Degradation Of Plastics Research Articles

A Scienciometric Review On Microplastics As Chemical Pollutant Vectors In Aquatic Ecosystems

The production and disposal of plastic material has increased exponentially in recent decades. As a result, microplastics resulting from plastic degradation processes are now present in all environmental compartments, in particular, aquatic ecosystems. These microparticles can interact with different chemical pollutants, representing a significant risk to living organisms. In this context, the present study aimed to assess microplastics as chemical pollutant vectors in aquatic ecosystems, evaluating adsorption processes between these particles and both organic and inorganic pollutants. To this end, a scienciometric review was carried out, retrieving a total of 56 scientific articles. The retrieved studies indicate microplastic particles are capable of associating with different environmental chemical contaminants and that interactions depends on abiotic factors such as pH, salinity, light and temperature, the type of polymeric material and its aging characteristics and, finally, the organic matter adhered to the particle. Further studies on this topic are required to understand potential deleterious effects on aquatic biota due to microplastic-adsorbed chemical pollutants and establish measures capable of reducing and controlling these pollutants.

Investigation of Adsorptive Removal of Methylene Blue from Synthetic Wastewater Using Polymeric Composite

Recycling polymeric waste into another useful material is considered to be the preferred way of taking care of the issues of slow degradable plastic waste, particularly in anticipation of natural contamination. In this study, the adsorptive treatment of Methylene Blue (MB) using adsorbents from chemically recycled polymeric waste was investigated. Three polymeric materials were employed in this study: styrofoam waste (EPS1), intruded extended polystyrene (EPS2), and sunflower xylem (Tithonia diversifolia xylem) (TDX). The alterations in microscopic surface morphology before and after the adsorption process were examined using scanning electron microscopy (SEM) system to resolve the intercalation of MB with the adsorbent. The experimental batch data was collected and the effects of concentration and contact time on the removal of MB from synthetic wastewater were studied. Adsorption kinetics, equilibrium, and thermodynamics were studied and fitted by various models. According to the result, the uptake of adsorbate increased as contact time and concentration rose, with the pseudo-second-order model best depicting the adsorption kinetics.

Organocatalytic depolymerization of poly(3-hydroxybutyrate) to crotonic acid

Utilizing end-of-life poly(3-hydroxybutyrate) (PHB) as a carbon source for the production of value-added chemicals has attracted increasing interest in recent years. In this report, an organocatalytic pyrolysis method was explored for chemical recycling of PHB into trans-crotonic acid (CA). Under relatively mild conditions and through the promotion of organic base catalysts, the CA was recovered with high efficiency and yield. The effect of reaction conditions on the depolymerization process, such as types of catalysts, solvent polarity, temperature, and molar equivalents of PHB to catalyst, was investigated in detail. This work is the first to achieve the pyrolysis of PHB using organic base catalysts, which provides a green and efficient option for plastic degradation and promotes the development of circular plastic economy.

Hydrogen production and value-added chemical recovery from the photo-reforming process using waste plastics

Photo-reforming is a novel and promising green H2 production method with enhanced catalytic efficiency via optimizing the oxidation reaction by introducing an organic compound as the sacrificial agent. This study focuses on the degradation of different plastic wastes, such as polyethylene terephthalate (PET), low-density polyethylene (LDPE), and polystyrene (PS) as sacrificial agents in the photo-reforming process for H2 production. The process was optimized by evaluating H2 production under different plastic pretreatment methods and the polymer-to-catalyst ratio. Disodium terephthalate (Na2TP) and terephthalic acid (TPA) were identified as byproducts after the alkaline pretreatment of PET, and these extracted products were re-applied in the photo-reforming process and tested for their applicability in H2 generation. The degradation of plastics and their respective pretreatment byproducts were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA). PET was the best sacrificial agent in H2 production under almost all conditions whereas 4026 μmol/gcat/gPET was produced under ethanol-induced pretreatment at 40 °C. This combined analysis indicates H2 can be successfully generated from LDPE, PET, PS, and degradation byproducts. Further, TPA and Na2TP can be extracted from the reaction mixture for reuse. This study revealed the mechanisms of using plastics as sacrificial agents and the intermediate byproducts in the photo-reforming process on H2 evolution efficiency. It provides the opportunity for green H2 generation while degrading plastic waste by solving multiple environmental issues with revenue generation.

