Biodegradation Of Polyethylene Research Articles

PRODUCTION AND CHARACTERIZATION OF THERMOSTABLE LIGNOLYTIC ENZYMES PRODUCED FROM Staphylococcus saprophyticus EXPOSED TO LOW-DENSITY POLYETHYLENE (LDPE)

Enzymatic degradation has been revealed as an effective method of eradicating polyethylene pollution and different studies have opined lignolytic enzymes to be involved in the process of low-density polyethylene biodegradation. This study focused on screening and characterization of manganese peroxidase and laccase produced by Staphylococcus saprophyticus exposed to low- density polyethylene. The result showed that Staphylococcus saprophyticus produced optimum manganese peroxidase and laccase activities on the third and second days. A study of the physicochemical properties of manganese peroxidase and laccase revealed that their activities were optimum and stable at acidic pH (pH 3 and pH 3 respectively). Manganese peroxidase had optimum temperature activity at 50 oC and was stable at 60°C while laccase was active at 70°C and most stable at 80°C. Staphylococcus saprophyticus produced thermostable acidophile lignolytic enzymes, therefore it can be used for polyethylene biodegradation.

The role of nitrogen metabolism on polyethylene biodegradation

Polyethylene (PE) is the most widely used plastic and its accumulation on natural environments has reached alarming levels causing severe damage to wildlife and human health. Despite the significance of this global issue, little is known about specific metabolic mechanisms behind PE biodegradation—a promising and sustainable remediation method. Herein, we describe a novel role of nitrogen metabolism in the fragmentation and oxidation of PE mediated by biological production of NOx in three PE-degrading strains of Comamonas, Delftia, and Stenotrophomonas. Resultant nitrated PE fragments are assimilated and then metabolized by these bacteria in a process assisted by nitronate monooxygenases and nitroreductases to support microbial growth. Due to the conservation of nitrogen metabolism genes, we anticipate that this oxidative mechanism is potentially shared by other nitrifier and denitrifier microbes.

Enhanced peroxidase-mediated biodegradation of polyethylene using the bacterial consortia under H2O2-biostimulation

Biotreatment is an environmentally friendly process for pollution control. A novel biotreatment process was investigated for the degradation of plastic wastes. The biodegradation of low-density polyethylene (LDPE) films using a bacterial consortium capable of peroxidase production in the presence of H2O2 was investigated for a 12-month period. Effective biodegradation was observed using the selected bacterial consortia; a 19.8% weight loss was detected during 12 months of biotreatment of the LDPE films. The daily addition of H2O2 to the bioreactor stimulated the microbial activity resulted in improving the weight loss to 22.5% due to the in-situ production of peroxidase. The number average molecular weight (Mn) decreased by 20.1 and 49.5% when the polyethylene sample was biotreated for 12 months in the absence and presence of H2O2, respectively. The depolymerization of the LDPE films during the biotreatment using the selected bacterial consortia was confirmed by increasing the value of polydispersity index. The morphological and structural analyses confirmed the efficient decomposition of the LDPE films using the selected bacterial species, showing that the selected bacteria could use the LDPE films and/or their degradation intermediates as carbon and energy sources. Overall, using a peroxidase-generating bacterial mixed culture is a promising biotechnique for the efficient biodegradation of the polyethylene wastes.

Polyethylene degradation by larvae of wax moth

Recently various reports on biodegradation of plastics by wax moths, Galleria mellonella and Achoria grisella have emerged upon and these offer an opportunity for development of technology to degrade the polyethylene polymer biologically. Galleria mellonella and Achoria grisella which are most damage causing honeybee pests were recently found causing disintegration of the plastic waste. Present review article provides the detailed description about the morphology of the insect and also provides description about plastic degradation capacity of wax moth. This also includes comprehensive informative account on microbiota dependent and microbiota independent biodegradation of polyethylene.

Characteristics and Polyethylene Biodegradation Function of a Novel Cold-Adapted Bacterial Laccase from Antarctic Sea Ice Psychrophile Psychrobacter Sp. Nj228

Characteristics and Polyethylene Biodegradation Function of a Novel Cold-Adapted Bacterial Laccase from Antarctic Sea Ice Psychrophile Psychrobacter Sp. Nj228

