, Polymers, and Carbohydrate Polymers. The most common terms were "starch" (349 occurrences), "cellulose" (207), and "tensile strength" (175). China (58 articles), Brazil (38), and India (33) led scientific production, with authors like Ilyas (13 articles) and Sapuan (10) at the forefront. Approximately 41.7 % of the studies used corn starch. The analysis revealed that 66 % of the studies investigated films with cellulose nanofibrils (CNF), 32 % with cellulose nanocrystals (CNC), and 2 % with bacterial nanocellulose (CB). The majority of studies (94.1 %) used the casting method for film production. Additionally, 35.44 % focused on reinforcing films with nanocellulose, while 7 % developed blends with other biopolymers. About 59.44 % examined the performance of starch films for food packaging, 11.25 % explored practical applications in various foods. Furthermore, 7.94 % incorporated active agents to improve antioxidant and antimicrobial properties, 1.30 % investigated active packaging. Moreover, 2.36 % explored the use of films in materials engineering, and 2.36 % explored biomedical potential. Only 0.40 % evaluated the impact of films on wastewater treatment. The analysis highlights the potential of starch films with nanocellulose, demonstrating their diverse applications and the growing interest in the field.

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.

An engineered enzyme embedded into PLA to make self-biodegradable plastic

Plastic production reached 400 million tons in 2022 (ref. 1), with packaging and single-use plastics accounting for a substantial amount of this2. The resulting waste ends up in landfills, incineration or the environment, contributing to environmental pollution3. Shifting to biodegradable and compostable plastics is increasingly being considered as an efficient waste-management alternative4. Although polylactide (PLA) is the most widely used biosourced polymer5, its biodegradation rate under home-compost and soil conditions remains low6-8. Here we present a PLA-based plastic in which an optimized enzyme is embedded to ensure rapid biodegradation and compostability at room temperature, using a scalable industrial process. First, an 80-fold activity enhancement was achieved through structure-based rational engineering of a new hyperthermostable PLA hydrolase. Second, the enzyme was uniformly dispersed within the PLA matrix by means of a masterbatch-based melt extrusion process. The liquid enzyme formulation was incorporated in polycaprolactone, a low-melting-temperature polymer, through melt extrusion at 70 °C, forming an 'enzymated' polycaprolactone masterbatch. Masterbatch pellets were integrated into PLA by melt extrusion at 160 °C, producing an enzymated PLA film (0.02% w/w enzyme) that fully disintegrated under home-compost conditions within 20-24 weeks, meeting home-composting standards. The mechanical and degradation properties of the enzymated film were compatible with industrial packaging applications, and they remained intact during long-term storage. This innovative material not only opens new avenues for composters and biomethane production but also provides a feasible industrial solution for PLA degradation.

Accelerating Biodegradation: Enhancing Poly(lactic acid) Breakdown at Mesophilic Environmental Conditions with Biostimulants

Poly(lactic acid) (PLA) has garnered interest due to its low environmental footprint and ability to replace conventional polymers and be disposed of in industrial composting environments. Although PLA is compostable when subjected to a suitable set of conditions, its broader acceptance in industrial composting facilities has been affected adversely due to longer degradation timeframes than the readily biodegradable organic waste fraction. PLA must be fully exposed to thermophilic conditions for prolonged periods to biodegrade, which has restricted its adoption and hindered its acceptance in industrial composting facilities, negating its home composting potential. Thus, enhancing PLA biodegradation is crucial to expand its acceptance. PLA's biodegradability is investigated in a compost matrix under mesophilic conditions at 37 °C for 180 days by biostimulating the compost environment with skim milk, gelatin, and ethyl lactate to enhance the different stages of PLA biodegradation. The evolved CO2, number average molecular weight (Mn), and crystallinity evolution are tracked. To achieve a Mn ≲ 10 kDa for PLA, the biodegradation rate is accelerated by 15% by adding skim milk, 25% by adding gelatin, and 22% by adding ethyl lactate. This work shows potential techniques to help biodegrade PLA in home composting setting by adding biostimulants.

Recent advances in microbial and enzymatic engineering for the biodegradation of micro- and nanoplastics

This review examines the escalating issue of plastic pollution, specifically highlighting the detrimental effects on the environment and human health caused by microplastics and nanoplastics. The extensive use of synthetic polymers such as polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS) has raised significant environmental concerns because of their long-lasting and non-degradable characteristics. This review delves into the role of enzymatic and microbial strategies in breaking down these polymers, showcasing recent advancements in the field. The intricacies of enzymatic degradation are thoroughly examined, including the effectiveness of enzymes such as PETase and MHETase, as well as the contribution of microbial pathways in breaking down resilient polymers into more benign substances. The paper also discusses the impact of chemical composition on plastic degradation kinetics and emphasizes the need for an approach to managing the environmental impact of synthetic polymers. The review highlights the significance of comprehending the physical characteristics and long-term impacts of micro- and nanoplastics in different ecosystems. Furthermore, it points out the environmental and health consequences of these contaminants, such as their ability to cause cancer and interfere with the endocrine system. The paper emphasizes the need for advanced analytical methods and effective strategies for enzymatic degradation, as well as continued research and development in this area. This review highlights the crucial role of enzymatic and microbial strategies in addressing plastic pollution and proposes methods to create effective and environmentally friendly solutions.

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.

