Biodegradation of used polyethylene bags by a new marine strain of Alcaligenes faecalis LNDR-1

Biodegradation of polyethylene by the marine fungus Parengyodontium album

Plastic pollution in the marine realm is a severe environmental problem. Nevertheless, plastic may also serve as a potential carbon and energy source for microbes, yet the contribution of marine microbes, especially marine fungi to plastic degradation is not well constrained. We isolated the fungus Parengyodontium album from floating plastic debris in the North Pacific Subtropical Gyre and measured fungal-mediated mineralization rates (conversion to CO2) of polyethylene (PE) by applying stable isotope probing assays with 13C-PE over 9 days of incubation. When the PE was pretreated with UV light, the biodegradation rate of the initially added PE was 0.044 %/day. Furthermore, we traced the incorporation of PE-derived 13C carbon into P. album biomass using nanoSIMS and fatty acid analysis. Despite the high mineralization rate of the UV-treated 13C-PE, incorporation of PE-derived 13C into fungal cells was minor, and 13C incorporation was not detectable for the non-treated PE. Together, our results reveal the potential of P. album to degrade PE in the marine environment and to mineralize it to CO2. However, the initial photodegradation of PE is crucial for P. album to metabolize the PE-derived carbon.

Isolation and characterization of bio-prospecting gut strains Bacillus safensis CGK192 and Bacillus australimaris CGK221 for plastic (HDPE) degradation

The present work reports the application of novel gut strains Bacillus safensis CGK192 (Accession No. OM658336) and Bacillus australimaris CGK221 (Accession No. OM658338) in the biological degradation of synthetic polymer i.e., high-density polyethylene (HDPE). The biodegradation assay based on polymer weight loss was conducted under laboratory conditions for a period of 90 days along with regular evaluation of bacterial biomass in terms of total protein content and viable cells (CFU/cm2). Notably, both strains achieved significant weight reduction for HDPE films without any physical or chemical pretreatment in comparison to control. Hydrophobicity and biosurfactant characterization were also done in order to assess strains ability to form bacterial biofilm over the polymer surface. The post-degradation characterization of HDPE was also performed to confirm degradation using analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electronic microscopy (FE-SEM) coupled with energy dispersive X-ray (EDX), and Gas chromatography-mass spectrometry (GC-MS). Interestingly strain CGK221 was found to be more efficient in forming biofilm over polymer surface as indicated by lower half-life (i.e., 0.00032 day-1) and higher carbonyl index in comparison to strain CGK192. The findings reflect the ability of our strains to develop biofilm and introduce an oxygenic functional group into the polymer surface, thereby making it more susceptible to degradation.

Mining strategies for isolating plastic-degrading microorganisms

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

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.

Biodegradation of low-density polyethylene (LDPE) through application of indigenous strain Alcaligenes faecalis ISJ128

The resiliency of plastic products against microbial degradation in natural environment often creates devastating changes for humans, plants, and animals on the earth's surface. Biodegradation of plastics using indigenous bacteria may serve as a critical approach to overcome this resulting environmental stress. In the present work, a polyethylene degrading bacterium Alcaligenes faecalis strain ISJ128 (Accession No. MK968769) was isolated from partially degraded polyethylene film buried in the soil at plastic waste disposal site. The biodegradation studies were conducted by employing various methods such as hydrophobicity assessment of the strain ISJ128, measurement of viability and total protein content of bacterial biofilm attached to the polyethylene surface. The proliferation of bacterial cells on polyethylene film, as indicated by high growth response in terms of protein content (85.50 µg mL-1) and viability (1010 CFU mL-1), proposed reasonable suitability of our strain A. faecalis ISJ128 toward polyethylene degradation. The results of biodegradation assay revealed significant degradation (10.40%) of polyethylene film within a short period of time (i.e., 60 days), whereas no signs of degradation were seen in control PE film. A. faecalis strain ISJ128 also demonstrated a removal rate of 0.0018 day-1 along with half-life of 462 days. The scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy studies not only displayed changes on polyethylene surface but also altered level of intensity of functional groups and an increase in the carbonyl indexes justifying the degradation of polyethylene film due to bacterial activity. In addition, the secondary structure prediction (M fold software) of 16SrDNA proved the stable nature of the bacterial strain, thereby reflecting the profound scope of A. faecalis strain ISJ128 as a potential degrader for the eco-friendly disposal of polyethylene waste. Schematic representation of methodology.

