Novel consortia of enterobacter and pseudomonas formulated from cow dung exhibited enhanced biodegradation of polyethylene and polypropylene

Selection of engineered degradation method to remove microplastics from aquatic environments

Microplastics (MPs) in the aquatic environment are difficult to degrade naturally due to their hydrophobicity and structure. A variety of engineered degradation methods were developed to treat MPs contamination in the aquatic environment. Current reviews of MPs degradation methods only provided an inventory but lacked systematic comparisons and application recommendations. However, selecting suitable degradation methods for different types of MPs contamination may be more effective. This work examined the present engineered degradation methods for MPs in the aquatic environment. They were categorized into chemical degradation, biodegradation, thermal degradation and photodegradation. These degradation methods were systematically summarized in terms of degradation efficiency, technical limitations and production of environmental hazards. Also, the potential influences of different environmental factors and media on degradation were analyzed, and the selection of degradation methods were suggested from the perspectives of contamination types and degradation mechanisms. Finally, the development trend and challenges for studying MPs engineered degradation were proposed. This work will contribute to a better selection of customized degradation methods for different types of MPs contamination scenarios in aquatic environments.

ATR-FTIR characterisation of daily-use plastics mycodegradation

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

Biotransformation of microplastics from three-layer face masks by nitrifying-denitrifying consortia

COVID-19 increased microplastics (MP) contamination due to the extensive use of single-use personal protective equipment, particularly three-layer face masks. MP from face masks enter wastewater treatment plants (WWTPs), which were not designed to remove them. We utilized nitrifying-denitrifying microbial consortia and synthetic urban wastewater to evaluate the biotransformation of MP from each layer of three-layer face masks made of polypropylene (PP). The biotransformation carried out by the nitrifying-denitrifying consortia altered the surface of the outer, middle, and inner layers, as a consequence of the chemical modification of the PP-MP structure. Abiotic controls did not show changes on the physicochemical and thermal properties of PP-MP. Biotic tests showed increments in both the carbonyl and hydroxyl indices of the three layers in 42 days. The outer layer showed the greatest degree of biotransformation, which was consistent with morphological changes detected by scanning electron microscopy and in physicochemical properties such as crystallinity, evaporation, and fusion temperature. The nitrifying-denitrifying consortia, which removed 99 % of the total nitrogen from the synthetic urban wastewater, had several genera with proven capacity to biotransform MP such as Cephaloticoccus and Pseudomonas.

Isolation and Identification of Four Strains of Bacteria with Potential to Biodegrade Polyethylene and Polypropylene from Mangrove

With the rapid growth of global plastic production, the degradation of microplastics (MPs) has received widespread attention, and the search for efficient biodegradation pathways has become a hot topic. The aim of this study was to screen mangrove sediment and surface water for bacteria capable of degrading polyethylene (PE) and polypropylene (PP) MPs. In this study, two strains of PE-degrading bacteria and two strains of PP-degrading candidate bacteria were obtained from mangrove, named Pseudomonas sp. strain GIA7, Bacillus cereus strain GIA17, Acinetobacter sp. strain GIB8, and Bacillus cereus strain GIB10. The results showed that the degradation rate of the bacteria increased gradually with the increase in degradation time for 60 days. Most of the MP-degrading bacteria had higher degradation rates in the presence of weak acid. The appropriate addition of Mg2+ and K+ was favorable to improve the degradation rate of MPs. Interestingly, high salt concentration inhibited the biodegradation of MPs. Results of scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy (FTIR) indicated the degradation and surface changes of PP and PE MPs caused by candidate bacteria, which may depend on the biodegradation-related enzymes laccase and lipase. Our results indicated that these four bacterial strains may contribute to the biodegradation of MPs in the mangrove environment.

Enterobacter cloacae-mediated polymer biodegradation: in-silico analysis predicts broad spectrum degradation potential by Alkane monooxygenase

Plastic pollution poses a significant environmental challenge. In this study, the strain Enterobacter cloacae O5-E, a bacterium displaying polyethylene-degrading capabilities was isolated. Over a span of 30 days, analytical techniques including x-ray diffractometry, scanning electron microscopy, optical profilometry, hardness testing and mass spectrometric analysis were employed to examine alterations in the polymer. Results revealed an 11.48% reduction in crystallinity, a 50% decrease in hardness, and a substantial 25-fold increase in surface roughness resulting from the pits and cracks introduced in the polymer by the isolate. Additionally, the presence of degradational by-products revealed via gas chromatography ascertains the steady progression of degradation. Further, recognizing the pivotal role of alkane monooxygenase in plastic degradation, the study expanded to detect this enzyme in the isolate molecularly. Molecular docking studies were conducted to assess the enzyme's affinity with various polymers, demonstrating notable binding capability with most polymers, especially with polyurethane (- 5.47 kcal/mol). These findings highlight the biodegradation potential of Enterobacter cloacae O5-E and the crucial involvement of alkane monooxygenase in the initial steps of the degradation process, offering a promising avenue to address the global plastic pollution crisis.

Microbial strategies for effective microplastics biodegradation: Insights and innovations in environmental remediation

Microplastics (MPs), diminutive yet ubiquitous fragments arising from the degradation of plastic waste, pervade environmental matrices, posing substantial risks to ecological systems and trophic dynamics. This review meticulously examines the origins, distribution, and biological impacts of MPs, with an incisive focus on elucidating the molecular and cellular mechanisms underpinning their toxicity. We highlight the indispensable role of microbial consortia and enzymatic pathways in the oxidative degradation of MPs, offering insights into enhanced biodegradation processes facilitated by innovative pretreatment methodologies. Central to our discourse is the interplay between MPs and biota, emphasizing the detoxification capabilities of microbial metabolisms and enzymatic functions in ameliorating MPs' deleterious effects. Additionally, we address the practical implementations of MP biodegradation in environmental remediation, advocating for intensified research to unravel the complex biodegradation pathways and to forge effective strategies for the expeditious elimination of MPs from diverse ecosystems. This review not only articulates the pervasive challenges posed by MPs but also positions microbial strategies at the forefront of remedial interventions, thereby paving the way for groundbreaking advancements in environmental conservation.

Gut microbiota, a key to understanding the knowledge gaps on micro-nanoplastics-related biological effects and biodegradation

Micro-nanoplastics (MNPs) pollution as a global environmental issue has received increasing interest in recent years. MNPs can enter and accumulate in the organisms including human beings mainly via ingestion and inhalation, and large amounts of foodborne MNPs have been frequently detected in human intestinal tracts and fecal samples. MNPs regulate the structure composition and metabolic functions of gut microbiota, which may cause the imbalance of intestinal ecosystems of the hosts and further mediate the occurrence and development of various diseases. In addition, a growing number of MNPs-degrading strains have been isolated from organismal feces. MNPs-degraders colonize the plastic surfaces and form the biofilms, and the long-chain polymers of MNPs can be biologically depolymerized into short chains. In general, MNPs are gradually degraded into small molecule substances (e.g., N2, CH4, H2O, and CO2) via a series of enzymatic catalyses, mainly including biodeterioration, fragmentation, assimilation, and mineralization. In this review, we outline the current progress of MNPs effects on gut microbiota and MNPs degradation by gut microbiota, which provide a certain theoretical basis for fully understanding the knowledge gaps on MNPs-related biological effect and biodegradation.