Molecular docking and metagenomics assisted mitigation of microplastic pollution

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

Using Fungi in Artificial Microbial Consortia to Solve Bioremediation Problems

There is currently growing interest in the creation of artificial microbial consortia, especially in the field of developing and applying various bioremediation processes. Heavy metals, dyes, synthetic polymers (microplastics), pesticides, polycyclic aromatic hydrocarbons and pharmaceutical agents are among the pollutants that have been mainly targeted by bioremediation based on various consortia containing fungi (mycelial types and yeasts). Such consortia can be designed both for the treatment of soil and water. This review is aimed at analyzing the recent achievements in the research of the artificial microbial consortia that are useful for environmental and bioremediation technologies, where various fungal cells are applied. The main tendencies in the formation of certain microbial combinations, and preferences in their forms for usage (suspended or immobilized), are evaluated using current publications, and the place of genetically modified cells in artificial consortia with fungi is assessed. The effect of multicomponence of the artificial consortia containing various fungal cells is estimated, as well as the influence of this factor on the functioning efficiency of the consortia and the pollutant removal efficacy. The conclusions of the review can be useful for the development of new mixed microbial biocatalysts and eco-compatible remediation processes that implement fungal cells.

Application of liquid-based colorimetric method for high throughput screening of bioplastic-degrading strains using esterase assay

To alleviate environmental problems caused by using conventional plastics, bioplastics have garnered significant interest as alternatives to petroleum-based plastics. Despite possessing better degradability traits compared to traditional plastics, the degradation of bioplastics still demands a longer duration than initially anticipated. This necessitates the utilization of degradation strains or enzymes to enhance degradation efficiency, ensuring timely degradation. In this study, a novel screening method to identify bioplastic degraders faster was suggested to circumvent the time-consuming and laborious characteristics of solid-based plate assays. This liquid-based colorimetric method confirmed the extracellular esterase activity with p-nitrophenyl esters. It eliminated the needs to prepare plastic emulsion plates at the initial screening system, shortening the time for the overall screening process and providing more quantitative data. p-nitrophenyl hexanoate (C6) was considered the best substrate among the various p-nitrophenyl esters as substrates. The screening was performed in liquid-based 96-well plates, resulting in the discovery of a novel strain, Bacillus sp. SH09, with a similarity of 97.4% with Bacillus licheniformis. Furthermore, clear zone assays, degradation investigations, scanning electron microscopy, and gel permeation chromatography were conducted to characterize the biodegradation capabilities of the new strain, the liquid-based approach offered a swift and less labor-intensive option during the initial stages.

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.

Elicitation of E-waste (acrylonitrile-butadiene styrene) enriched soil bioremediation and detoxification using Priestia aryabhattai MGP1

Given the rise in both usage and disposal of dangerous electronics, there is a catastrophic rise in assemblage of electronic waste (e-waste). E-waste including various plastic resins are among the most frequently discarded materials in electronic gadgets. In current digital era, managing e-waste has become universal concern. From the viewpoint of persisting lacuna of e-waste managing methods, the current study is designed to fabricate an eco-friendly e-waste treatment with native soil bacteria employing an enrichment culture method. In the presence of e-waste, indigenous soil microbes were stimulated to degrade e-waste. Microbial cultures were isolated using enrichment medium containing acrylonitrile-butadiene styrene (ABS) as the primary carbon source. Priestia aryabhattai MGP1 was found to be the most dominant e-polymer degrading bacterial isolate, as it was reported to degrade ABS plastic in disposed-off television casings. Furthermore, to increase degradation potential of MGP1, Response Surface Methodology (RSM) was adopted which resulted in optimized conditions (pH 7, shaking-speed 120 rpm, and temperature 30 °C), for maximum degradation (18.88%) after 2 months. The structural changes induced by microbial treatment were demonstrated by comparing the findings of Field emission scanning electron microscopy (FESEM) images and Fourier Transform Infrared (FTIR) spectra confirming the disappearance of ≡ C─H peaks along with C-H, C=C and C ≡N bond destabilization following degradation. Energy-dispersive X-ray (EDX) analyzers of the native and decomposed e-polymer samples revealed a considerable loss in elemental weight % of oxygen by 8.4% and silica by 0.5%. Magnesium, aluminium and chlorine which were previously present in the untreated sample, were also removed after treatment by the bacterial action. When seeds of Vigna radiata were screened using treated soil in the presence of both e-waste and the chosen potent bacterial strain, it was also discovered that there was reduced toxicity in terms of improved germination and growth metrics as a phytotoxicity criterion.

Biodegradation of plastics by white-rot fungi: A review

Plastic pollution is one of the most environmental problems in the last two centuries, because of their excessive usage and their rapidly increasing production, which overcome the ability of natural degradation. Moreover, this problem become an escalating environmental issue caused by inadequate disposal, ineffective or nonexistent waste collection methods, and a lack of appropriate measures to deal with the problem, such as incineration and landfilling. Consequently, plastic wastes have become so ubiquitous and have accumulated in the environment impacting ecosystems and wildlife. The above, enhances the urgent need to explore alternative approaches that can effectively reduce waste without causing harsh environmental consequences. For example, white-rot fungi are a promising alternative to deal with the problem. These fungi produce ligninolytic enzymes able to break down the molecular structures of plastics, making them more bioavailable and allowing their degradation process, thereby mitigating waste accumulation. Over the years, several research studies have focused on the utilization of white-rot fungi to degrade plastics. This review presents a summary of plastic degradation biochemistry by white-rot fungi and the function of their ligninolytic enzymes. It also includes a collection of different research studies involving white-rot fungi to degrade plastic, their enzymes, the techniques used and the obtained results. Also, this highlights the significance of pre-treatments and the study of plastic blends with natural fibers or metallic ions, which have shown higher levels of degradation. Finally, it raises the limitations of the biotechnological processes and the prospects for future studies.

