Low-density Polyethylene Surface Research Articles

Identification of plastic-degrading bacteria in the human gut

Environmental pollution caused by the excessive use of plastics has resulted in the inflow of microplastics into the human body. However, the effects of microplastics on the human gut microbiota still need to be better understood. To determine whether plastic-degrading bacteria exist in the human gut, we collected the feces of six human individuals, did enrichment cultures and screened for bacterial species with a low-density polyethylene (LDPE) or polypropylene (PP)-degrading activity using a micro-spray method. We successfully isolated four bacterial species with an LDPE-degrading activity and three with a PP-degrading activity. Notably, all bacterial species identified with an LDPE or PP-degrading activity were opportunistic pathogens. We analyzed the microbial degradation of the LDPE or PP surface using scanning electron microscopy and confirmed that each bacterial species caused the physical changes. Chemical structural changes were further investigated using X-ray photoelectron spectroscopy and Fourier-transform-infrared spectroscopy, confirming the oxidation of the LDPE or PP surface with the formation of carbonyl groups (C=O), ester groups (CO), and hydroxyl groups (-OH) by each bacterial species. Finally, high temperature gel permeation chromatography (HT-GPC) analysis showed that these bacterial species performed to a limited extent depolymerization. These results indicate that, as a single species, these opportunistic pathogens in the human gut have a complete set of enzymes and other components required to initiate the oxidation of the carbon chains of LDPE or PP and to degrade them. Furthermore, these findings suggest that these bacterial species can potentially biodegrade and metabolize microplastics in the human gut.

Biodegradation of low-density polyethylene by novel halophilic bacteria from mangrove ecosystem

Low-density polyethylene (LDPE) is identified as the primary constituent (approximately 18.9%) in plastic waste pollution. Crystalline structure, high molecular weight, and hydrophobic nature make LDPE recalcitrant to degradation. In the current study, the biodegradation of LDPE was studied by using three novel Malaysian mangrove bacterial isolates Brevundimonas naejangsanensis (strain MGS1), Arthrobacter crystallopoietes (strain SW4), and Arthrobacter pokkalii (strain PD2). Biodegradation of UV-treated LDPE was determined by the gradual increase in microbial count and production of laccase and lipase enzymes over a period of thirty days. All the isolates reduced the weight of the residual polymer and modified the chemical structure of LDPE by forming carbonyl and hydroxyl groups as a result of oxidation reactions by enzymes. Strain MGS1 reduced the maximum weight by 4.64 ± 0.5% and produced maximum laccase (2.19 ± 0.15 U/mL) and lipase enzyme (1.35 ± 0.05 U/mL). Field emission scanning electron microscopy (FESEM) showed visual images of bacterial colonization, and surface erosion (cracks/holes) on the LDPE surface. The production of enzymes reduced the hydrophobicity of the LDPE as evidenced by the biofilm formation, addition of new functional groups, surface erosion, and weight loss. The study is significant in addressing the biodegradation of plastic waste in Malaysia by exploring the mangrove microbiome.

Improved biodegradability of low-density polyethylene using plasma pretreatment and plastic-degrading bacteria

Polyethylene is widely used and is a major cause of serious environmental problems because it is non-biodegradable and difficult to recycle. To overcome these environmental problems, in this study, low-density polyethylene (LDPE) was treated with low-temperature plasma at atmospheric pressure, an eco-friendly technology. After inducing oxidation on the LDPE film by plasma treatment, a method for improving the biodegradation efficiency of LDPE-degrading bacteria was identified, and the underlying mechanism was investigated. Fourier-transform infrared and X-ray photoelectron spectroscopy analyses showed that the plasma treatment resulted in the formation of new peaks corresponding to the C–O and –CC– bonds and stronger –CO– bond groups than the –C–O– bond groups, showing that the oxidation of LDPE film was strong. Additionally, the –C–H– bond ratio on LDPE surfaces inoculated with Pseudomonas putida increased by 13–25.5% compared to that on untreated controls. Pseudomonas putida reduced the thermal stability by forming a biofilm on the oxidized LDPE film during the plasma treatment. The weight of untreated LDPE film was reduced by 50%, while that of treated LDPE film was reduced by 80%, confirming more efficient degradation. Thus, LDPE decomposition efficiency can be improved using a short plasma treatment to increase the adhesion and fixation of LDPE-degrading bacteria on the surface of oxidized LDPE films. Therefore, plasma pretreatment technology could be used to reduce plastic contamination in agricultural environments.