Efficiency of Microorganisms and Effectiveness of Biodegradation Techniques on LDPE Plastics: A Systematic Review

Introduction

The aim of the research was to demonstrate the efficiency of microorganisms and the effectiveness of biodegradation techniques on Low-density polyethylene (LDPE) plastics. The research question was: What is the efficiency of LDPE-degrading microorganisms and the effectiveness of biodegradation techniques?

Methods

The systematic review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Articles were obtained from Scopus, Web of Science (WOS), Embase, and Google Scholar. The DeCS/Mesh search terms were: Low-density polyethylene, efficiency, biodegradation, microbial consortia, fungi, bacteria. Inclusion criteria were: scientific articles that included bacteria, fungi, and microbial consortia reported as LDPE degraders that report the percentage of weight loss; articles published from January 2010 to October 2022, and publications in Spanish and English with open access. Exclusion criteria were: studies that do not report gravimetry, the biodegradation time of LDPE, and the genus or species of the polyethylene-degrading microorganism.

Results

Out of 483 studies found, 50 were included in this Systematic Review (SR). The most frequent study techniques were scanning electron microscopy (SEM), gravimetry, and fourier transform infrared spectroscopy (FTIR), and in the case of microorganisms, the most studied belonged to the genus Pseudomonas, Bacillus, and Aspergillus. Regarding the isolation place, the most frequent mentioned in the reviewed articles were landfill soil and sanitary landfill soil. The efficiency of LDPE-degrading microorganisms was higher in bacteria such as Enterobacter spp., Pantoea spp., Pseudomonas spp., Escherichia coli, and Bacillus spp., which obtained a range of DE of 9.00-70.00%, 24.00-64%, 1.15 - 61.00%, 45.00%, and 1.5-40% with DT of 4-150, 120, 4-150, 30, and 30-120 days, respectively; in the case of fungi, the main microorganisms are Neopestalotiopsis phangngaensis, Colletotrichum fructicola, and Thyrostroma jaczewskii with efficiencies of 54.34, 48.78, and 46.34%, in 90 days, respectively; and the most efficient microbial consortia were from Enterobacter spp. and Pantoea sp. with 38.00 - 81.00%, in 120 days; and, Pseudomonas protegens, Stenotrophomonas sp., B. vallismortis and Paenibacillus sp. with 55. 00 - 75.00% in 120 days.

Conclusions

The most efficient microorganisms in LDPE degradation are Enterobacter spp., Pantoea spp., Pseudomonas spp., Escherichia coli, and Bacillus spp.; in fungi Neopestalotiopsis phangngaensis, Colletotrichum fructicola, and Thyrostroma jaczewskii; and in microbial consortia, those formed by Enterobacter spp. and Pantoea sp., and that of P. protegens, Stenotrophomonas sp., B. vallismortis and Paenibacillus sp.; and the most effective techniques used in LDPE biodegradation are SEM, gravimetry, and FTIR.

Biodegradation of low-density polythene (LDPE) by a novel strain of Pseudomonas aeruginosa WD4 isolated from plastic dumpsite

The present study was proposed with the idea to screen and isolate efficient low-density polyethylene (LDPE) degrading novel bacterial strains from the plastic-contaminated dumping site. The identification of the bacterial isolate was performed with the help of microbiological and molecular characterization approaches. The screening of the best isolate was performed based on its growth in Bushnell-Hass broth supplemented with LDPE sheets as the sole carbon source. The molecular characterization revealed that the isolate WD4 showed a similarity with the Pseudomonas aeruginosa species. A comparative analysis of Pseudomonas aeruginosa WD4 identified in the current study with Pseudomonas putida MTCC 2445 strain was performed. The present study demonstrated that the bacterial isolate showed 9.2% degradation of LDPE films while Pseudomonas putida revealed a 6.5% weight reduction after 100 days of incubation at 37 °C. The end products of the LDPE degradation were analysed using Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). The LDPE degradation products eluted include fatty acids such as octadecanoic, hexadecanoic acid, dodecanal, and octyl palmitoleate, alkanes, and some of the unknown compounds after 100 days of microbial treatment with the isolated strain. The detailed analysis of the by-products generated in the current study indicates their contribution to the biochemical pathway of LDPE degradation. The profound scope lies in the scalability of these bacterial strains at the industrial level to combat the LDPE waste and similar plastic garbage problems, globally.

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

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

Bio-Polyethylene and Polyethylene Biocomposites: An Alternative toward a Sustainable Future

Polyethylene (PE), a highly prevalent non-biodegradable polymer in the field of plastics, presents a waste management issue. To alleviate this issue, bio-based PE (bio-PE), derived from renewable resources like corn and sugarcane, offers an environmentally friendly alternative. This review discusses various production methods of bio-PE, including fermentation, gasification, and catalytic conversion of biomass. Interestingly, the bio-PE production volumes and market are expanding due to the growing environmental concerns and regulatory pressures. Additionally, the production of PE and bio-PE biocomposites using agricultural waste as filler materials, highlights the growing demand for sustainable alternatives to conventional plastics. According to previous studies, addition of ≈50% defibrillated corn and abaca fibers into bio-PE matrix and a compatibilizer, results in the highest Young's modulus of 4.61 and 5.81 GPa, respectively. These biocomposites have potential applications in automotive, building construction, and furniture industries. Moreover, the advancement made in abiotic and biotic degradation of PE and PE biocomposites is elucidated to address their environmental impacts. Finally, the paper concludes with insights into the opportunities, challenges, and future perspectives in the sustainable production and utilization of PE and bio-PE biocomposites. In summary, production of PE and bio-PE biocomposites can contribute to a cleaner and sustainable future.

Microplastics and environmental effects: investigating the effects of microplastics on aquatic habitats and their impact on human health

Microplastics (MPs) are particles with a diameter of <5 mm. The disposal of plastic waste into the environment poses a significant and pressing issue concern globally. Growing worry has been expressed in recent years over the impact of MPs on both human health and the entire natural ecosystem. MPs impact the feeding and digestive capabilities of marine organisms, as well as hinder the development of plant roots and leaves. Numerous studies have shown that the majority of individuals consume substantial quantities of MPs either through their dietary intake or by inhaling them. MPs have been identified in various human biological samples, such as lungs, stool, placenta, sputum, breast milk, liver, and blood. MPs can cause various illnesses in humans, depending on how they enter the body. Healthy and sustainable ecosystems depend on the proper functioning of microbiota, however, MPs disrupt the balance of microbiota. Also, due to their high surface area compared to their volume and chemical characteristics, MPs act as pollutant absorbers in different environments. Multiple policies and initiatives exist at both the domestic and global levels to mitigate pollution caused by MPs. Various techniques are currently employed to remove MPs, such as biodegradation, filtration systems, incineration, landfill disposal, and recycling, among others. In this review, we will discuss the sources and types of MPs, the presence of MPs in different environments and food, the impact of MPs on human health and microbiota, mechanisms of pollutant adsorption on MPs, and the methods of removing MPs with algae and microbes.

