Strategies for Improving the Bacterial Biodegradation of PET

Plastic waste and its persistent presence in the environment pose significant global challenges. Among various types of plastics, synthetic ones like polyethylene terephthalate (PET) are mostly used for packaging and has comprised a major part of plastic waste. PET is particularly resistant to degradation, mainly due to its high content of aromatic terephthalate units. While biodegradation is an environmentally friendly method for tackling this waste, it is proven to be somewhat inefficient. One contributing factor is that the temperature required for bacterial growth is significantly lower than the glass transition temperature of PET. To circumvent this limitation, various complementary techniques have been proposed in this project to enhance biodegradation of PET using Ideonella sakaiensis (I. sakaiensis) and Pseudomonas mendocina (P. mendocina). These methods encompass physical approaches (e.g., UV radiation), chemical treatments (e.g., alkaline treatment), biochemical strategies (utilizing surfactants like cationic surfactant dodecyl trimethylammonium bromide (DTAB) and non-ionic surfactant Dodecyl polyethylene oxide-23 ether (Brij-35)), as well as enzymatic treatment using Fusarium culmorum supernatant (FSC) which contains cutinase. Furthermore, the impact of the quorum sensing molecule (QSM) (specifically, 3-oxo-C12-HSL) on PET degradation was investigated in the context of DTAB-treated, FSC-treated, and DTAB-FSC-treated PET up to eight weeks in the presence of the mentioned bacteria with particular emphasis on I. sakaiensis for its better performance compared to P. mendocina under the chosen process conditions. A range of analytical techniques, including Fourier Transform Infra-Red spectroscopy (FTIR), biofilm assays, high-pressure liquid chromatography (HPLC), high-resolution microscopy, and scanning electron microscopy (SEM), were employed to evaluate the outcomes of these treatments on PET and its biodegradation potential. Notably, FSC treatment, in conjunction with the presence of the I. sakaiensis bacterial culture supplemented with QSM in Yeast Extract-Sodium Carbonate and Vitamins (YSV) medium, exhibited significant promise for enhancing PET degradation within one week. FTIR spectroscopic analyses were employed to probe structural alterations within the PET polymer. The FTIR findings demonstrated the substantial progress achieved, unveiling an impressive ~89.0% transmittance rate post FSC treatment of PET followed by one week of incubation using the I. sakaiensis culture supplemented by QSM. This enhanced transmittance reflects notable modification in PET molecular bonds, signifying successful polymer breakdown. Furthermore, assessments of microstructural transformations were carried out through high-resolution microscopy and Scanning Electron Microscopy (SEM). These observations concurred with the FTIR results, visually attesting to the efficacy of FSC treatment in the I. sakaiensis culture supplemented by QSM. The surfaces of FSC-treated PET exhibited notable roughness compared to untreated PET, coupled with an increased surface porosity. These structural modifications validate the findings derived from FTIR spectroscopy, fortifying the substantial strides made in PET biodegradation

An overview of the water remediation potential of nanomaterials and their ecotoxicological impacts

Nanomaterials, i.e., those materials which have at least one dimension in the 1-100 nm size range, have produced a new generation of technologies for water purification. This includes nanosized adsorbents, nanomembranes, photocatalysts, etc. On the other hand, their uncontrolled release can potentially endanger biota in various environmental domains such as soil and water systems. In this review, we point out the opportunities created by the use of nanomaterials for water remediation and also the adverse effects of such small potential pollutants on the environment. While there is still a large need to further identify the potential hazards of nanomaterials through extensive lab or even field studies, an overview on the current knowledge about the pros and cons of such systems should be helpful for their better implementation.Peer reviewe