Biodegradation of low-density polyethylene microplastic by new halotolerant bacteria isolated from saline mud in Bledug Kuwu, Indonesia

Biodegradation of low-density polyethylene (LDPE) microplastics by newly halotolerant bacteria from saline mud in Bledug Kuwu, Indonesia was investigated. Of the eight bacteria, S. maltophilia BK1 and Enterococcus sp. BK3 showed a clear zone in agar containing LDPE and degraded 5 % and 6 % (w/w) of LDPE in artificial seawater after 90 d. During the biodegradation, the bacterial growth rate, biofilm formation, and hydrophobicity significantly increased after 40 d when the glucose concentration in the media was limited. Scanning electron microscopy (SEM) analysis displayed the destruction of the LDPE surface after treatment. Fourier transform infrared (FTIR) analysis showed the removal of the CC group at 861 cm−1, the addition of alkyl at 1019–1058 cm−1, and hydroxyl groups at 3000–3500 cm−1, indicating biodegradation. X-ray diffraction (XRD) analysis corroborated the degradation by decreasing the crystallinity index from 36 % (control) to 23 % (BK1) and 24 % (BK3), respectively.

Force-Based Characterization of the Wetting Properties of LDPE Surfaces Treated with CF4 and H2 Plasmas.

Low-density polyethylene (LDPE) films are widely used in packaging, insulation and many other commodity applications due to their excellent mechanical and chemical properties. However, the water-wetting and water-repellant properties of these films are insufficient for certain applications. In this study, bare LDPE and textured LDPE (T-LDPE) films were subjected to low-pressure plasmas, such as carbon tetrafluoride (CF4) and hydrogen (H2), to see the effect of plasma treatment on the wetting properties of LDPE films. In addition, the surface of the LDPE film was textured to improve the hydrophobicity through the lotus effect. The LDPE and T-LDPE films had contact angle (θ) values of 98.6° ± 0.6 and 143.6° ± 1.0, respectively. After CF4 plasma treatments, the θ values of the surfaces increased for both surfaces, albeit within the standard deviation for the T-LDPE film. On the other hand, the contact angle values after H2 plasma treatment decreased for both surfaces. The surface energy measurements supported the changes in the contact angle values: exposure to H2 plasma decreased the contact angle, while exposure to CF4 plasma increased the contact angle. Kinetic friction force measurements of water drops on LDPE and T-LDPE films showed a decrease in friction after the CF4 plasma treatment, consistent with the contact angle and surface energy measurements. Notably, the kinetic friction force measurements proved to be more sensitive compared to the contact angle measurements in differentiating the wetting properties of the T-LDPE versus 3× CF4-plasma-treated LDPE films. Based on Atomic Force Microscopy (AFM) images of the flat LDPE samples, the 3× CF4 plasma treatment did not significantly change the surface morphology or roughness. However, in the case of the T-LDPE samples, Scanning Electron Microscopy (SEM) images showed noticeable morphological changes, which were more significant at sharp edges of the surface structures.

Low-Density Polyethylene Degradation and Energy Yield Using Dielectric Barrier Discharge under Various Electrical Conditions

The increased use of plastics has seen the emergence of microplastics, which have become progressively more problematic. Although many degradation studies have been conducted to address the problem of microplastics, their impact has not been significant, and much time has been consumed. In this study, low-density polyethylene (LDPE) was degraded using a dielectric barrier discharge (DBD) plasma under various electrical conditions. The experimental results showed that after 120 min of treatment, the removal efficiency reached 5.44%, the carbonyl index (CI) was 1.7308, and the O/C ratio was 0.028. The degree of degradation shown in previous studies was achieved rapidly, and experimental results showed that the degree of LDPE degradation and energy yield was proportional to the voltage and frequency—more specifically, the degree of LDPE surface and internal degradation differed, which should be considered in terms of reducing the extent of mass loss. The results of this study should be helpful for future studies on microplastic degradation using DBD techniques.