Recent advances in the relationships between biofilms and microplastics in natural environments

Plastic pollution in the form of microplastics (MPs), poses a significant threat to natural ecosystems, with detrimental ecological, social, and economic impacts. This review paper aims to provide an overview of the existing research on the interaction between microbial biofilms and MPs in natural environments. The review begins by outlining the sources and types of MPs, emphasizing their widespread presence in marine, freshwater, and terrestrial ecosystems. It then discusses the formation and characteristics of microbial biofilms on MPs surfaces, highlighting their role in altering the physicochemical properties of MPs and facilitating processes such as vertical transport, biodegradation, dispersion of microorganisms, and gene transfer. Different methods used to assess these interactions are discussed, including microbiological and physicochemical characterization. Current gaps and challenges in understanding the complex relationships between biofilms and MPs are identified, highlighting the need for further research to elucidate the mechanisms underlying these complex interactions and to develop effective mitigation strategies. Innovative solutions, including bioremediation techniques and their combination with other strategies, such as nanotechnology, advanced filtration technologies, and public awareness campaigns, are proposed as promising approaches to address the issue of MPs pollution. Overall, this review underscores the urgent need for a multidisciplinary approach to combating MPs pollution, combining scientific research, technological innovation, and public engagement to safeguard the health and integrity of natural ecosystems.

Biodegradation of low-density polyethylene film by Bacillus gaemokensis strain SSR01 isolated from the guts of earthworm

In recent years, low-density polyethylene (LDPE) has emerged as an essential component of the routine tasks that people engage in on a daily basis. However, over use of it resulted in environmental buildup that contaminated aquatic habitats and human health. Biodegradation is the most effective way for controlling pollution caused by synthetic plastic waste in a sustainable manner. In the present study, the LDPE degrading bacterial strain was screened from gut of Earthworms collected from plastic waste dumped area Mettur dam, Salem district, Tamil Nadu, India. The LDPE degrading bacterial strain was screened and identified genotypically. The LDPE degrading Bacillus gaemokensis strain SSR01 was submitted in NCBI. The B. gaemokensis strain SSR01 bacterial isolate degraded LDPE film after 14 days of incubation and demonstrated maximum weight loss of up to 4.98%. The study of deteriorated film using attenuated total reflection-Fourier transform infrared revealed the presence of a degraded product. The degradation of LDPE film by B. gaemokensis strain SSR01 was characterized by field-emission scanning electron microscopy analysis for surface alterations. The energy dispersive X-ray spectroscopy test confirmed that the broken-down LDPE film had basic carbon reduction. The present study of LDPE flim biodegradation by B. gaemokensis strain SSR01 has acted as a suitable candidate and will help in decreasing plastic waste.

Mining strategies for isolating plastic-degrading microorganisms

Plastic waste is a growing global pollutant. Plastic degradation by microorganisms has captured attention as an earth-friendly tactic. Although the mechanisms of plastic degradation by bacteria, fungi, and algae have been explored over the past decade, a large knowledge gap still exists regarding the identification, sorting, and cultivation of efficient plastic degraders, primarily because of their uncultivability. Advances in sequencing techniques and bioinformatics have enabled the identification of microbial degraders and related enzymes and genes involved in plastic biodegradation. In this review, we provide an outline of the situation of plastic degradation and summarize the methods for effective microbial identification using multidisciplinary techniques such as multiomics, meta-analysis, and spectroscopy. This review introduces new strategies for controlling plastic pollution in an environmentally friendly manner. Using this information, highly efficient and colonizing plastic degraders can be mined via targeted sorting and cultivation. In addition, based on the recognized rules and plastic degraders, we can perform an in-depth analysis of the associated degradation mechanism, metabolic features, and interactions.

Bacterial screening in Indian coastal regions for efficient polypropylene microplastics biodegradation

Polypropylene based medical devices significantly increased production and usage in COVID-19 pandemic states, and this material is very resilient in the environment. Thus, more than ever, rapid action is needed to reduce this pollution. This study focuses on the degradation of polypropylene microplastics (PP MPs) by unique marine bacterial strains obtained from the Thoundi (Bacillus tropicus, Bacillus cereus, Stenotrophomonas acidaminiphila, and Brucella pseudintermedia) and Rameshwaram coasts (Bacillus cereus). Those above five bacterial strains were chosen after preliminary screening of their hydrophobicity, biofilm-forming capabilities, and responsiveness to the zone of clearance technique. During the biodegradation process (28 days), the growth, metabolic activity, and viability of these five isolates were all raised. After the post-biodegradation process, the weight loss percentages of the mentioned bacterial strains treated with PP MPs gradually decreased, with values of 51.5 ± 0.5 %, 47.5 ± 0.5 %, 33 ± 1 %, 28.5 ± 0.5 and 35.5 ± 0.5 %, respectively. UV-Vis DRS and SEM analysis confirmed that bacterial strains adhering to MPs cause cracks and cavities on their surface. The degradation of PP MPs can be inferred from alterations in the FT-IR spectrum, specifically in the carbonyl group range of 1100-1700 cm-1, as well as changes in the 1H NMR spectrum, including chemical shift and proton peak pattern alterations. Bacterial strains facilitated the degradation of PP MPs through the secretion of hydrolase-categorized enzymes of protease, lipase, and esterase. The findings of this study indicate that marine bacteria may possess distinctive characteristics that facilitate the degradation of plastic waste and contribute to environmental conservation.

Elucidating polyethylene microplastic degradation mechanisms and metabolic pathways via iron-enhanced microbiota dynamics in marine sediments

The extensive use of plastics has given rise to microplastics, a novel environmental contaminant that has sparked considerable ecological and environmental concerns. Biodegradation offers a more environmentally friendly approach to eliminating microplastics, but their degradation by marine microbial communities has received little attention. In this study, we used iron-enhanced marine sediment to augment the natural bacterial community and facilitate the decomposition of polyethylene (PE) microplastics. The introduction of iron-enhanced sediment engendered an augmented bacterial biofilm formation on the surface of polyethylene (PE), thereby leading to a more pronounced degradation effect. This novel observation has been ascribed to the oxidative stress-induced generation of a variety of oxygenated functional groups, including hydroxyl (-OH), carbonyl (-CO), and ether (-C-O) moieties, within the microplastic substrate. The analysis of succession in the community structure of sediment bacteria during the degradation phase disclosed that Acinetobacter and Pseudomonas emerged as the principal bacterial players in PE degradation. These taxa were directly implicated in oxidative metabolic pathways facilitated by diverse oxidase enzymes under iron-facilitated conditions. The present study highlights bacterial community succession as a new pivotal factor influencing the complex biodegradation dynamics of polyethylene (PE) microplastics. This investigation also reveals, for the first time, a unique degradation pathway for PE microplastics orchestrated by the multifaceted marine sediment microbiota. These novel insights shed light on the unique functional capabilities and internal biochemical mechanisms employed by the marine sediment microbiota in effectively degrading polyethylene microplastics.

