Microbial degradation of high impact polystyrene (HIPS), an e-plastic with decabromodiphenyl oxide and antimony trioxide

Integrating genomics, molecular docking, and protein expression to explore new perspectives on polystyrene biodegradation

Faced with the escalating challenge of global plastic pollution, this study specifically addresses the research gap in the biodegradation of polystyrene (PS). A PS-degrading bacterial strain was isolated from the gut of Tenebrio molitor, and genomics, molecular docking, and proteomics were employed to thoroughly investigate the biodegradation mechanisms of Pseudomonas putida H-01 against PS. Using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (ATR-FTIR), and contact angle analysis, significant morphological and structural changes in the PS films under the influence of the H-01 strain were observed. The study revealed several potential degradation genes and ten enzymes that were specifically upregulated in the PS degradation environment. Additionally, a novel protein with laccase-like activity, LacQ1, was purified from this strain for the first time, and its crucial role in the PS degradation process was confirmed. Through molecular docking and molecular dynamics (MD) simulations, the interactions between the enzymes and PS were detailed, elucidating the binding and catalytic mechanisms of the degradative enzymes with the substrate. These findings have deepened our understanding of PS degradation.

A Valuable Source of Promising Extremophiles in Microbial Plastic Degradation

Plastics have accumulated in open environments, such as oceans, rivers, and land, for centuries, but their effect has been of concern for only decades. Plastic pollution is a global challenge at the forefront of public awareness worldwide due to its negative effects on ecological systems, animals, human health, and national economies. Therefore, interest has increased regarding specific circular economies for the development of plastic production and the investigation of green technologies for plastic degradation after use on an appropriate timescale. Moreover, biodegradable plastics have been found to contain potential new hazards compared with conventional plastics due to the physicochemical properties of the polymers involved. Recently, plastic biodegradation was defined as microbial conversion using functional microorganisms and their enzymatic systems. This is a promising strategy for depolymerizing organic components into carbon dioxide, methane, water, new biomass, and other higher value bioproducts under both oxic and anoxic conditions. This study reviews microplastic pollution, the negative consequences of plastic use, and the current technologies used for plastic degradation and biodegradation mediated by microorganisms with their drawbacks; in particular, the important and questionable role of extremophilic multi-enzyme-producing bacteria in synergistic systems of plastic decomposition is discussed. This study emphasizes the key points for enhancing the plastic degradation process using extremophiles, such as cell hydrophobicity, amyloid protein, and other relevant factors. Bioprospecting for novel mechanisms with unknown information about the bioproducts produced during the plastic degradation process is also mentioned in this review with the significant goals of CO2 evolution and increasing H2/CH4 production in the future. Based on the potential factors that were analyzed, there may be new ideas for in vitro isolation techniques for unculturable/multiple-enzyme-producing bacteria and extremophiles from various polluted environments.

Understanding the Ecological Robustness and Adaptability of the Gut Microbiome in Plastic-Degrading Superworms (Zophobas atratus) in Response to Microplastics and Antibiotics

Recent discoveries indicate that several insect larvae are capable of ingesting and biodegrading plastics rapidly and symbiotically, but the ecological adaptability of the larval gut microbiome to microplastics (MPs) remains unclear. Here, we described the gut microbiome assemblage and MP biodegradation of superworms (Zophobas atratus larvae) fed MPs of five major petroleum-based polymers (polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate) and antibiotics. The shift of molecular weight distribution, characteristic peaks of C═O, and metabolic intermediates of residual polymers in egested frass proved depolymerization and biodegradation of all MPs tested in the larval intestines, even under antibiotic suppression. Superworms showed a wide adaptation to the digestion of the five polymer MPs. Antibiotic suppression negatively influenced the survival rate and plastic depolymerization patterns. The larval gut microbiomes differed from those fed MPs and antibiotics, indicating that antibiotic supplementation substantially shaped the gut microbiome composition. The larval gut microbiomes fed MPs had higher network complexity and stability than those fed MPs and antibiotics, suggesting that the ecological robustness of the gut microbiomes ensured the functional adaptability of larvae to different MPs. In addition, Mantel's test indicated that the gut microbiome assemblage was obviously related to the polymer type, the plastic degradability, antibiotic stress, and larval survival rate. This finding provided novel insights into the self-adaptation of the gut microbiome of superworms in response to different MPs.

Optimizing polystyrene degradation, microbial community and metabolite analysis of intestinal flora of yellow mealworms, Tenebrio molitor

This study explored a direct feeding of expanded polystyrene as the sole diet for breeding Tenebrio molitor larvae. Temperature and relative humidity were manipulated to evaluate polystyrene biodegradation efficiency, survival rate, and formation of micro-polystyrene residue. Efficient conditions were at temperature of 25 °C with a humidity of 65 ± 5 %. Comparative metabolomic and metabolic-metabolic network analyses was performed for visualizing detailed pathway. Possibility of forming 4 (p)-hydroxyphenylacetic acid from phenylacetic acid with further conversion to 4-methylphenol, 4-hydroxybenzaldehyde, and 4-hydroxybenzoate could be seen as a side chain route for further biodegrading process. Key species identified in the gut of T. molitor larvae included Citrobacter sp., Serratia marcescens, Klebsiella aerogenes, and Klebsiella oxytoca. Pseudomonas aeruginosa was detected only under an anaerobic condition whereas Acinetobacter sp. was present only under an aerobic condition. These results demonstrate the potential to decrease micro-polystyrene by optimizing breeding conditions and biodegradation process of polystyrene.

Polyethylene and sulfa antibiotic remediation in soil using a multifunctional degrading bacterium

To obtain a multifunctional bacterium that can effectively degrade polyethylene (PE) and sulfonamide antibiotics (SAs), PE and SAs were selected as the primary research objects. Multifunctional degrading bacteria were isolated and screened from an environment in which plastics and antibiotics have existed for a long time. An efficient degrading strain, Raoultella sp., was screened by measuring the degradation performance of PE and SAs. We analyzed the changes in the microbial community of indigenous bacteria using 16S rRNA. After 60 d of degradation at 28 °C, the Raoultella strain to PE degradation rate was 4.20 %. The SA degradation rates were 96 % (sulfonathiazole, (ST)), 86 % (sulfamerazine, (SM)), 72 % (sulfamethazine, (SM2)) and 64 % (sulfamethoxazole, (SMX)), respectively. This bacterium increases the surface roughness of PE plastic films and produces numerous gullies, pits, and folds. In addition, after 60 d, the contact angle of the plastic film decreased from 92.965° to 70.205°, indicating a decrease in hydrophobicity. High-throughput sequencing analysis of the degrading bacteria revealed that the Raoultella strain encodes enzymes involved in PE and SA degradation. The results of this study not only provide a theoretical basis for further study of the degradation mechanism of multifunctional and efficient degrading bacteria but also provide potential strain resources for the biodegradation of waste plastics and antibiotics in the environment.

