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  • Open access
  • 205 Reads
Co-Production of Polyhydroxyalkanoates and Carotenoids by Haloferax mediterranei DSM 1411

Polyhydroxyalkanoates (PHA) are naturally occurring biopolymers that possess high performance material properties such as biodegradability and biocompatibility. PHA can be produced from renewable carbon sources. However, the industrial production of PHA is still hindered by the costly feed materials. Co-production of other high-value products in addition to PHA can be helpful in alleviating overall production of PHA. In this work, the effect of temperature on PHA and carotenoids co-production by Haloferax mediterranei DSM 1411 was investigated using 1% glucose as carbon source. Under batch fermentation at 37°C, Haloferax mediterranei synthesized 3.37 g L-1 PHA with concomitant production of 0.76 mg L-1 of carotenoids at 144 h. The maximum dry cell weight (DCW) was 6.54 g L-1 and PHA content was 51.6%, with 3-hydroxyvalerate (3HV) fraction of 8.01 mol%. By increasing temperature to 42°C, an increase in PHA and carotenoids production was noticed reaching a maximum of 3.99 g L-1 and 0.92 mg L-1, respectively, at 120 h. Likewise, DCW was increased to 7.06 g L-1 and PHA content was 56.5%, with 3HV fraction of 8.42 mol%.

  • Open access
  • 159 Reads
Bio-Polymers in the World of Plasma: Effects of Cold Plasma on Seed Surface

Seeds can be considered as natural biopolymers. They are an essential source of nutrients for agriculture and food production. However, to gain optimal yield of important crops, many use pesticides and agrochemicals before, during, or/and after harvesting of crops. This represents a global threat to the environment, as its wide and common use can cause the resistance of pests to these chemicals and harmful effects on soil and the surrounding environment.

The non-thermal or “cold” plasma has been successfully used for treatment of various types of polymers and has recently shown great potential also in the field of agriculture. Many researchers have reported changes in hydrophilic properties of seed surface, increased water uptake and altered surface morphology, which was correlated with a selective etching of biopolymer matrix. Moreover, plasma treated seeds were showed improved growth and possible resistance to abiotic stress such as drought and salinity.

The objective of our experiment is to identify surface changes after cold plasma treatment, and the influence of changed seed morphology and chemistry. Different plasma treatments were applied on seeds of two winter wheat varieties. We examined and detected changes in the chemical composition of seed coat with X-ray photoelectron spectroscopy (XPS) and changes in hydrophilic properties of seed surface. Plasma treatment also affected the dynamics of water uptake of seeds. The XPS analysis detected the chemical changes on seed surface, depending on the mode of plasma exposure: either direct (glow) or indirect (afterglow) and time-dependent plasma exposure.

  • Open access
  • 141 Reads
Fully Bio-Based Polymers Derived from Acrylated Epoxidized Soybean Oil by Thiol-ene Reaction

Researchers estimate that more than 8.3 billion tonnes of plastic has been produced over the past decades and about 60 % of plastic has ended up in either a landfill or the natural environment. With the rapid growth of consumerism, research on innovative starting materials for preparation of polymers may help to reduce the negative impact of petroleum-based plastic materials on the global ecosystem and on animal and human health. Therefore, photochemical thiol-ene coupling reaction of squalene was performed to obtain thiol functional groups. Then, hexathiolated squalene was used as cross-linker in UV curing reactions with acrylated epoxidized soybean oil. Two photoinitiators (2-hydroxy-2-methylpropiophenone and ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate) in different quantities were tested. Rheological properties of compositions were monitored by real time photorheometry. The obtained polymers were characterized by differential scanning calorimetry and thermogravimetry. Polymers had higher rheological and thermal properties due to highest cross-linking density when ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate was used in the compositions.

Acknowledgements. This research was funded by the Research Council of Lithuania (project No. S-MIP-20-17).

  • Open access
  • 107 Reads
Biodegradable Coating on Packaging Paper Made from Fibres of Invasive Plant Spieces Fallopia japonica

Fallopia japonica is a plant, native to East Asia, Japan, China and Korea, but in North America and Europe it is classified as invasive species. The root system and strong growth of these plants can damage buildings, streets, paving, retaining walls etc. It forms thick colonies, which crowd out other herbaceous species. In our project it was found out that the stem biomass of Fallopia japonica contains 40 percent of cellulose, which is comparable to the raw materials from which paper fibers are typically produced. With chemical and mechanical procedures and treatments, the fibers from Fallopia japonica were prepared and successfully the packaging paper has been produced.