The programmed sequence-based oxygenase screening for polypropylene degradation

Enzymatic degradation of plastic is an effective means of plastic recycling and pollution control. However, the strong chemical inertness of polypropylene plastic (PP) severely impedes its oxidative cleavage, making it resistant to degradation. In this study, based on sequence screening of Hidden Markov Model (HMM), a dioxygenase (HIS1) was identified and characterized to be effective in PP oxidation. Various kinds of PP products, including plastic films, microplastics, and disposable water cups or bags, were HIS1-degraded with cracks and holes on the surface. The hydrophobic binding was the primary force driving oxidative degradation in the specific cavity of HIS1. The discovery of HIS1 achieved a zero breakthrough in PP biodegradation, providing a promising candidate for the selection and evolution of degrading enzymes.

Reproducible Polybutylene Succinate (PBS)-Degrading Artificial Consortia by Introducing the Least Type of PBS-Degrading Strains

Polybutylene succinate (PBS) stands out as a promising biodegradable polymer, drawing attention for its potential as an eco-friendly alternative to traditional plastics due to its biodegradability and reduced environmental impact. In this study, we aimed to enhance PBS degradation by examining artificial consortia composed of bacterial strains. Specifically, Terribacillus sp. JY49, Bacillus sp. JY35, and Bacillus sp. NR4 were assessed for their capabilities and synergistic effects in PBS degradation. When only two types of strains, Bacillus sp. JY35 and Bacillus sp. NR4, were co-cultured as a consortium, a notable increase in degradation activity toward PBS was observed compared to their activities alone. The consortium of Bacillus sp. JY35 and Bacillus sp. NR4 demonstrated a remarkable degradation yield of 76.5% in PBS after 10 days. The degradation of PBS by the consortium was validated and our findings underscore the potential for enhancing PBS degradation and the possibility of fast degradation by forming artificial consortia, leveraging the synergy between strains with limited PBS degradation activity. Furthermore, this study demonstrated that utilizing only two types of strains in the consortium facilitates easy control and provides reproducible results. This approach mitigates the risk of losing activity and reproducibility issues often associated with natural consortia.

Degradation and potential metabolism pathway of polystyrene by bacteria from landfill site

Microplastics pollution has garnered significant attention in recent years. The unique cross-linked structure of polystyrene microplastics makes them difficult to biodegrade. In this study, we investigated the microbial community in landfill soil that has the ability to degrade polystyrene, as well as two isolated strains, named Lysinibacillus sp. PS-L and Pseudomonas sp. PS-P. The maximum weight loss of polystyrene film and microplastic in 30 days is 2.25% and 6.99% respectively. The water contact angle of polystyrene film decreased by a maximum of 35.70% during biodegradation. The increase in hydrophilicity is attributed to the oxidation reaction and formation of hydroxyl groups during the degradation of polystyrene. The carbon and oxygen element contents of polystyrene decreased and increased by a maximum of 3.81% and 0.79% respectively. The peak intensity changes at wavelengths of 3285-3648 cm-1 and 1652 cm-1 in Fourier transform infrared spectroscopy confirmed the formation of hydroxyl and carbonyl groups. Furthermore, quantitative PCR revealed the gene expression levels of alkane monooxygenase and alcohol dehydrogenase were upregulated by 8.8-fold and 8.5-fold respectively in PS biodegradation. Additionally, genome annotation of Pseudomonas sp. PS-P identified nine genes associated with polystyrene metabolism. These findings highlight Pseudomonas sp. PS-P as a potential candidate strain for polystyrene degradation enzymes or genes. Thus, they lay the groundwork for understanding the potential metabolic mechanisms and pathways involved in polystyrene degradation.

Exploitation of Enterobacter hormaechei for biodegradation of multiple plastics

The escalating problem of environmental ecological pollution caused by plastics presents a significant challenge, which makes the management of plastic waste urgent nowadays. In this study, a bacterium named WX-2 was isolated and screened for its potential in polymer degradation. Through standard microbiological techniques and 16SrDNA gene sequencing, it was identified as Enterobacter hormaechei. To assess its biodegradability potential, various plastics including High density polyethylene, Polypropylene, Linear low density polyethylene, Poly (butyleneadipate-co-terephthalate) and Polyvinyl chloride were subjected to the study. The biodegradability of the plastics was evaluated using multiphase approaches involving techniques such as Scanning electron microscopy, Fourier transform infrared spectroscopy, Mass loss, X-ray diffraction, X-ray photoelectron spectroscopy, Water contact angle, and Gas chromatography-mass spectrometry. Results indicated that WX-2 possesses the capability to utilize diverse plastic polymers as sole carbon sources, displaying distinct biodegradation capacities. Notably, PBAT exhibited heightened susceptibility to degradation by the screened bacterial population.

Biodegradation and Detoxification of Low-Density Polyethylene (LDPE) by Stenotrophomonas sp. and Alcaligenaceae bacterium

Every year, human activities introduce large amounts of synthetic plastics into the environment. Decomposition of the plastic derivatives is very difficult and time consuming, so it is essential to eliminate these pollutants using different methods. Bioremediation, is suitable option, because of the low cost and environmentally safe. In this research, degradation of low-density polyethylene (LDPE) was investigated by two strains, isolated from Hamadan province (Iran) landfill soil. After identification by 16sr DNA primers, their abilities of polyethylene biodegradation were examined by Fourier transform infrared (FTIR), SEM and Gas Chromatography-Mass Spectrometry (GC-MS). Using media contain polyethylene) after and before addition of bacteria), toxicity test was conducted by measuring the germination index, root and hypocotyl length of Lactuca sativa seed. After three months, 10.15% ± 1.04 weight loss of LDPE achieved through strain Stenotrophomonas sp. degradation. Both strains had high biofilm formation capacity, confirmed by Electron microscope images and FTIR analysis. GC-MS confirmed the presence of the end-product of LDPE degradation (Pentacosane, Hexacosane, and Octadecane). Both, Stenotrophomonas sp. and Alcaligenaceae bacterium had significant detoxification ability. In media contain LDPE (without bacteria), decrease in the germination of lettuce seeds was observed.

Advances in enzymatic and organismal technologies for the recycling and upcycling of petroleum-derived plastic waste

Biological catalysts are emerging with the capability to depolymerize a wide variety of plastics. Improving and discovering these catalysts has leveraged a range of tools, including microbial ecology studies, high-throughput selections, and computationally guided mutational studies. In this review, we discuss the prospects for biological solutions to plastic recycling and upcycling with a focus on major advances in polyethylene terephthalate depolymerization, expanding the range of polymers with known biological catalysts, and the utilization of derived products. We highlight several recent improvements in enzymes and reaction properties, the discovery of a wide variety of novel plastic-depolymerizing biocatalysts, and how depolymerization products can be utilized in recycling and upcycling.