Evaluation of Biodegradation Efficiency of Xylene Pretreated Polyethylene Wastes by Isolated Lysinibacillus fusiformis

The ability of the bacterial degradation of low-density polyethylene (LDPE) waste by Lysinibacillus fusiformis isolated from hydrocarbon-contaminated soil was investigated in the present study. The potential of the bacterial isolate to utilize LDPE waste bags of two different thicknesses in a month as a sole carbon source in mineral salt media was assessed. Further, the effect of pretreatment by xylene on the bacterial degradation of LDPE waste bags (0.5 percent w/v) in 30 days was investigated. The isolated Lysinibacillus fusiformis was able to degrade 9.51 percent of LDPE with 30 μm thickness but able to degrade only 1.45 percent of LDPE having 50 μm thickness. The bacterial biomass was 1.77 times higher on LDPE- 30 μm containing media in comparison to LDPE- 50 μm. The xylene pretreatment of LDPE wastes enhanced the biodegradation efficiency of isolated Lysinibacillus fusiformis to 12.09 and 1.97 percent respectively in 30 μm and 50 μm thick LDPE bags. The xylene pre-treatment improved the bacterial growth on media with LDPE of both thicknesses. The adherence of bacterium on the surface of LDPE was found more on 50 μm thick xylene treated LDPE compared to its untreated LDPE than 30 μm thick LDPE films. The xylene pre-treatment of polyethylene waste had an additive effect on the biodegradation of waste LDPE films with a significant effect on thickness.

Antibacterial Activity of Rose Bengal Entrapped in Organically Modified Silica Matrices.

Photosensitizers (PSs) are known as powerful antibacterial agents that are activated by direct exposure to visible light. PSs can be noncovalently entrapped into the silica gel network for their controlled release into a contaminated area. The immobilization of PS-containing gel matrices on a polymer support expands their possible applications, such as antibacterial surfaces and coatings, which can be used for the disinfection of liquids. In the current study, we report the use of Rose Bengal (RB) incorporated into organically modified silica matrices (RB@ORMOSIL matrices) by the sol-gel technique. The RB matrices exhibit high activity against Gram-positive and Gram-negative bacteria under illumination by white light. The amount and timing of solidifier addition to the matrix affected the interaction of the latter with the RB, which in turn could affect the antibacterial activity of RB. The most active specimen against both Gram-positive and Gram-negative bacterial cells was the RB6@ORMOSIL matrix immobilized on a linear low-density polyethylene surface, which was prepared by an easy, cost-effective, and simple thermal adhesion method. This specimen, RB6@OR@LLDPE, showed the low release of RB in an aqueous environment, and exhibited high long-term antibacterial activity in at least 14 rounds of recycled use against S. aureus and in 11 rounds against E. coli.