On the Effect of Non-Thermal Atmospheric Pressure Plasma Treatment on the Properties of PET Film

The aim of the work was to investigate the effect of non-thermal plasma treatment of an ultra-thin polyethylene terephthalate (PET) film on changes in its physicochemical properties and biodegradability. Plasma treatment using a dielectric barrier discharge plasma reactor was carried out in air at room temperature and atmospheric pressure twice for 5 and 15 min, respectively. It has been shown that pre-treatment of the PET surface with non-thermal atmospheric plasma leads to changes in the physicochemical properties of this polymer. After plasma modification, the films showed a more developed surface compared to the control samples, which may be related to the surface etching and oxidation processes. After a 5-min plasma exposure, PET films were characterized by the highest wettability, i.e., the contact angle decreased by more than twice compared to the untreated samples. The differential scanning calorimetry analysis revealed the influence of plasma pretreatment on crystallinity content and the melt crystallization behavior of PET after soil degradation. The main novelty of the work is the fact that the combined action of two factors (i.e., physical and biological) led to a reduction in the content of the crystalline phase in the tested polymeric material.

Study on the Biodegradation of Poly(Butylene Succinate)/Wheat Bran Biocomposites

This paper presents the results of a study investigating the biodegradation of poly(butylene succinate) (PBS)/wheat bran (WB) biocomposites. Injection mouldings were subjected to biodegradation in compost-filled bioreactors under controlled humidity and temperature conditions. The effects of composting time (14, 42 and 70 days) and WB mass content (10%, 30% and 50% wt.) on the structural and thermal properties of the samples were investigated. Measurements were made by infrared spectral analysis, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. Results demonstrated that both the thermal and structural properties of the samples depended greatly on the biodegradation time. Specifically, their crystallinity degree increased significantly while molecular mass sharply decreased with biodegradation time, whereas their thermal resistance only showed a slight increase. This resulted from enzymatic hydrolysis that led to the breakdown of ester bonds in polymer chains. It was also found that a higher WB content led to a higher mass loss in the biocomposite samples during biodegradation and affected their post-biodegradation properties. A higher bran content increased the degree of crystallinity of the biocomposite samples but reduced their thermal resistance and molecular mass.

A Review of Biodegradable Plastics: Chemistry, Applications, Properties, and Future Research Needs

Environmental concerns over waste plastics' effect on the environment are leading to the creation of biodegradable plastics. Biodegradable plastics may serve as a promising approach to manage the issue of environmental accumulation of plastic waste in the ocean and soil. Biodegradable plastics are the type of polymers that can be degraded by microorganisms into small molecules (e.g., H2O, CO2, and CH4). However, there are misconceptions surrounding biodegradable plastics. For example, the term "biodegradable" on product labeling can be misconstrued by the public to imply that the product will degrade under any environmental conditions. Such misleading information leads to consumer encouragement of excessive consumption of certain goods and increased littering of products labeled as "biodegradable". This review not only provides a comprehensive overview of the state-of-the-art biodegradable plastics but also clarifies the definitions and various terms associated with biodegradable plastics, including oxo-degradable plastics, enzyme-mediated plastics, and biodegradation agents. Analytical techniques and standard test methods to evaluate the biodegradability of polymeric materials in alignment with international standards are summarized. The review summarizes the properties and industrial applications of previously developed biodegradable plastics and then discusses how biomass-derived monomers can create new types of biodegradable polymers by utilizing their unique chemical properties from oxygen-containing functional groups. The terminology and methodologies covered in the paper provide a perspective on directions for the design of new biodegradable polymers that possess not only advanced performance for practical applications but also environmental benefits.

Recent advances in biodegradation of emerging contaminants - microplastics (MPs): Feasibility, mechanism, and future prospects

Plastics have become an essential part of life. When it enters the environment, it migrates and breaks down to form smaller size fragments, which are called microplastics (MPs). Compared with plastics, MPs are detrimental to the environment and pose a severe threat to human health. Bioremediation is being recognized as the most environmentally friendly and cost-effective degradation technology for MPs, but knowledge about the biodegradation of MPs is limited. This review explores the various sources of MPs and their migration behavior in terrestrial and aquatic environments. Among the existing MPs removal technologies, biodegradation is considered to be the best removal strategy to alleviate MPs pollution. The biodegradation potential of MPs by bacteria, fungi and algae is discussed. Biodegradation mechanisms such as colonization, fragmentation, assimilation, and mineralization are presented. The effects of MPs characteristics, microbial activity, environmental factors and chemical reagents on biodegradation are analyzed. The susceptibility of microorganisms to MPs toxicity might lead to decreased degradation efficiency, which is also elaborated. The prospects and challenges of biodegradation technologies are discussed. Eliminating prospective bottlenecks is necessary to achieve large-scale bioremediation of MPs-polluted environment. This review provides a comprehensive summary of the biodegradability of MPs, which is crucial for the prudent management of plastic waste.