A novel marine bacterium Exiguobacterium marinum a-1 isolated from in situ plastisphere for degradation of additive-free polypropylene

As the ecological niche most closely associated with polymers, microorganisms in the 'plastisphere' have great potential for plastics degradation. Microorganisms isolated from the 'plastisphere' could colonize and degrade commercial plastics containing different additives, but the observed weight loss and surface changes were most likely caused by releasing the additives rather than actual degradation of the plastics itself. Unlike commercial plastics that contain additives, whether marine microorganisms in the 'plastisphere' have adapted to additive-free plastics as a surface to colonize and potentially degrade is not yet known. Herein, a novel marine bacterium, Exiguobacterium marinum a-1, was successfully isolated from mature 'plastisphere' that had been deployed in situ for up to 20 months. Strain a-1 could use additive-free polypropylene (PP) films as its primary energy and carbon source. After strain a-1 was incubated with additive-free PP films for 80 days, the weight of films decreased by 9.2%. The ability of strain a-1 to rapidly form biofilms and effectively colonize the surface of additive-free PP films was confirmed by Scanning Electron Microscopy (SEM), as reflected by the increase in roughness and visible craters on the surface of additive-free PP films. Additionally, the functional groups of -CO, -C-H, and -OH were identified on the treated additive-free PP films according to Fourier Transform Infrared (FTIR). Genomic data from strain a-1 revealed a suite of key genes involved in biosurfactant synthesis, flagellar assembly, and cellular chemotaxis, contributing to its rapid biofilm formation on hydrophobic polymer surfaces. In particular, key enzymes that may be responsible for the degradation of additive-free PP films, such as glutathione peroxidase, cytochrome p450 and esterase were also recognized. This study highlights the potential of microorganisms present in the 'plastisphere' to metabolize plastic polymers and points to the intrinsic importance of the new strain a-1 in the mitigation of plastic pollution.

Synthetic biology tools for environmental protection

Synthetic biology transforms the way we perceive biological systems. Emerging technologies in this field affect many disciplines of science and engineering. Traditionally, synthetic biology approaches were commonly aimed at developing cost-effective microbial cell factories to produce chemicals from renewable sources. Based on this, the immediate beneficial impact of synthetic biology on the environment came from reducing our oil dependency. However, synthetic biology is starting to play a more direct role in environmental protection. Toxic chemicals released by industries and agriculture endanger the environment, disrupting ecosystem balance and biodiversity loss. This review highlights synthetic biology approaches that can help environmental protection by providing remediation systems capable of sensing and responding to specific pollutants. Remediation strategies based on genetically engineered microbes and plants are discussed. Further, an overview of computational approaches that facilitate the design and application of synthetic biology tools in environmental protection is presented.

Polystyrene microplastics biodegradation by gut bacterial Enterobacter hormaechei from mealworms under anaerobic conditions: Anaerobic oxidation and depolymerization

Synthetic plastic is used throughout daily life and industry, threatening organisms with microplastic pollution. Polystyrene is a major plastic polymer and also widely found sources of plastic wastes and microplastics. Here, we report that Enterobacter hormaechei LG3 (CP118279.1), a facultative anaerobic bacterial strain isolated from the gut of Tenebrio molitor larvae (mealworms) can oxidize and depolymerize polystyrene under anaerobic conditions. LG3 performed biodegradation while forming a biofilm on the plastic surface. PS biodegradation was characterized by analyses of surface oxidation, change in morphology and molecular weights, and production of biodegraded derivative. The biodegradation performance by LG3 was compared with PS biodegradation by Bacillus amyloliquefaciens SCGB1 under both anaerobic and aerobic conditions. In addition, through nanopore sequencing technology, we identified degradative enzymes, including thiol peroxidase (tpx), alkyl hydroperoxide reductase C (ahpC) and bacterioferritin comigratory protein (bcp). Along with the upregulation of degradative enzymes for biodegradation, changes in lipid A and biofilm-associated proteins were also observed after the cells were incubated with polystyrene microplastics. Our results provide evidence for anaerobic biodegradation by polystyrene-degrading bacteria and show alterations in gene expression patterns after polystyrene microplastics treatment in the opportunistic pathogen Enterobacter hormaechei.

Fipronil Degradation in Soil by Enterobacter chengduensis Strain G2.8: Metabolic Perspective

Fipronil is an insecticide widely used in the agricultural and veterinary sectors for its efficacy in pest control. The presence of fipronil in the environment is mainly due to agricultural and domestic practices and is frequently found in different types of environmental matrices in concentrations ranging from µg/L to mg/L and can be hazardous to non-target organisms due to its high toxicity. This study was carried out to obtain and characterize microorganisms from soil which are capable of biodegrading fipronil that could be of great biotechnological interest. For this purpose, bioprospecting was carried out using fipronil (0.6 g/L) as the main source of carbon and nitrogen for growth. Once obtained, the strain was identified by sequencing the 16S ribosomal RNA (rRNA) gene and the capacity to degrade fipronil was monitored by GC-MS. Our study showed a presence in soil samples of the strain identified as Enterobacter chengduensis, which was able to metabolize fipronil and its metabolites during the mineralization process. Enterobacter chengduensis was able to biodegrade fipronil (96%) and its metabolites fipronil-sulfone (92%) and fipronil-sulfide (79%) in 14 days. Overall, the results of this study provided a bacterium with great potential that could contribute to the degradation of fipronil in the environment.

Salinity significantly reduces plastic-degrading bacteria from rivers to oceans

Microplastics (MPs) are found in rivers and offshore areas. However, there is a lack of detailed research on the changes of surface microbial species attached to MPs when MPs enter the sea. Moreover, no study has been conducted on changes to plastic-degrading bacteria during this process. In this study, using rivers and offshore in Macau, China as examples, bacterial diversity and bacterial species composition attached to surface water and MPs at four river sampling stations and four offshore sampling stations around Macau were studied. Plastic-degrading bacteria, plastic-related metabolic processes, and plastic-related enzymes were analyzed. The results showed that MPs-attached bacteria in rivers and offshore were different with the planktonic bacteria (PB). The proportion of major families on the surface of MPs continued to increase from rivers to estuaries. MPs could significantly enrich plastic-degrading bacteria both in rivers and offshore. The proportion of plastic-related metabolic pathways on the surface bacteria of MPs in rivers was higher than that in offshore waters. Bacteria on the surface of MPs in rivers may induce higher plastic degradation than offshore. Salinity significantly alters the distribution of plastic-degrading bacteria. MPs may degrade more slowly in the oceans, posing a long-term threat to marine life and human health.

