Abiotic and biotic degradation of oxo-biodegradable plastic bags by Pleurotus ostreatus

Is Laccase derived from Pleurotus ostreatus effective in microplastic degradation? A critical review of current progress, challenges, and future prospects

Exploration of Pleurotus ostreatus as a biological agent in the degradation of persistent plastics like polyethylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate, revealing a promising avenue toward mitigating the environmental impacts of plastic pollution. Leveraging the intrinsic enzymatic capabilities of this fungus, mainly its production of laccase, presents a sustainable and eco-friendly approach to breaking down complex polymer chains into less harmful constituents. This review focused on enhancements in the strain's efficiency through genetic engineering, optimized culture conditions, and enzyme immobilization to underscore the potential for scalability and practical application of this bioremediation process. The utilization of laccase from P. ostreatus in plastic waste management demonstrates a vital step forward in pursuing sustainable environmental solutions. By using the potential of fungal bioremediation, researchers can move closer to a future in which the adverse effects of plastic pollution are significantly mitigated, benefiting the health of our planet and future generations.

Characterization of low-density polyethylene (LDPE) films degraded using bacteria strains isolated from oil-contaminated soil

This study assessed the low-density polyethylene (LDPE) film degradation potential of microorganisms isolated from oil-contaminated soil and also analyzed the morphological and chemical composition of LDPE films after the biodegradation period. The bacteria strains isolated from oil-contaminated soil were standardized and used to degrade the pretreated LDPE films in mineral salt media. Thereafter, they were incubated for 78 days at 37°C in an incubator shaker, and the degraded LDPE films were analyzed quantitatively and qualitatively (using scanning electron microscope (SEM) images and energy dispersal x-ray (EDX)). Isolates A32 and BTT4 amongst other bacteria isolates showed the highest LDPE film degradation activity, with a weight reduction of 71.80% and 89.72% respectively, and were identified using the 16S rRNA sequencing technique. The EDX results showed that LDPE film incubated with A32 has the highest reduction in carbon and nitrogen (23.8% and 44.9% respectively) when compared with the Control. However, LDPE film incubated with BTT4 had an increase in calcium and chlorine (139% and 40% respectively), when compared with the control. Similarly, the SEM images showed the appearance of pinholes, cracks and particles on the surfaces of LDPE films incubated with A32 and BTT4 contrary to the controls. A32 and BTT4 were identified as Proteus mirabilis (Accession number: MN124173.1) and Proteus mirabilis (Accession number: KY027145.1) respectively. Proteus mirabilis showed viable plastic biodegradation potentials and may be useful in the management of plastic waste, leading to a reduction in global plastic waste and a clean environment.

Myco-remediation of plastic pollution: current knowledge and future prospects

To date, enumerable fungi have been reported to participate in the biodegradation of several notorious plastic materials following their isolation from soil of plastic-dumping sites, marine water, waste of mulch films, landfills, plant parts and gut of wax moth. The general mechanism begins with formation of hydrophobin and biofilm proceding to secretion of specific plastic degarding enzymes (peroxidase, hydrolase, protease and urease), penetration of three dimensional substrates and mineralization of plastic polymers into harmless products. As a result, several synthetic polymers including polyethylene, polystyrene, polypropylene, polyvinyl chloride, polyurethane and/or bio-degradable plastics have been validated to deteriorate within months through the action of a wide variety of fungal strains predominantly Ascomycota (Alternaria, Aspergillus, Cladosporium, Fusarium, Penicillium spp.). Understanding the potential and mode of operation of these organisms is thus of prime importance inspiring us to furnish an up to date view on all the presently known fungal strains claimed to mitigate the plastic waste problem. Future research henceforth needs to be directed towards metagenomic approach to distinguish polymer degrading microbial diversity followed by bio-augmentation to build fascinating future of waste disposal.

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.

Face masks: a COVID-19 protector or environmental contaminant?