Plastic bio-mitigation by Pseudomonas mendocina ABF786 and simultaneous conversion of its CO2 byproduct to microalgal biodiesel

Bio-mitigation of plastics by microorganisms generates carbon dioxide (CO2) that can be utilized for algal biomass generation. Pseudomonas mendocina ABF786, reportedly the most efficient plastic-degrading bacteria, was screened using the modified most probable number technique. This study highlights the use of an integrative prototype for the production of microalgal biomass (Chlorella vulgaris) in combination with bio-mitigation of plastics, which serves a dual purpose: (i) increased plastic-degradation capability by microorganisms (53%–85% increase in plastic weight loss) due to removal of CO2 feedback inhibition and (ii) increased algal biomass generation (200%–237%) due to supply of extra CO2 from plastic degradation to the algal cultivation flask. Whole-genome sequencing and functional annotation confirmed that all the genes involved in the mineralization of plastic to CO2 are present within the genome of P. mendocina ABF786. Using two or more microbial cultures for remediation may increase the process efficiency.

Microbial degradation of marine plastic debris: A comprehensive review on the environmental effects, disposal, and biodegradation

The uncontrolled utilization of plastics and their disposal method presents a global threat owing to their abundance in the marine ecosystem. An exponential upsurge in the practice of synthetic polymers has been reported in the past decade. The degradation of these synthetic polymers is achieved by employing several physiochemical methods. The limited competence of these methods results in the release of hazardous compounds or by-products in the environment. The microbial species isolated from different sources aid in plastic degradation by utilizing them as a sole carbon and energy source. The involvement of microbes in plastic degradation has a profound scope as a cost-effective and eco-friendly alternative to the preexisting techniques. The current review focuses on the environmental effects of plastics and their mitigation through microbial intervention. This review complies with the microplastics and their disposal methods in the environment. The role of microbes and bacterial consortiums in the degradation of plastics and marine plastic debris is also emphasized. The factors affecting microbial degradation and future perspectives were also deliberated in an aspect of environmental welfare.

Microplastics in the environment: A critical overview on its fate, toxicity, implications, management, and bioremediation strategies

Microplastics are small plastic pieces ranging in size from 1μ to <5 mm in diameter, are water-soluble, and can be either primary as they are initially created in small sizes or secondary as they develop due to plastic degradation. Approximately 360 million tons of plastic are produced globally every year, with only 7% recycled, leaving the majority of waste to accumulate in the environment and pose a serious threat in the form of microplastics. All ecosystems, particularly freshwater ecosystems, experience microplastic accumulation and are also prone to degrading processes. Degraded microplastics accumulate in many aquatic systems, contaminate them, and enter the food chain as a result of the excessive discharge of plastic trash annually from the domestic to the industrial sector. Due to their pervasiveness, these tiny plastic particles are constantly present in freshwater environments, which are essential to human life. In this sense, microplastic pollution is seen as a worldwide problem that has a detrimental impact on every component of the freshwater environment. Microplastics act as carriers for various toxic components such as additives and other hazardous substances from industrial and urbanized areas. These microplastic-contaminated effluents are ultimately transferred into water systems and directly ingested by organisms associated with a particular ecosystem. The microplastics components also pose an indirect threat to aquatic ecosystems by adsorbing surrounding water pollutants. This review mainly focuses on the sources of microplastics, the ecotoxicity of microplastics and the impact microplastics have on aquatic and marine life, management, and bioremediation of microplastics. Policies and strategies adopted by the Government to combat microplastic pollution are also discussed in this review.

Shotgun metagenomics and computational profiling of the plastisphere microbiome: unveiling the potential of enzymatic production and plastic degradation.