Efficient removal of endocrine disrupting compounds 17 α-ethynyl estradiol and 17 β-estradiol by Enterobacter sp. strain BHUBP7 and elucidation of the degradation pathway by HRAMS analysis

Owing to the increased population and their overuse, estrogens are being detected in the environment at alarming levels. They act as endocrine disrupting compounds (EDC's) posing adverse effects on animals and humans. In this study, a strain belonging to Enterobacter sp. strain BHUBP7 was recovered from a Sewage Treatment Plant (STP) situated in Varanasi city, U.P., India, and was capable of metabolizing both 17 α-Ethynylestradiol (EE2) and 17 β-Estradiol (E2) separately as a sole carbon source. The strain BHUBP7 exhibited high rates of E2 degradation as compared to EE2 degradation. The degradation of E2 (10 mg/L) was 94.3% after four days of incubation, whereas the degradation of EE2 (10 mg/L) under similar conditions was 98% after seven days of incubation. The kinetics of EE2 and E2 degradation fitted well with the first-order reaction rate. FTIR analysis revealed the involvement of functional groups like C = O, C-C, C-OH during the degradation process. The metabolites generated during degradation of EE2 and E2 were identified using HRAMS and a plausible pathway was elucidated. It was observed that metabolism of both E2 and EE2 proceeded with the formation of estrone, which was then hydroxylated to 4-hydroxy estrone, followed by ring opening at the C4-C5 position, and was further metabolized by the 4,5 seco pathway leading to the formation of 3-(7a-methyl-1,5-dioxooctahydro-1H-inden-4-yl) propanoic acid (HIP). It is the first report on the complete pathway of EE2 and E2 degradation in Enterobacter sp. strain BHUBP7. Moreover, the formation of Reactive Oxygen Species (ROS) during the degradation of EE2 and E2 was observed. It was concluded that both hormones elicited the generation of oxidative stress in the bacterium during the degradation process.

Biodegradation of low density polyethylene (LDPE) by mesophilic fungus 'Penicillium citrinum' isolated from soils of plastic waste dump yard, Bhopal, India

Low density Polyethylene (LDPE) in various forms has become a part of life. Its accretion due to non degradable nature is concern, endangering life on earth. Amongst various methods of LDPE disposal bioremediation is regarded as ecofriendly & widely accepted. Current investigation was an attempt to isolate potent PE degrading fungus from municipal landfill soils of Bhopal, India loaded with plastic waste.16 fungal isolates were recorded from the site; PE deteriorating fungus was screened using mineral salt agar medium amended with 3% LDPE powder as sole carbon source. The isolate Penicillium citrinum showed fast fungal colony growth in screening medium was selected for biodegradation study. P.citrinum showed 38.82 ± 1.08% weight loss of untreated LDPE pieces; to improve the degradation capacity nitric acid pretreatment was performed; biodegradation was significantly stimulated by 47.22 ± 2.04% after it's pretreatment. Laccase, lipase, esterase & manganese peroxidase activities were assayed by spectrophotometer. LDPE biodegradation was analyzed by weight loss %, change in pH during fungal growth, field emission scanning electron microscopy (FE-SEM), fourier transform infrared spectroscopy (FTIR) & thermogravimetric analysis (TGA). FTIR spectra showed appearance of new functional groups assigned to hydrocarbon biodegradation, confirming enzymatic role in process. Changes in FTIR spectra of LDPE samples (untreated & pretreated) before & after biodegradation & surface changes in the biodegraded LDPE (indicated from FE-SEM) confirmed depolymerization of LDPE. Further changes in thermal decomposition rates of biodegraded samples in comparison to control, validate biodegradation. This is the first report signifying high competence of P.citrinum in LDPE degradation without prior pretreatment.

Biodegradation of low-density polyethylene plastic waste by a constructed tri-culture yeast consortium from wood-feeding termite: Degradation mechanism and pathway

Polyethylene (PE) is one of the most common synthetic polymers, and PE waste pollution has been an environmental and health concern for decades. Biodegradation is the most eco-friendly and effective approach for plastic waste management. Recently, an emphasis has been placed on novel symbiotic yeasts isolated from termite guts as promising microbiomes for multiple biotechnological applications. This study might be the first to explore the potential of a constructed tri-culture yeast consortium, designated as DYC, isolated from termites for the degradation of low-density polyethylene (LDPE). The yeast consortium DYC stands for the molecularly identified species Sterigmatomyces halophilus, Meyerozyma guilliermondii, and Meyerozyma caribbica. The LDPE-DYC consortium showed a high growth rate on UV-sterilized LDPE as a sole carbon source, resulting in a reduction in tensile strength (TS) of 63.4% and a net LDPE mass reduction of 33.2% compared to the individual yeasts. All yeasts, individually and in consortium, showed a high production rate for LDPE-degrading enzymes. The hypothetical LDPE biodegradation pathway that was proposed revealed the formation of several metabolites, including alkanes, aldehydes, ethanol, and fatty acids. This study emphasizes a novel concept for using LDPE-degrading yeasts from wood-feeding termites for plastic waste biodegradation.

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.

Recent advances and challenges in sustainable management of plastic waste using biodegradation approach

Versatility and desirable attributes of synthetic plastics have greatly contributed towards their wide applications. However, vast accumulation of plastic wastes in environment as a result of their highly recalcitrant nature has given rise to plastic pollution. Existing strategies in alleviating plastic wastes accumulation are inadequate, and there is a pressing need for alternative sustainable approaches in tackling plastic pollution. In this context, plastic biodegradation has emerged as a sustainable and environmental-friendly approach in handling plastic wastes accumulation, due to its milder and less energy-intensive conditions. In recent years, extensive research effort has focused on the identification of microorganisms and enzymes with plastic-degrading abilities. This review aims to provide a timely and holistic view on the current status of plastic biodegradation, focusing on recent breakthroughs and discoveries in this field. Furthermore, current challenges associated to plastic biodegradation are discussed, and the future perspectives for continuous advancement of plastic biodegradation are highlighted.

Call for biotechnological approach to degrade plastic in the era of COVID-19 pandemic

Plastic pollution is a global issue and has become a major concern since Coronavirus disease (COVID)-19. In developing nations, landfilling and illegal waste disposal are typical ways to dispose of COVID-19-infected material. These technologies worsen plastic pollution and other human and animal health problems. Plastic degrades in light and heat, generating hazardous primary and secondary micro-plastic. Certain bacteria can degrade artificial polymers using genes, enzymes, and metabolic pathways. Microorganisms including bacteria degrade petrochemical plastics slowly. High molecular weight, strong chemical bonds, and excessive hydrophobicity reduce plastic biodegradation. There is not enough study on genes, enzymes, and bacteria-plastic interactions. Synthetic biology, metabolic engineering, and bioinformatics methods have been created to biodegrade synthetic polymers. This review will focus on how microorganisms' degrading capacity can be increased using recent biotechnological techniques.

Biotechnological methods to remove microplastics: a review

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

Assembly strategies for polyethylene-degrading microbial consortia based on the combination of omics tools and the "Plastisphere"

Numerous microorganisms and other invertebrates that are able to degrade polyethylene (PE) have been reported. However, studies on PE biodegradation are still limited due to its extreme stability and the lack of explicit insights into the mechanisms and efficient enzymes involved in its metabolism by microorganisms. In this review, current studies of PE biodegradation, including the fundamental stages, important microorganisms and enzymes, and functional microbial consortia, were examined. Considering the bottlenecks in the construction of PE-degrading consortia, a combination of top-down and bottom-up approaches is proposed to identify the mechanisms and metabolites of PE degradation, related enzymes, and efficient synthetic microbial consortia. In addition, the exploration of the plastisphere based on omics tools is proposed as a future principal research direction for the construction of synthetic microbial consortia for PE degradation. Combining chemical and biological upcycling processes for PE waste could be widely applied in various fields to promote a sustainable environment.