Face masks, a prime component of personal protective equipment (PPE) items, have become an integral part of human beings to survive under the ongoing COVID-19 pandemic situation. The global population requires an estimated 130 billion face masks and 64 billion gloves/month, while the COVID-19 pandemic has led to the daily disposal of approximately 3.5 billion single-use face masks, resulting in a staggering 14,245,230.63 kg of face mask waste. The improper disposal of face mask wastes followed by its mismanagement is a challenge to the scientists as the wastes create pollution leading to environmental degradation, especially plastic pollution (macro/meso/micro/nano). Each year, an estimated 0.15-0.39 million tons of COVID-19 face mask waste, along with 173,000 microfibers released daily from discarded surgical masks, could enter the marine environment, while used masks have a significantly higher microplastic release capacity (1246.62 ± 403.50 particles/piece) compared to new masks (183.00 ± 78.42 particles/piece). Surgical face masks emit around 59 g CO2-eq greenhouse gas emissions per single use, cloth face masks emit approximately 60 g CO2-eq/single mask, and inhaling or ingesting microplastics (MPs) caused adverse health problems including chronic inflammation, granulomas or fibrosis, DNA damage, cellular damage, oxidative stress, and cytokine secretion. The present review critically addresses the role of face masks in reducing COVID-19 infections, their distribution pattern in diverse environments, the volume of waste produced, degradation in the natural environment, and adverse impacts on different environmental segments, and proposes sustainable remediation options to tackle environmental challenges posed by disposable COVID-19 face masks.

Polyethylene terephthalate (PET) biodegradation by Pleurotus ostreatus and Pleurotus pulmonarius

The essential properties of polyethylene terephthalate (PET), such as chemical inertness and durability that make it a suitable material for the packaging of mineral and soft drinks, have led to it becoming a major environmental pollutant and a threat to the planet. Ecologically friendly solutions such as bioremediation are now being advocated for by scientists. This paper, therefore, seeks to explore the potential capacity of Pleurotus ostreatus and Pleurotus pulmonarius in biodegrading PET plastic on two different substrates (soil and rice straw). The substrates were combined with 5% and 10% plastic before inoculation with Pleurotus ostreatus and Pleurotus pulmonarius and then left to incubate for 2 months. Biodegradation, monitored by FT-IR pointed to the formation of new peaks in the incubated plastics after 30 and 60 days unlike in the control. Changes in band intensity and shifts in the wavenumbers caused by stretching of functional groups, C-H, O-H and N-H in the band region of 2898 cm^-1 to 3756 cm^-1 are confirmed indicators of successful breakdown caused by contact with P. ostreatus and P. pulmonarius. The FT-IR analysis also gave an indication of N-H stretching at 3338.04 cm^-1 and 3228.62 cm^-1 for PET flakes incubated with Pleurotus sp. Furthermore, degradation products like hydrocarbons, carboxylic acids, alcohols, esters, and ketones were also detected in the GC-MS analysis of the decomposed PET plastic after 30 and 60 days. These compounds are formed due to chain scission caused by the fungal species. There was a discoloration of the PET flakes caused by an increase in carboxyl-terminated species as a result of enzymes secreted by the fungi in the process of biodegradation.

Biological effects on the migration and transformation of microplastics in the marine environment

Microplastics(MPs) are ubiquitous, difficult to degrade, and potentially threatening to organisms in marine environment, so it is important to clarify the factors that affect their biogeochemical processes. The impact of biological activities on the MPs in marine environment is ubiquitous and complex, and there is currently a lack of systematic summaries. This paper reviews the effects of biological actions on the migration, distribution and degradation of MPs in marine environment from four aspects: biological ingestion and digestion, biological movement, biological colonization and biological adhesion. MPs in seawater and sediments can be closely combined with organisms through three pathways: biological ingestion, biofilm formation or adhesion to organisms, and are passed between species at different trophic levels through the food chain. The generation and degradation of faecal pellets and biofilms can alter the density of "environmental MPs", thereby affecting their vertical migration and deposition in water bodies. The movement of swimming organisms and the disturbance by benthic organisms can promote the migration of MPs in water and vertical migration and resuspension in sediments, thereby changing the distribution of MPs in local sea areas. The grinding effect of the digestive tract and the secretion of chemicals from the biofilm (such as enzymes and acids) can reduce the particle size and increase surface roughness of MPs, or even degrade them completely. Besides, biological adhesion may be an important mechanism affecting the distribution, migration and preservation of MPs. There may be complex interactions and linkages among marine dynamical processes, photochemical degradation and biological processes that collectively affect the biogeochemical processes of MPs, but their relative contributions remain to be more studied.

