Iza K Radecka - Academia.edu (original) (raw)

Papers by Iza K Radecka

RSC Advances, 2017

A convenient synthetic route of poly(3HB-co-3HH-co-SEB) terpolyesters has been reported. The deve... more A convenient synthetic route of poly(3HB-co-3HH-co-SEB) terpolyesters has been reported. The developed protocol consists of two steps; poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx) oligoesterdiols were synthesized via selective reduction of biopolyesters and then via their polycondensation with sebacoyl chloride the biodegradable terpolyesters, poly(3HB-co-3HH-co-SEB), were obtained. The structure of the obtained terpolyesters was established by NMR analysis supported by mass spectrometry. Modification of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by incorporating units derived from sebacic acid into its chains resulted in terpolyesters with better physico-chemical properties than the starting PHBHx biopolyester. These new polyester materials have greater thermal stability than the starting biopolyester. Furthermore, the introduction of sebacic acid units to a polyester chain leads to the reduction of the glass transition temperatures of the materials and reduces the required processing temperature. A preliminary study confirmed that poly(3HB-co-3HH-co-SEB) terpolyesters can be used to create scaffolds for cell cultures in the form of a three-dimensional spatial structure. Moreover, a toxicity test of the obtained terpolyester carried out on human cells demonstrated that the novel terpolyester is not toxic to human cells in vitro.

Waste Management, Jun 1, 2017

The public awareness of the quality of environment stimulates the endeavor to safe polymeric mate... more The public awareness of the quality of environment stimulates the endeavor to safe polymeric materials and their degradation products. The aim of the forensic engineering case study presented in this paper is to evaluate the aging process of commercial oxo-degradable polyethylene bag under real industrial composting conditions and in distilled water at 70 o C, for comparison. Partial degradation of the investigated material was monitored by changes in molecular weight, thermal properties and Keto Carbonyl Bond Index and Vinyl Bond Index, which were calculated from the FTIR spectra. The results indicate that such an oxo-degradable product offered in markets degrades slowly under industrial composting conditions. Even fragmentation is slow, and it is dubious that biological mineralization of this material would occur within a year under industrial composting conditions. The slow degradation and fragmentation is most likely due to partially crosslinking after long time of degradation, which results in the limitation of low molecular weight residues for assimilation. The work suggests that these materials should not be labeled as biodegradable, and should be further analyzed in order to avoid the spread of persistent artificial materials in nature. Polyethylene is generally considered as a non-biodegradable plastic widely used as a packaging material. For several decades producers of conventional polyethylene are searching for methods

Polymers, Aug 29, 2018

Excessive levels of plastic waste in our oceans and landfills indicate that there is an abundance... more Excessive levels of plastic waste in our oceans and landfills indicate that there is an abundance of potential carbon sources with huge economic value being neglected. These waste plastics, through biological fermentation, could offer alternatives to traditional petrol-based plastics. Polyhydroxyalkanoates (PHAs) are a group of plastics produced by some strains of bacteria that could be part of a new generation of polyester materials that are biodegradable, biocompatible, and, most importantly, non-toxic if discarded. This study introduces the use of prodegraded high impact and general polystyrene (PS0). Polystyrene is commonly used in disposable cutlery, CD cases, trays, and packaging. Despite these applications, some forms of polystyrene PS remain financially and environmentally expensive to send to landfills. The prodegraded PS0 waste plastics used were broken down at varied high temperatures while exposed to ozone. These variables produced PS flakes (PS1-3) and a powder (PS4) with individual acid numbers. Consequently, after fermentation, different PHAs and amounts of biomass were produced. The bacterial strain, Cupriavidus necator H16, was selected for this study due to its well-documented genetic profile, stability, robustness, and ability to produce PHAs at relatively low temperatures. The accumulation of PHAs varied from 39% for prodegraded PS0 in nitrogen rich media to 48% (w/w) of dry biomass with the treated PS. The polymers extracted from biomass were analyzed using nuclear magnetic resonance (NMR) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) to assess their molecular structure and properties. In conclusion, the PS0-3 specimens were shown to be the most promising carbon sources for PHA biosynthesis; with 3-hydroxybutyrate and up to 12 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units generated.