Development of Green-Synthesized Carbon-Based Nanoparticle for Prevention of Surface Wound Biofilm

The development of microbial biofilm occurs with the adherence of the microbial cells on biotic and abiotic surfaces with the help of pili and with extracellular polymeric substances. The surfaces on which biofilm formation take place can be inert, abiotic, or biotic. The sessile microbial cells behave differently from their planktonic counterpart. The biofilm developed by Alcaligenes faecalis is responsible for the development of skin and soft-tissue infection. It was observed that green-synthesized carbon nanoparticles (NPs) from Ocimum sanctum showed a prolonged stability and activity. It showed a marked reduction in the viability of sessile microbial species with least revival in comparison to the plant extract and amoxicillin. It was observed that carbon NP was able to maximally reduce the quorum sensing (QS) activity of A. faecalis. Thus, the use of green-synthesized NPs would be an alternative in the treatment of the biofilm-associated chronic wound infections.

Pragmatic Treatment Strategies for Polyaromatic Hydrocarbon Remediation and Anti-biofouling from Surfaces Using Nano-enzymes: a Review

In this review, two important environmental pollutants have been considered for its potential remediation using microbial-derived nano-enzymes. Firstly, polyaromatic hydrocarbons (PAHs) are one of the major industrial contaminants in the environment due to their ubiquitous occurrence, toxicity, and proclivity for bioaccumulation. Secondly, biofouling due to biofilm-forming organisms that impact tremendous economic and environmental consequences in many industries, especially marine vessels where it causes an increase in hydrodynamic drag, which results in a loss of ship speed at constant power or a power increase to maintain the same speed with higher fuel consumption and emissions into the atmosphere, particularly Green House Gases (GHGs). Among the remediation strategies, biological routes are found to be promising, efficient, and sustainable. Natural ligninolytic enzymes such as MnP, LiP, laccase, peroxidases, and polysaccharide and protein degradative enzymes are found to be highly efficient for PAH degradation and antifouling respectively. However, large-scale usage of these enzymes is difficult due to various reasons like their poor stability, adaptation, and high-cost production of these enzymes. In recent years, the use of nanoparticles, particularly nano-enzymes, is found to be an innovative and synergistic approach to detoxify contaminated areas with concomitant maintenance of enzyme stability.

Ability of marine-derived fungi isolated from polluted saline environment for enzymatic hydrocarbon remediation

Marine-derived fungi have attracted much attention due to their ability to present a new biosynthetic diversity. About 50 fungal isolates were obtained from Tunisian Mediterranean seawater and then screened for the presence of lignin-peroxidase (LiP), manganese-dependent peroxidase (MnP), and laccase (Lac) activities. The results obtained from both qualitative and quantitative assays showed that four of marine fungi isolates had a high potential to produce lignin-degrading enzymes. They were characterized taxonomically by a molecular method, based on international spacer (ITS) rDNA sequence analysis, as Chaetomium jodhpurense (MH667651.1), Chaetomium maderasense (MH665977.1), Paraconiothyrium variabile (MH667653.1), and Phoma betae (MH667655.1) which have been reported as producers of ligninolytic enzyme in the literature. The enzymatic activities and culture conditions were optimized using a Fractional Factorial design (2 7- 4). Then, fungal strains were incubated with the addition of 1% of crude oil in 50% of seawater for 25 days to evaluate their abilities to simultaneously degrade hydrocarbon compounds and to produce ligninolytic enzymes. The strain P. variabile exhibited the highest crude oil degradation rate (48.3%). Significant production of ligninolytic enzymes was recorded during the degradation process, which reached 2730 U/L for the MnP, 410 U/L for LiP, and 168.5 U/L for Lac. The FTIR and GC-MS analysis confirmed that the isolates rapidly biodegrade crude oil under ecological and economic conditions.