Effective assessment of biopolymer-based multifunctional sorbents for the remediation of environmentally hazardous contaminants from aqueous solutions

Persistent contaminants in wastewater effluent pose a significant threat to aquatic life and are one of the most significant environmental concerns of our time. Although there are a variety of traditional methods available in wastewater treatment, including adsorption, coagulation, flocculation, ion exchange, membrane filtration, co-precipitation and solvent extraction, none of these have been found to be significantly cost-effective in removing toxic pollutants from the water environment. The upfront costs of these treatment methods are extremely high, and they require the use of harmful synthetic chemicals. For this reason, the development of new technologies for the treatment and recycling of wastewater is an absolute necessity. Our way of life can be made more sustainable by the synthesis of adsorbents based on biomass, making the process less harmful to the environment. Biopolymers offer a sustainable alternative to synthetic polymers, which are manufactured by joining monomer units through covalent bonding. This review presents a detailed classification of biopolymers such as pectin, alginate, chitosan, lignin, cellulose, chitin, carrageen, certain proteins, and other microbial biomass compounds and composites, with a focus on their sources, methods of synthesis, and prospective applications in wastewater treatment. A concise summary of the extensive body of knowledge on the fate of biopolymers after adsorption is also provided. Finally, consideration is given to open questions about future developments leading to environmentally friendly and economically beneficial applications of biopolymers.

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

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

Development of plastic-degrading microbial consortia by induced selection in microcosms

The increase in the production of highly recalcitrant plastic materials, and their accumulation in ecosystems, generates the need to investigate new sustainable strategies to reduce this type of pollution. Based on recent works, the use of microbial consortia could contribute to improving plastic biodegradation performance. This work deals with the selection and characterization of plastic-degrading microbial consortia using a sequential and induced enrichment technique from artificially contaminated microcosms. The microcosm consisted of a soil sample in which LLDPE (linear low-density polyethylene) was buried. Consortia were obtained from the initial sample by sequential enrichment in a culture medium with LLDPE-type plastic material (in film or powder format) as the sole carbon source. Enrichment cultures were incubated for 105 days with monthly transfer to fresh medium. The abundance and diversity of total bacteria and fungi were monitored. Like LLDPE, lignin is a very complex polymer, so its biodegradation is closely linked to that of some recalcitrant plastics. For this reason, counting of ligninolytic microorganisms from the different enrichments was also performed. Additionally, the consortium members were isolated, molecularly identified and enzymatically characterized. The results revealed a loss of microbial diversity at each culture transfer at the end of the induced selection process. The consortium selected from selective enrichment in cultures with LLDPE in powder form was more effective compared to the consortium selected in cultures with LLDPE in film form, resulting in a reduction of microplastic weight between 2.5 and 5.5%. Some members of the consortia showed a wide range of enzymatic activities related to the degradation of recalcitrant plastic polymers, with Pseudomonas aeruginosa REBP5 or Pseudomonas alloputida REBP7 strains standing out. The strains identified as Castellaniella denitrificans REBF6 and Debaryomyces hansenii RELF8 were also considered relevant members of the consortia although they showed more discrete enzymatic profiles. Other consortium members could collaborate in the prior degradation of additives accompanying the LLDPE polymer, facilitating the subsequent access of other real degraders of the plastic structure. Although preliminary, the microbial consortia selected in this work contribute to the current knowledge of the degradation of recalcitrant plastics of anthropogenic origin accumulated in natural environments.

Development of biopolymers from microbes and their environmental applications

Inventions begin with the invasion of humans and furnish a better livelihood. In some cases, it turns out to be imperative. The environmental issues of using synthetic polymers, including bio-incompatibility, toxicity, high cost, poor hydrophilicity, and pro-inflammatory degradation of byproducts, are increasing the need for and application of eco-friendly, alternative polymeric substances from medicine to biotechnology, which includes the industries of medicine, cosmetics, confectionery, wastewater treatment, etc., as tissue scaffolds, wound dressings, drug packaging material, dermal fillers, moisturising cream, carriers, sun protectants, antiperspirants, and deodorants; gelling agents; stabilisers, emulsifiers, photographic films, etc. Biopolymers are available in different compounds, produced by microbes, plants, and animals, where microbes, for example, Pseudomonas aeruginosa and Kamagataeibacter sucrofermetans, retain these compounds at an exorbitant level, helping them to sustain adverse conditions. Moreover, compared to plant and animal biopolymers, microbial biopolymers are preferred due to their ease of production, design, and processing at an industrial levels. In this regard, polyhydroxyalkanoates (PHA) and poly-3-hydroxybutyrate (PHB) have together attained assiduity for their biodegradable properties and possess similar features as petrochemical-based polymers, commonly synthetic polymers like polyethylene, polypropylene, etc. This attributes to its non-toxic nature, i.e., it behaves eco-friendly by degrading the components through a carbon-neutral energy cycle to carbon dioxide and water, which lessens the dependence on petroleum-based polymers. This chapter contemplates the methods to develop biopolymers from microbes and their environmental applications, focusing on the confiscation of heavy metals, organic dyes or oils, etc.