African Journal of Biotechnology, Mar 8, 2017

Bacterial cellulose (BC) is produced by bacteria such as Gluconacetobacter xylinus. It has unique... more Bacterial cellulose (BC) is produced by bacteria such as Gluconacetobacter xylinus. It has unique structural and mechanical properties and is highly pure as compared to plant cellulose. In this study, BC was produced in Hestrin-Schramm (HS) medium. G. xylinus produced an average dry yield of 1.4 ± 0.09 g/L BC after 9 days of fermentation period. Scanning Electron Microscopy (SEM) analysis confirmed BC to be highly structured while Fourier Transform infrared spectroscopy (FTIR) analysis indicated that the absorption peaks at 3000-3700, 2800-2970 and 1023-1024 cm-1 were derived from-OH bending,-CH stretching and C-C/C-OH/C-H ring vibrations. X-Ray Diffraction (XRD) revealed a high purity of BC indicating type I cellulose with high crystalline nature. The solid state 13 C Nuclear magnetic resonance (NMR) spectroscopy of the untreated BC sample also indicated high crystallinity while the cellulase treated BC sample was different, but dominated by a polysaccharide signal between 55 and 110 ppm. The results suggest the prospects of the production and recycling of biopolymers from bacterial sources.

Polymer Degradation and Stability, Jun 1, 2018

The use of biobased plastics is of great importance for many applications. Blending thermoplastic... more The use of biobased plastics is of great importance for many applications. Blending thermoplastic polylactide (PLA) with polyhydroxyalkanoate (PHA) enables the formulation of a more mechanically powerful material and this enables tailored biodegradation properties. In this study we demonstrate the 3D printing of a PLA/PHA blend as a potential candidate for biocompatible material applications. The filament for 3D printing consisted of PHA, which contains predominantly 3-hydroxybutyrate units and a small amount of 3hydroxyvalerate units, as revealed by multistage mass spectrometry (ESI-MS n). This research

Materials, Apr 25, 2016

The (trans)esterification reaction of bacterial biopolymers with a selected bioactive compound wi... more The (trans)esterification reaction of bacterial biopolymers with a selected bioactive compound with a hydroxyl group was applied as a convenient method for obtaining conjugates of such compound. Tyrosol, a naturally occurring phenolic compound, was selected as a model of a bioactive compound with a hydroxyl group. Selected biodegradable polyester and polyamide, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) and poly-γ-glutamic acid (γ-PGA), respectively, were used. The (trans)esterification reactions were carried out in melt mediated by 4-toluenesulfonic acid monohydrate. The structures of (trans)esterification products were established at the molecular level with the aid of ESI-MS 2 (electrospray ionization tandem mass spectrometry) and/or 1 H NMR (nuclear magnetic resonance) techniques. Performed analyses confirmed that the developed method leads to the formation of conjugates in which bioactive compounds are covalently bonded to biopolymer chains. The amount of covalently bonded bioactive compounds in the resulting conjugates depends on the type of biopolymers applied in synthesis.

International Journal of Molecular Sciences, Jul 19, 2016

Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. E... more Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. Extensive progress has been made in our understanding of PHAs' biosynthesis, and currently, it is possible to engineer bacterial strains to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are primarily derived from food-based carbon sources, raising concerns over the sustainability of their production in terms of their impact on food prices. This paper gives an overview of the current carbon sources used for PHA production and the methods used to transform these sources into fermentable forms. This allows us to identify the opportunities and restraints linked to future sustainable PHA production. Hemicellulose hydrolysates and crude glycerol are identified as two promising carbon sources for a sustainable production of PHAs. Hemicellulose hydrolysates and crude glycerol can be produced on a large scale during various second generation biofuels' production. An integration of PHA production within a modern biorefinery is therefore proposed to produce biofuels and bioplastics simultaneously. This will create the potential to offset the production cost of biofuels and reduce the overall production cost of PHAs.

The FASEB Journal, Apr 1, 2015

Bacterial cellulose (BC) is produced by bacteria has a unique structural and mechanical propertie... more Bacterial cellulose (BC) is produced by bacteria has a unique structural and mechanical properties and is highly pure as compared to plant cellulose. In this study, BC was produced using Hestrin-Schramm (HS) media. Two forms of cellulose were observed; a gel-like membrane and a leathery membrane. Fourier Transform infrared spectroscopy (FTIR) investigation revealed both forms to be cellulose and indicated the presence of CH2 and OH group at the absorption wavelength of 3300 cm-1, 1650 cm-1 and 1025 cm-1. Scanning Electron Microscopy (SEM) results showed fine morphology of the cellulose matrix and fibre; and XRD indicated the majority of the cellulose to be type-1 cellulose (crystalline in nature). Plasmid DNA sequence analysis revealed an open reading frame of 678 bp. The significance of this work is discussed.