In vitro biodegradation of low-density polyethylene by soil microorganisms

The accumulation of recalcitrant plastics in the environment, particularly polyethylene, is a major threat to the ecology. Among the different kinds of polyethylene, low-density polyethylene (LDPE) is the most widely used polyethylene. The goal of this work was to isolate and discover a powerful polyethylene degrading microbial strain from plastic waste disposal soil. The bacterial and fungal strains were isolated by enrichment technique and were identified based on the morphological and biochemical characteristics. Further, they were screened individually for their lowdensity polyethylene (LDPE) degrading efficiency by in vitro biodegradation assay. The efficiency of the potent strain to colonize on the LDPE surface and its biodegradation ability were investigated. The degraded products of low-density polyethylene were analysed by FTIR after the biodegradation study which was conducted for a long incubation period by inoculating the selected bacterial strain in synthetic medium (SM) with LDPE as the carbon source. Totally six different bacterial and five different fungal strains were isolated from the polluted soil. Among the bacterial strains, the JSB2, JSB3 and JSB4 and among the fungal strains, JSF1, JSF3 and JSF4 showed maximum growth, more cell surface hydrophobicity and weight loss and they were selected for further studies. The incubation of LDPE films with bacteria and fungi led to the formation of new absorbance bands such as dehydrated dimer of carbonyl group (1720 cm-1), CH3 deformation (1463 cm-1) and C=C conjugation band (862 cm-1). The results inferred that the exogenous addition of these microbes to LDPE contaminated soil causes an enhanced degradation. Among the microbial isolates, Bacillus species showed high degradation.

Carbon-derived Substrate Accelerated the Biodegradation of Low-density Polyethylene

Carbon-derived Substrate Accelerated the Biodegradation of Low-density Polyethylene

Transcriptomic analysis of Rhodococcus opacus R7 grown on polyethylene by RNA-seq

Plastic waste management has become a global issue. Polyethylene (PE) is the most abundant synthetic plastic worldwide, and one of the most resistant to biodegradation. Indeed, few bacteria can degrade polyethylene. In this paper, the transcriptomic analysis unveiled for the first time Rhodococcus opacus R7 complex genetic system based on diverse oxidoreductases for polyethylene biodegradation. The RNA-seq allowed uncovering genes putatively involved in the first step of oxidation. In-depth investigations through preliminary bioinformatic analyses and enzymatic assays on the supernatant of R7 grown in the presence of PE confirmed the activation of genes encoding laccase-like enzymes. Moreover, the transcriptomic data allowed identifying candidate genes for the further steps of short aliphatic chain oxidation including alkB gene encoding an alkane monooxygenase, cyp450 gene encoding cytochrome P450 hydroxylase, and genes encoding membrane transporters. The PE biodegradative system was also validated by FTIR analysis on R7 cells grown on polyethylene.

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 21days. 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.

Photocatalytic degradation of low-density polythene using protein-coated titania nanoparticles and Lactobacillus plantarum

ABSTRACT The biodegradation of low-density Polyethylene (LDPE) is usually time-consuming, In the presence of Titania-nanoparticles, LDPE is photocatalytically degraded in smaller fragments afterward the bacteria can effectively degrade polyethylene. In the current study, potent polyethylene degrading bacteria were screened from the soil of the local dumpsite and identified using 16s rRNA sequencing. The protein-coated titania nanoparticle (TNPs) was synthesized using Sol-gel Method and characterized by XRD, and SAED-HRTEM. The photocatalytic biodegradation of LDPE (30 microns) in presence of 1M NaOH was studied by exposing it to UV irradiation, visible light, and high temperature (50°C) for 21 days separately and photocatalytic biodegradation was assessed by monitoring % weight loss at every 7 days’ time interval, tensile strength, and FTIR. After 21 days of photocatalytic biodegradation, LDPE film containing both TNPs and Lactobacillus plantarum along with 1M NaOH in presence of visible light was unveiled oxidation and enumerated via the occurrence of strong absorptions band of the carbonyl group (C=O) and also the breaking and weakening of existing absorptions bonds along with the new carbonyl functional group formation. The decline in tensile strength was measured at 21% after 21 days. Thus, experimental results on LDPE after exposure to visible irradiation along with Lactobacillus plantarum and 5% protein-coated TNP showed improvement in degradation rate and elongation 59 % and 51% within 21 days, respectively in comparison to another study (49 % Weight loss and 12% elongation after 45 days). An excellent application of this research is significantly reduced plastic waste via a maintained procedure.