The escalated potential of the novel isolate Bacillus cereus NJD1 for effective biodegradation of LDPE films without pre-treatment

This study focused on the biodegradation of LDPE films using a novel isolate of Bacillus obtained from soil samples collected from a 20-year-old plastic waste dump. The aim was to evaluate the biodegradability of LDPE films treated with this bacterial isolate. The results indicated a 43% weight loss of LDPE films within 120 days of treatment. The biodegradability of LDPE films was confirmed through various testing methods, including BATH, FDA, CO₂ evolution tests, and changes in total cell growth count, protein content, viability, p^H of the medium, and release of microplastics. The bacterial enzymes, including laccases, lipases, and proteases, were also identified. SEM analysis revealed biofilm formation and surface changes in treated LDPE films, while EDAX analysis showed a reduction in carbon elements. AFM analysis demonstrated differences in roughness compared to the control. Furthermore, wettability increased and tensile strength decreased, confirming the biodegradation of the isolate. FTIR spectral analysis showed changes in skeletal vibrations, such as stretches and bends, in the linear structure of polyethylene. FTIR imaging and GC-MS analysis also confirmed the biodegradation of LDPE films by the novel isolate identified as Bacillus cereus strain NJD1. The study highlights the potentiality of the bacterial isolate for safe and effective microbial remediation of LDPE films.

Microbial degradation of low-density polyethylene by Neopestalotiopsis phangngaensis

Low-density polyethylene (LDPE) has been commercially used and accumulated as plastic solid waste. LDPE has also been found to be a non-degradable waste for decades and found as a pollution source in the environment. In this study, 65 fungi were screened for their biodegradation of LDPE. The fungi Neopestalotiopsis phangngaensis, Alternaria burnsii, Alternaria pseudoeichhorniae, and Arthrinium sacchari showed significant potential in LDPE biodegradation. These fungi were individually cultured with an LDPE sheet as a carbon source for 90 days. A maximum weight loss of the LDPE sheet was detected by the fungus N. phangngaensis (54.34%). This fungus also revealed the highest reduction rate of tensile strength of the LDPE sheet (0.33 MPa). The morphological surface of LDPE culturing with N. phangngaensis was crack, pit, and rough analyzed by scanning electron microscopy. The biodegradation of the LDPE sheet by N. phangngaensis was also confirmed by the Sturm test and analysis of enzymatic activities. The Sturm test showed the highest decomposition of the LDPE sheet by N. phangngaensis into CO₂ with 2.14 g/L after incubation. Enzymatic activities of laccase, manganese peroxidase, and lignin peroxidase enzymes were found by N. phangngaensis during the LDPE degradation. The volatile organic compounds in culture supernatant of N. phangngaensis were also investigated. The major compounds were 3Z-diethyl acetal hexenal, 2E,4E-decadienol, and 2Z-diethyl acetal hexenal. This study reveals the utilization of the fungus N. phangngaensis as the carbon source at a considerable biodegradation rate without any prior treatment. Therefore, the fungus N. phangngaensis may be applied as an alternative degrader for LDPE degradation in the environment.

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

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

Microbial engineering strategies for synthetic microplastics clean up: A review on recent approaches

Microplastics are the small fragments of the plastic molecules which find their applications in various routine products such as beauty products. Later, it was realized that it has several toxic effects on marine and terrestrial organisms. This review is an approach in understanding the microplastics, their origin, dispersal in the aquatic system, their biodegradation and factors affecting biodegradation. In addition, the paper discusses the major engineering approaches applied in microbial biotechnology. Specifically, it reviews microbial genetic engineering, such as PET-ase engineering, MHET-ase engineering, and immobilization approaches. Moreover, the major challenges associated with the plastic removal are presented by evaluating the recent reports available.