Polyhydroxyalkanoates (PHAs) are biopolymers, which can replace petrochemical plastics in many ap... more Polyhydroxyalkanoates (PHAs) are biopolymers, which can replace petrochemical plastics in many applications. However, these bioplastics are currently far more expensive than petrochemical plastics. Many researchers are investigating the use of inexpensive substrates derived from waste streams. Waste frying oil is abundant and can be used in PHA production without filtration. Cupriavidus necator (formerly known as Ralstonia eutropha) is a versatile organism for the production of PHAs. Small-scale batch fermentation studies have been set up, using different concentrations of pure vegetable oil, heated vegetable oil and waste frying oil. These oils are all rapeseed oils. It has been shown that Cupriavidus necator produced the homopolymer polyhydroxybutyrate (PHB) from the rapeseed oils. The achieved PHB concentration from waste frying oil was 1.2 g/l, which is similar to a concentration that can be obtained from glucose. The PHB harvest from pure oil and heated oil was 0.62 g/l and 0.9...

Polymers, 2019

This study investigated the molecular structure of the polyhydroxyalkanoate (PHA) produced via a ... more This study investigated the molecular structure of the polyhydroxyalkanoate (PHA) produced via a microbiological shake flask experiment utilizing oxidized polypropylene (PP) waste as an additional carbon source. The bacterial strain Cupriavidus necator H16 was selected as it is non-pathogenic, genetically stable, robust, and one of the best known producers of PHA. Making use of PHA oligomers, formed by controlled moderate-temperature degradation induced by carboxylate moieties, by examination of both the parent and fragmentation ions, the ESI-MS/MS analysis revealed the 3-hydroxybutyrate and randomly distributed 3-hydroxyvalerate as well as 3-hydroxyhexanoate repeat units. Thus, the bioconversion of PP solid waste to a value-added product such as PHA tert-polymer was demonstrated.

Waste management (New York, N.Y.), 2018

Prediction studies of advanced (bio)degradable polymeric materials are crucial when their potenti... more Prediction studies of advanced (bio)degradable polymeric materials are crucial when their potential applications as compostable products with long shelf-life is considered for today's market. The aim of this study was to determine the effect of the polylactide (PLA) content in the blends of PLA and poly(butylene adipate-co-terephthalate) (PBAT); specifically how the material's thickness corresponded to changes that occurred in products during the degradation process. Additionally, the influence of talc on the degradation profile of all samples in all environments was investigated. It was found that, differences in the degradation rate of materials tested with a similar content of the PLA component could be caused by differences in their thickness, the presence of commercial additives used during processing or a combination of both. The obtained results indicated that the presence of talc may interfere with materials behavior towards water and consequently alter their degrada...

Biomacromolecules, Feb 9, 2018

The herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) conjugated with poly(3-hydroxybutyrate-c... more The herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) conjugated with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was prepared via a melt transesterification route. The resultant bioactive oligomer was then mixed with a blend of polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) with different loadings to manufacture films to be used as a bioactive, biodegradable mulch to deliver the herbicide to target broadleaf weed species. The biological targeting of the MCPA-PHBV conjugate in the mulch film was investigated under glasshouse conditions using faba bean (Vicia faba) as a selective (nontarget) model crop species having broadleaf morphology. The presence of the MCPA-PHBV conjugate in the biodegradable PBTA/PLA blend was shown to completely suppress the growth of broadleaf weed species while displaying only a mild effect on the growth of the model crop. The degradation of the mulch film under glasshouse conditions was quite slow. The release of the MCPA-P...