Bacterial dynamics during the burial of starch-based bioplastic and oxo-low-density-polyethylene in compost soil

BACKGROUND

Plastic waste accumulation is one of the main ecological concerns in the past decades. A new generation of plastics that are easier to degrade in the environment compared to conventional plastics, such as starch-based bioplastics and oxo-biodegradable plastics, is perceived as a solution to this issue. However, the fate of these materials in the environment are unclear, and less is known about how their presence affect the microorganisms that may play a role in their biodegradation. In this study, we monitored the dynamics of bacterial community in soil upon introduction of commercial carrier bags claimed as biodegradable: cassava starch-based bioplastic and oxo-low-density polyethylene (oxo-LDPE). Each type of plastic bag was buried separately in compost soil and incubated for 30, 60, 90, and 120 days. Following incubation, soil pH and temperature as well as the weight of remaining plastics were measured. Bacterial diversity in soil attached to the surface of remaining plastics was analyzed using Illumina high-throughput sequencing of the V3-V4 region of 16SrRNA gene.

RESULTS

After 120 days, the starch-based bioplastic weight has decreased by 74%, while the oxo-LDPE remained intact with only 3% weight reduction. The bacterial composition in soil fluctuated over time with or without the introduction of either type of plastic. While major bacterial phyla remained similar for all treatment in this study, different types of plastics led to different soil bacterial community structure. None of these bacteria were abundant continuously, but rather they emerged at specific time points. The introduction of plastics into soil increased not only the population of bacteria known for their ability to directly utilize plastic component for their growth, but also the abundance of those that may interact with direct degraders. Bacterial groups that are involved in nitrogen cycling also arose throughout burial.

CONCLUSIONS

The introduction of starch-based bioplastic and oxo-LDPE led to contrasting shift in soil bacterial population overtime, which may determine their fate in the environment.

Microbial biodegradation of plastics: Challenges, opportunities, and a critical perspective

The abundance of synthetic polymers has increased due to their uncontrolled utilization and disposal in the environment. The recalcitrant nature of plastics leads to accumulation and saturation in the environment, which is a matter of great concern. An exponential rise has been reported in plastic pollution during the corona pandemic because of PPE kits, gloves, and face masks made up of single-use plastics. The physicochemical methods have been employed to degrade synthetic polymers, but these methods have limited efficiency and cause the release of hazardous metabolites or by-products in the environment. Microbial species, isolated from landfills and dumpsites, have utilized plastics as the sole source of carbon, energy, and biomass production. The involvement of microbial strains in plastic degradation is evident as a substantial amount of mineralization has been observed. However, the complete removal of plastic could not be achieved, but it is still effective compared to the preexisting traditional methods. Therefore, microbial species and the enzymes involved in plastic waste degradation could be utilized as eco-friendly alternatives. Thus, microbial biodegradation approaches have a profound scope to cope with the plastic waste problem in a cost-effective and environmental-friendly manner. Further, microbial degradation can be optimized and combined with physicochemical methods to achieve substantial results. This review summarizes the different microbial species, their genes, biochemical pathways, and enzymes involved in plastic biodegradation.