Catalytic and biocatalytic degradation of microplastics

In recent years, there has been a surge in annual plastic production, which has contributed to growing environmental challenges, particularly in the form of microplastics. Effective management of plastic and microplastic waste has become a critical concern, necessitating innovative strategies to address its impact on ecosystems and human health. In this context, catalytic degradation of microplastics emerges as a pivotal approach that holds significant promise for mitigating the persistent effects of plastic pollution. In this article, we critically explored the current state of catalytic degradation of microplastics and discussed the definition of degradation, characterization methods for degradation products, and the criteria for standard sample preparation. Moreover, the significance and effectiveness of various catalytic entities, including enzymes, transition metal ions (for the Fenton reaction), nanozymes, and microorganisms are summarized. Finally, a few key issues and future perspectives regarding the catalytic degradation of microplastics are proposed.

Enhancing plastic biodegradation process: strategies and opportunities

Plastic biodegradation has emerged as a sustainable approach and green alternative in handling the ever-increasing accumulation of plastic wastes in the environment. The complete biodegradation of polyethylene terephthalate is one of the most recent breakthroughs in the field of plastic biodegradation. Despite the success, the effective and complete biodegradation of a wide variety of plastics is still far from the practical implementation, and an on-going effort has been mainly devoted to the exploration of novel microorganisms and enzymes for plastic biodegradation. However, alternative strategies which enhance the existing biodegradation process should not be neglected in the continuous advancement of this field. Thus, this review highlights various strategies which have shown to improve the biodegradation of plastics, which include the pretreatment of plastics using UV irradiation, thermal, or chemical treatments to increase the susceptibility of plastics toward microbial action. Alternative pretreatment strategies are also suggested and compared with the existing techniques. Besides, the effects of additives such as pro-oxidants, natural polymers, and surfactants on plastic biodegradation are discussed. In addition, considerations governing the biodegradation performance, such as the formulation of biodegradation medium, cell-free biocatalysis, and physico-chemical properties of plastics, are addressed. Lastly, the challenges and future prospects for the advancement of plastic biodegradation are also highlighted.

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.

Identification of the bacterial community that degrades phenanthrene sorbed to polystyrene nanoplastics using DNA-based stable isotope probing

In the Anthropocene, plastic pollution has become a new environmental biotope, the so-called plastisphere. In the oceans, nano- and micro-sized plastics are omnipresent and found in huge quantities throughout the water column and sediment, and their large surface area-to-volume ratio offers an excellent surface to which hydrophobic chemical pollutants (e.g. petrochemicals and POPs) can readily sorb to. Our understanding of the microbial communities that breakdown plastic-sorbed chemical pollutants, however, remains poor. Here, we investigated the formation of 500 nm and 1000 nm polystyrene (PS) agglomerations in natural seawater from a coastal environment, and we applied DNA-based stable isotope probing (DNA-SIP) with the 500 nm PS sorbed with isotopically-labelled phenanthrene to identify the bacterial members in the seawater community capable of degrading the hydrocarbon. Whilst we observed no significant impact of nanoplastic size on the microbial communities associated with agglomerates that formed in these experiments, these communities were, however, significantly different to those in the surrounding seawater. By DNA-SIP, we identified Arcobacteraceae, Brevundimonas, Comamonas, uncultured Comamonadaceae, Delftia, Sphingomonas and Staphylococcus, as well as the first member of the genera Acidiphilum and Pelomonas to degrade phenanthrene, and of the genera Aquabacterium, Paracoccus and Polymorphobacter to degrade a hydrocarbon. This work provides new information that feeds into our growing understanding on the fate of co-pollutants associated with nano- and microplastics in the ocean.

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

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

Exploring genetic landscape of low-density polyethylene degradation for sustainable troubleshooting of plastic pollution at landfills

Plastic pollution increases globally due to the high volume of its production and inadequate mismanagement, leading to dumps in landfills affecting terrestrial and aquatic ecosystems. Landfills, as sink for plastics, leach various toxic chemicals and microplastics into the environment. We scrutinized the genetic expression for low-density polyethylene (LDPE) degradation via microorganisms to investigate cell viability and metabolic activities for biodegradation and genetic profiling. Samples were collected from the Pirana waste landfill at Ahmedabad, Gujarat, which is one of the largest and oldest municipal solid waste (MSW) dump sites in Asia. Results analyzed that isolated bacterial culture PN(A)1 (Bacillus cereus) is metabolically active on LDPE as carbon source during starvation conditions when incubated for up to 60 days, which was confirmed via 2,3,5-triphenyl-tetrazolium chloride (TTC) reduction test, reported cell viability and LDPE degradation. Abrasions, surface erosions, and cavity formations were analyzed via scanning electron microscopy (SEM), whereas the breakdown of high molecular polymers converted to low molecules, i.e., depolymerization, was also observed via Fourier-transform infrared (FTIR) spectroscopy over 90 days, along with changes in functional groups of carboxylic acids and aldehyde as well as the formation of polysulfide, aliphatic compounds, aromatic ethers, alcohols, and ether linkages. Further, transcriptomic analysis was performed via DESeq2 analysis to understand key gene expression patterns and pathways involved in LDPE degradation. During the initial phase of LDPE degradation, genes related to biological processes, like membrane transportation, ABC transporters, carbon and lipid metabolism, fatty acid degradation/oxidation, and TCA cycle, are likely to indicate pathways for stress response and molecular functions, like oxidoreductase, catalytic, lyase, transferase, and hydrolase activities were expressed. Interlinking between metabolic pathways indicates biodegradation process that mineralizes LDPE during subsequent incubation days. These pathways can be targeted for increasing the efficiency of LDPE degradation using microbes in future studies. Thus, considering microbial-mediated biodegradation as practical, eco-friendly, and low-cost alternatives, healthy biomes can degrade polymers in natural environments explored by understanding the genetic and enzymatic expression, connecting their role in the process to the likely metabolic pathways involved, thereby increasing the rate of their biodegradation.

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.

Comprehensive understanding of the aging and biodegradation of polystyrene-based plastics

The extensive utilization and inadequate handling of plastics have resulted in severe environmental ramifications. In particular, plastics composed solely of a carbon-carbon (C-C) backbone exhibit limited degradation due to the absence of hydrolyzable functional groups. Plastics with enduring longevity in the natural environment are susceptible to environmental factors and their intrinsic properties, subsequently undergoing a series of aging processes that culminate in biodegradation. This article focuses on polystyrene (PS), which constitutes 20% of total plastic waste, as a case study. Initially, the application of PS in life and the impacts it poses are introduced. Following that, the key factors influencing the aging of PS are discussed, primarily encompassing its properties (e.g., surface characteristics, additives) and environmental factors (e.g., water matrices, biofilms). Lastly, an overview of microbial degradation of PS is provided, including potential microorganisms involved in PS degradation (bacteria, fungi, algae, and insects), four processes of microbial degradation (colonization, bio-fragmentation, assimilation, and mineralization), and potential mechanisms of microbial degradation. This study provides a comprehensive understanding of the multifaceted influences affecting the aging and biodegradation mechanisms of PS, thereby contributing valuable insights for the future management of plastic pollution.