Efficacy of Cavern Isolates for Biodegradation of Synthetic Plastic

Abstract: Synthetic plastic waste management is a tenacious environmental concern at global level. Although all types of synthetic plastics are a nuisance to the environment, however, versatility and one time use has made polyethylene (PE) a foremost environmental issue. Current study has investigated cavern bacterial strains isolated from PE samples from San Giovanni cave, Sardinia, Italy for their efficacy to biodegrade low density polyethylene (LDPE) film. It was an initial effort to use cavern bacteria in plastic biodegradation studies. Chemical and physical changes in the composition of LDPE were studied by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) after incubation with the bacterial consortium for two months. Collected cavern PE plastic samples were also studied for biodegradation after incubation in nutrient broth for two months. FTIR revealed obvious signs of degradation with the appearance of two new peaks of functional groups, nitriles (C≡N) and amines (N-H) in LDPE film, which are intermediate metabolites of β-oxidation pathway. An increase in various existing peaks of several intermediate metabolites, including aldehydes, ketones, alcohols, and carboxylic acids, were also observed in experimental LDPE compared to control. Peaks of alkanes decreased significantly owing to cavern bacterial activity. SEM revealed biofilm formation on experimental LDPE surface with substantial mechanical damage. Similar signs of degradation were observed in the cavern PE samples. Four bacterial strains in the current consortium including Bacillus sonorensis, Bacillus subtilis, Aneurinibacillus spp., and Alcaligenes faecalis are first time reported to be linked with biodegradation of plastics. The cavern bacteria under study have the potential to biodegrade LDPE.

Microbial Consortiums of Putative Degraders of Low-Density Polyethylene-Associated Compounds in the Ocean.

ABSTRACTPolyethylene (PE) is one of the most abundant plastics in the ocean. The development of a biofilm on PE in the ocean has been reported, yet whether some of the biofilm-forming organisms can biodegrade this plastic in the environment remains unknown. Via metagenomics analysis, we taxonomically and functionally analyzed three biofilm communities using low-density polyethylene (LDPE) as their sole carbon source for 2 years. Several of the taxa that increased in relative abundance over time were closely related to known degraders of alkane and other hydrocarbons. Alkane degradation has been proposed to be involved in PE degradation, and most of the organisms increasing in relative abundance over time harbored genes encoding proteins essential in alkane degradation, such as the genes alkB and CYP153, encoding an alkane monooxygenase and a cytochrome P450 alkane hydroxylase, respectively. Weight loss of PE sheets when incubated with these communities and chemical and electron microscopic analyses provided evidence for alteration of the PE surface over time. Taken together, these results provide evidence for the utilization of LDPE-associated compounds by the prokaryotic communities. This report identifies a group of genes potentially involved in the degradation of the LDPE polymeric structure and/or associated plastic additives in the ocean and describes a phylogenetically diverse community of plastic biofilm-dwelling microbes with the potential for utilizing LDPE-associated compounds as carbon and energy source.IMPORTANCE Low-density polyethylene (LDPE) is one of the most used plastics worldwide, and a large portion of it ends up in the ocean. Very little is known about its fate in the ocean and whether it can be biodegraded by microorganisms. By combining 2-year incubations with metagenomics, respiration measurements, and LDPE surface analysis, we identified bacteria and associated genes and metabolic pathways potentially involved in LDPE biodegradation. After 2 years of incubation, two of the microbial communities exhibited very similar taxonomic compositions mediating changes to the LDPE pieces they were incubated with. We provide evidence that there are plastic-biofilm dwelling bacteria in the ocean that might have the potential to degrade LDPE-associated compounds and that alkane degradation pathways might be involved.

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.

Aging Process and DOC Analysis of Four Different Types of Plastic Particles in Freshwater Systems

Although the pollution of freshwater systems by microplastics and the resulting ecological effects have attracted widespread attention from scholars at home and abroad, the fragmentation of different types of microplastics in the natural environment has not yet received enough attention. To analyze the fragmentation processes and products of different types of microplastics, a 40 d natural light fragmentation experiment was carried out using four microplastics commonly found in water:polystyrene (PS), low-density polyethylene (LDPE), polypropylene (PP), and polyhydroxybutyrate (PHB). The pH, ORP, EC, and DO of the four types of plastic-aging liquids changed significantly during the aging process. During the weathering process, cracks and pores formed on the surface of LDPE and were later identified through scanning electron microscopy. Fourier transform infrared spectrometry indicated that the carbonyl index of LDPE increased the most in the experiment (an increase of 31.48%), suggesting that PP experienced significant aging. Dissolved organic carbon (DOC), a product of microplastics fragmentation, increased as weathering time progressed, and the concentration of DOC increased significantly after weathering for about 40 d. Compared with the baseline value, the concentration of DOC from PHB, PP, and LDPE in the leaching solution increased significantly, by 61.29%, 69.49%, and 89.15%, respectively. These results suggest that evident aging of microplastics in natural aquatic environments releases significant amounts of dissolved organic matter, and the ecological effects of this should be the subject of future research.