Face masks: protecting the wearer but neglecting the aquatic environment? - A perspective from Bangladesh

In Bangladesh, as with many countries, the spread of COVID-19 made the wearing of single-use face masks, a non-pharmaceutical intervention to reduce viral transmission, surge in popularity amongst the general population. Consequently, irresponsible discarding of used masks into the environment, and mismanagement of the waste they produce, is potentially placing a large pollution burden on aquatic ecosystems in the country. Slow degradation of mask-derived polypropylene and polyethylene fibres creates large reservoirs of microplastic pollutants and these have acute and chronic effects on aquatic organism physiology. Using literature reviews, extrapolation of published data, and field observations, we present an emerging issue of pollution from COVID-19 personal protective equipment such as face masks in Bangladesh. We have estimated the volume of waste generated and document the potential consequences of its improper disposal, and subsequent degradation, in aquaculture ponds within country. In a field survey of 30 ponds in the Muktagacha upazilla, 76.7% were found to have plastics in contact with the water, or within 1m of the pond, and there was an average of 63 pieces of macro-plastic pollution per 5m2. This included floating discarded face masks. Bangladesh has a rich freshwater and marine resource which it depends upon for export trade, nutrition of the population, and jobs. To mitigate potential acute and chronic impacts on aquaculture and the environment, recommendations are made that, if adopted, would reduce entry of microplastics into the aquatic environments via face mask waste mismanagement.

Evaluation of two microcosm systems for co-treatment of LDPEoxo and lignocellulosic biomass for biochar production

BACKGROUND

The co-transformation of solid waste of natural and anthropogenic origin can be carried out through solid-state-fermentation systems to obtain bio-products with higher added value and lower environmental impact.

METHODS

To evaluate the effect of Pleurotus ostreatus on co-transformation of oxo-degradable low-density polyethylene (LDPE_oxo) sheets and lignocellulosic biomass (LCB), were assembled two 0.75 L microcosm systems in vertical (VMS) and horizontal (HMS) position. The pre-treated sheets with luminescent O₂ plasma discharges were mixed with pine bark, hydrolyzed brewer's yeast and paper napkin fragments and incubated for 135 days at 20 ± 1.0 °C in the presence of the fungus. With the co-transformation residues, biochar (BC) was produced at 300 ± 1.0 °C (BC300) for 1 h, then used to carry out adsorption studies, using the malachite green dye (MG) at pH 4.0, 7.0 and 9.0 ± 0.2. Finally, the biochar was the substrate for the germination of carnation seeds (Dianthus caryophyllus) and Ray-grass (Lolium sp.) in vitro.

RESULTS

For HMS, the decrease in static contact angle (SCA) was 63.63% (p = 0.00824) and for VMS 74.45% (p = 0.00219), concerning the pristine. Plastic roughness in VMS was higher (26%) concerning the control. Throughout the 135 days, there were fungal growth and consequently laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) activities. During the first 75 days, CO₂ production increased to 4.78 ± 0.01 and 4.98 ± 0.01 mg g-1 for HMS and VMS, respectively. In MG adsorption studies, the highest amount of the colourant adsorbed at both pH 4.0 and 7.0 ± 0.2.

CONCLUSIONS

Finally, the biochar or the biochar enriched with low concentrations of plant growth-promoting microorganisms and inorganic fertilizer favours the germination of Dianthus caryophyllus and Lolium sp., seeds.

Inspired by nature: Microbial production, degradation and valorization of biodegradable bioplastics for life-cycle-engineered products

The global environmental pollution by micro- and macro-plastics reveals the consequences of an extensive use of recalcitrant plastic products together with inappropriate waste management practices that fail to sufficiently recycle the broad types of conventional plastic waste. Biobased and biodegradable plastics are experiencing an uprising as their properties offer alternative waste management solutions for a more circular material economy. However, although the production of such bioplastics has advanced on scale, the end-of-life (EOL) (bio)technologies to promote circularity are lacking behind. While composting and biogas plants are the only managed EOL options today, advanced biotechnological recycling technologies for biodegradable bioplastics are still in an embryonic stage. Thus, developing efficient biotechnologies capable of transforming bioplastic waste into high-value chemical building blocks or into the constituents of the original polymer offers promising routes towards life-cycle-engineered products. This review aims at providing a comprehensive state-of-the-art overview of microbial-based processes involved in the complete lifecycle of bioplastics. The current trends in the bioplastic market, the beginning and EOL scenarios of bioplastics, and a critical discussion on the key factors and mechanisms governing microbial degradation are systematically presented. Also, a critical evaluation of terminology and international standards to quantify polymer biodegradability is provided together with the latest biotechnological recycling strategies, including the use of different pre-treatments for (bio)plastic waste. Finally, the challenges and future perspectives for the development of life-cycle-engineered biobased and biodegradable plastic products are discussed.