Generally, paper is widely used in packaging applications and it is considered as environmentally friendly substrate. It consists of a porous cellulose structure, composed of long-chain molecules in a crystalline state with amorphous regions in-between. Due to hydrophilic nature of cellulose and fiber network porosity, water barrier properties are limited. Conventional coatings that are used to improve water resistance, involve synthetic polymers such as polyethylene, rubber latex, polyvinyl alcohol etc. Natural renewable polymers have been the focus of many researches in recent years. Paper coatings are also commonly used with wax, but the recyclability of laminated and waxed papers is limited due to the separation from the paper, which is connected to the environmental issues.

In this study biodegradable coating such as polysaccharide chitosan, was applied to paper made from Fallopia japonica. Namely, non coated paper from Fallopia japonica has high hydrophilic character and therefore it is not suitable for all packaging products. The aim of the research was to investigate the influence of different concentrations of chitosan in coating solution (5 and 10% w/w) on the physical and mechanical properties of the mentioned paper substrate. The water and moisture resistance of the coated paper substrates were determined via Cobb60 value tests, water vapor permeability and moisture. Scanning electron microscopy (SEM) was used to evaluate the effect of coating on the microstructures and the porosity of the paper. The results showed the compatibility of chitosan and paper substrate. Tensile properties of the coated paper has given promising results already at lower concentration (5%) of chitosan. Tensile strength and elongation at break increased, mainly by connectedness of chitosan matrix and polymer chain interactions. With thermogravimetric analysis (TGA) thermal stability and weight changes were detected at coated paper. A high weight loss of 20%, between 300°C and 400°C was detected at 5% and 10% chitosan coated paper, due to the degradation of chitosan main chains. The coated papers possessed better thermal, mechanical and water resistant properties. Considering the biobased nature of the coating and used paper substrate, the procedure can offer environmentally friendly and sustainable solution toward new packaging material. Using a Fallopia japonica as a source for the paper fibers, the need for the wood fibers could decrease and at the same time, the negative impact on the environment could reduce.

  • Open access
  • 114 Reads
Amphiphilic Poly(ε-caprolactone) Copolyesters of Different Architectures for Drug Delivery Applications: Synthesis, Characterization and Molecular Dynamics

Bio-based and biodegradable aliphatic polyesters, such as poly(L-lactide), poly(ε-caprolactone), poly(alkylene succinate)s, polyglycerol hyperbranched polyesters etc. serve as excellent “green” candidates for a broad range of applications (biomedical, pharmaceutical, agricultural and industrial), combining biocompatibility, renewability and generally good performance. Further improvement of their properties (mechanical performance, biodegradation rate) can be achieved by copolymerization with a variety of bio-based monomers or by the introduction of reinforcing materials. Especially when it comes to drug delivery applications, where the release rate is severely affected by several parameters, including the glass transition, melting point and crystallinity of the employed polyesters, it is crucial to study and potentially tune all these properties.

Poly(ε-caprolactone), PCL, the polymer of interest here, is a hydrophobic, non-toxic, biodegradable and biocompatible aliphatic polyester displaying slow in vivo hydrolysis in addition to quite high crystalline fractions. It also exhibits a unique compatibilizing ability with various polymers of different types, which most often results in new, modified and enhanced material properties.

In the present work, we initially synthesized and for the first time comparatively studied the properties of three amphiphilic copolymers based on PCL, differing in architecture, namely, two star-like copolyesters with 3 and 4 PCL arms based on glycerol and pentaerythritol as multifunctional cores/initiators, respectively, as well as a linear block copolymer based on PCL and methoxy-poly(ethylene glycol) (mPEG). Neat PCL and all copolymers were prepared in situ via the ROP of ε-CL and characterized by a combination of techniques (1HNMR/ FT-IR spectroscopy, X-ray diffraction, calorimetry, polarized optical microscopy and broadband dielectric spectroscopy). Focus has been given to the impact of copolymer structure on the crystallization, melting and glass transition and hydration of PCL.