Microbial strategies for degradation of microplastics generated from COVID-19 healthcare waste

COVID-19 pandemic has led to the generation of massive plastic wastes, comprising of onetime useable gloves, masks, tissues, and other personal protective equipment (PPE). Recommendations for the employ of single-use disposable masks made up of various polymeric materials like polyethylene, polyurethane, polyacrylonitrile, and polypropylene, polystyrene, can have significant aftermath on environmental, human as well as animal health. Improper disposal and handling of healthcare wastes and lack of proper management practices are creating serious health hazards and an extra challenge for the local authorities designated for management of solid waste. Most of the COVID-19 medical wastes generated are now being treated by incineration which generates microplastic particles (MPs), dioxin, furans, and various toxic metals, such as cadmium and lead. Moreover, natural degradation and mechanical abrasion of these wastes can lead to the generation of MPs which cause a serious health risk to living beings. It is a major threat to aquatic lives and gets into foods subsequently jeopardizing global food safety. Moreover, the presence of plastic is also considered a threat owing to the increased carbon emission and poses a profound danger to the global food chain. Degradation of MPs by axenic and mixed culture microorganisms, such as bacteria, fungi, microalgae etc. can be considered an eco-sustainable technique for the mitigation of the microplastic menace. This review primarily deals with the increase in microplastic pollution due to increased use of PPE along with different disinfection methods using chemicals, steam, microwave, autoclave, and incineration which are presently being employed for the treatment of COVID-19 pandemic-related wastes. The biological treatment of the MPs by diverse groups of fungi and bacteria can be an alternative option for the mitigation of microplastic wastes generated from COVID-19 healthcare waste.

Bioaugmentation with a defined bacterial consortium: A key to degrade high molecular weight polylactic acid during traditional composting

Polylactic acid (PLA) is commercialized as a compostable bio-thermoplastic. PLA degrades under industrial composting conditions where elevated temperatures are maintained for a long timeframe. However, these conditions cannot be achieved in a non-industrial compost pile. Therefore, this study aims to degrade high molecular weight PLA films by adding a PLA-degrading bacterial consortium (EAc) comprised of Nocardioides zeae EA12, Stenotrophomonas pavanii EA33, Gordonia desulfuricans EA63, and Chitinophaga jiangningensis EA02 during traditional composting. With EAc-bioaugmentation, PLA films (5-30% w/w) had complete disintegration (35 d), 77-82% molecular weight reduction (16 d), and higher CO₂ liberation and mineralization than non-bioaugmented composting. Bacterial community analyses showed that EAc-bioaugmentation increased the relative abundance of Schlegelella, a known polymer degrader, and interacted positively with beneficial indigenous microbes like Bacillus, Schlegelella and Thermopolyspora. The bioaugmentation also decreased compost phytotoxicity. Hence, consortium EAc shows potential in PLA-waste treatment applications, such as backyard and small-scale composting.

Degradation of polyethylene plastic bags and bottles using microorganisms isolated from soils of Morogoro, Tanzania

Plastics are of great significance in today's world due to their extensive use such as packaging food and carrying other goods, which have improved the quality of human life. However, plastics have low biodegradability and are persistent in the environment, becoming a major source of pollution. With regard to the current methods used in the management of plastic wastes, the degradation of plastics using beneficial soil microorganisms has recently gained attention due to their ability to degrade different types of plastics including polyethylene (PE) polymers. The study herein was conducted to isolate and identify microorganisms from agricultural soils capable of degrading plastics. Soil samples were inoculated into nutrient, potato dextrose, and starch-casein agar for the isolation of bacteria, fungi, and actinomycetes, respectively. During isolation, fungi and bacterial plates were incubated for 5 days and for 14 days, respectively. The population of bacteria ranged from 1 × 105 to 1.215 × 105 and that of fungi from 1.604 × 104 to 8.6 × 104 whereby actinomycetes ranged from 1.045 × 105 to 2.995 × 105 CFU/g of soil. However, the tested microorganisms showed significant (p ≤ 0.05) differences in the ability to degrade PE bags and bottles as depicted by the diameters of clear zones around the colonies. The diameters of clear zones ranged from 19.3 to 47.5 mm and 25.9 to 32.2 mm after 17 days for bacteria and actinomycetes, respectively, and those of fungi ranged from 30.0 to 66.3 mm after 13 days. Among the bacteria, actinomycetes, and fungi, unsequenced bacterial and actinomycete isolates B1 and A3 as well as Aspergillus sp. (F7) were the most efficient degraders of PE plastic bags. This retrospective study sheds light on our understanding and the need for the bioprospecting of agricultural soils, water bodies, and landfills containing plastic wastes that could lead to the identification of more efficient microbial species with the ability to degrade plastics.

Isolation of Thermophilic Bacteria and Investigation of Their Microplastic Degradation Ability Using Polyethylene Polymers

Microplastics (MPs) pose potential public health challenges because of their widespread occurrences in all environmental compartments. While most studies have focused on the occurrence fate of microplastics in wastewater treatment systems, the biodegradation of microplastics in wastewater is generally little understood. Therefore, we used two Gram-positive and thermophilic bacteria, called strain ST3 and ST6, which were identified by morphological, biochemical, physiological, and molecular analyses, to assess the growth and biodegradation potential of two different sized (50 and 150 m) polyethylene particles. The degradation was monitored based on structural and surface morphological changes. According to 16S rRNA analyses, ST3 and ST6 were identified as Anoxybacillus flavithermus ST3 and Anoxybacillus sp. ST6, respectively. The occurrence of cracks, holes, and dimensional changes was detected by scanning electron microscopy. Moreover, critical characteristic absorption band formation and modifications were determined by Fourier transform infrared spectroscopy. In addition to these, it was found that Anoxybacillus flavithermus ST3 and Anoxybacillus sp. ST6 produced high level of alpha-Amylase. These results showed that thermophilic bacteria are capable of the biodegradation of microplastics and production of alpha-Amylase.

Critical Review on the Progress of Plastic Bioupcycling Technology as a Potential Solution for Sustainable Plastic Waste Management

Plastic production worldwide has doubled in the last two decades and is expected to reach a four-fold increase by 2050. The durability of plastic makes them a perfect material for many applications, but it is also a key limitation to their end-of-life management. The current plastic lifecycle is far from circular, with only 13% being collected for recycling and 9% being successfully recycled, indicating the failure of current recycling technology. The remaining plastic waste streams are thus incinerated, landfilled, or worse, mismanaged, leading to them leaking into the environment. To promote plastic circularity, keeping material in the loop is a priority and represents a more sustainable solution. This can be achieved through the reuse of plastic items, or by using plastic waste as a resource for new materials, instead of discarding them as waste. As the discovery of plastic-degrading/utilizing microorganisms and enzymes has been extensively reported recently, the possibility of developing biological plastic upcycling processes is opening up. An increasing amount of studies have investigated the use of plastic as a carbon source for biotechnological processes to produce high-value compounds such as bioplastics, biochemicals, and biosurfactants. In the current review, the advancements in fossil-based plastic bio- and thermochemical upcycling technologies are presented and critically discussed. In particular, we highlight the developed (bio)depolymerization coupled with bioconversion/fermentation processes to obtain industrially valuable products. This review is expected to contribute to the future development and scale-up of effective plastic bioupcycling processes that can act as a drive to increase waste removal from the environment and valorize post-consumer plastic streams, thus accelerating the implementation of a circular (plastic) economy.