Plastics and the microbiome: impacts and solutions

Global plastic production has increased exponentially since manufacturing commenced in the 1950's, including polymer types infused with diverse additives and fillers. While the negative impacts of plastics are widely reported, particularly on marine vertebrates, impacts on microbial life remain poorly understood. Plastics impact microbiomes directly, exerting toxic effects, providing supplemental carbon sources and acting as rafts for microbial colonisation and dispersal. Indirect consequences include increased environmental shading, altered compositions of host communities and disruption of host organism or community health, hormone balances and immune responses. The isolation and application of plastic-degrading microbes are of substantial interest yet little evidence supports the microbial biodegradation of most high molecular weight synthetic polymers. Over 400 microbial species have been presumptively identified as capable of plastic degradation, but evidence for the degradation of highly prevalent polymers including polypropylene, nylon, polystyrene and polyvinyl chloride must be treated with caution; most studies fail to differentiate losses caused by the leaching or degradation of polymer monomers, additives or fillers. Even where polymer degradation is demonstrated, such as for polyethylene terephthalate, the ability of microorganisms to degrade more highly crystalline forms of the polymer used in commercial plastics appears limited. Microbiomes frequently work in conjunction with abiotic factors such as heat and light to impact the structural integrity of polymers and accessibility to enzymatic attack. Consequently, there remains much scope for extremophile microbiomes to be explored as a source of plastic-degrading enzymes and microorganisms. We propose a best-practice workflow for isolating and reporting plastic-degrading taxa from diverse environmental microbiomes, which should include multiple lines of evidence supporting changes in polymer structure, mass loss, and detection of presumed degradation products, along with confirmation of microbial strains and enzymes (and their associated genes) responsible for high molecular weight plastic polymer degradation. Such approaches are necessary for enzymatic degraders of high molecular weight plastic polymers to be differentiated from organisms only capable of degrading the more labile carbon within predominantly amorphous plastics, plastic monomers, additives or fillers.

Biodegradable Plastics: Standards, Policies, and Impacts

Plastics are ubiquitous in our society. They are in our phones, clothes, bottles, and cars. Yet having improved our lives considerably, they now threaten our environment and our health. The associated carbon emissions and persistency of plastics challenge the fragile balance of many ecosystems. One solution is using biodegradable plastics. Ideally, such plastics are easily assimilated by microorganisms and disappear from our environment. This can help reduce the problems of climate change, microplastics, and littering. However, biodegradable plastics are still only a tiny portion of the global plastics market and require further efforts in research and commercialization. Here, a critical overview of the state of the art of biodegradable plastics is given. Using a material flow analysis, the challenges of the plastic market are highlighted, and with it the large market potential of biodegradable plastics. The environmental and socio-economic impact of plastics, government policies, standards and certifications, physico-chemical properties, and analytical techniques are covered. The Review concludes with a personal outlook on the future of bioplastics, based on our own experience with their development and commercialization.

Degradability and biofouling of oxo-biodegradable polyethylene in the planktonic and benthic zones of the Arabian Gulf

Little is known about the degradability of oxo-biodegradable polyethylene (OXO-PE) and its surface fouling bacterial communities in the marine environment. The degradation of OXO-PE, PE and polyethylene terephthalate (PET) was compared at two depths (2 m and 6 m) in the Arabian Gulf. Scanning electron microcopy (SEM) revealed more fissure formation on OXO-PE and PE than on PET, indicating physical degradation. The formation of hydroxyl groups and carbonyl bonds, by Fourier-transform infrared spectroscopy (FTIR), suggests chemical degradation of OXO-PE. Plastisphere bacterial communities on OXO-PE and PE were different than on PET. Proteobacteria, Bacteriodetes and Planctomycetes were detected on all plastics, however, sequences of Alteromonas and Zoogloea were OXO-PE-specific suggesting a possible involvement of these bacterial genera in OXO-PE degradation. We conclude that OXO-PE shows increased signs of degradation with time owing to the combination of abiotic and biotic processes, and its degradation is higher in the benthic than in the planktonic zone.