Analysis and microbial degradation of Low-Density Polyethylene (LDPE) in Winogradsky column

Plastic pollution is threatening the world and the life in it. Cost-effective and eco-friendly treatment is the need of the hour. Treating plastics using chemical methods adds up chemicals into the environment with toxic byproducts. The physical method, a slow and expensive process, is not the better alternative. The process should rely on the environmental sources producing eco-friendly byproducts. The byproducts such as biofuel could be utilized for a sustainable environment, but the conversion of plastics into biofuel is expensive. Hence, biodegradation is the better, sustainable, and cost-effective process for plastic/any other pollutant removal. The study focuses on the construction of Winogradsky column using dumpsite soil. The column amended with Low-Density Polyethylene (LDPE) serves as a carbon source for native microbes. The utilization of microbes in every niche for the degradation enhances the degradation of LDPE. The Otteri soil resulted in 35.4 ± 0.3%, while Kodungaiyur and agriculture soil show 29.7 ± 0.6% and 19.8 ± 0.8%. The AFM analysis shows the disruption of smooth LDPE surface by forming ridges and grooves, which further confirms the occurrence of degradation. The FTIR analysis shows the incorporation of OH, CO, and other CO–O–CO in the CH backbone of LDPE. The oxidation of LDPE will aid in cleavage and result in the process of weathering. The tensile strength decreased after LDPE treatment (23.88 MPa - control, 22.50 MPa – Kodungaiyur, and 14.92 MPa – Otteri). Thus, utilizing the native microbes present in every niche enhances the degradation of pollutants.

Insight into the effect of He atmospheric pressure plasma jets on low-density polyethylene surfaces by fixed-point treatment

In order to further investigate the modification effect of atmospheric pressure plasma jets (APPJ) on the surface of low-density polyethylene (LDPE) film and related mechanisms, a series of experiments and simulations were carried out in this paper. A laminar helium flow with a flow rate of 6.0 standard liters per minute was used as a working gas and a homogeneous glow-like He APPJ was generated by an AC voltage with a peak-to-peak voltage of 10.1 kV and a frequency of 20 kHz. After 15 min He APPJ treatment at a fixed point on the film, the surface properties at different radial positions from this point were analyzed. This study was performed using water contact angle (WCA) measurement, x-ray photoelectron spectroscopy and atomic force microscopy. The results of WCA and surface free energy (SFE) indicate that the modification effect range is larger than APPJ’s spread range on the surface. Along the radial direction, the surface properties did not change monotonously but had extreme points: the change of the surface morphology was first etching and then deposition; APPJ incorporated oxygen containing functional groups including C–O, C=O/O–C–O and O–C=O into the LDPE surface, and their distributions on the surface were different. To explore what caused the difference, quantum chemical simulation analysis by ORCA software was used to explain the relationship between the change of surface energy and oxygen-containing functional groups. The simulation showed that C–O has more influence on the SFE of the LDPE surface.

Efficacy of saturated steam against Listeria innocua biofilm on common food-contact surfaces