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

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

Microbial degradation of polyethylene terephthalate: a systematic review

Plastic pollution levels have increased rapidly in recent years, due to the accumulation of plastic waste, including polyethylene terephthalate (PET). Both high production and the lack of efficient methods for disposal and recycling affect diverse aquatic and terrestrial ecosystems owing to the high accumulation rates of plastics. Traditional chemical and physical degradation techniques have caused adverse effects on the environment; hence, the use of microorganisms for plastic degradation has gained importance recently. This systematic review was conducted for evaluating the reported findings about PET degradation by wild and genetically modified microorganisms to make them available for future work and to contribute to the eventual implementation of an alternative, an effective, and environmentally friendly method for the management of plastic waste such as PET. Both wild and genetically modified microorganisms with the metabolic potential to degrade this polymer were identified, in addition to the enzymes and genes used for genetic modification. The most prevalent wild-type PET-degrading microorganisms were bacteria (56.3%, 36 genera), followed by fungi (32.4%, 30 genera), microalgae (1.4%; 1 genus, namely Spirulina sp.), and invertebrate associated microbiota (2.8%). Among fungi and bacteria, the most prevalent genera were Aspergillus sp. and Bacillus sp., respectively. About genetically modified microorganisms, 50 strains of Escherichia coli, most of them expressing PETase enzyme, have been used. We emphasize the pressing need for implementing biological techniques for PET waste management on a commercial scale, using consortia of microorganisms. We present this work in five sections: an Introduction that highlights the importance of PET biodegradation as an effective and sustainable alternative, a section on Materials and methods that summarizes how the search for articles and manuscripts in different databases was done, and another Results section where we present the works found on the subject, a final part of Discussion and analysis of the literature found and finally we present a Conclusion and prospects.

Degradation of Xenobiotic Pollutants: An Environmentally Sustainable Approach

The ability of microorganisms to detoxify xenobiotic compounds allows them to thrive in a toxic environment using carbon, phosphorus, sulfur, and nitrogen from the available sources. Biotransformation is the most effective and useful metabolic process to degrade xenobiotic compounds. Microorganisms have an exceptional ability due to particular genes, enzymes, and degradative mechanisms. Microorganisms such as bacteria and fungi have unique properties that enable them to partially or completely metabolize the xenobiotic substances in various ecosystems.There are many cutting-edge approaches available to understand the molecular mechanism of degradative processes and pathways to decontaminate or change the core structure of xenobiotics in nature. These methods examine microorganisms, their metabolic machinery, novel proteins, and catabolic genes. This article addresses recent advances and current trends to characterize the catabolic genes, enzymes and the techniques involved in combating the threat of xenobiotic compounds using an eco-friendly approach.

Microbial degradation of low density polyethylene by Exiguobacterium sp. strain LM-IK2 isolated from plastic dumped soil

Low-Density Polyethylene (LDPE) is one of the significant environmental pollutants as it is resistant to natural degradation. In this study, we reported the LDPE-degrading bacterial strain i.e., Exiguobacterium sp. strain LM-IK2 isolated from plastic dumped soil which shows potential degradation capability. The percent weight loss of LDPE was calculated as - 5.70 ± 0.7 after 90 days of incubation in a carbon-free MSM medium. The Field Emission Scanning Electron Microscopy (FE-SEM) analysis shows that LDPE films show slight surface disruption after treatment with bacteria. The Fourier Transform Infrared Spectroscopy (FTIR) revealed the chemical changes in LDPE films e.g., formation and reduction of typical carbonyl peaks after incubation with bacteria. The X-Ray Diffraction (XRD) analysis displayed an increase in percent crystallinity, with a slight change in total carbon content. Genetic analysis showed the presence of Laccase (167 bp) and Alkane Hydroxylase (330 bp) genes that are responsible for LDPE degradation. Thus, Exiguobacterium sp. strain LM-IK2 has the potential to degrade LDPE and could be further explored to improve its efficiency in the bioremediation of LDPE.