Biodegradation of Ultra-violet Irradiated Waste Polyethylene Bags by Bacterial Community from Soil around Coal -fired Thermal Power Plant

The current study focused on biotic degradation of waste polyethylene bags using bacterial community from hydrocarbon contaminated soil near coal fired thermal power plant and also the effect of UV irradiation on its biodegradation.The predominant groups in the bacterial community in the hydrocarbon contaminated soil near coal fired thermal power plant were identified by 16s DNA sequencing were Steroidobacter, Flavisolibacter, Planctomyces, Balneimonas, Gemmata, Alicyclobacillus, Lactobacillus, Mycobacterium, Geodermatophilus, Prevotella, Virgisporangium and Adhaeribacter. The native bacterial community from hydrocarbon contaminated soil was capable of polyethylene degradation.The bacterial community in the hydrocarbon contaminated soil metabolized 12.85± 0.16 percent of polyethylene (10 g/L) as sole carbon source in mineral salt media within 30 days.The UV irradiation of polyethylene enhanced weight loss of 22.80 percent higher than untreated polyethylene. The improvement in bacterial degradation by UV exposure of waste polyethylene in-vitro for 144 hresulted 15.78± 0.32 percent weight loss in 30 days. The photo-oxidation by UV irradiation of polyethylene had surface disruption and was confirmed by Field Emission Scanning Electron Microscopy (FE-SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The photochemical reaction induced by UV irradiation of polyethylene resulted in formation of carbonyl peaks on polymer surface and addition as well as shifting of peaks. The morphological changes of polyethylene by UV exposure enhanced colonization, metabolism by and synergistic effect on polyethylene biodegradation by bacterial community from hydrocarbon contaminated soil.

Long-term effect of plastic feeding on growth and transcriptomic response of mealworms (Tenebrio molitor L.)

Plastic waste has been considered a serious global environmental problem for decades. Despite the high recalcitrance of synthetic plastics, the biodegradation of polyethylene (PE), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) by some insect larvae has been reported; however, the mechanism of degradation remains largely unknown. We investigated the effects of plastics on the growth of mealworms (larvae of Tenebrio molitor) and their role in PS and PE degradation. Mealworms were capable of ingesting high-impact polystyrene (HIPS), expanded polystyrene (EPS) and low-density polyethylene (LDPE) but not linear low-density polyethylene (LLDPE) or polypropylene (PP). Plastic consumption was negatively dependent on plastic crystallinity. Transcriptome analysis and KEGG mapping revealed that mealworms act as downstream decomposers in plastic depolymerization and that fatty acid degradation pathways may play important roles in the digestion of plastic degradation intermediates produced by gut bacteria. In addition, PS and PE degradation was achieved via the diffusion of extracellular depolymerases, which probably acted on the distal backbone and produce shorter linear chains that containing ≤16 C atoms instead of branched chains. Additionally, the intermediates of PS degradation are expected to be further decomposed by mealworms as xenobiotics. This study provided a preliminary understanding of plastic degradation mechanism by mealworms.

Biodegradation of low-density polyethylene (LDPE) and starch – based plastic (SBP) by thermophiles Bacillus subtilis and Candida tropicalis

This project was carried out to study the biodegradation of low-density polyethylene (LDPE) and starch-based plastics (SBP) by two types of thermophiles microorganisms namely B.subtilis and C. tropicalis in a lab scale method. A few specific objectives were set to identify the growth curve of both strains on LDPE and SBP films, changes in physical and chemical properties by weight loss, carbon dioxide (CO2) evolved, topography changes of plastics surfaces and the efficiency on biodegradation rate of LDPE and SBP. The results showed that after 49 days incubation period, the optimum growth of B. subtilis for both LDPE and SBP is at week 5 of incubation with 8.9 x 108 CFU/mL and 9.1 x 108 CFU/mL respectively. While for C. tropicalis the highest growth was recorded at week 4 of incubation with 9.6 x 108 for both LDPE and SBP. The weight loss reduction percentage of LDPE and SBP by C.tropicalis was 3.2% and 22.3% respectively while for B. subtilis the results recorded were 4.6% and 12.9% respectively. SEM analysis revealed that there are topography changes for LDPE with bubbling on surface while cracks and holes formed on SBP surface. The strum test used to identify CO2 evolved in SBP by C. tropicalis is 2.7 g/L which was 5-fold higher as compared to LDPE while in SBP by B. subtilis the results is 2.5 g/L which 5-fold higher compared to LDPE. Based on this study, it can be concluded that C. tropicalis have great potential in degrading SBP as compared to LDPE.

Biodegradation of polyethylene and polypropylene by Lysinibacillus species JJY0216 isolated from soil grove

Petroleum-based plastic is a widely used commodity in modern living due to its extensive industrial and domestic applications. Polyethylene and polypropylene account for more than 50% of total plastic usage, and they resist decomposition in a natural environment. In this study, Lysinibacillus sp., isolated and identified as a novel strain, was investigated to decompose polyethylene and polypropylene. In the microbial cultivation medium without any physicochemical pretreatment, the Lysinibacillus sp. reduced the weight of polypropylene and polyethylene by approximately 4 and 9%, respectively, over 26 days. During the biodegradation of polyethylene and polypropylene, a rough surface increase was observed by scanning electron microscope (SEM) imaging.Moreover, various oxidation products containing CH2 groups produced from the decomposition of polyethylene and polypropylene were observed by GC–MS analysis. Results suggest that microorganisms can be used to degrade polyethylene and polypropylene without a physicochemical process. This can be a starting point for developing methods for remediating soil contaminated with plastics.