Oberflächenmodifizierung von Synthetische Fasern für antibakterielle Anwendungen

Photo-chemical reactions and surface modifications of poly(ethylene terephthalate) 100% (PET) fabrics with active monomer dimethylaminopropyl methacrylamide (DMAPMA) and benzophenone (BP) as photo-initiator using a broad-band UV lamp source were investigated. The quaternization reactions were initially optimized for homo PDMAPMA, prior to reaction on the PET grafted PDMAPMA chains. The quaternization reaction of homo PDMAPMA was confirmed by one and two dimensional NMR spectroscopy (1D and 2D 1HNMR), and attenuated total reflection- Fourier transform infrared spectroscopy (ATR-FTIR) The molecular weights (Mn and Mw) and molecular weight distributions (Mw/Mn; poly dispersity index, PDI) of homo PDMAPMA and quaternized homo PDMAPMA with C8H17Br (C8) were analyzed by gel permeation chromatograph (GPC). The tertiary amino groups of the grafted polyDMAPMA chains on the surface of PET fabrics were subsequently quaternized with alkyl bromides of different chain lengths to establish antibacterial activity. The surface composition, structure and morphology of modified PET fabrics were characterized by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). To evaluate the amount of quaternary and tertiary ammonium groups on the modified surface, PET was dyed with an acid dye (Telon Red AFG) which binds to the ammonium groups. Therefore, the color depth is a direct indicator of the amount of ammonium groups. The amount of positive charges on the surface PET was measured by polyelectrolyte titration and the nitrogen content of the PET-g-PDMAPMA and quaternized PET-g-PDMAPMA was determined. The resulting antibacterial activity of the modified PET fabrics was tested with Escherichia coli. The results of all experiments show that a photochemical modification of PET is possible using DMAPMA, benzophenone and UV light. Also, the quaternization of tertiary amino groups as well as the increase of antibacterial activity of the modified PET by the established quaternary ammonium groups were successful. Silver nanoparticles (NPs) were prepared by a simple and inexpensive single step synthesis based on UV activation of mixture solution of silver nitrate and poly(methacrylic acid) which acts as stabilizer agent at pH 8. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to prove the occurrence of nanoparticles and the size distribution of the Ag nanoparticle was measured. The UV-VIS spectroscopy revealed the formation of silver NPs by exciting the typical surface plasmon absorption from the UV–Vis spectrum. The mechanism of formation of those silver nanoparticles was also discussed. The streaming potential versus pH curve was negative. Ag NPs colloid was stable at pH values more than 6 (sufficient negative charge is present). The isoelectric point has been observed at pH values of 3.5 - 4. Silver NPs colloid showed high antimicrobial and bactericidal activity against bacteria such as Micrococcus luteus (M. luteus) and Escherichia coli (E. coli). Deposition of silver NPs on the fabrics made from polyester 100% (PET) and polyamide-6 100% (PA) surface was studied by the exhaustion method using a dyeing machine at temperature 80°C. In order to enhance wettability, the fabrics were plasma pre-treated in air. Energy dispersive X-ray spectroscopy (EDX) confirmed presence of elemental silver on the surface of PET fibers, and silver NPs were well dispersed on the surface as indicated by SEM. The amount of silver particles loaded on the PET and PA 6 samples before and after laundering was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Additionally, the antibacterial activity of the modified fabrics was measured by quantitative and qualitative methods. After the deposition of silver nanoparticles, the fabrics showed high antimicrobial and bactericidal activity with regard to M. luteus and E. coli. The samples which had been pre-treated by plasma exhibited antibacterial efficacy of the impregnated fabrics with Ag NPs was maintained also after laundering. Moreover, antibacterial efficacy of the impregnated fabrics with Ag NPs was maintained also after many times laundering

Advances in Plasma Processes for Polymers

Polymerized nanoparticles and nanofibers can be prepared using various processes, such as chemical synthesis, the electrochemical method, electrospinning, ultrasonic irradiation, hard and soft templates, seeding polymerization, interfacial polymerization, and plasma polymerization. Among these processes, plasma polymerization and aerosol-through-plasma (A-T-P) processes have versatile advantages, especially due to them being “dry", for the deposition of plasma polymer films and carbon-based materials with functional properties suitable for a wide range of applications, such as electronic and optical devices, protective coatings, and biomedical materials. Furthermore, it is well known that plasma polymers are highly cross-linked, pinhole free, branched, insoluble, and adhere well to most substrates. In order to synthesize the polymer films using the plasma processes, therefore, it is very important to increase the density and electron temperature of plasma during plasma polymerization

Functional Coatings for Food Packaging Applications

The food packaging industry is experiencing one of the most relevant revolutions associated with the transition from fossil-based polymers to new materials of renewable origin. However, high production costs, low performance, and ethical issues still hinder the market penetration of bioplastics. Recently, coating technology was proposed as an additional strategy for achieving a more rational use of the materials used within the food packaging sector. According to the packaging optimization concept, the use of multifunctional thin layers would enable the replacement of multi-layer and heavy structures, thus reducing the upstream amount of packaging materials while maintaining (or even improving) the functional properties of the final package to pursue the goal of overall shelf life extension. Concurrently, the increasing requirements among consumers for convenience, smaller package sizes, and for minimally processed, fresh, and healthy foods have necessitated the design of highly sophisticated and engineered coatings. To this end, new chemical pathways, new raw materials (e.g., biopolymers), and non-conventional deposition technologies have been used. Nanotechnology, in particular, paved the way for the development of new architectures and never-before-seen patterns that eventually yielded nanostructured and nanocomposite coatings with outstanding performance. This book covers the most recent advances in the coating technology applied to the food packaging sector, with special emphasis on active coatings and barrier coatings intended for the shelf life extension of perishable foods