Plastic pollution is one of the most resilient types of pollution and is considered a global environmental threat, particularly in the marine environment. This study aimed to identify plastic-degrading bacteria from the plastisphere and their pharmaceutical and therapeutic potential. We collected samples from soil and aquatic plastisphere to identify the bacterial communities using shotgun metagenomic sequencing and bioinformatic tools. Results showed that the microbiome comprised 93% bacteria, 0.29% archaea, and 3.87% unidentified microbes. Of these 93% of bacteria, 54% were Proteobacteria, 23.9% were Firmicutes, 13% were Actinobacteria, and 2.1% were other phyla. We found that the plastisphere microbiome was involved in degrading synthetic and polyhydroxy alkanoate (PHA) plastic, biosurfactant production, and can thrive under high temperatures. However, no association existed between thermophiles, synthetic plastic or PHA degraders, and biosurfactant-producing bacterial species except for Pseudomonas. Other plastisphere inhabiting plastic degrading microbes include Streptomyces, Bacillus, Achromobacter, Azospirillum, Bacillus, Brevundimonas, Clostridium, Paenibacillus, Rhodococcus, Serratia, Staphylococcus, Thermobifida, and Thermomonospora. However, the plastisphere microbiome showed potential for producing secondary metabolites that were found to act as anticancer, antitumor, anti-inflammatory, antimicrobial, and enzyme stabilizers. These results revealed that the plastisphere microbiome upholds clinical and environmental significance as it can open future portals in a multi-directional way.

A Preliminary Study on the Utilization of Hyperspectral Imaging for the On-Soil Recognition of Plastic Waste Resulting from Agricultural Activities

Plastic in agriculture is frequently used to protect crops and its use boosts output, enhances food quality, contributes to minimize water consumption, and reduces the environmental impacts of agricultural activities. On the other hand, end-of-life plastic management and disposal are the main issues related to their presence in this kind of environment, especially in respect of plastic degradation, if not properly handled (i.e., storage places directly in contact with the ground, exposure of stocks to meteoric agents for long periods, incorrect or incomplete removal). In this study, the possibility of using an in situ near infrared (NIR: 1000–1700 nm) hyperspectral imaging detection architecture for the recognition of various plastic wastes in agricultural soils in order to identify their presence and also assess their degradation from a recovery/recycling perspective was explored. In more detail, a Partial Least Squares—Discriminant Analysis (PLS-DA) classifier capable of identifying plastic waste from soil was developed, implemented, and set up. Results showed that hyperspectral imaging, in combination with chemometric approaches, allows the utilization of a rapid, non-destructive, and non-invasive analytical approach for characterizing the plastic waste produced in agriculture, as well as the potential assessment of their lifespan.

Principal component analysis and deep neural networks in modeling the melt flow index of degradable plastics

Principal component analysis and deep neural networks in modeling the melt flow index of degradable plastics

Rapid marine degradable poly(butylene oxalate) by introducing promotion building blocks

The design and development of high-performance marine-degradable plastics have long been considered a superior strategy to address marine plastic pollution. To achieve a balance between rapid marine degradability and high performance of polyester plastics, this work designed two series of poly(butylene oxalate) (PBOx) copolymers with intrinsic hydrolysis ability using poly(ethylene oxalate) (PEOx) and poly(glycolic acid) (PGA) as promotion building blocks. The synthesis process, crystallization properties, barrier performance, and mechanical properties of copolymers were comparatively investigated. Additionally, the marine degradability of copolymers received specific focus. The theoretical calculation demonstrated that the introduction of promotion blocks reduced the hydrolysis energy barrier of the copolymers. In general, the results revealed the advantages of PBEOx copolymer in satisfying practicality and better regulating marine degradability. The high gas barrier performance, suitable thermal properties, tunable mechanical properties, and rapid marine degradability endow the copolymer as a promising candidate toward sustainable and marine-degradable plastics.

Biotechnological Plastic Degradation and Valorization Using Systems Metabolic Engineering.

Various kinds of plastics have been developed over the past century, vastly improving the quality of life. However, the indiscriminate production and irresponsible management of plastics have led to the accumulation of plastic waste, emerging as a pressing environmental concern. To establish a clean and sustainable plastic economy, plastic recycling becomes imperative to mitigate resource depletion and replace non-eco-friendly processes, such as incineration. Although chemical and mechanical recycling technologies exist, the prevalence of composite plastics in product manufacturing complicates recycling efforts. In recent years, the biodegradation of plastics using enzymes and microorganisms has been reported, opening a new possibility for biotechnological plastic degradation and bio-upcycling. This review provides an overview of microbial strains capable of degrading various plastics, highlighting key enzymes and their role. In addition, recent advances in plastic waste valorization technology based on systems metabolic engineering are explored in detail. Finally, future perspectives on systems metabolic engineering strategies to develop a circular plastic bioeconomy are discussed.