Journal of The American Society for Mass Spectrometry, 2017

The novel copolymers composed of poly-γ-glutamic acid (γ-PGA) and oligoesters have been developed... more The novel copolymers composed of poly-γ-glutamic acid (γ-PGA) and oligoesters have been developed. The structures of the obtained copolymers including variety of end groups were determined at the molecular level with the aid of electrospray ionization multistage mass spectrometry (ESI-MS n). The fragmentation experiment performed for the selected sodium adducts of the copolymers confirmed that the developed methods lead to the formation of graft copolymers composed of poly-γ-glutamic acid (γ-PGA) backbone and oligoesters pendant chains. Moreover, it was established that fragmentation of selected sodium adducts of graft copolymers proceeded via random breakage of amide bonds along the backbone and ester bonds of the oligoesters pendant chains. Considering potential applications of the synthesized copolymers in the area of biomaterials, the hydrolytic degradation under laboratory conditions and in vitro cytotoxicity tests were performed. The ESI-MS n technique applied in this study has been proven to be a useful tool in structural studies of novel graft copolymers as well as their degradation products.

Bioengineering, 2017

There is an increasing demand for bio-based polymers that are developed from recycled materials. ... more There is an increasing demand for bio-based polymers that are developed from recycled materials. The production of biodegradable polymers can include biotechnological (utilizing microorganisms or enzymes) or chemical synthesis procedures. This report demonstrates the corroboration of the molecular structure of polyhydroxyalkanoates (PHAs) obtained by the conversion of waste polyethylene (PE) via non-oxygenated PE wax (N-PEW) as an additional carbon source for a bacterial species. The N-PEW, obtained from a PE pyrolysis reaction, has been found to be a beneficial carbon source for PHA production with Cupriavidus necator H16. The production of the N-PEW is an alternative to oxidized polyethylene wax (O-PEW) (that has been used as a carbon source previously) as it is less time consuming to manufacture and offers fewer industrial applications. A range of molecular structural analytical techniques were performed on the PHAs obtained; which included nuclear magnetic resonance (NMR) and electrospray ionisation tandem mass spectrometry (ESI-MS/MS). Our study showed that the PHA formed from N-PEW contained 3-hydroxybutyrate (HB) with 11 mol% of 3-hydroxyvalerate (HV) units.

Green Polymer Composites Technology, 2016

Materials, 2016

We report on the ability of bacteria to produce biodegradable polyhydroxyalkanoates (PHA) using o... more We report on the ability of bacteria to produce biodegradable polyhydroxyalkanoates (PHA) using oxidized polyethylene wax (O-PEW) as a novel carbon source. The O-PEW was obtained in a process that used air or oxygen as an oxidizing agent. R. eutropha H16 was grown for 48 h in either tryptone soya broth (TSB) or basal salts medium (BSM) supplemented with O-PEW and monitored by viable counting. Study revealed that biomass and PHA production was higher in TSB supplemented with O-PEW compared with TSB only. The biopolymers obtained were preliminary characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The detailed structural evaluation at the molecular level was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The study revealed that, when TSB was supplemented with O-PEW, bacteria produced PHA which contained 3-hydroxybutyrate and up to 3 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units. The ESI-MS/MS enabled the PHA characterization when the content of 3-hydroxybutyrate was high and the appearance of other PHA repeating units was very low.

Desalination and Water Treatment, 2016

AbstractZeolite X was synthesized in the laboratory and was characterized using X-ray diffraction... more AbstractZeolite X was synthesized in the laboratory and was characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, energy dispersive X-ray spectrometer, and Fourier transformed infrared spectrometry. Desalination activity of zeolite X was investigated by the ion-exchange process. The pH of the seawater prior to desalination analysis was 7.87 ± 0.03 through the period of the investigation. The conductivity of the seawater was found to be 16.2 ± 0.01 mS/cm. Effect of time on ion removal was measured. Removal efficiencies of ions showed a trend of Ca2+ > K+ > Mg2+ > Na+. Equilibrium data were fitted by Langmuir and Freundlich isotherms and parameters were evaluated using these models. Adsorption capacities obtained followed the order Ca2+ > K+ > Mg2+ > Na+ with R2 values K+ > Na+ > Ca2+ > Mg2+ for both Langmuir and Freundlich parameters. Equilibrium kinetic data were analyzed using adsorption kinetic models: pseudo-first-order and pseudo-second-order kinetic models. ...