Untersuchung zum Fouling in der Ultrafiltration - Mechanismen und Kontrolle durch Oberflächenmodifizierung von Membranen

Two important issues in application of ultrafiltration (UF) membrane, i.e. study of fouling mechanism and synthesis of low fouling membrane have been performed. Study on fouling mechanism was done by investigation of membrane−solute interactions (static adsorption) and membrane−solute−solute interactions (UF) using dextran and myoglobin as the model for polysaccharide and protein, respectively. Low fouling UF membranes have been synthesized by photograft copolymerization of water soluble monomers, poly(ethylene glycol) methacrylate (PEGMA) and N,N-dimethyl-N-(2-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium betaine (SPE), onto polyethersulfone (PES) membrane with and without cross-linker monomer N,N’-methylene bisacrylamide (MBAA). Commercial polyethersulfone (PES) and cellulose−based UF membranes were used during fouling mechanism study whereas two commercial PES UF membranes with different nominal cut−off were used as the base membrane upon surface modification. In both studies, the membranes were characterized with respect to the membrane chemistry (by IR−ATR spectroscopy and elemental analysis), surface wettability (by contact angle), surface charge (by zeta potential) and pure water permeability, pore structure and surface morphology (by hydraulic permeability and rejection measurements, scanning electron microscopy, and atomic force microscopy). In addition, in the fouling mechanism study, quantification of solute attached on the membrane surface was performed by simultaneously diffusion adsorption measurements (SDAM). The results obtained from fouling mechanism study showed that significant changes in membrane characteristics and water permeability were observed for PES membranes after static adsorption using dextran. However, such changes were not observed for cellulose−based membrane. Good correlations were obtained between the water flux reduction (RFR) caused by dextran adsorption and the quantitative data for bound dextran on the PES membranes. Further, a pronounced effect of dextran size on adsorptive membrane fouling was identified. Contact angle and zeta potential measurements with non−porous films, where solute entrapment in pores can be ruled out, gave additional clear evidence for dextran binding on the PES surface. Complementary data for adsorption and fouling of PES membranes and non−porous films by the protein myoglobin indicate that the larger fouling tendency for protein than for dextran is due to a higher surface coverage of PES by the adsorbed biomacromolecule layer. Data for UF confirmed the conclusions from the static contact experiments because significant fouling was observed for PES membranes (more severe for myoglobin than for dextrans), while no fouling was observed for a cellulose−based UF membrane with the same nominal cut−off. Finally, two mechanisms for the attractive PES−dextran interaction − multiple hydrogen bonding involving the SO 2 groups of PES and “surface dehydration” of the relatively hydrophobic PES – are discussed. Study on the synthesis of low fouling UF membrane suggests that PEGMA/SPE−modified membranes showed much higher fouling resistance evaluated by using protein, sugarcane juice, dextran and humic acid solutions than unmodified membranes having similar and larger nominal cut−off. However, contribution of membrane pore structure on membrane−solute interactions was still clearly observed. In some cases, the presence of cross-linker could improve both flux permeate and rejection during ultrafiltration. Modified membranes prepared using “period 2” for the first batch and PEGMA−modified membrane (PES-g-PEGMA) and PEGMA−modified with low concentration of cross-linker (PES-g-PEGMA/MBAA) for the second batch showed the best performance during evaluation. Furthermore, modified membranes prepared with an “old generation” non fouling material, PEGMA, showed better performances than modified membrane prepared with a “new generation” non fouling material, zwitterionic SPE. The surface chemistry as well as surface wettability of modified membranes did not change after incubating in sodium hypochlorite solution for a period of 8 days. Finally, their combined high fouling resistance and high rejection supported by chemical stability by cleaning suggest that those modified membranes were very attractive as new generation of thin layer composite low fouling UF membranes

Biomimetic elastomeric poly(glycerol sebacate)-based scaffolds for adipose tissue engineering

In spite of recent progress in the field of adipose tissue engineering, the optimal adipose tissue scaffold still remains illusive and the tailoring of the structure and properties of tissue scaffolds according to adipose tissue were less explored or even neglected. Thus, synthetic poly(glycerol sebacate) (PGS)-based scaffolds and hydrogels which mimic the properties of adipose tissue were developed in this PhD project for potential application in adipose tissue engineering