Mechanical degradation of sugar palm crystalline nanocellulose reinforced thermoplastic sugar palm starch (TPS)/poly (lactic acid) (PLA) blend bionanocomposites in aqueous environments

The concerning issue regarding petrochemical plastic wastes had prompted scientists and researchers to develop biodegradable plastic in effort to tackle environmental pollution. Alternative bioresources such as poly (lactic acid), sugar palm starch and nanocellulose fibre were utilized in producing cheap, biodegradable and sustainable plastic with satisfactory mechanical properties for food packaging application. In this study, sugar palm crystalline nanocellulose (SPCNC) was priorly dispersed in thermoplastic sugar palm starch (TPS) before melt blended with poly (lactic acid) (PLA) and later compress moulded into a sheet form. Initial biodegradation test of PLA100 and all PLA/TPS blends bionanocomposite samples indicated that PLA60TPS40 has the least variation in weight loss due to the good miscibility between TPS and PLA promoting the reinforcement of SPCNC. Greater weight losses in seawater (17.54%), river water (18.97%) and sewer water (22.27%) result in greater mechanical degradation as observed at the reduction of tensile strength from 12.11 MPa to 2.72 MPa in seawater, 1.48 MPa in river water and 0.40 MPa in sewer water. Similarly, higher weight losses in seawater (22.16%), river water (21.6%) and sewer water (23.09%) correlated with the reduction of flexural strength from 18.37 MPa to 3.5 MPa in seawater, 3.83 MPa in river water and 3.6 MPa in sewer water. The scanning electron microscope (SEM) images of tensile fracture morphology demonstrated clear porous structure due to the removal of starch particles by microbial activity. The homogenous structure of PLA60TPS40 had a steady and consistent degradation, which wholly diminished the interfacial adhesion that led to mechanical properties losses. The mechanical strength reduction clarified that the biodegradation rate within the media used might be able to resolve the excessive non-biodegradable plastic waste in open waters.

Understanding challenges associated with plastic and bacterial approach toward plastic degradation

Plastic is widely used in every sector due to its stability, durability, and low cost. The widespread use of plastic results in the compilation of plastic waste in the environment. The buildup of such a vast volume of plastic garbage has emerged as the primary cause of environmental pollution, including air, land, and water pollution. Plastics contain various harmful chemicals and toxic substances that can leak and adversely affect humans and other organisms. Managing this much plastic waste is a very challenging task; therefore, an appropriate technique is needed to address this problem. Various methods are used, such as chemical, physical, and biological, to degrade plastic waste. Bacterial degradation is known to be the most effective technique for the biodegradation approach to overcome this issue. Biodegradation has played a crucial role in removing these polluting wastes more efficiently and eco-friendly. The process of biodegradation involves a variety of bacteria, such as Acinetobacter baumannii, Bacillus weihenstephanensis, Pseudomonas aeruginosa, Pseudomonas fluorescens, Rhodococcus ruber, and so on. Biodegradation of plastic takes place through various biochemical pathways, including biodeterioration, biofragmentation, assimilation, and mineralization. During biodegradation, bacteria produce enzymes like esterase, cutinase, laccase, lipase, and others that break down and transform plastic polymers into microbial biomass and gases. This review aims to explain how bacteria contribute to the breakdown of plastic.

Biopolymer - A sustainable and efficacious material system for effluent removal

Undesired discharge of various effluents directly into the aquatic ecosystem can adversely affect water quality, endangering aquatic and terrestrial flora and fauna. Therefore, the conceptual design and fabrication of a sustainable system for alleviating the harmful toxins that are discharged into the atmosphere and water bodies using a green sustainable approach is a fundamental standpoint. Adsorptive removal of toxins (∼99% removal efficacy) is one of the most attractive and facile approaches for cleaner technologies that remediate the environmental impacts and provide a safe operating space. Recently, the introduction of biopolymers for the adsorptive abstraction of toxins from water has received considerable attention due to their eclectic accessibility, biodegradability, biocompatibility, non-toxicity, and enhanced removal efficacy (∼ 80-90% for electrospun fibers). This review summarizes the recent literature on the biosorption of various toxins by biopolymers and the possible interaction between the adsorbent and adsorbate, providing an in-depth perspective of the adsorption mechanism. Most of the observed results are explained in terms of (1) biopolymers classification and application, (2) toxicity of various effluents, (3) biopolymers in wastewater treatment and their removal mechanism, and (4) regeneration, reuse, and biodegradation of the adsorbent biopolymer.

Biodegradation of macro- and micro-plastics in environment: A review on mechanism, toxicity, and future perspectives

Plastic waste has gained remarkable research attention due to its accumulation, associated environmental issues, and impact on living organisms. In order to overcome this challenge, there is an urgent need for its removal from the environment. Under this menace, finding appropriate treatment methods like biodegradation instead of typical treatment methods is of supreme importance. However, there is a limited review on bio-decomposition of plastics, existing microbial species, their degradation efficacy, and mechanism. From this point of view, this study focused on a brief overview of biodegradation such as influencing factors on biodegradation, existing species for macro- and micro-plastics, and present research gap. Degradation percentage, limitations of existing species, and future recommendations are proposed. Microbial species such as bacteria, algae, and fungi have the ability to decompose plastics but they are unable to completely mineralize the plastics. Meanwhile, there is limited knowledge about the involved enzymes in plastics degradation, especially in the case of algae. Bio-decomposition of plastics requires more stringent conditions which are usually feasible for field application. This work will be a reference for new researchers to use this effective strategy for plastic pollution removal.