Simultaneous bioconversion of lignocellulosic residues and oxodegradable polyethylene by Pleurotus ostreatus for biochar production, enriched with phosphate solubilizing bacteria for agricultural use

A simultaneous treatment of lignocellulosic biomass (LCB) and low density oxodegradable polyethylene (LDPE_oxo) was carried-out using Pleurotus ostreatus at microcosm scale to obtain biotransformed plastic and oxidized lignocellulosic biomass. This product was used as raw matter (RM) to produce biochar enriched with phosphate solubilizing bacteria (PSB). Biochar potential as biofertilizer was evaluated in Allium cepa culture at greenhouse scale. Experiments including lignocellulosic mix and LDPE_oxo were performed for 75 days in microcosm. Biotransformation progress was performed by monitoring total organic carbon (TOC), CO₂ production, laccase (Lac), manganese peroxidase (MnP), and lignin peroxidase (LiP) enzymatic activities. Physical LDPE_oxo changes were assessed by atomic force microscopy (AFM), scanning electron microscopy (SEM) and static contact angle (SCA) and chemical changes by Fourier transform infrared spectroscopy (FTIR). Results revealed P. ostreatus was capable of LCB and LDPE_oxo biotransformation, obtaining 41% total organic carbon (TOC) removal with CO₂ production of 2,323 mg Kg^-1 and enzyme activities of 169,438 UKg^-1, 5,535 UKg^-1 and 5,267 UKg^-1 for LiP, MnP and Lac, respectively. Regarding LDPE_oxo, SCA was decreased by 84%, with an increase in signals at 1,076 cm^-1 and 3,271 cm^-1, corresponding to C-O and CO-H bonds. A decrease in signals was observed related to material degradation at 2,928 cm^-1, 2,848 cm^-1, agreeing with CH₂ asymmetrical and symmetrical stretching, respectively. PSB enriched biochar favored A. cepa plant growth during the five-week evaluation period. To the best of our knowledge, this is the first report of an in vitro circular production model, where P. ostreatus was employed at a microcosmos level to bioconvert LCB and LDPE_oxo residues from the agroindustrial sector, followed by thermoconversion to produce an enriched biochar with PSB to be used as a biofertilizer to grow A. cepa at greenhouse scale.

Biodeterioration of plasma pretreated LDPE sheets by Pleurotus ostreatus

Low-density polyethylene (LDPE) waste generates an environmental impact. To achieve the most suitable option for their degradation, it is necessary to implement chemical, physical and biological treatments, as well as combining procedures. Best treatment was prognosticated by Plackett-Burman Experimental Design (PB), evaluating five factors with two levels (0.25 mM or 1.0 gL^-1 glucose, 1.0 or 2.0 mM CuSO₄, 0.1 or 0.2 mM ABTS [2, 20-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)], pH 4.5 ± 0.2 or 7.0 ± 0.2 and 30 or 90 day incubation), which was reproduced for 150 days. Therefore, PB identified a sequential treatment (plasma followed by fungus) for partial LDPE biodeterioration. Sheets were pretreated with glow discharge plasma (O₂, 3.0 x 10⁻² mbar, 600 V, 6 min.), followed by Pleurotus ostreatus biodeterioration. Fungus growth, colonization percentage, and pigment generation followed. Laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) activities were appraised. Additionally, contact angle (CA), functional group presence and changes and carbonyl and vinyl indices (Fourier transformed infrared spectroscopy) were evaluated. LDPE surface changes were assessed by Young’s modulus, yield strength, scanning electronic microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Plasma discharge increased hydrophilicity, decreasing CA by 76.57% and increasing surface roughness by 99.81%. P. ostreatus colonization was 88.72% in 150 days in comparison with untreated LDPE (45.55%). After this treatment carbonyl groups (C = O), C = C insaturations, high hydrophilicity CA (16 ± 4) °, and low surface roughness (7 ± 2) nm were observed. However, the highest Lac and LiP activities were detected after 30 days (Lac: 2.817 U Lac g^-1 and LiP: 70.755 U LiP g^-1). In addition, highest MnP activity was observed at day 120 (1.097 U MnP g^-1) only for P. ostreatus treated LDPE. Plasma favored P. ostreatus adsorption, adherence, growth and colonization (88.72%), as well as partial LDPE biodeterioration, supported by increased hydrophilicity and presence of specific functional chemical groups. The approximate 27% changes in LDPE physical properties support its biodeterioration.