Comparative e-waste plastics biodegradation efficacy of monoculture Pseudomonas aeruginosa strain PE10 and bacterial consortium under in situ condition

A significant amount of electronic obsoletes or electronic waste (e-waste) is being generated globally each year; of these, ~20% of obsolete electronic items have plastic components. Current remediation practices for e-waste have several setbacks due to its negative impact on the environment, agro-ecosystem, and human health. Therefore, comparative biodegradation studies of e-waste plastics by monoculture Pseudomonas aeruginosa strain PE10 and bacterial consortium consisting of Achromobacter insolitus strain PE2 (MF943156), Acinetobacter nosocomialis strain PE5 (MF943157), Pseudomonas lalkuanensis PE8 (CP043311), and Stenotrophomonas pavanii strain PE15 (MF943160) were carried out in situ. Biological treatment of e-waste with these candidates in soil ecosystems has been analyzed through diversified analytical techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric-derivative thermogravimetry-differential thermal analysis (TG-DTG-DTA), and scanning electron microscopy (SEM). Both P. aeruginosa strain PE10 and the bacterial consortium have a tremendous ability to accelerate the biodegradation process in the natural environment. However, FTIR analysis implied that the monoculture had better efficacy than the consortium, and it was consistent until the incubation period used for the study. Some polymeric bonds such as ν C=C and δ C-H were completely removed, and ν C=C ring stretching, νasym C-O-C, νsym C-H, etc. were introduced by strain PE10. Furthermore, thermal analysis results validated the structural deterioration of e-waste as the treated samples showed nearly two-fold weight loss (WL; 6.8%) than the untreated control (3.1%) at comparatively lower temperatures. SEM images provided the details of surface disintegrations. Conclusively, individual monoculture P. aeruginosa strain PE10 could be explored for e-waste bio-recycling in agricultural soil ecosystems thereby reducing the cost, time, and management of bioformulation in addition to hazardous pollutant reduction.

Diversity and community composition of strictly anaerobic and culturable bacteria from the feces of Styrofoam-fed Tenebrio molitor larvae: a culturomics-based study

Introduction

In recent years, researchers have been exploring the plastic-degrading abilities of bacteria residing in the guts of Styrofoam-eating Tenebrio molitor larvae. However, none of the reported strains have displayed highly efficient plastic degradation capabilities, and it's noteworthy that none of the existing studies have focused on strictly anaerobic microbes.

Methods

In this study, we exclusively fed Styrofoam to T. molitor larvae and examined how this dietary change influence the gut's bacterial community composition, as observed through fecal bacteria using bacterial 16S rRNA gene amplicon sequencing and the small-scale culturomics method with 20 types of anaerobic media under four different conditions.

Results

The results revealed a significant shift in the dominant phylogroup from Lactococcus (37.8%) to Escherichia-Shigella (54.7%) when comparing the feces of larvae fed with bran and Styrofoam, as analyzing through the bacterial 16S rRNA gene amplicon sequencing. For small-scale culturomics method, a total of 226 strains of anaerobic bacteria were isolated and purified using the rolling-tube/strictly anaerobic technique. Among them, 226 strains were classified into 3 phyla, 7 classes, 9 orders, 17 families, 29 genera, 42 known species and 34 potential novel species.

Discussion

Interestingly, 24 genera in total, identified through the culturomics method, were not found in the results obtained from amplicon sequencing. Here, we present a collection of culturable anaerobic bacteria from the feces of T. molitor larvae, which might be a promising avenue for investigating the biodegradability of plastics by combining specific strains, either randomly or intentionally, while considering the abundance ratio of the microbial community composition.

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.

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.

Degradation characteristics of polyethylene film by microorganisms from lake sediments

Polyethylene (PE) exists widely in many habitats as a persistent organic pollution and poses a major threat to the ecological environment. In this study, bacterial communities in freshwater lake sediments were exposed to culture media using PE films as the sole carbon source in aerobic and anaerobic microculture environments, and they were able to adhere and adapt to the PE films for a longer period of time. The results demonstrated that the pH value of the medium in the two cultural conditions was distinct, as were the rates of films weight loss and surface functional group alterations. We also concluded the certain bacterial genera from freshwater lake sediments who may be able to degrade PE films under either aerobic or anaerobic conditions. Simultaneously, the dominating bacterial communities between the medium and the film differed significantly under two cultural settings, as did the community composition, while metabolism was the primary function.

Biodegradation of polystyrene by intestinal symbiotic bacteria isolated from mealworms, the larvae of Tenebrio molitor

Objectives

Polystyrene is a plastic that leads to environmental pollution. In particular, expanded polystyrene is very light and takes up much space, causing additional environmental problems. The aim of this study was to isolate new symbiotic bacteria which degraded polystyrene from mealworms.

Methods

The population of polystyrene degrading bacteria was increased by enrichment culture of intestinal bacteria from mealworms with polystyrene as a sole carbon source. The degradation activity of isolated bacteria was evaluated by morphological change of micro-polystyrene particles and the surface change of polystyrene films.

Results

Eight isolated species (Acinetobacter septicus, Agrobacterium tumefaciens, Klebsiella grimontii, Pseudomonas multiresinivorans, Pseudomonas nitroreducens, Pseudomonas plecoglossicida, Serratia marcescens, and Yokenella regensburgei) were identified that degrade polystyrene.

Conclusion

Bacterial identification shows that a broad spectrum of bacteria decomposing polystyrene coexists in the intestinal tract of mealworms.

Novel CuMgAlTi-LDH Photocatalyst for Efficient Degradation of Microplastics under Visible Light Irradiation

Microplastics (MPs) in the water system could easily enter the human body and pose a potential threat, so finding a green and effective solution remains a great challenge. At present, the advanced oxidation technology represented by photocatalysis has been proven to be effective in the removal of organic pollutants, making it a feasible method to solve the problem of MP pollution. In this study, the photocatalytic degradation of typical MP polystyrene (PS) and polyethylene (PE) by a new quaternary layered double hydroxide composite photomaterial CuMgAlTi-R400 was tested under visible light irradiation. After 300 h of visible light irradiation, the average particle size of PS decreased by 54.2% compared with the initial average particle size. The smaller the particle size, the higher the degradation efficiency. The degradation pathway and mechanism of MPs were also studied by GC-MS, which showed that PS and PE produced hydroxyl and carbonyl intermediates in the process of photodegradation. This study demonstrated a green, economical, and effective strategy for the control of MPs in water.