Biopolymer Non-Parametric Analysis: A Degradation Study under Accelerated Destructive Tests

The degradation of biopolymers such as polylactic acid (PLA) has been studied for several years; however, the results regarding the mechanism of degradation are not completely understood yet. PLA is easily processed by traditional techniques including injection molding, blow molding, extrusion, and thermoforming; in this research, the extrusion and injection molding processes were used to produce PLA samples for accelerated destructive testing. The methodology employed consisted of carrying out material testing under the guidelines of several ASTM standards; this research hypothesized that the effects of UV light, humidity, and temperature exposure have a statistical difference in the PLA degradation rate. The multivariate analysis of non-parametric data is presented as an alternative to multivariate analysis, in which the data do not satisfy the essential assumptions of a regular MANOVA, such as multivariate normality. A package in the R software that allows the user to perform a non-parametric multivariate analysis when necessary was used. This paper presents a study to determine if there is a significant difference in the degradation rate after 2000 h of accelerated degradation of a biopolymer using the multivariate and non-parametric analyses of variance. The combination of the statistical techniques, multivariate analysis of variance and repeated measures, provided information for a better understanding of the degradation path of the biopolymer.

Identification, characteristics and rice growth promotion of a highly efficient cellulolytic bacterial strain, Cellulomonas iranensis ZJW-6, isolated from paddy soil in central China

The microbial degradation of lignocellulose is the best way to treat straw, which has a broad application prospect. It is consistent with the idea of agricultural sustainable development and has an important impact on the utilization of biomass resources. To explore and utilize the microbial resources of lignocellulose degradation, 27 lignocellulose degrading strains were screened from 13 regions in China. ZJW-6 was selected because of its 49.6% lignocellulose weight loss rate. According to the theoretical analysis of the experimental results, the following straw degradation conditions were obtained by ZJW-6: nitrogen source input of 8.45 g/L, a pH of 8.57, and a temperature of 31.63°C, the maximum weight loss rate of rice straw could reach 54.8%. It was concluded that ZJW-6 belonged to Cellulomonas iranensis according to 16S rRNA-encoding gene sequence comparison and identification. ZJW-6 is a Gram-positive bacterium that grows slowly and has a small yellowish green colony. To explain the degradation mechanism of lignocellulose, the experiment of enzymatic properties of the strain was prepared and carried out. It was discovered that ZJW-6 has an excellent ability to degrade cellulose, hemicellulose, and lignin, with cellulose and hemicellulose loss rates reaching almost 50% in 4 days and lignin loss rates reaching nearly 30%. Furthermore, ZJW-6 demonstrated lignocellulose degradation under aerobic and anaerobic conditions, indicating the strain's broad application potential. ZJW-6 was found to be more effective than ordinary humic acid in improving rice soil (available phosphorus, available nitrogen, organic matter) and promoting rice growth in a rice pot experiment (increasing root-shoot ratio, root activity, chlorophyll content and net photosynthetic rate). ZJW-6 plays an important role in promoting the development and utilization of straw resources. It has important significance for the advancement of green agriculture.

Structure and properties of flexible starch-based double network composite films induced by dopamine self-polymerization

Starch-based packaging materials are being developed to alleviate environmental pollution and greenhouse gas emissions associated with plastic-based ones. However, the high hydrophilicity and poor mechanical properties of pure-starch films limit their widespread application. In this study, dopamine self-polymerization was used as a strategy to improve the performance of starch-based films. Spectroscopy analysis showed that strong hydrogen bonding occurred between polydopamine (PDA) and starch molecules within the composite films, which significantly altered their internal and surface microstructures. The composite films had a greater water contact angle (> 90°), which indicated that the incorporation of PDA reduced their hydrophilicity. Additionally, the elongation at break of the composite films was 11-fold higher than pure-starch films, indicating that PDA improved film flexibility, while the tensile strength decreased to some extent. The composite films also exhibited excellent UV-shielding performance. These high-performance films may have practical applications in food and other industries as biodegradable packaging materials.

Key issues for bio-based, biodegradable and compostable plastics governance

Among global efforts facing plastic pollution, their gradual replacement with alternative materials has gained strength during the last decade. We identified five stakeholders and their respective key participation in the chain of bio-based, biodegradable and compostable plastics (BBCP), which have contributed to several flaws on governance of these materials. The widespread unfamiliarity of the consumers about biodegradability concepts has been leading to misguided purchase decisions and disposal practices, along with possible littering behavior. Simultaneously, the adoption of greenwashing practices by stores and manufacturers contribute to disseminating misguided decisions on plastic consumption. Such issues are further aggravated by the lack of certification standards concerning the impact of littering, including the assessment of persistency and toxicity, also covering those made with biodegradable plastics.". Moreover, even though such alternative polymers were originally conceived as a strategy to minimize plastics pollution, the almost inexistence of specific regulatory frameworks in different political scales may convert them in a relevant part of the problem. Therefore, the governance systems and management strategies need to incorporate BBCP as potentially hazardous waste as they do for conventional plastics.

Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments

Finding alternatives to diminish plastic pollution has become one of the main challenges of modern life. A few alternatives have gained potential for a shift toward a more circular and sustainable relationship with plastics. Biodegradable polymers derived from bio- and fossil-based sources have emerged as one feasible alternative to overcome inconveniences associated with the use and disposal of non-biodegradable polymers. The biodegradation process depends on the environment's factors, microorganisms and associated enzymes, and the polymer properties, resulting in a plethora of parameters that create a complex process whereby biodegradation times and rates can vary immensely. This review aims to provide a background and a comprehensive, systematic, and critical overview of this complex process with a special focus on the mesophilic range. Activity toward depolymerization by extracellular enzymes, biofilm effect on the dynamic of the degradation process, CO2 evolution evaluating the extent of biodegradation, and metabolic pathways are discussed. Remarks and perspectives for potential future research are provided with a focus on the current knowledge gaps if the goal is to minimize the persistence of plastics across environments. Innovative approaches such as the addition of specific compounds to trigger depolymerization under particular conditions, biostimulation, bioaugmentation, and the addition of natural and/or modified enzymes are state-of-the-art methods that need faster development. Furthermore, methods must be connected to standards and techniques that fully track the biodegradation process. More transdisciplinary research within areas of polymer chemistry/processing and microbiology/biochemistry is needed.