Listeria monocytogenes forms biofilms on food-contact surfaces providing this pathogen with the potential to serve as a constant cross-contamination source. The objective of this study is to examine the efficacy of steam treatment against the biofilm of L. innocua, a well-known L. monocytogenes surrogate, on common food-contact surfaces using a pilot-scale steam treatment blancher. Saturated steam at 100 °C was effective in inactivating L. innocua in biofilms on all tested food-contact surfaces with a 6-sec steam treatment attaining a 2.4–3.1 log10 CFU/coupon (1.5 cm × 1.5 cm) reduction depending on the type of surface. However, the effectiveness of steam decreased dramatically during prolonged steam treatment with tailing effects more pronounced on rubber, low-density polyethylene (LDPE), polyvinyl chloride (PVC), followed by polyester (polyethylene terephthalate, PET), and then stainless steel (SS). A 30–180 s steam exposure at 100 °C caused a 4.0–6.4 log10 CFU/coupon reduction of L. innocua biofilm on SS, and 3.0–4.8, 2.8–4.2, 2.7–4.5 and 2.6–3.3 log10 reductions on PET, LDPE, PVC, and rubber surfaces, respectively. Organic soil from 1:10 diluted apple juice did not compromise the bactericidal effects of steam against L. innocua biofilm on all tested surfaces. Repeated steam exposure did not impact hydrophobicity and roughness parameters of SS, PET, and rubber coupons, but decreased hydrophobicity of PVC and LDPE, increased the Rz value of PVC, and decreased Rp and Rz values for LDPE surface. Data suggested that a short time steam exposure alone or in combination with other interventions likely provides effective mitigation treatments to control Listeria biofilm on SS, PET, and rubber surfaces.

Marine bacterial biodegradation of low-density polyethylene (LDPE) plastic.

Polyethylene has considered as non-degradable for decades, and their degradation through marine bacteria has rarely studied. However, LDPE found a significant source of pollution in the marine environment. In the present study, four bacterial strains capable of biodegradation of LDPE were isolated from the marine environment. These bacterial isolates H-237, H-255, H-256 and H-265 were revealed close similarity with Cobetia sp., Halomonas sp., Exigobacterium sp. and Alcanivorax sp., respectively based on 16S rRNA gene sequencing method. These bacterial isolates were individually incubated for 90days supplied with LDPE films as a carbon source using the Bushnell-Haas medium. During the biodegradation assay, bacterial isolates were formed the viable biofilm on the LDPE surface, which decreased the thermal stability of the films. At the end of the incubation study, a maximum weight loss of 1.72% of LDPE film was observed by the bacterial isolate H-255. The bacterial attachment on the film changed the physical structure (surface erosion, roughness and degradation) which were confirmed by field emission scanning electron microscopy and atomic force microscopy. The changes in the chemical structure of the LDPE film were analyzed by Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR). This ATR-FTIR showed the shifting of peaks of C-H stretch and C=C bond stretching and the new peaks formation of C-O and -C=C- bonds in comparison to control LDPE film. Further, biodegradation of LDPE film was alsoconfirmed by remineralization of carbon and enzymatic activities. This study revealed that the active biodegradation of LDPE film by marine bacteria and these bacteria could reduce plastic pollution in the marine environment.

Plastic ingestion by the Wels catfish (Silurus glanis L.): detailed chemical analysis and degradation state evaluation.

Plastic ingestion by various organisms within different trophic levels, including humans, is becoming a serious problem worldwide. Plastic waste samples are often found concentrated in an organism's digestive tract and can be degraded and further translocate to the surrounding tissue or circulatory systems and accumulate in food chains. In the present work, we report a detailed chemical analysis and degradation state evaluation of a relatively large piece of plastic waste found in the gastrointestinal tract of a Wels catfish (Silurus glanis L.) caught in the Bodrog River (Danube River basin), eastern Slovakia. Chemical analysis by surface-sensitive X-ray photoelectron spectroscopy (XPS) was performed to identify the surface composition of the digested plastic piece. Micro-Fourier transform infrared (μFTIR) spectroscopy showed that the plastic waste was oxidized low-density polyethylene (LDPE), with some nylon fibers adhered on the surface. Glyceraldehyde adhered onto LDPE was also detected, which might come from the carbohydrate metabolism of that fish. A morphology study by digital optical microscopy indicated solid inorganic particles attached to the surface of LDPE. A degradation study by differential scanning calorimetry (DSC) showed considerable oxidation of LDPE, leading to fragmentation and disintegration of the plastic waste material.