Exploration of Strategies for the Enhanced Biodegradation of Low-Density Polyethylene (LDPE) by A Soil Bacterium Enterobacter Cloacae AKS7

In the context of sustainable bioremediation of Low-density polyethylene (LDPE), in this study, several strategies were explored to enhance the LDPE degradation by the bacterium Enterobacter cloacae AKS7. Initially, Mineral oil and Tween 80 were used to test whether they could modulate microbial colonization and polymer degradation by AKS7. Results indicated Mineral oil could increase microbial colonization and LDPE degradation whereas Tween 80 compromised the same. Since LDPE holds hydrophobic characteristics, the organism showing higher cell-surface hydrophobicity could adhere efficiently to the polymer. Thus, the organism AKS7 was grown in media with different concentrations of glucose and ammonium sulphate to exhibit differences in cell-surface hydrophobicity. We noticed that with increasing cell-surface hydrophobicity, the microbial colonization and LDPE degradation got enhanced considerably. The observations indicated that cell-surface hydrophobicity promoted microbial colonization to LDPE that increased the degree of biodegradation. Besides, LDPE films were photo-oxidized before microbial exposure which showed that AKS7 could degrade ultra-violet (UV) treated LDPE more proficiently compared to the UV-untreated polymer. Moreover, AKS7 could colonize more effectively to the UV-treated LDPE in contrast to the untreated LDPE. Furthermore, it was observed that UV exposure increased the carbonyl bond index of the polymer which got utilized by the organism efficiently thereby increasing the polymer degradation. Hence, the observations indicated that effective microbial colonization to UV-treated LDPE films exhibited a promising metabolic activity that could show an enhanced degradation of LDPE. Therefore, AKS7 warrants to be considered as a promising organism for enhanced degradation of LDPE.

Role of nanotechnology for improving properties of biosurfactant from newly isolated bacterial strains from Rajasthan

Biologically synthesized surfactant are commercially used in various biotechnology sectors as cosmetic, cleaning, and agriculture products. In this study, Bacillus paramycoides was isolated as new bacterial strain from plastic disposal site of Banasthali Vidyapith (Rajasthan) for producing lipopeptide biosurfactant. Surface tension, emulsification index, oil-displacement are some primary screening methods done to validate the production of biosurfactant. The emulsification analysis elucidated at 62.50% and reduction of surface tension noticed at 33.10 mN/m. The nano-encapsulation of this biosurfactant onto silver nanoparticles had efficiently improved its ability for biodegradation of polyethylene. UV sterilized polyethylene films were treated with biosurfactant mediated silver nanoparticles and its maximum degradation was observed within 70 days. The synthesized silver nanoparticles were characterized by UV spectrum, zeta size potential, scanning electron microscope analysis. The total weight loss of low-density polyethylene (cling films) and high-density polyethylene (grocery bags) was observed 36.30% and 31.11%, respectively after treatment with silver nanoparticles for these lipopeptide biosurfactant. The higher degree of biodegradation rate of LDPE and HDPE polyethylene after treating with silver nano-biosurfactant might be due to their high degree of biocompatibility and stability. These nano-biosurfactant could be effectively used for biodegradation of plastic pollutant at large scale.

Response of the yellow mealworm (Tenebrio molitor) gut microbiome to diet shifts during polystyrene and polyethylene biodegradation

Plastic biodegradation by mealworm is regarded as an emerging strategy for plastic disposal. In this study, the polystyrene (PS) and low density polyethylene (LDPE) degradation efficiency by yellow mealworms (Tenebrio molitor larvae) supplemented with bran and the effects of plastics on the gut core microbiome were explored to construct a circular and continuous reactor for plastic biodegradation in the future. The gut microbiome was also investigated with dietary shift to explore the relationship between specific diets and gut microbes. The bran plus plastic (7:1 ratio, w/w) co-diet contributed to the mealworm survival and growth. The formation of −C˭O−/−C−O− groups in the plastic-fed mealworms frass represented the oxidation process of plastic biodegradation in the mealworm gut. The changes in molecular weights (Mw, Mn and Mz) of residual PS and LDPE in mealworms frass compared with that of PS and PE feedstock confirmed the plastic depolymerization and biodegradation. Lactobacillus and Mucispirillum were significantly associated with PE + bran diet compared to bran diet and PE diet, representing the response of mealworm gut microbiome to the bran and plastic mixture was distinguished from either bran or plastics alone. The gut microbiome changed substantially with the diet shift, indicating that microbial community assembly was a stochastic process and diverse plastic-degrading bacteria might occur in the mealworm gut.