Coexistence of specialist and generalist species within mixed plastic derivative-utilizing microbial communities

BackgroundPlastic-degrading microbial isolates offer great potential to degrade, transform, and upcycle plastic waste. Tandem chemical and biological processing of plastic wastes has been shown to substantially increase the rates of plastic degradation; however, the focus of this work has been almost entirely on microbial isolates (either bioengineered or naturally occurring). We propose that a microbial community has even greater potential for plastic upcycling. A microbial community has greater metabolic diversity to process mixed plastic waste streams and has built-in functional redundancy for optimal resilience.ResultsHere, we used two plastic-derivative degrading communities as a model system to investigate the roles of specialist and generalist species within the microbial communities. These communities were grown on five plastic-derived substrates: pyrolysis treated high-density polyethylene, chemically deconstructed polyethylene terephthalate, disodium terephthalate, terephthalamide, and ethylene glycol. Short-read metagenomic and metatranscriptomic sequencing were performed to evaluate activity of microorganisms in each treatment. Long-read metagenomic sequencing was performed to obtain high-quality metagenome assembled genomes and evaluate division of labor.ConclusionsData presented here show that the communities are primarily dominated by Rhodococcus generalists and lower abundance specialists for each of the plastic-derived substrates investigated here, supporting previous research that generalist species dominate batch culture. Additionally, division of labor may be present between Hydrogenophaga terephthalate degrading specialists and lower abundance protocatechuate degrading specialists.CMb_gViqtb7nKA_3vS-tKdVideo

Enzymatic Degradation of PET plastic

Polyethylene terephthalate (PET) plastic is one of the most commonly used polymers worldwide and found in high rates as environmental waste. Previous studies have shown that the degradation of plastics using commercial grade enzymes is possible and highly effective in lab settings. However, the effectiveness and rates of enzymatic plastic degradation at environmentally relevant conditions is less known. In this study, we set up a series of sacrificial incubation experiments using a commercial enzyme, Humicola insolens cutinase (HiC), to examine the effect of various environmental variables, including temperature, pH, and salinity, on the hydrolytic degradation of PET. This was performed by measuring the mass loss at different time points during degradation, dissolved organic carbon produced in solution by PET hydrolysis, the Fourier transform infrared (FTIR) spectra of the PET surfaces, and scanning electron microscope (SEM) images of the PET surfaces. The results indicate that the degradation rate is 15-times faster at 55 °C than at 40 °C at pH 8 (1.93 mg day-1 versus 0.13 mg day-1), giving an initial estimate for the activation energy of PET hydrolysis of 2.2 kJ mol-1. In the 55 °C experiment which ran for 10 days, there was a noticeable decrease in the plastic strength and deformation of the plastic after 1 week of degradation. In the 40 °C experiment (duration 16 weeks), FTIR spectral changes were observed as early as week 6, with peaks of interest at 2,970 cm-1, 2,350 cm-1, 1,240 cm-1 , and between 1,300-1,000 cm-1. Ongoing experiments with pH and salinity will provide insight into their effects on the PET degradation rate. Altogether, these results will provide a comprehensive framework for predicting PET degradation rates, and by extension, other plastics that are degraded by hydrolysis, at environmentally relevant pH, temperature, and salinity conditions. In addition, these results provide insight into the effect of degradation on the chemical spectra of plastics and microplastics.

Soil microbial community parameters affected by microplastics and other plastic residues.