Removal of microplastics and nanoplastics from urban waters: Separation and degradation

The omnipresent micro/nanoplastics (MPs/NPs) in urban waters arouse great public concern. To build a MP/NP-free urban water system, enormous efforts have been made to meet this goal via separating and degrading MPs/NPs in urban waters. Herein, we comprehensively review the recent developments in the separation and degradation of MPs/NPs in urban waters. Efficient MP/NP separation techniques, such as adsorption, coagulation/flocculation, flotation, filtration, and magnetic separation are first summarized. The influence of functional materials/reagents, properties of MPs/NPs, and aquatic chemistry on the separation efficiency is analyzed. Then, MP/NP degradation methods, including electrochemical degradation, advanced oxidation processes (AOPs), photodegradation, photocatalytic degradation, and biological degradation are detailed. Also, the effects of critical functional materials/organisms and operational parameters on degradation performance are discussed. At last, the current challenges and prospects in the separation, degradation, and further upcycling of MPs/NPs in urban waters are outlined. This review will potentially guide the development of next-generation technologies for MP/NP pollution control in urban waters.

Current Advances in Biodegradation of Polyolefins

Polyolefins, including polyethylene (PE), polypropylene (PP) and polystyrene (PS), are widely used plastics in our daily life. The excessive use of plastics and improper handling methods cause considerable pollution in the environment, as well as waste of energy. The biodegradation of polyolefins seems to be an environmentally friendly and low-energy consumption method for plastics degradation. Many strains that could degrade polyolefins have been isolated from the environment. Some enzymes have also been identified with the function of polyolefin degradation. With the development of synthetic biology and metabolic engineering strategies, engineered strains could be used to degrade plastics. This review summarizes the current advances in polyolefin degradation, including isolated and engineered strains, enzymes and related pathways. Furthermore, a novel strategy for polyolefin degradation by artificial microbial consortia is proposed, which would be helpful for the efficient degradation of polyolefin.

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.

Recent developments in microbial degradation of polypropylene: Integrated approaches towards a sustainable environment

Fossil-fuel-based plastics have many enticing properties, but their production has resulted in significant environmental issues that require immediate attention. Despite the fact that these polymers are manmade, some bacteria can degrade and metabolise them, suggesting that biotechnologies based on the principle of plastic biodegradation could be beneficial. Among different types of plastics, polypropylene (PP), either having low or high density, is one of the most consumed plastics (18.85%). Their debasement under natural conditions is somewhat tricky. Still, their debasement under natural conditions is rather difficult slightly. However, different scientists have still made efforts by employing other microbes such as bacteria, fungi, and guts bacteria of larvae of insects to bio-deteriorate the PP plastic. Pre-irradiation techniques (ultraviolet and gamma irradiations), compatibilizers, and bio-additives (natural fibers, starch, and polylactic acid) have been found to impact percent bio-deterioration of different PP derivatives stronglythe various. The fungal and bacterial study showed that PP macro/microplastic might serve as an energy source and sole carbon during bio-degradation. Generally, gravimetric method or physical characterization techniques such as FTIR, XRD, SEM, etc., are utilized to affirm the bio-degradation of PP plastics-based materials. However, these techniques are not enough to warrant the bio-deterioration of PP. In this regard, a new technique approach that measures the amount of carbon dioxide emitted during bacterial or fungus degradation has also been discussed. In addition, further exploration is needed on novel isolates from plastisphere environments, sub-atomic strategies to describe plastic-debasing microorganisms and improve enzymatic action strategies, and omics-based innovations to speed up plastic waste bio-deterioration.

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

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

Lessons From Insect Fungiculture: From Microbial Ecology to Plastics Degradation

Anthropogenic activities have extensively transformed the biosphere by extracting and disposing of resources, crossing boundaries of planetary threat while causing a global crisis of waste overload. Despite fundamental differences regarding structure and recalcitrance, lignocellulose and plastic polymers share physical-chemical properties to some extent, that include carbon skeletons with similar chemical bonds, hydrophobic properties, amorphous and crystalline regions. Microbial strategies for metabolizing recalcitrant polymers have been selected and optimized through evolution, thus understanding natural processes for lignocellulose modification could aid the challenge of dealing with the recalcitrant human-made polymers spread worldwide. We propose to look for inspiration in the charismatic fungal-growing insects to understand multipartite degradation of plant polymers. Independently evolved in diverse insect lineages, fungiculture embraces passive or active fungal cultivation for food, protection, and structural purposes. We consider there is much to learn from these symbioses, in special from the community-level degradation of recalcitrant biomass and defensive metabolites. Microbial plant-degrading systems at the core of insect fungicultures could be promising candidates for degrading synthetic plastics. Here, we first compare the degradation of lignocellulose and plastic polymers, with emphasis in the overlapping microbial players and enzymatic activities between these processes. Second, we review the literature on diverse insect fungiculture systems, focusing on features that, while supporting insects' ecology and evolution, could also be applied in biotechnological processes. Third, taking lessons from these microbial communities, we suggest multidisciplinary strategies to identify microbial degraders, degrading enzymes and pathways, as well as microbial interactions and interdependencies. Spanning from multiomics to spectroscopy, microscopy, stable isotopes probing, enrichment microcosmos, and synthetic communities, these strategies would allow for a systemic understanding of the fungiculture ecology, driving to application possibilities. Detailing how the metabolic landscape is entangled to achieve ecological success could inspire sustainable efforts for mitigating the current environmental crisis.

Toward Microbial Recycling and Upcycling of Plastics: Prospects and Challenges

Annually, 400 Mt of plastics are produced of which roughly 40% is discarded within a year. Current plastic waste management approaches focus on applying physical, thermal, and chemical treatments of plastic polymers. However, these methods have severe limitations leading to the loss of valuable materials and resources. Another major drawback is the rapid accumulation of plastics into the environment causing one of the biggest environmental threats of the twenty-first century. Therefore, to complement current plastic management approaches novel routes toward plastic degradation and upcycling need to be developed. Enzymatic degradation and conversion of plastics present a promising approach toward sustainable recycling of plastics and plastics building blocks. However, the quest for novel enzymes that efficiently operate in cost-effective, large-scale plastics degradation poses many challenges. To date, a wide range of experimental set-ups has been reported, in many cases lacking a detailed investigation of microbial species exhibiting plastics degrading properties as well as of their corresponding plastics degrading enzymes. The apparent lack of consistent approaches compromises the necessary discovery of a wide range of novel enzymes. In this review, we discuss prospects and possibilities for efficient enzymatic degradation, recycling, and upcycling of plastics, in correlation with their wide diversity and broad utilization. Current methods for the identification and optimization of plastics degrading enzymes are compared and discussed. We present a framework for a standardized workflow, allowing transparent discovery and optimization of novel enzymes for efficient and sustainable plastics degradation in the future.