Materials, 2016

Poly-γ-glutamic acid (γ-PGA) is a naturally occurring polymer, which due to its biodegradable, no... more Poly-γ-glutamic acid (γ-PGA) is a naturally occurring polymer, which due to its biodegradable, non-toxic and non-immunogenic properties has been used successfully in the food, medical and wastewater industries. A major hurdle in bacteriophage application is the inability of phage to persist for extended periods in the environment due to their susceptibility to environmental factors such as temperature, sunlight, desiccation and irradiation. Thus, the aim of this study was to protect useful phage from the harmful effect of these environmental factors using the γ-PGA biodegradable polymer. In addition, the association between γ-PGA and phage was investigated. Formulated phage (with 1% γ-PGA) and non-formulated phage were exposed to 50˝C. A clear difference was noticed as viability of non-formulated phage was reduced to 21% at log 10 1.3 PFU/mL, while phage formulated with γ-PGA was 84% at log 10 5.2 PFU/mL after 24 h of exposure. In addition, formulated phage remained viable at log 10 2.5 PFU/mL even after 24 h of exposure at pH 3 solution. In contrast, non-formulated phages were totally inactivated after the same time of exposure. In addition, non-formulated phages when exposed to UV irradiation died within 10 min. In contrast also phages formulated with 1% γ-PGA had a viability of log 10 4.1 PFU/mL at the same exposure time. Microscopy showed a clear interaction between γ-PGA and phages. In conclusion, the results suggest that γ-PGA has an unique protective effect on phage particles.

The kinetics of the release profile of silver ions from zeolite X framework and its effect on fat... more The kinetics of the release profile of silver ions from zeolite X framework and its effect on fatty acid composition of two gram-negative: Escherichia coli K12 W-T and Pseudomonas aeruginosa NCIMB 8295 and one gram-positive Staphylococcus aureus NCIMB 6571. Silver ions were released from the zeolite framework in ananomalous manner with time. The fatty acid composition was significantly altered when they were exposed to silver-loaded zeolite X. Interaction of silver ions with fatty acid of bacterial cells is likely to affect the survival of the cell.

International Journal of Polymer Science, 2014

The properties of PHB may be affected by the carbon source used in its production and this may af... more The properties of PHB may be affected by the carbon source used in its production and this may affect nanofibres made from this polymer by electrospinning. In this study, P(3-HB) was produced from glucose, rapeseed oil, and olive oil byRalstonia eutrophaH16. Cell growth and polymer production were higher in olive or rapeseed oil supplemented media compared to glucose supplemented media. FT-IR,1H-,13C-NMR, and ESI/MSnconfirmed that the synthesized polymers were P(3-HB). SEM micrograph showed the formation of nanofibres from P(3-HB) samples with the fibre diameters dependent on the source of the carbon used in polymer synthesis and the concentration of the polymer in the electrospinning solution. GPC showed that P(3-HB) from glucose (G-PHB) had a higher molecular weight (7.35×105 gmol−1) compared to P(3-HB) from rapeseed (R-PHB) and olive (O-PHB) oil. Differential scanning calorimetry (DSC) showed that the crystallinity of the electrospun polymers reduces with decreasing polymer conce...

RSC Advances, 2017

A convenient synthetic route of poly(3HB-co-3HH-co-SEB) terpolyesters has been reported. The deve... more A convenient synthetic route of poly(3HB-co-3HH-co-SEB) terpolyesters has been reported. The developed protocol consists of two steps; poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx) oligoesterdiols were synthesized via selective reduction of biopolyesters and then via their polycondensation with sebacoyl chloride the biodegradable terpolyesters, poly(3HB-co-3HH-co-SEB), were obtained. The structure of the obtained terpolyesters was established by NMR analysis supported by mass spectrometry. Modification of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by incorporating units derived from sebacic acid into its chains resulted in terpolyesters with better physico-chemical properties than the starting PHBHx biopolyester. These new polyester materials have greater thermal stability than the starting biopolyester. Furthermore, the introduction of sebacic acid units to a polyester chain leads to the reduction of the glass transition temperatures of the materials and reduces the required processing temperature. A preliminary study confirmed that poly(3HB-co-3HH-co-SEB) terpolyesters can be used to create scaffolds for cell cultures in the form of a three-dimensional spatial structure. Moreover, a toxicity test of the obtained terpolyester carried out on human cells demonstrated that the novel terpolyester is not toxic to human cells in vitro.