Potential effects of micro- and nanoplastics on phyllosphere microorganisms and their evolutionary and ecological responses

Plastic pollution is among the most urgent environmental and social challenges of the 21st century, and their influxes in the environment have altered critical growth drivers in all biomes, attracting global concerns. In particular, the consequences of microplastics on plants and their associated soil microorganisms have gained a large audience. On the contrary, how microplastics and nanoplastics (M/NPs) may influence the plant-associated microorganisms in the phyllosphere (i.e., the aboveground portion of plants) is nearly unknown. We, therefore, summarize evidence that may potentially connect M/NPs, plants, and phyllosphere microorganisms based on studies on other analogous contaminants such as heavy metals, pesticides, and nanoparticles. We show seven pathways that may link M/NPs into the phyllosphere environment, and provide a conceptual framework explaining the direct and indirect (soil legacy) effects of M/NPs on phyllosphere microbial communities. We also discuss the adaptive evolutionary and ecological responses, such as acquiring novel resistance genes via horizontal gene transfer and microbial degradation of plastics of the phyllosphere microbial communities, to M/NPs-induced threats. Finally, we highlight the global consequences (e.g., disruption of ecosystem biogeochemical cycling and impaired host-pathogen defense chemistry that can lead to reduced agricultural productivity) of altered plant-microbiome interactions in the phyllosphere in the context of a predicted surge of plastic production and conclude with pending questions for future research priorities. In conclusion, M/NPs are very likely to produce significant effects on phyllosphere microorganisms and mediate their evolutionary and ecological responses.

Biodegradation of Expanded and Extruded Polystyrene with Different Diets by Using Zophobas atratus Larvae (Coleoptera: Tenebrionidae)

Polystyrene waste pollutes the environment and poses a significant health risk to humans, animals, and marine ecology. This study aims to evaluate the effectiveness of degradation on expanded (EPS) and extruded (XPS) polystyrene with different diets using superworms (Zophobas atratus larvae) obtained in Malaysia. The growth and development of the larvae after consumption of EPS and XPS and the gut microbial community changes in response to high polystyrene consumption diets were also identified. The oatmeal, wheat bran, and cornmeal were used as supplement diets and showed significantly enhanced EPS and XPS consumption and degradation compared to sole diet treatment. Gel permeation chromatography was carried out using egested frass of Z. atratus larvae to characterize depolymerization of EPS and XPS, indicating a significant reduction in the average molecular weight and average molecular weight. The highest reduction occurred in the presence of oatmeal. Proton nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses indicated functional group changes and chemical modification occurred with depolymerization and partial oxidation of EPS and XPS. The larvae length increased, while the number of instars and duration of larvae became shorter with the addition of supplement diets. Oatmeal is predominantly effective among other supplements in assisting Z. atratus larvae with EPS and XPS degradation. The results of this study support the ubiquity of polystyrene biodegradation in Z. atratus and the next-generation sequencing studies. Kluyvera sp., Klebsiella sp., and Enterobacter sp. were found to be strongly associated with degrading EPS and XPS polystyrene with oatmeal as a supplemental diet.

Evaluation of the Deterioration of Untreated Commercial Polystyrene by Psychrotrophic Antarctic Bacterium

Polystyrene (PS) and microplastic production pose persistent threats to the ecosystem. Even the pristine Antarctic, which is widely believed to be pollution-free, was also affected by the presence of microplastics. Therefore, it is important to comprehend the extent to which biological agents such as bacteria utilise PS microplastics as a carbon source. In this study, four soil bacteria from Greenwich Island, Antarctica, were isolated. A preliminary screening of the isolates for PS microplastics utilisation in the Bushnell Haas broth was conducted with the shake-flask method. The isolate AYDL1 identified as Brevundimonas sp. was found to be the most efficient in utilising PS microplastics. An assay on PS microplastics utilisation showed that the strain AYDL1 tolerated PS microplastics well under prolonged exposure with a weight loss percentage of 19.3% after the first interval (10 days of incubation). Infrared spectroscopy showed that the bacteria altered the chemical structure of PS while a deformation of the surface morphology of PS microplastics was observed via scanning electron microscopy after being incubated for 40 days. The obtained results may essentially indicate the utilisation of liable polymer additives or "leachates" and thus, validate the mechanistic approach for a typical initiation process of PS microplastics biodeterioration by the bacteria (AYDL1)-the biotic process.

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.

Microbial Enzyme Biotechnology to Reach Plastic Waste Circularity: Current Status, Problems and Perspectives

The accumulation of synthetic plastic waste in the environment has become a global concern. Microbial enzymes (purified or as whole-cell biocatalysts) represent emerging biotechnological tools for waste circularity; they can depolymerize materials into reusable building blocks, but their contribution must be considered within the context of present waste management practices. This review reports on the prospective of biotechnological tools for plastic bio-recycling within the framework of plastic waste management in Europe. Available biotechnology tools can support polyethylene terephthalate (PET) recycling. However, PET represents only ≈7% of unrecycled plastic waste. Polyurethanes, the principal unrecycled waste fraction, together with other thermosets and more recalcitrant thermoplastics (e.g., polyolefins) are the next plausible target for enzyme-based depolymerization, even if this process is currently effective only on ideal polyester-based polymers. To extend the contribution of biotechnology to plastic circularity, optimization of collection and sorting systems should be considered to feed chemoenzymatic technologies for the treatment of more recalcitrant and mixed polymers. In addition, new bio-based technologies with a lower environmental impact in comparison with the present approaches should be developed to depolymerize (available or new) plastic materials, that should be designed for the required durability and for being susceptible to the action of enzymes.

Isolation and Degradation Characteristics of PBAT Film Degrading Bacteria

In recent years, PBAT (polybutylene adipate-co-terephthalate) mulch has become one of the most commonly used biodegradable mulching films. In this paper, five potential strains of PBAT film degrading bacteria were screened from the soil sample using PBAT film as the sole carbon source. A highly efficient PBAT degrading strain JZ1 was isolated by comparing the degradation performance of PBAT mulching film identified as Peribacillus frigoritolerans S2313 by 16S rDNA sequence analysis. The capacity of the strain to degrade PBAT film was optimized by adjusting the cultivation conditions such as nitrogen source, pH, and inoculum volume. After 8 weeks of cultivation, the actual degradation rate of the strain to PBAT mulch film reached 12.45%. SEM (scanning electron microscopy) coupled with EDX (energy dispersive spectroscopy) analysis showed that microbial degradation is an oxidation process and is mainly due to the amorphous regions of the PBAT film. The biodegradation of PBAT film by Peribacillus frigoritolerans may provide a promising method for regulating the degradation progress of PBAT film in the farmlands.

Synergism Between Multi-Pseudomonas and Cutinase for Biodegradation of Crude Oil-Based Derivatives

Polyethylene terephthalate (PET) as one of the main crude oil-based derivatives, produces a significant amount of waste that is difficult to degrade. Currently, microbial degradation of PET is an eco-friendly, efficient, and economical method. This study was conducted to propose a novel screening strategy for PET-degrading bacteria, and evaluate their degradation efficiency of PET. Two strains, Pseudomonas nitroreducens S8 and Pseudomonas monteilii S17, were isolated and could utilize PET as a carbon source by co-culture. The combined use of both bacteria gave a synergistic effect on the disruption of the PET surface through colonization behavior, which could enhance the subsequent degradation of PET. Its time of reaching a peak value of PET degradation rate (94.5% at 6 d) was 2 days earlier than these of single bacteria. A similar synergistic effect was also observed in the metabolization of PET monomers, and the metabolic rate was expressed as 82.4% of bis (2-hydroxyethyl) terephthalate (BHET), 64.0% of mono (2-hydroxyethyl) terephthalate (MHET), and 20.0% of terephthalic acid (TPA), respectively. This study is novel in showing the degradation of PET waste by combinations of bacterial pretreatment and enzymatic treatment, which can be a promising method.