  • Open access
  • 68 Reads
Modification of Ca2+-crosslinked Sodium Alginate/Gelatin Films with Propolis for an Improved Antimicrobial Action

Problems associated with microbial resistance to antibiotics are growing due to their overuse. In this scenario, plant extracts have been considered as potential alternatives to antibiotics, since they can inhibit the action of the most common bacteria found colonizing infected wounds. The propolis extract (PE) has been used for centuries in folk medicine due to its antimicrobial, antioxidant, and anti-inflammatory properties as well as to its ability to induce tissue regeneration. Also known as “bee glue”, propolis is a complex mixture of chemical constituents (such as resin, waxes, pollen, essential oil and organic compounds) with a high polyphenol content. To improve the stability and long-term effectiveness of PE in wound healing, polymeric films composed of biodegradable and biocompatible polymers are being engineered as delivery vehicles. Here, sodium alginate/gelatin (SA/GN) films (2 wt% SA concentration, polymer ratio 70/30 v/v), containing PE, were prepared via a simple, green process of solvent casting/phase inversion technique, followed by crosslinking with calcium chloride (2 wt%) solutions. The minimum inhibitory concentration (MIC) of PE was established as 0.338 mg/mL for Staphylococcus aureus and 1.353 mg/mL for Pseudomonas aeruginosa, the most prevalent bacteria in infected wounds. The extract was incorporated at P. aeruginosa MIC (a value effective against both bacteria) within the polymeric films before (blended with the polymeric solution) and after (immobilization via physisorption) film production. Flexible, highly hydrated films were obtained. Successful incorporation of PE was confirmed via Fourier-transformed infrared spectroscopy (FTIR). The antibacterial activity of the films was assessed via agar diffusion (qualitative) and killing time kinetics (quantitative) examinations. Data confirmed the modified films effectiveness to fight bacteria infections caused by S. aureus and P. aeruginosa and their ability to be applied in the treatment of infected wounds.

  • Open access
  • 102 Reads
Controlled Release of Cinnamon Leaf Oil from Chitosan Microcapsules Embedded within a Sodium Alginate/Gelatin Hydrogel-Like Film for Pseudomonas aeruginosa Elimination

The multidrug-resistant Pseudomonas aeruginosa is considered a public threat. With antibiotics increasing bacteria resistance, alternative natural origin biomolecules are being examined for their potential against this bacterium. Essential oils (EOs) have demonstrated significant effects against several microorganisms, revealing as well strong anti-inflammatory, antiseptic, analgesic and antioxidative properties. However, due to their volatile nature they cannot be delivered to the infected site in their free-state. As such, biodegradable polymeric delivery platforms are being engineered. Chitosan has been commonly used as a protective barrier for many biomolecules, preserving their activity until reaching their destination. It is also highly effective against Gram-negative bacteria. Here, hydrogel-like films were produced from an optimized combination of sodium alginate (SA) and gelatin (GN) to serve as delivery platforms for the controlled release of cinnamon leaf oil (CLO) entrapped within chitosan microcapsules. The minimum inhibitory concentration (MIC) of CLO was established at 39.3 mg/mL against P. aeruginosa. Chitosan microcapsules were prepared via ionotropic gelation with tripolyphosphate, containing at the core the CLO at MIC. Successful production was confirmed by fluorescent microscopy using Nile red as detection agent. The encapsulation efficiency and controlled release of the oil were monitored in basic (infected wounds) and physiological pH for a period of 24 h. Microcapsules were then embedded within a biodegradable SA/GN polymeric matrix processed via a solvent casting/phase inversion methodology with SA/GN at 70/30 polymer ratio and 2 wt% SA concentration in distilled water. The coagulation bath was composed of a 2 wt% CaCl2 aqueous solution. The CLO-containing chitosan microcapsules homogeneous distribution was guaranteed by successive vortex and blending processes applied prior to casting. Flexible, highly hydrated films were obtained, with the presence of loaded chitosan capsules being confirmed by FTIR. Qualitative and quantitative antimicrobial examinations validated the modified film potential to fight infections caused by P. aeruginosa bacteria.

  • Open access
  • 76 Reads
Optical Properties of Vanadium Oxide/Cellulose Triacetate Photochromic Films

Cellulose acetate is one of the most versatile polymers due to its non-toxic nature and low price. Its blend with inorganic nanoparticles enables the design of new multifunctional materials, in which a good dispersion of the nanoparticles is essential to improve the properties of the matrix. In this work, micrometric films of cellulose triacetate based nanocomposites modified with both sol-gel synthesised V2O5 nanoparticles and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) triblock copolymer (PEO-b-PPO-b-PEO or EPE) were prepared and characterised by colour measurements, UV-vis spectroscopy, tensile tests, atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR).

In some cases, the use of different preparation methods involves the modification of the final properties of the nanocomposites. Thus, nanocomposites were prepared by solvent casting (SC) and solvent vapour annealing (SVA) methods. In the case of SC, nanocomposites were dried at ambient conditions, whereas SVA nanocomposites were dried in an oven at constant temperature. The use of different preparation methods affected the final macroscale properties of the nanocomposites, including the surface finish.