The impact of plastics on terrestrial ecosystems is receiving increasing attention. Although of great importance to soil biogeochemical processes, how plastics influence soil microbes have yet to be systematically studied. The primary objectives of this study are to evaluate whether plastics lead to divergent responses of soil microbial community parameters, and explore the potential driving factors. We performed a meta-analysis of 710 paired observations from 48 published articles to quantify the impact of plastic on the diversity, biomass, and functionality of soil microbial communities. This study indicated that plastics accelerated soil organic carbon loss (effect size = -0.05, p = 0.004) and increased microbial functionality (effect size = 0.04, p = 0.003), but also reduced microbial biomass (effect size = -0.07, p < 0.001) and the stability of co-occurrence networks. Polyethylene significantly reduced microbial richness (effect size = -0.07, p < 0.001) while polypropylene significantly increased it (effect size = 0.17, p < 0.001). Degradable plastics always had an insignificant effect on the microbial community. The effect of the plastic amount on microbial functionality followed the "hormetic dose-response" model, the infection point was about 40 g/kg. Approximately 3564.78 μm was the size of the plastic at which the response of microbial functionality changed from positive to negative. Changes in soil pH, soil organic carbon, and total nitrogen were significantly positively correlated with soil microbial functionality, biomass, and richness (R2 = 0.04-0.73, p < 0.05). The changes in microbial diversity were decoupled from microbial community structure and functionality. We emphasize the negative impacts of plastics on soil microbial communities such as microbial abundance, essential to reducing the risk of ecological surprise in terrestrial ecosystems. Our comprehensive assessment of plastics on soil microbial community parameters deepens the understanding of environmental impacts and ecological risks from this emerging pollution.

Occurrence of microplastics (MPs) in Antarctica and its impact on the health of organisms

Antarctica, and its surrounding environment, is considered untouched, and it is thought that it is free from microplastic (MP) pollution. However, recent studies and science projects have reported MPs in both water and sediment in the South Polar Regions. These reports state that MP pollution occurs in this region due to fishing, tourism, and research activities by the nearby countries, with natural circulation also part of it. The Antarctic Treaty System (ATS) has given attention to MP pollution and has initiated research on it. MPs are tiny plastic particles with a size of less than 5 mm. They have two types: 1. Primary MPs, which have been manufactured directly from various applications like cosmetics and scrubbing, etc. 2. Secondary MPs, which are generated by the photochemical degradation of large plastics. Although several studies have been done, there is a quite gap in our understanding of the concentration, characteristics, and impact of plastics on the ecosystem of the Antarctic Region. The impact of MP pollution in this region may be very high. The presence of MPs is a serious issue that is affecting not only the aquatic environment but also humans. It is an alarming situation that causes environmental damage. The main objective of this paper is to review MP introduction, occurrence in biotic and abiotic components, sources, harmful effects, and detection methods/techniques. This review highlights the various methodologies and analyses like density separation, microscope observation of MP’s properties Fourier-transform infrared spectroscopy (FTIR), and Raman spectrometer, respectively, and urges for more research in the future, giving several recommendations to maintain the pristine region near Antarctica. Highlights Antarctica is a pristine land and is separated from other continents Microplastics (MPs) are ubiquitous in nature with a size of &lt; 5 mm These tiny particles are of two types primary MPs and secondary MPs MP pollution occurs in the Antarctic region due to fishing, tourism, and research activities MPs may be carcinogenic and act as endocrine disruptors in nature

Environmental impacts of 5-year plastic waste deposition on municipal waste landfills: A follow-up study

Depositing plastic waste has long been a prevalent method of utilization, persisting today. Plastic waste within municipal waste landfills (MWL) undergoes diverse (bio-)degradation processes, which may be a potential source of chemicals and microorganisms harmful to the environment and human health. Soil and air samples were collected from modern MWL to identify environmental contamination caused by 5 years of plastic (bio-)degradation. The pH of soil samples was higher than in the reference area (RA), which was possibly caused by alterations in soil anionic composition detected with ion chromatography. The presence of plastic additives with a toxic potential was detected in soil samples by gas chromatography coupled with tandem mass spectrometry (GC–MS/MS). With the use of thermal desorption and GC – MS, hazardous substances (phthalic anhydride, phenylmaleic anhydride, ethylbenzene, xylene) with a known impact on the human endocrine system were also detected. The number of microorganisms, both fungi, and bacteria, was highly increased in soil and air in the MWL as compared to the RA. The soil collected in the MWL area appeared to be phytotoxic, and inhibited seed germination (Phytotoxkit FTM bioassay), while acute toxicity Microtox® bioassay showed a hormetic effect towards Aliivibrio fischeri. Obtained results exhibited massive soil and air contamination, with both chemical substances and microorganisms while plastic waste undergoes (bio-)degradation. It may contribute to serious environmental contamination and pose a threat to human health.