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

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

Biodeterioration of Microplastics: A Promising Step towards Plastics Waste Management

Polyethylene and Polyester materials are resistant to degradation and a significant source of microplastics pollution, which is an emerging concern. In the present study, the potential of a dumped site bacterial community was evaluated. After primary screening, it was observed that 68.5% were linear low-density polyethylene, 33.3% were high-density, and 12.9% were Polyester degraders. Five strains were chosen for secondary screening, in which they were monitored by FTIR, SEM and weight loss degradation trials. Major results were observed for Alcaligenes faecalis (MK517568) and Bacillus cereus (MK517567), as they showed the highest degradation activity. Alcaligenes faecalis (MK517568) degrades LLDPE by 3.5%, HDPE by 5.8% and Polyester by 17.3%. Bacillus cereus (MK517567) is better tolerated at 30 °C and degrades Polyester by 29%. Changes in infrared spectra indicated degradation pathways of different strains depending on the types of plastics targeted. Through SEM analysis, groves, piths and holes were observed on the surface. These findings suggest that soil bacteria develop an effective mechanism for degradation of microplastics and beads that enables them to utilize plastics as a source of energy without the need for pre-treatments, which highlights the importance of these soil bacteria for the future of effective plastic waste management in a soil environment.

Simultaneously pollutant removal and S0 recovery from composite wastewater containing Cr(VI)-S2- based on biofilm enhancement

Bioaugmentation of extracellular polymeric substances-producing bacteria was applied in pollutant removal and S⁰ recovery from composite wastewater in a mixotrophic denitrification system. In the presence of 200 mg·L^-1 S^2- and 50 mg·L^-1 Cr(VI), the removal efficiencies of chemical oxygen demand, NO₃^-, S^2- and Cr(VI) were 86.38%, 91.82%, 95.75%, and 100.00% respectively, while S⁰ recovery efficiency reached 79.17%. Increased contents of protein and polysaccharide, especially the high ratio of protein/polysaccharide verified the structural stability of biofilm was promoted by biofilm enhancement. The widespread distribution of bacteria/extracellular polymeric substance (EPS) revealed the more obvious biofilms formation in biofilm-enhanced group. High-throughput sequencing analysis showed that EPS-producing bacteria (Flavobacterium, Thauera, Thiobacillus and Simplicispira) were dominant bacteria in the biofilm-enhanced group. Moreover, by comprehensive considering of redundancy analysis, the colonization of selected bacteria improved the robustness of the reactor and treatment performance to wastewater contained toxic pollutions.

Experimental Investigation on Bioremediation of Heavy Metal Contaminated Solution by Sporosarcina pasteurii under Some Complex Conditions

Bioremediation of contaminated solutions has attracted extensive attention in recent years due to its wide range of applicability to various types of contaminants and environmental friendliness. Previous studies adequately confirmed the potential of Sporosarcina pasteurii (i.e., S. pasteurii)-based bioremediation for heavy metal contaminated solutions, but they focused mainly on the bioremediation ability of single-heavy-metal contaminated solutions. This study focuses on S. pasteurii-based bioremediation under more complex pollution conditions. A series of laboratory experiments were performed to explore the efficiency and mechanism of S. pasteurii-based bioremediation to heavy metal contaminated solutions under various conditions, including single-heavy-metal pollution condition, heavy metal pollution under high mineral salinity context and multi-heavy-metal pollution scenarios. The results show that S. pasteurii can effectively remove heavy metals such as Cd, Cr(III), and Zn through biomineralization; for the typical range of mineral salinity (including NaCl and KCl) possibly encountered in practice in some contaminated solutions, such as leachate of landfills, the detrimental influence of high mineral salinity on efficiency of S. pasteurii-based bioremediation can be neglected; more importantly, S. pasteurii-based bioremediation can be considered as a potential option for remedying multi-heavy-metal contaminated solutions, though the addition of some heavy metals tends to produce a substantially detrimental influence on the bioremediation ability of S. pasteurii to other heavy metals.