Waste Management, Jun 1, 2017

The public awareness of the quality of environment stimulates the endeavor to safe polymeric mate... more The public awareness of the quality of environment stimulates the endeavor to safe polymeric materials and their degradation products. The aim of the forensic engineering case study presented in this paper is to evaluate the aging process of commercial oxo-degradable polyethylene bag under real industrial composting conditions and in distilled water at 70 o C, for comparison. Partial degradation of the investigated material was monitored by changes in molecular weight, thermal properties and Keto Carbonyl Bond Index and Vinyl Bond Index, which were calculated from the FTIR spectra. The results indicate that such an oxo-degradable product offered in markets degrades slowly under industrial composting conditions. Even fragmentation is slow, and it is dubious that biological mineralization of this material would occur within a year under industrial composting conditions. The slow degradation and fragmentation is most likely due to partially crosslinking after long time of degradation, which results in the limitation of low molecular weight residues for assimilation. The work suggests that these materials should not be labeled as biodegradable, and should be further analyzed in order to avoid the spread of persistent artificial materials in nature. Polyethylene is generally considered as a non-biodegradable plastic widely used as a packaging material. For several decades producers of conventional polyethylene are searching for methods

Polymers, Aug 29, 2018

Excessive levels of plastic waste in our oceans and landfills indicate that there is an abundance... more Excessive levels of plastic waste in our oceans and landfills indicate that there is an abundance of potential carbon sources with huge economic value being neglected. These waste plastics, through biological fermentation, could offer alternatives to traditional petrol-based plastics. Polyhydroxyalkanoates (PHAs) are a group of plastics produced by some strains of bacteria that could be part of a new generation of polyester materials that are biodegradable, biocompatible, and, most importantly, non-toxic if discarded. This study introduces the use of prodegraded high impact and general polystyrene (PS0). Polystyrene is commonly used in disposable cutlery, CD cases, trays, and packaging. Despite these applications, some forms of polystyrene PS remain financially and environmentally expensive to send to landfills. The prodegraded PS0 waste plastics used were broken down at varied high temperatures while exposed to ozone. These variables produced PS flakes (PS1-3) and a powder (PS4) with individual acid numbers. Consequently, after fermentation, different PHAs and amounts of biomass were produced. The bacterial strain, Cupriavidus necator H16, was selected for this study due to its well-documented genetic profile, stability, robustness, and ability to produce PHAs at relatively low temperatures. The accumulation of PHAs varied from 39% for prodegraded PS0 in nitrogen rich media to 48% (w/w) of dry biomass with the treated PS. The polymers extracted from biomass were analyzed using nuclear magnetic resonance (NMR) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) to assess their molecular structure and properties. In conclusion, the PS0-3 specimens were shown to be the most promising carbon sources for PHA biosynthesis; with 3-hydroxybutyrate and up to 12 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units generated.

African Journal of Biotechnology, Mar 8, 2017

Bacterial cellulose (BC) is produced by bacteria such as Gluconacetobacter xylinus. It has unique... more Bacterial cellulose (BC) is produced by bacteria such as Gluconacetobacter xylinus. It has unique structural and mechanical properties and is highly pure as compared to plant cellulose. In this study, BC was produced in Hestrin-Schramm (HS) medium. G. xylinus produced an average dry yield of 1.4 ± 0.09 g/L BC after 9 days of fermentation period. Scanning Electron Microscopy (SEM) analysis confirmed BC to be highly structured while Fourier Transform infrared spectroscopy (FTIR) analysis indicated that the absorption peaks at 3000-3700, 2800-2970 and 1023-1024 cm-1 were derived from-OH bending,-CH stretching and C-C/C-OH/C-H ring vibrations. X-Ray Diffraction (XRD) revealed a high purity of BC indicating type I cellulose with high crystalline nature. The solid state 13 C Nuclear magnetic resonance (NMR) spectroscopy of the untreated BC sample also indicated high crystallinity while the cellulase treated BC sample was different, but dominated by a polysaccharide signal between 55 and 110 ppm. The results suggest the prospects of the production and recycling of biopolymers from bacterial sources.