The obtained nanocomposites displayed green colour due to V2O5 nanoparticles, presenting the serie with EPE a darker hue. Using the SVA method, nanocomposites with smoother surfaces and without any visual defects were obtained due to a controlled slow solvent evaporation in an acetone vapour atmosphere. In both preparation methods, nanocomposites presented high flexibility as long as high transparency. Furthermore, nanocomposites displayed photochromic properties when exposed them to UV radiation, changing their colour from green to pale blue. The speed to change the colour and recover the initial state depend on the preparation method, V2O5 nanoparticles content and the presence of EPE triblock copolymer. In conclusion, the developed nanocomposites presented interesting properties and good surface finish to be employed in different applications fields.

  • Open access
  • 219 Reads
A Characterization Study of Morphology and Properties of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) / Aloe Vera Fibers Biocomposites: Effect of Fiber Surface Treatments

The depletion of petroleum resources and the environmental concerns during the last decade, led both academia and industry to look for a new class of ecofriendly materials with improved functional properties. In this regard, the biodegradable composites, also called "green composites" have been paid increasing attention by researchers worldwide. Among all the biodegradable polymers, polyhydroxyalcanoates (PHA) are considered as the potential candidates to replace the petroleum-based polymers. On the other hand, cellulose-based fibers which have many advantages including low cost, good biodegradability and thermal insulation can be used as reinforcement in polymer composites. However, to ensure good adhesion between lignocellulosic fibers and the matrix, the fibersurface is modified using chemical (alkaline, silane, acetylation, benzoylation, acrylation, permanganate, peroxide or isocyanate treatment) or physical treatments (corona or plasma treatment) prior to processing. Therefore, the objective of the paper was to investigate the effect of various surface treatments of Aloe Vera fibers (AVF) used as reinforcement in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) biocomposites. Indeed, various fiber treatments were carried out involving alkaline, organosilanes and combined alkaline/organosilanes. PHBHHx/AVF biocomposites samples were prepared by melt compounding at loading ratio of 20 wt% selected as an optimal composition. The results showed that the biocomposite PHBHHx/ combined alkaline/organosilanes treated AVF exhibits a finer and homogeneous surface morphology indicating a good fiber/matrix interfacial adhesion. Accordingly, the rheological properties (complex viscosity and storage modulus) were increased and the water uptake was reduced. This study highlights the effectiveness of combined alkaline/organo-silanes treatment of AVF over alkaline and organo-silanes and their applications in PHBHHx biocomposites as an interesting source of cellulosic reinforcing materials.

  • Open access
  • 83 Reads
Morphological and Properties Characterization of Melt-Spun Poly(Lactic Acid)/Cellulose Nanowhiskers Fibers: Effect of Filler Content

In recent years, much attention has been paid to biopolymers as an answer to the environmental issues and to the depletion of fossil resources. However, the application of biopolymers is often limited by their poorly mechanical and thermal properties. In order to be competitive to petroleum based polymers, they need to be modified. The attraction for cellulose nanowhiskers (CNW) as fillers in polymer matrices has largely increased due to the unique combination of their impressive mechanical properties with their high aspect ratio. Indeed, CNW offer many advantages such as high reactivity, renewability, biodegradability and natural abundance. Poly(lactic acid) (PLA) is one of the most representative bio-based and biodegradable polymers. However, some of its properties, like flexural properties and gas permeability are too low for widespread applications. The production of PLA/CNW bionanocomposites could be therefore, an efficient route to extend their utilization in many fields, with the possibility to adjust properties by filler content adjustment. In the field of textiles, the electrospinning process of various polymers filled with CNW is well documented including various polymeric matrices. Nevertheless, the need to develop new processing techniques, as an extension of conventional plastics industry, remains an important challenge. In this paper, melt spinning process was used to elaborate both neat PLA and PLA/CNW bionanocomposite fibers filled at 1 and 3 wt% in the presence of PLA-grafted-Maleic anhydride (PLA-g-MA) used as the compatibilizer at 7 wt%. The morphology and thermo-mechanical properties of the samples were investigated with respect to filler content ratio. PLA/CNW1 bionanocomposite fibers led to the best results compared to those filled at 3 wt%. Indeed at 1 wt%, SEM showed that CNW were homogeneously dispersed in the PLA matrix compared to 3 wt% loading and almost 18% increase in elongation at maximum force were obtained compared to neat PLA. In addition, a better thermal stability to PLA was observed.