Confirmation of biodegradation of low-density polyethylene in dark- versus yellow- mealworms (larvae of Tenebrio obscurus versus Tenebrio molitor) via. gut microbe-independent depolymerization

Tenebrio obscurus (Coleoptera: Tenebrionidae) larvae are capable of biodegrading polystyrene (PS) but their capacity for polyethylene (PE) degradation and pattern of depolymerization remains unknown. This study fed the larvae of T. obscurus and Tenebrio molitor, which have PE degrading capacity, two commercial low-density PE (LDPE) foams i.e., PE-1 and PE-2, with respective number-average molecular weights (Mn) of 28.9 and 27.3 kDa and weight-average molecular weights (Mw) of 342.0 and 264.1 kDa, over a 36-day period at ambient temperature. The Mw of residual PE in frass (excrement) of T. obscurus, fed with PE-1 and PE-2, decreased by 45.4 ± 0.4% and 34.8 ± 0.3%, respectively, while the respective decrease in frass of T. molitor was 43.3 ± 0.5% and 31.7 ± 0.5%. Data analysis showed that low molecular weight PE (<5.0 kDa) was rapidly digested while longer chain portions (>10.0 kDa) were broken down or cleaved, indicating a broad depolymerization pattern. Mass balance analysis indicated nearly 40% of ingested LDPE was digested to CO2. Antibiotic suppression of gut microbes in T. molitor and T. obscurus larvae with gentamicin obviously reduced their gut microbes on day 15 but did not stop depolymerization because the Mn, Mw and size- average molecular weight (Mz) decreased. This confirmed that LDPE biodegradation in T. obscurus was independent of gut microbes as observed during previous PS degradation in T. molitor, suggesting that the intestinal digestive system could perform LDPE depolymerization. High-throughput sequencing revealed significant shifts in the gut microbial community during bran-fed and unfed conditions in response to LDPE feeding in both Tenebrio species. The respective predominant gut genera of Spiroplasma sp. and Enterococcus sp. were observed in LDPE-fed T. molitor and T. obscurus larvae.

Fungal biodegradation of low-density polyethylene using consortium of Aspergillus species under controlled conditions

Low-Density polyethylene is subject to biodegradation using a fungal consortium comprising of Aspergillus niger, Aspergillus flavus and Aspergillus oryzae under laboratory conditions. The extent of biodegradation has been compared with the use of potato dextrose broth and czapek dox broth media and also in the presence and absence of Tween 80 additive. Biodegradation was performed replacing the sucrose in czapek dox broth with shredded Low-Density polyethylene as well. The biodegradation was carried out for a period of 55 days. The degree of biodegradation has been analyzed using the loss of weight, FT-IR, and SEM analysis. A maximum weight loss of 26.15% was obtained by using potato dextrose broth over a period of 55 days.

Whole-genome sequence-based analysis of the Paenibacillus aquistagni strain DK1, a polyethylene-degrading bacterium isolated from landfill.

Polyethylene-degrading bacteria have been emerging as a rational and safe alternative in bioremediation strategies. In this context, some Paenibacillus species produce enzymes involved in the biodegradation of pollutants. Among the enzymes involved in the biodegradation of polyethylene, the alkane hydroxylases, encoded by alkB homologous genes, play a key role in this process. Therefore, this study aimed to identify and perform a genomic investigation of the first polyethylene-degrading Paenibacillus sp. strain, named DK1. The whole-genome sequence-based analysis revealed that the DK1 strain belonged to the species Paenibacillus aquistagni and shared a total of 4327 CDSs with P. aquistagni strain 11. On the other hand, a comparison of the gene clusters showed that DK1 strain harbored a genetic context surrounding the alkB-like gene similar to that found in Pseudomonas sp. strains. The percentage of similarity ranged from 47.88 to 99.76% among all complete amino acid sequences of AlkB-like proteins analyzed. Nevertheless, the predicted amino acid sequences of AlkB-like contained typical structural motifs of alkane hydroxylases, such as His boxes and the HYG motif. These findings associated with the previously reported phenotypic results highlighted the potential of P. aquistagni strain DK1 to biodegrade polyethylene. Therefore, further studies focusing on the biochemical and structural properties of the AlkB-like protein from Paenibacillus may also contribute to the development of sustainable bioremediation strategies.