Potential Value of Konjac Glucomannan Microcrystalline/Graphene Oxide Dispersion Composite Film in Degradable Plastics

Konjac glucomannan (KGM) is a promising bio-based material that can effectively mitigate the global petroleum-based plastic pollution exacerbated by the responses to COVID-19. This study first acidified KGM to obtain KGM microcrystals (MKGM) with a relatively low molecular mass. Next, different volumes of graphene oxide (GO) dispersions were mixed with MKGM to prepare composite films via physical cross-linking using glycerol as a plasticizer. The UV barrier capability, mechanical strength, thermal stability, and water resistance of these films were subsequently assessed. GO enhanced the tensile strength of the polysaccharide, while limiting its toughness. Thus, the tensile strength of the MKGM film improved from 7.80 MPa to 39.92 MPa following the addition of 12 mL of GO dispersion, and the elongation at break decreased from 46.31% to 19.2%. A morphological study revealed that the addition of different volumes of GO caused the composite films to exhibit various degrees of porosity and an enhanced water barrier capability. Introducing GO also improved the UV barrier capability and thermal stability of the composite film. Meanwhile, the composite films exhibited excellent degradation properties. Therefore, composite films prepared via the acidification of KGM and the incorporation of GO are suitable for extensive utilization in degradable plastics.

Circular waste management: Superworms as a sustainable solution for biodegradable plastic degradation and resource recovery

Bioplastics offer a promising solution to plastic pollution, however, their production frequently relies on edible biomass, and their degradation rates remain inadequate. This study investigates the potential of superworms (Zophobas atratus larvae) for polybutylene succinate (PBS) waste management, aiming to achieve both resource recovery and biodegradation. Superworms exclusively fed on PBS for a month exhibited the same survival rate as those on a standard bran diet. PBS digestion yielded a 5.13% weight gain and a 23.23% increase in protein composition in superworms. Additionally, carbon isotope analyses substantiated the conversion of PBS into superworm components. Gut microbes capable of PBS biodegradation became progressively prominent, further augmenting the degradation rate of PBS under composting conditions (ISO 14855-1). Gut-free superworms fed with PBS exhibited antioxidant activities comparable to those of blueberries, renowned for their high antioxidant activity. Based on these findings, this study introduces a sustainable circular solution encompassing recycling PBS waste to generate insect biomass, employing insect gut and frass for PBS degradation and fertilizer, and harnessing insect residue as a food source. In essence, the significance of this research extends to socio-economic and environmental spheres, impacting waste management, resource efficiency, circular economy promotion, environmental preservation, industrial advancement, and global sustainability objectives. The study's outcomes possess the potential to reshape society’s approach to plastic waste, facilitating a shift toward more sustainable paradigms.

Evaluation of Galleria mellonella immune response as a key step toward plastic degradation

BackgroundPlastic's remarkable durability presents a significant challenge for our planet, leading to widespread environmental damage. However, some organisms, such as Galleria mellonella larvae, have shown a unique capability to consume and degrade plastic, offering potential solutions to plastic pollution. In this study, we investigated the response of G. mellonella larvae to different diets, including artificial diet (AD), polyethylene low density mixed with AD (PELD + AD), and PELD alone. Using various microscopy techniques, we examined the larvae's hemocyte hemogram and mid-gut characteristics to understand their immune response and digestive system when exposed to plastic.ResultsThe results revealed that PELD-only feeding negatively impacted hemocyte immunity, resulting in a significant decrease in total hemocyte counts compared to AD and AD + PELD feeding. Moreover, plastic consumption induced differential hemocyte alterations, affecting specific cell types. The presence of phagosomes in larval hemocytes and mid-gut cells during PELD-only feeding suggested active involvement in plastic breakdown.ConclusionsThese findings highlight the potential of G. mellonella larvae as a model organism to study responses to pollutants, emphasizing the urgent need to address plastic pollution's global threat. Further investigation is warranted to explore larval deformities, weight loss, and appetite changes, potentially influencing mortality rates and enzyme biochemistry. Understanding the impacts of plastic ingestion on G. mellonella larvae is crucial to develop effective strategies for mitigating plastic pollution's ecological implications.