Development of multifarious carrier materials and impact conditions of immobilised microbial technology for environmental remediation: A review

Microbial technology is the most sustainable and eco-friendly method of environmental remediation. Immobilised microorganisms were introduced to further advance microbial technology. In immobilisation technology, carrier materials distribute a large number of microorganisms evenly on their surface or inside and protect them from external interference to better treat the targets, thus effectively improving their bioavailability. Although many carrier materials have been developed, there have been relatively few comprehensive reviews. Therefore, this paper summarises the types of carrier materials explored in the last ten years from the perspective of structure, microbial activity, and cost. Among these, carbon materials and biofilms, as environmentally friendly functional materials, have been widely applied for immobilisation because of their abundant sources and favorable growth conditions for microorganisms. The novel covalent organic framework (COF) could also be a new immobilisation material, due to its easy preparation and high performance. Different immobilisation methods were used to determine the relationship between carriers and microorganisms. Co-immobilisation is particularly important because it can compensate for the deficiencies of a single immobilisation method. This paper emphasises that impact conditions also affect the immobilisation effect and function. In addition to temperature and pH, the media conditions during the preparation and reaction of materials also play a role. Additionally, this study mainly reviews the applications and mechanisms of immobilised microorganisms in environmental remediation. Future development of immobilisation technology should focus on the discovery of novel and environmentally friendly carrier materials, as well as the establishment of optimal immobilisation conditions for microorganisms. This review intends to provide references for the development of immobilisation technology in environmental applications and to further the improve understanding of immobilisation technology.

Insight into biofilm-forming patterns: biofilm-forming conditions and dynamic changes in extracellular polymer substances

The microbial biofilm adheres to the surface of the carrier, which protects the pollutant-degrading bacteria and resists harsh environments; thus, research on biofilm-forming patterns will help promote the application of biofilms in wastewater treatment. Herein, univariate analysis and response surface methodology (RSM) confirmed that glucose and mannose at 3-5 g/L promoted biofilm formation. Notably, the microplate method demonstrated that compared to trivalent cations, divalent cations could more greatly enhance the activity (especially magnesium) of the biofilm matrix, and the period of biofilm formation in the three strains was divided into the following stages: initial attachment (0-10 h), microcolony (10-24 h), maturation (24-48 h), and dispersion (36-72 h). During maturation, large amounts of extracellular polysaccharides (EPs) and extracellular DNA (eDNA) were distributed in the extracellular and intracellular spaces, respectively, as observed by super-resolution structured illumination microscopy (SR-SIM). This study enhances the understanding of the characteristics and patterns of biofilm formation and can facilitate the application of biofilms in wastewater treatment.

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.

Influence of nitric acid on biodegradation of polystyrene and low-density polyethylene by Cephalosporium species

Petroleum-based polymers are not susceptible to microorganisms because of its high molecular weight. Acid treatments convert the polymers into a more oxidized form having low molecular weight. The present in-vitro degradation study focuses on the potential of Cephalosporium species to degrade acid-treated polystyrene (PS) and low-density polyethylene (LDPE) films. A weight loss of around 12% and 13% was achieved for PS and LDPE films respectively in eight weeks of treatment with Cephalosporium species. Fourier transform infrared spectroscopy analysis showed the formation of hydroxyl and carbonyl groups in nitric acid treated PS and LDPE films, respectively. Scanning electron microscopy indicated modifications in the surface morphology of PS and LDPE films after chemical and microbial treatment. An increase in crystallinity of pre-treated polymer samples was observed after fungal treatment. The observations of present study confirmed the enzymatic deterioration and assimilation of pre-treated PS and LDPE samples by the microbial species.

Polystyrene shaping effect on the enriched bacterial community from the plastic-eating Alphitobius diaperinus (Insecta: Coleoptera)

Plastic pollution has become a serious issue of global concern, and biodegradation of plastic wastes is representing one attractive environment-friendly alternative to traditional disposal paths. It is known that insects are involved in the plastic polymer degradation process, with reported evidence of tenebrionid beetle larvae capable to degrade polystyrene (PS), one of the most used plastics worldwide. Recently, a ribosomal RNA based survey on the insect gut microbiota of the lesser mealworm Alphitobius diaperinus has revealed differentially abundant microbial taxa between PS-fed larvae and control group. Following these findings, an enrichment bacterial culture was set up in liquid carbon-free basal medium with PS film as sole carbon source using PS-fed larvae of A. diaperinus as inoculum. After two-months the culture was analysed both by molecular and culture-based methods. Isolated bacteria which had become prevalent under the selective enrichment conditions resulted ascribable to three taxonomic groups: Klebsiella, Pseudomonas, and Stenothrophomonas. The predominance of these groups in PS-fed larvae was confirmed by using bacterial 16S rRNA gene amplicon sequencing, and it was consistent with the results of previous reports. Isolated bacteria were able to attach to PS surfaces and SEM observations showed the presence of thin fibrillar structures connecting the bacterial cells to the abiotic surface.

Biodegradation of polyethylene and polystyrene: From microbial deterioration to enzyme discovery

The global production of plastics has continuously been soaring over the last decades due to their extensive use in our daily life and in industries. Although synthetic plastics offer great advantages from packaging to construction and electronics, their low biodegradability induce serious plastic pollution that damage the environment, human health and make irreversible changes in the ecological cycle. In particular, plastics containing only carbon-carbon (C-C) backbone are less susceptible to degradation due to the lack of hydrolysable groups. The representative polyethylene (PE) and polystyrene (PS) account for about 40% of the total plastic production. Various chemical and biological processes with great potential have been developed for plastic recycle and reuse, but biodegradation seems to be the most attractive and eco-friendly method to combat this growing environmental problem. In this review, we first summarize the current advances in PE and PS biodegradation, including isolation of microbes and potential degrading enzymes from different sources. Next, the state-of-the-art techniques used for evaluating and monitoring PE and PS degradation, the scientific toolboxes for enzyme discovery as well as the challenges and strategies for plastic biodegradation are intensively discussed. In return, it inspires a further technological exploration in expanding the diversity of species and enzymes, disclosing the essential pathways and developing new approaches to utilize plastic waste as feedstock for recycling and upcycling.