Interplay of plastic pollution with algae and plants: hidden danger or a blessing?

In the era of plastic pollution, plants have been discarded as a system that is not affected by micro and nanoplastics, but contrary to beliefs that plants cannot absorb plastic particles, recent research proved otherwise. The presented review gives insight into known aspects of plants' interplay with plastics and how plants' ability to absorb plastic particles can be utilized to remove plastics from water and soil systems. Microplastics usually cannot be absorbed by plant root systems due to their size, but some reports indicate they might enter plant tissues through stomata. On the other hand, nanoparticles can enter plant root systems, and reports of their transport via xylem to upper plant parts have been recorded. Bioaccumulation of nanoplastics in upper plant parts is still not confirmed. The prospects of using biosystems for the remediation of soils contaminated with plastics are still unknown. However, algae could be used to degrade plastic particles in water systems through enzyme facilitated degradation processes. Considering the amount of plastic pollution, especially in the oceans, further research is necessary on the utilization of algae in plastic degradation. Special attention should be given to the research concerning utilization of algae with restricted algal growth, ensuring that a different problem is not induced, "sea blooming", during the degradation of plastics.

A comprehensive review on recent advancements in biodegradation and sustainable management of biopolymers

Recent years have seen upsurge in plastic manufacturing and its utilization in various fields, such as, packaging, household goods, medical applications, and beauty products. Due to various adverse impacts imposed by synthetic plastics on the health of living well-being and the environment, the biopolymers have been emerged out an alternative. Although, the biopolymers such as polyhydroxyalkanoates (PHA) are entirely degradable. However, the other polymers, such as poly (lactic acid) (PLA) are only partially degradable and often not biosynthesized. Biodegradation of the polymers using microorganisms is considered an effective bioremediation approach. Biodegradation can be performed in aerobic and anaerobic environments. In this context, the present review discusses the biopolymer production, their persistence in the environment, aerobic biodegradation, anaerobic biodegradation, challenges associated with biodegradation and future perspectives. In addition, this review discusses the advancement in the technologies associated with biopolymer production, biodegradation, and their biodegradation standard in different environmental settings. Furthermore, differences in the degradation condition in the laboratory as well as on-site are discussed.

Bio-Based Degradable Poly(ether-ester)s from Melt-Polymerization of Aromatic Ester and Ether Diols

Vanillin, as a promising aromatic aldehyde, possesses worthy structural and bioactive properties useful in the design of novel sustainable polymeric materials. Its versatility and structural similarity to terephthalic acid (TPA) can lead to materials with properties similar to conventional poly(ethylene terephthalate) (PET). In this perspective, a symmetrical dimethylated dialkoxydivanillic diester monomer (DEMV) derived from vanillin was synthesized via a direct-coupling method. Then, a series of poly(ether-ester)s were synthesized via melt-polymerization incorporating mixtures of phenyl/phenyloxy diols (with hydroxyl side-chains in the 1,2-, 1,3- and 1,4-positions) and a cyclic diol, 1,4-cyclohexanedimethanol (CHDM). The polymers obtained had high molecular weights (M_w = 5.3–7.9 × 10⁴ g.mol⁻¹) and polydispersity index (Đ) values of 1.54–2.88. Thermal analysis showed the polymers are semi-crystalline materials with melting temperatures of 204–240 °C, and tunable glass transition temperatures (T_g) of 98–120 °C. Their 5% decomposition temperature (T_d,5%) varied from 430–315 °C, which endows the polymers with a broad processing window, owing to their rigid phenyl rings and trans-CHDM groups. These poly(ether-ester)s displayed remarkable impact strength and satisfactory gas barrier properties, due to the insertion of the cyclic alkyl chain moieties. Ultimately, the synergistic influence of the ester and ether bonds provided better control over the behavior and mechanism of in vitro degradation under passive and enzymatic incubation for 90 days. Regarding the morphology, scanning electron microscopy (SEM) imaging confirmed considerable surface degradation in the polymer matrices of both polymer series, with weight losses reaching up to 35% in enzymatic degradation, which demonstrates the significant influence of ether bonds for biodegradation.

Enhancing the biodegradation of (bio)plastic through pretreatments: A critical review

As plastic packaging becomes nearly indispensable in the plastic economy, rigorous efforts have been made to recapture the material value form this waste stream, which is mostly composed of highly resistant plastics. Biodegradation offers an attractive alternative for conventional plastic waste treatment as this approach is environmentally friendly, has low cost and facilitates valorisation. Moreover, there is also an increasing interest in plastic pretreatments waste to enhance biodegradation. This review investigates the pretreatment methods that optimise plastic biodegradation by examining the process's mechanisms and key influencing factors, which can be categorised into: biotic factors, abiotic factors and polymer characteristics. Various types of chemical and physical pretreatments have demonstrated to effectively enhance biodegradation through oxidation and surface changes on the plastics, leading to increased bioconversion rates and biogas production. A critical evaluation of the various categories of pretreatment methods is presented. This evaluation leads to the conclusion that the category of non-thermal physical treatments is most promising, due to the relatively low energy requirements and the absence of a need for chemical additions. Moreover, non-thermal physical treatments have demonstrated application potential at large scale. Based on these conclusions, pretreatments are expected to be an integral part of the biodegradation of plastics within a circular economy approach.