Biodegradation of thermally treated low density polyethylene by fungus Rhizopus oryzae NS 5

Polythene is considered as one of the important object used in daily life. Being versatile in nature and resistant to microbial attack, they effectively cause environmental pollution. In the present study, biodegradation of low-density polyethylene (LDPE) have been performed using fungal lab isolate Rhizopus oryzae NS5. Lab isolate fungal strain capable of adhering to LDPE surface was used for the biodegradation of LDPE. This strain was identified as Rhizopus oryzae NS5 (Accession No. KT160362). Fungal growth was observed on the surface of the polyethylene when cultured in potato dextrose broth at 30 °C and 120 rpm, for 1 month. LDPE film was characterized before and after incubation by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and universal tensile machine. About 8.4 ± 3% decrease (gravimetrically) in weight and 60% reduction in tensile strength of polyethylene was observed. Scanning electron microscope analysis showed hyphal penetration and degradation on the surface of polyethylene. Atomic force microscope analysis showed increased surface roughness after treatment with fungal isolate. A thick network of fungal hyphae forming a biofilm was also observed on the surface of the polyethylene pieces. Present study shows the potential of Rhizopus oryzae NS5 in polyethylene degradation in eco friendly and sustainable manner.

Microbial degradation of low-density polyethylene (LDPE) by Aspergillus clavatus strain JASK1 isolated from landfill soil

Polythene and plastic waste are found to accumulate in the environment, posing a major ecological threat. They are found to be considered non-degradable, once it enters the environment it has been found to remain there indefinitely. However, significant attention has been placed on biodegradable polymer, identification of microbes with degradative potential on plastic material. The aim of the present investigation was to biodegrade low-density polyethylene (LDPE) using potential fungi isolated from landfill soil. Based on 18S rRNA analyses the isolated strain was identified as Aspergillus clavatus. LDPE degradation by A. clavatus was monitored for 90 days of incubation in aqueous medium. The degradation was confirmed by changes in polyethylene weight, CO₂ evolution by Strum test, infrared spectra and morphological changes by SEM and AFM analysis.

Degradation of Green Polyethylene by Pleurotus ostreatus

We studied the biodegradation of green polyethylene (GP) by Pleurotus ostreatus. The GP was developed from renewable raw materials to help to reduce the emissions of greenhouse gases. However, little information regarding the biodegradation of GP discarded in the environment is available. P. ostreatus is a lignocellulolytic fungus that has been used in bioremediation processes for agroindustrial residues, pollutants, and recalcitrant compounds. Recently, we showed the potential of this fungus to degrade oxo-biodegradable polyethylene. GP plastic bags were exposed to sunlight for up to 120 days to induce the initial photodegradation of the polymers. After this period, no cracks, pits, or new functional groups in the structure of GP were observed. Fragments of these bags were used as the substrate for the growth of P. ostreatus. After 30 d of incubation, physical and chemical alterations in the structure of GP were observed. We conclude that the exposure of GP to sunlight and its subsequent incubation in the presence of P. ostreatus can decrease the half-life of GP and facilitate the mineralization of these polymers.