Biodegradation of petroleum based and bio-based plastics: approaches to increase the rate of biodegradation

Plastic production and consumption are on the rise due to their variety of uses. Plastics often accumulate in the environment and pose a risk due to the lack of a viable strategy for their safe disposal. Even prohibiting plastic covers does not solve the problems of plastic waste generation. Plastics are degraded by various microbes, although at a very slow rate. In addition, efforts to enhance plastic degradation efficiency by microbes are rarely addressed. This paper describes the biodegradation of both petroleum-based and bio-based plastics, as well as studies on plastic biodegradation in both the Indian and global scenarios. This paper also discusses the biochemical and molecular aspects of plastic biodegradation, which are essential since they disclose more about how bacteria break down plastics. We also shed light on initiatives to boost biodegradation rates using various strategies in this article. Understanding the enzymes and genes involved in biodegradation would also help researchers figure out how to use them to enhance microorganism's ability to degrade plastic.

Remediation potential of immobilized bacterial strain with biochar as carrier in petroleum hydrocarbon and Ni co-contaminated soil

The remediation of organic pollutant-heavy metal co-contaminated soil is a great challenge. Immobilized microorganism technology (IMT) is a potential approach to remediate co-contaminated soil. In this study, we evaluated the feasibility of IMT for the remediation of petroleum hydrocarbon-heavy metal nickel (Ni) co-contaminated soil. The Ni resistant and hydrocarbon-degrading bacteria strain Citrobacter sp. was added to co-contaminated soil by immobilizing on corncob biochar. The potential performance in biodegradation of petroleum hydrocarbon and changing the mobility and speciation of nickel (Ni) in soil were determined, with consideration of the influences of the soil properties and dehydrogenase activity. The results demonstrated that the degradation rate of petroleum hydrocarbons by immobilized microorganisms group (IM) was 45.52%, significantly higher than that of the free bacteria (30.15%), biochar (25.92%) and blank group (18.47%) (P<0.05). At the same time, IM was more effective in immobilizing Ni in the soil by transforming available Ni to a stable fraction with a maximum residual concentration increasing by 101.50 mg·kg^-1, and the carcinogenic nickel sulfide was not detected after remediation in IM. IM exhibited a higher level of soil dehydrogenase activity (0.3956 μg·mL^-1·h^-1·g^-1) than that of free bacteria (0.2878 μg·mL^-1·h^-1·g^-1). A linear correlation was found between the petroleum pollutants degradation rate and dehydrogenase activity (P<0.05). This study indicates the effectiveness and potential of IMT application in degrading petroleum hydrocarbon and immobilizing heavy metals in co-contaminated soil.

Plastic recycling and their use as raw material for the synthesis of carbonaceous materials

Pollution by polymeric materials - in particular plastics - has a negative effect on the health of our planet. Approximately 4.9 billion tons of plastic are estimated to have been improperly disposed of, with the environment as their final destination. This scenario comes from a linear economic system, extraction-production-consumption and finally disposal. The alarming panorama has created the need to find technological solutions that generate new uses for discarded polymeric materials or turn them into part of the production process to produce new and novel materials, such as carbon nanotubes, graphene, or other carbonaceous materials of high added value, modifying the economy for a circular and sustainable production model. This review highlights the negative impact that the disposal of plastic materials has on the environment and the research needs that allow solving the pollution problems generated in the environment by these wastes. Also, the review highlights the current and future directions of recovery plastic waste research-based to promote innovations in the plastic production sector that could allow obtaining breakpoints in other industrial sectors with the technology-based companies.

Biologically engineered microbes for bioremediation of electronic waste: Wayposts, challenges and future directions

In the face of a burgeoning stream of e-waste globally, e-waste recycling becomes increasingly imperative, not only to mitigate the environmental and health risks it poses but also as an urban mining strategy for resource recovery of precious metals, rare Earth elements, and even plastics. As part of the continual efforts to develop greener alternatives to conventional approaches of e-waste recycling, biologically assisted degradation of e-waste offers a promising recourse by capitalising on certain microorganisms' innate ability to interact with metals or degrade plastics. By harnessing emerging genetic tools in synthetic biology, the evolution of novel or enhanced capabilities needed to advance bioremediation and resource recovery could be potentially accelerated by improving enzyme catalytic abilities, modifying substrate specificities, and increasing toxicity tolerance. Yet, the management of e-waste presents formidable challenges due to its massive volume, high component complexity, and associated toxicity. Several limitations will need to be addressed before nascent laboratory-scale achievements in bioremediation can be translated to viable industrial applications. Nonetheless, vested groups, involving both start-up and established companies, have taken visionary steps towards deploying microbes for commercial implementation in e-waste recycling.

Biodegradation of plastics for sustainable environment

Plastics are a kind of utility product that has become part and parcel of one's life. Their continuous usage, accumulation, and contamination of soil and water pose a severe threat to the biotic and abiotic components of the environment. It not only increases the carbon footprints but also contributes to global warming. This calls for an urgent need to develop novel strategies for the efficient degradation of plastics. The microbial strains equipped with the potential of degrading plastic materials, which can further be converted into usable products, are blessings for the ecosystem. This review comprehensively summarizes the microbial technologies to degrade different plastic types, such as polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), and polyurethane (PU). The study also describes the utilization of degraded plastic material as feedstock for its conversion into high-value chemicals.

Accelerated biodegradation of polyethylene terephthalate by Thermobifida fusca cutinase mediated by Stenotrophomonas pavanii

Polyethylene terephthalate (PET) is a general plastic that produces a significant amount of waste due to its non-biodagradable properties. We obtained four bacteria (Stenotrophomonas pavanii JWG-G1, Comamonas thiooxydans CG-1, Comamonas koreensis CG-2 and Fulvimonas soli GM-1) that utilize PET as a sole carbon source through a novel stepwise screening and verification strategy. PET films pretreated with S. pavanii JWG-G1 exhibited weight loss of 91.4% following subsequent degradation by Thermobifida fusca cutinase (TfC). S. pavanii JWG-G1 was able to colonize the PET surface and maintain high cell viability (over 50%) in biofilm, accelerating PET degradation. Compared with PET films with no pretreatment, pretreatment with S. pavanii JWG-G1 caused the PET surface to be significantly rougher with greater hydrophilicity (contact angle of 86.3 ± 2° vs. 96.6 ± 2°), providing better opportunities for TfC to contact and act on PET. Our study indicates that S. pavanii JWG-G1 could be used as a novel pretreatment for efficiently accelerating PET biodegradation by TfC.

Enhanced microbial degradation of PET and PS microplastics under natural conditions in mangrove environment

In-situ bioremediation of mangrove soil contaminated with polyethylene terephthalate (PET) and polystyrene (PS) microplastics was investigated using indigenous microbial consortium with adequate capacity to degrade the plastics. Eight (8) bacteria were isolated from plastic/microplastic-inundated mangrove soil and screened for the ability to degrade PET and PS microplastics. Optical density at 600 nm and colony forming unit counts were measured to evaluate the growth response of the microbes in the presence of PS and PET microplastics at different times of exposure. Structural and surface changes that occurred post biodegradation on the microplastics were determined through EDS and SEM analysis. The obtained results demonstrated the elongation and disappearance of peaks, suggesting that the microbial consortium could modify both types of microplastics. The overall results of the microplastic degradation showed varied degrees of weight loss after 90 experimental days, with the treated plot recorded 18% weight loss. The augmented soil was increased in the concentrations of Si S, and Fe and decreased in the concentrations of C, O, Na, Mg, Al, Cl, and K after bioremediation.