Cloning, expression and characterization of PURase gene from Pseudomonas sp. AKS31

Polyurethane (PUR) is a soil and aquatic contaminant throughout the world. Towards bioremediation, in a previous study, a soil bacterium, Pseudomonas sp. AKS31, capable of efficiently degrading PUR was isolated. Polyurethanase (PURase) enzyme is capable of cleaving the ester bond of PUR and is considered as a key regulator of PUR biodegradation. Hence, for a high yield, easy purification, and further characterization, the aim of this study was to clone and overexpress the PURase gene of this isolate. The current study also investigated structural aspects of this enzyme through predictive bioinformatics analyses. In this context, the PURase gene of the isolate was cloned and expressed in E. coli using pET28(a)⁺ vector. The obtained recombinant protein was found insoluble. Therefore, first, the protein was made soluble with urea and purified using nickel-NTA beads. The purified enzyme exhibited substantial activities when tested on the LA-PUR plate. Bioinformatics-based analysis of the protein revealed the presence of a lipase serine active site and indicated that this PURase belongs to the Family 1.3 lipase. Hence, the present study shows that active PURase can be produced in large quantities using a prokaryotic expression system and thus, provides an effective strategy for in-vitro PUR-degradation.

Microbial biodegradation of plastics: Challenges, opportunities, and a critical perspective

The abundance of synthetic polymers has increased due to their uncontrolled utilization and disposal in the environment. The recalcitrant nature of plastics leads to accumulation and saturation in the environment, which is a matter of great concern. An exponential rise has been reported in plastic pollution during the corona pandemic because of PPE kits, gloves, and face masks made up of single-use plastics. The physicochemical methods have been employed to degrade synthetic polymers, but these methods have limited efficiency and cause the release of hazardous metabolites or by-products in the environment. Microbial species, isolated from landfills and dumpsites, have utilized plastics as the sole source of carbon, energy, and biomass production. The involvement of microbial strains in plastic degradation is evident as a substantial amount of mineralization has been observed. However, the complete removal of plastic could not be achieved, but it is still effective compared to the preexisting traditional methods. Therefore, microbial species and the enzymes involved in plastic waste degradation could be utilized as eco-friendly alternatives. Thus, microbial biodegradation approaches have a profound scope to cope with the plastic waste problem in a cost-effective and environmental-friendly manner. Further, microbial degradation can be optimized and combined with physicochemical methods to achieve substantial results. This review summarizes the different microbial species, their genes, biochemical pathways, and enzymes involved in plastic biodegradation.

Links among Microbial Communities, Soil Properties and Functions: Are Fungi the Sole Players in Decomposition of Bio-Based and Biodegradable Plastic?

The incomplete degradation of bio-based and biodegradable plastics (BBPs) in soils causes multiple threats to soil quality, human health, and food security. Plastic residuals can interact with soil microbial communities. We aimed to link the structure and enzyme-mediated functional traits of a microbial community composition that were present during poly (butylene succinate-co-butylene adipate (PBSA) decomposition in soil with (PSN) and without (PS) the addition of nitrogen fertilizer ((NH₄)₂SO₄). We identified bacterial (Achromobacter, Luteimonas, Rhodanobacter, and Lysobacter) and fungal (Fusarium, Chaetomium, Clonostachys, Fusicolla, and Acremonium) taxa that were linked to the activities of ß-glucosidase, chitinase, phosphatase, and lipase in plastic-amended soils. Fungal biomass increased by 1.7 and 4 times in PS and PSN treatment, respectively, as compared to non-plastic amended soil. PBSA significantly changed the relationships between soil properties (C: N ratio, TN, and pH) and microbial community structure; however, the relationships between fungal biomass and soil enzyme activities remained constant. PBSA significantly altered the relationship between fungal biomass and acid phosphatase. We demonstrated that although the soil functions related to nutrient cycling were not negatively affected in PSN treatment, potential negative effects are reasoned by the enrichment of plant pathogens. We concluded that in comparison to fungi, the bacteria demonstrated a broader functional spectrum in the BBP degradation process.

Degradation of Hydrogels Based on Potassium and Sodium Polyacrylate by Ionic Interaction and Its Influence on Water

Hydrogels are a very useful type of polymeric material in several economic sectors, acquiring great importance due to their potential applications; however, this type of material, similarly to all polymers, is susceptible to degradation, which must be studied to improve its use. In this sense, the present work shows the degradation phenomena of commercial hydrogels based on potassium and sodium polyacrylate caused by the intrinsic content of different types of potable waters and aqueous solutions. In this way, a methodology for the analysis of this type of phenomenon is presented, facilitating the understanding of this type of degradation phenomenon. In this context, the hydrogels were characterized through swelling and FTIR to verify their performance and their structural changes. Likewise, the waters and wastewaters used for the swelling process were characterized by turbidity, pH, hardness, metals, total dissolved solids, electrical conductivity, DLS, Z-potential, and UV-vis to determine the changes generated in the types of waters caused by polymeric degradation and which are the most relevant variables in the degradation of the studied materials. The results obtained suggest a polymeric degradation reducing the swelling capacity and the useful life of the hydrogel; in addition, significant physicochemical changes such as the emergence of polymeric nanoparticles are observed in some types of analyzed waters.