Biofilm development of Bacillus siamensis ATKU1 on pristine short chain low-density polyethylene: A case study on microbe-microplastics interaction

A low-density polyethylene (LDPE) degrading bacterial strain (ATKU1) was isolated (99.86% similar with Bacillus siamensis KCTC 13613T) from a plastic dumping site to study interactions between microplastics (< 5 mm) and microorganisms. The strain was found (by scanning electron microscopy) to form biofilm on the microplastic surface after its interaction with LDPE (avg. Mw~4,000 Da and avg. Mn~1,700 Da) as a sole carbon source. Atomic force microscopy (AFM) showed the biofilm’s 3-D developmental patterns and significantly increased Young’s modulus of the LDPE surface after microbial treatment. Most of the viable bacteria attached to biofilms rather than media, which suggested their ability to utilize LDPE. Absorption bands of carbonyl, alkenyl, acyl, ester, primary-secondary alcohol, alkene groups and nitric oxides were found on the treated LDPE particles using Fourier-transform infrared spectroscopy. Fourier transform-ion cyclotron resonance mass spectrometry of the media indicated compositional shifts of the compounds after treatment (i.e., increase in the degree of unsaturation and increment in oxygen-to-carbon ratio) and presence of unsaturated hydrocarbons, polyketides, terpenoids, aliphatic/peptides, dicarboxylic acids, lipid-like compounds were hinted. The plastic degrading abilities of Bacillus siamensis ATKU1 suggest its probable application for large scale plastic bioremediation facility.

Combined Effect of Naturally-Derived Biofilm Inhibitors and Differentiated HL-60 Cells in the Prevention of Staphylococcus aureus Biofilm Formation.

Nosocomial diseases represent a huge health and economic burden. A significant portion is associated with the use of medical devices, with 80% of these infections being caused by a bacterial biofilm. The insertion of a foreign material usually elicits inflammation, which can result in hampered antimicrobial capacity of the host immunity due to the effort of immune cells being directed to degrade the material. The ineffective clearance by immune cells is a perfect opportunity for bacteria to attach and form a biofilm. In this study, we analyzed the antibiofilm capacity of three naturally derived biofilm inhibitors when combined with immune cells in order to assess their applicability in implantable titanium devices and low-density polyethylene (LDPE) endotracheal tubes. To this end, we used a system based on the coculture of HL-60 cells differentiated into polymorphonuclear leukocytes (PMNs) and Staphylococcus aureus (laboratory and clinical strains) on titanium, as well as LDPE surfaces. Out of the three inhibitors, the one coded DHA1 showed the highest potential to be incorporated into implantable devices, as it displayed a combined activity with the immune cells, preventing bacterial attachment on the titanium and LDPE. The other two inhibitors seemed to also be good candidates for incorporation into LDPE endotracheal tubes.

Influence of Structure of Chemically Grafted onto Polyethylene Surface Two-Component Titanium-Phosphoroxide Nanostructures on the Properties of Composite Material

Nanostructures with different mutual arrangement of phosphorus and titanium oxide groups were synthesized on the surface of low-density polyethylene (LDPE) films using the molecular layering technology by treatment in a different predetermined sequence with TiCl4, POCl3 and H2O vapors. Based on the data of atomic force microscopy, differential thermal analysis, as well as the assessment of the energy characteristics of the surface by the value of the contact angle, it is shown that the sequence of formation of elemental oxide structures has a significant effect both on the chemical composition of surface nanostructures and on the surface morphology and thermal oxidation resistance of polyethylene. Depending on the sequence of introduction of additives, their concentration and ratio in grafted nanostructures change, surface energy increases by 30–50%, and the amounts of polar and dispersion components in its composition largely depend on the moisture content of the environment. It has been found that chemical modification with elemental oxide groups results in a smoothing of the matrix surface, and local destruction of the polymer is observed during the synthesis of two-component nanostructures. The presence of modifiers leads to an increase in the thermal-oxidative resistance of the composition by 50–110°, depending on its structure and composition, in comparison with the original LDPE. Therewith titanium is the most active inhibitor of polymer oxidation.