Feeding preference of insect larvae to waste electrical and electronic equipment plastics

Waste electrical and electronic equipment (WEEE) plastics not only pollute the environment, but are challenging to treat in an environmentally friendly manner. Biodegradation by insect larvae is potentially an eco-friendly method to treat WEEE plastics, but information about the feeding preference of insect larvae to WEEE plastics is lacking. In this study, a total of nine WEEE and pristine plastics were chosen to feed larvae of the following two insect species, i.e. Galleria mellonella and Tenebrio molitor. G. mellonella larvae significantly favor corresponding pristine plastics compared to two types of WEEE plastics, waste rigid polyurethane (RPU) and waste polystyrene (PS). One possible explanation is the increased chlorine or metals in the WEEE plastics measured using X-ray fluorescence spectrometer analysis. Scanning electron microscopy and Fourier transform infrared spectroscopy show that the destruction of physical structures and changes in surface functional groups were found in the two types of WEEE plastics in the larval frass, implying that the larvae partly biodegraded the plastics. Meanwhile, the powdered waste high impact polystyrene plastics (WHIPS) were ingested, but not the lumpy ones, indicating that the consumption by G. mellonella larvae is improved by the WHIPS physical modification. In addition, G. mellonella larvae presented the following decreasing preference for pristine plastics under individual-plastic-fed mode: RPU > phenol-formaldehyde resin > polyethylene (PE) > polypropylene > PS ≈ polyvinyl chloride; this is possibly due to differences in physical properties and chemical structures of the plastics; feeding preference of the larvae under multiple-plastics-fed mode is relatively consistent to that under individual-plastic-fed mode. Interestingly, the consumption by G. mellonella larvae of PE is higher than that of PS, while T. molitor larvae showed the opposite trend, implying that insect larvae have different plastics preference. The findings provide insights into biodegradation of WEEE plastics by insect larvae.

A critical review on microbial degradation of petroleum-based plastics: quantitatively effects of chemical addition in cultivation media on biodegradation efficiency

Petroleum-based plastics (PBP) with different properties have been developed to suit various needs of modern lives. Nevertheless, these well-developed properties also present the double-edged sword effect that significantly threatens the sustainability of the environment. This work focuses on the impact of microbial cultivating conditions (the elementary compositions and temperature) to provide insightful information for the process optimization of microbial degradation. The major elementary compositions in cultivation media and temperature from the literature were radically reviewed and assessed using the constructed supervised machine learning algorithm. Fifty-two literatures were collected as a training dataset to investigate the impact of major chemical elements and cultivation temperature upon PBP biodegradation. Among six singular parameters (NH₄⁺, K⁺, PO₄^3-, Mg²⁺, Ca²⁺, and temperature) and thirty corresponding binary parameters, four singular (NH₄⁺, K⁺, PO₄^3-, and Mg²⁺) and six binary parameters (NH₄⁺/K⁺, NH₄⁺/PO₄^3-, NH₄⁺/Ca²⁺, K⁺/PO₄^3-, PO₄^3-/Mg²⁺, Mg²⁺/Temp) were identified as statistically significant towards microbial degradation through analysis of variance (ANOVA). The binary effect (PO₄^3-/Mg²⁺) is found to be the most statistically significant towards the microbial degradation of PBP. The concentration range, which locates at 0.1-0.6 g/L for Mg²⁺ and 0-2.8 g/L for PO₄^3-, was identified to contribute to the maximum PBP biodegradation. Among all the investigated elements, Mg²⁺ is the only element that is statistically and significantly associated with the variations of cultivation temperature. The optimal preparation conditions within ± 20% uncertainties based upon the range of collected literature reports are recommended. Five representative cultivation elementary compositions (NH₄⁺, K⁺, PO₄^3-, Mg²⁺, and Ca²⁺) and temperature were reviewed from fifty two different literature reports to investigate their impacts on the microbial degradation of PBP using supervised machine learning algorithm. The optimal cultivation conditions based upon collected literature reports to achieve biodegradation over 80% were identified.

Fate of a biobased polymer via high-solid anaerobic co-digestion with food waste and following aerobic treatment: Insights on changes of polymer physicochemical properties and the role of microbial and fungal communities

Degradation of bioplastics in food-waste-treating anaerobic digestion (AD) plants is becoming an increasingly concerning issue as they are inevitably mixed with food waste during the waste collection process. The aim of this study was to assess the degradation of PBAT/PLA based biopolymer bags during mesophilic and thermophilic AD, co-digested with food waste, and subsequent aerobic post-treatment. After the AD process, no discernable biological degradation was observed for all of the PBAT/PLA polymers. The comparison of FTIR, XRD, TG analysis and contact angle analysis between raw and degraded PBAT/PLA polymer revealed structural changes after anaerobic incubation. Subsequent aerobic treatment facilitated the degradation of the PBAT/PLA polymers from thermophilic AD, which was attributed to the polymer-degrading microorganisms Brevundimonas and Sphingobacterium. Physical disintegration of the PBAT/PLA polymer was observed under thermophilic conditions. Those undegraded polymer fragments could affect digestate quality and increase the risk of releasing microplastics into the environment.

Microbial Degradation of Plastics and Approaches to Make it More Efficient

Abstract—

The growing worldwide production of synthetic plastics leads to increased amounts of plastic pollution. Even though microbial degradation of plastics is known to be a very slow process, this capacity has been found in many bacteria, including invertebrate symbionts, and microscopic fungi. Research in this field has been mostly focused on microbial degradation of polyethylene, polystyrene, and polyethylene terephthalate (PET). Quite an arsenal of different methods is available today for detecting processes of plastic degradation and measuring their rates. Given the lack of generally accepted protocols, it is difficult to compare results presented by different authors. PET degradation by recombinant hydrolases from thermophilic actinobacteria happens to be the most efficient among the currently known plastic degradation processes. Various approaches to accelerating microbial plastic degradation are also discussed.

Isolation and identification of low-density polyethylene degrading novel bacterial strains

Plastics are usually made up of low-density polyethylene (LDPE) that serve as the environmental nuisance. The recalcitrant nature of plastics is a huge concern, whereas the increasing demand has made it difficult to handle the plastic waste that eventually leads to plastic pollution. In recent years, due to increasing demand and high pressure for its safe disposal, plastic biodegradation has gained a lot of attention. In the current study, four bacterial strains were isolated from the solid-waste dumpsites of Faisalabad, Pakistan, using enrichment culture technique. The isolated bacterial strains were capable of growing on media having polystyrene as the sole carbon source. Based on 16S rRNA gene sequencing and phylogenetic analysis of the isolated strains Serratia sp., Stenotrophomonas sp. and Pseudomonas sp. were identified as the potential strains for the biodegradation of LDPE. Serratia sp. resulted in 40% weight loss of the LDPE plastic pieces after 150 days of treatment. Stenotrophomonas sp. and Pseudomonas species resulted in 32 and 21% weight loss of the treated piece of plastics (LDPE), respectively. Polyethylene pieces were characterized by Fourier-transform infrared spectroscopy (FTIR) analysis before and after biodegradation. The FTIR spectra indicated that the isolated bacterial strains have a good potential to degrade LDPE. Future studies are required to investigate the bacterial genetic makeup, mechanisms of LDPE biodegradation and the factors that can enhance the biodegradable characteristics of these indigenously isolated bacterial strains.

Photo-catalytic and biotic degradation of polystyrene packaging film: Effect of zinc oxide photocatalyst nanoparticles and nanoclay

Synergistic effect of zinc oxide nanoparticles (ZnO-NPs) as photocatalyst and organonanoclay (ONC) as biodegradable promoter on the degradation of polystyrene (PS) film was investigated. The films were exposed to ultraviolet irradiation under ambient air at room temperature for photo-catalytic degradation and then submitted to biodegradation test in soil using respirometric procedure. Fourier-transform infrared and ultraviolet-visible spectroscopy, thermogravimetric analysis, colorimeter technique, contact angle measurement, and the carbon dioxide evolution results showed higher photo- and biodegradation efficiency of PS-ONC-ZnO nanocomposite compared to the neat PS, PS-ONC and PS-ZnO nanocomposites. Thermal stability, optical band gap, and water contact angle of photo-degraded PS-ONC-ZnO nanocomposite decreased by 11.37, 18.33 and 63.99%, respectively, while that of PS film was only 6.20, 6.44 and 5.84%, respectively. The photo-degraded PS-ONC-ZnO and PS-ZnO film indicated a biodegradation percentage value of 3.3 and 2.1%, respectively, over 16 weeks of incubation in soil. The possible degradation mechanism of nanocomposites was briefly discussed.

Biodegradation of Polystyrene by Tenebrio molitor, Galleria mellonella, and Zophobas atratus Larvae and Comparison of Their Degradation Effects

Plastic waste pollution and its difficult degradation process have aroused widespread concern. Research has demonstrated that the larvae of Tenebrio molitor (yellow mealworm), Galleria mellonella (greater wax moth), and Zophobas atratus (superworm) possess a biodegradation ability for polystyrene (PS) within the gut microbiota of these organisms. In this study, the difference in PS degradation and the changes of the gut microbiota were compared before and after feeding PS. The results showed that superworm had the strongest PS consumption capacity and the highest survival rate during the 30 d experiment period. They all could degrade PS to different degrees. Superworm showed the highest ability to degrade PS into low-molecular-weight substances, while yellow mealworm depolymerized PS strongly by destroying the benzene ring. The changes of the intestinal microbiome caused by feeding PS showed that after ingesting PS, there was a decrease in community diversity in superworm and yellow mealworm, but an increase in greater wax moth. Meanwhile, Enterococcus and Enterobacteriaceae, found in all three species’ larvae upon 20 d of PS feeding, might play an important role in PS degradation. The results will provide more accurate PS degradation comparative data of the three species’ larvae and theoretical guidance for further research on the efficient PS biodegradations.

Biodegradation of low-density polyethylene and polypropylene by microbes isolated from Vaigai River, Madurai, India

The present study aimed to evaluate the microplastic degradation efficiency of bacterial isolates collected from Vaigai River, Madurai, India. The isolates were processed with proper methods and incorporated in to the UV-treated polyethylene (PE) and polypropylene (PP) degradation. Based on preliminary screening, four bacterial isolates such as Bacillus sp. (BS-1), Bacillus cereus (BC), Bacillus sp. (BS-2), and Bacillus paramycoides (BP) were proceed to further degradation experiment for 21 days. The microplastics were filled with bacterial isolates which is use microplastic (PE, PP) as carbon source for their growth and proceed for shake flask experiment were carried out by two approaches with control. The microplastic degradation was confirmed through their weight loss, increasing fragmentations and changes of surface area against control experiments (microplastic without isolates) also confirms degrading efficiency of isolated bacterial strains through non-changes in their weight and surface area. The highest degradation of PP and PE were observed in BP (78.99 ± 0.005%), and BC (63.08 ± 0.009%) in single approach, while in combined approach BC & BP recorded the highest degradation in both PP (78.62 ± 2.16%), and PE (72.50 ± 20.53%). The formation of new functional groups is confirming the biofilm formation in the surface area of microplastics by isolates and proving their efficiency in degrade the microplastics. The degradation of microplastic experiments should be cost effective and zero waste which is helpful to save the environment and the present findings could reveal the way to degrade the microplastics and prevent the microplastic pollution in aquatic environment.

Plastic wastes biodegradation: Mechanisms, challenges and future prospects

The growing accumulation of plastic wastes is one of the main environmental challenges currently faced by modern societies. These wastes are considered a serious global problem because of their effects on all forms of life. There is thus an urgent need to demonstrate effective eco-environmental techniques to overcome the hazardous environmental impacts of traditional disposal paths. However, our current knowledge on the prevailing mechanisms and the efficacy of synthetic plastics' biodegradation still appears limited. Under this scope, our review aims to comprehensively highlight the role of microbes, with special emphasis on algae, on the entire plastic biodegradation process focusing on the depolarization of various synthetic plastic types. Moreover, our review emphasizes on the ability of insects' gut microbial consortium to degrade synthetic plastic wastes. In this view, we discuss the schematic pathway of the biodegradation process of six types of synthetic plastics. These findings may contribute to establishing bio-upcycling processes of plastic wastes towards biosynthesis of valuable metabolic products. Finally, we discuss the challenges and opportunities for microbial valorization of degraded plastic wastes.

Degradation of primary nanoplastics by photocatalysis using different anodized TiO2 structures

In recent years, plastic pollution has become an environmental problem requiring urgent attention. Recently, the release of nano-sized plastics (<1 µm) into the environment has raised concern due to the possible adverse effects that their small size can have on the trophic web. Advanced oxidation processes are efficient at removing organic pollutants such as dyes and pharmaceuticals, making them a viable approach for treating these hazardous materials. This study proposes the use of photocatalysis as an alternative for removing polystyrene nanoparticles (PS-NPs) from aqueous media. A comparative study was carried out to determine the photocatalytic activity of three different TiO₂ photocatalysts synthesized by anodization. Elimination and degradation were monitored by turbidimetry, TOC, FTIR, and GC/MS, and the presence of carbonyl groups and intermediate products was recorded to confirm PS-NP degradation. Statistical analysis revealed that PS-NP elimination using TiO₂/T and TiO₂/M as photocatalysts was more efficient than with photolysis. The results indicate that the mixed structure (nanotubes/nanograss) reduces the concentration of PS-NPs in dispersion 2 times more efficiently than photolysis with UV light does. Despite the challenges posed by nanoplastic contamination, this study provides a useful remediation approach; a technique that, to date, has received little attention.