Polymer Degradation and Stability, Jun 1, 2018

The use of biobased plastics is of great importance for many applications. Blending thermoplastic... more The use of biobased plastics is of great importance for many applications. Blending thermoplastic polylactide (PLA) with polyhydroxyalkanoate (PHA) enables the formulation of a more mechanically powerful material and this enables tailored biodegradation properties. In this study we demonstrate the 3D printing of a PLA/PHA blend as a potential candidate for biocompatible material applications. The filament for 3D printing consisted of PHA, which contains predominantly 3-hydroxybutyrate units and a small amount of 3hydroxyvalerate units, as revealed by multistage mass spectrometry (ESI-MS n). This research

Materials, Apr 25, 2016

The (trans)esterification reaction of bacterial biopolymers with a selected bioactive compound wi... more The (trans)esterification reaction of bacterial biopolymers with a selected bioactive compound with a hydroxyl group was applied as a convenient method for obtaining conjugates of such compound. Tyrosol, a naturally occurring phenolic compound, was selected as a model of a bioactive compound with a hydroxyl group. Selected biodegradable polyester and polyamide, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) and poly-γ-glutamic acid (γ-PGA), respectively, were used. The (trans)esterification reactions were carried out in melt mediated by 4-toluenesulfonic acid monohydrate. The structures of (trans)esterification products were established at the molecular level with the aid of ESI-MS 2 (electrospray ionization tandem mass spectrometry) and/or 1 H NMR (nuclear magnetic resonance) techniques. Performed analyses confirmed that the developed method leads to the formation of conjugates in which bioactive compounds are covalently bonded to biopolymer chains. The amount of covalently bonded bioactive compounds in the resulting conjugates depends on the type of biopolymers applied in synthesis.

International Journal of Molecular Sciences, Jul 19, 2016

Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. E... more Polyhydroxyalkanoates (PHAs) are a group of bioplastics that have a wide range of applications. Extensive progress has been made in our understanding of PHAs' biosynthesis, and currently, it is possible to engineer bacterial strains to produce PHAs with desired properties. The substrates for the fermentative production of PHAs are primarily derived from food-based carbon sources, raising concerns over the sustainability of their production in terms of their impact on food prices. This paper gives an overview of the current carbon sources used for PHA production and the methods used to transform these sources into fermentable forms. This allows us to identify the opportunities and restraints linked to future sustainable PHA production. Hemicellulose hydrolysates and crude glycerol are identified as two promising carbon sources for a sustainable production of PHAs. Hemicellulose hydrolysates and crude glycerol can be produced on a large scale during various second generation biofuels' production. An integration of PHA production within a modern biorefinery is therefore proposed to produce biofuels and bioplastics simultaneously. This will create the potential to offset the production cost of biofuels and reduce the overall production cost of PHAs.

The FASEB Journal, Apr 1, 2015

Bacterial cellulose (BC) is produced by bacteria has a unique structural and mechanical propertie... more Bacterial cellulose (BC) is produced by bacteria has a unique structural and mechanical properties and is highly pure as compared to plant cellulose. In this study, BC was produced using Hestrin-Schramm (HS) media. Two forms of cellulose were observed; a gel-like membrane and a leathery membrane. Fourier Transform infrared spectroscopy (FTIR) investigation revealed both forms to be cellulose and indicated the presence of CH2 and OH group at the absorption wavelength of 3300 cm-1, 1650 cm-1 and 1025 cm-1. Scanning Electron Microscopy (SEM) results showed fine morphology of the cellulose matrix and fibre; and XRD indicated the majority of the cellulose to be type-1 cellulose (crystalline in nature). Plasmid DNA sequence analysis revealed an open reading frame of 678 bp. The significance of this work is discussed.

Polyhydroxyalkanoates (PHAs) are biopolymers, which can replace petrochemical plastics in many ap... more Polyhydroxyalkanoates (PHAs) are biopolymers, which can replace petrochemical plastics in many applications. However, these bioplastics are currently far more expensive than petrochemical plastics. Many researchers are investigating the use of inexpensive substrates derived from waste streams. Waste frying oil is abundant and can be used in PHA production without filtration. Cupriavidus necator (formerly known as Ralstonia eutropha) is a versatile organism for the production of PHAs. Small-scale batch fermentation studies have been set up, using different concentrations of pure vegetable oil, heated vegetable oil and waste frying oil. These oils are all rapeseed oils. It has been shown that Cupriavidus necator produced the homopolymer polyhydroxybutyrate (PHB) from the rapeseed oils. The achieved PHB concentration from waste frying oil was 1.2 g/l, which is similar to a concentration that can be obtained from glucose. The PHB harvest from pure oil and heated oil was 0.62 g/l and 0.9...

Polymers, 2019

This study investigated the molecular structure of the polyhydroxyalkanoate (PHA) produced via a ... more This study investigated the molecular structure of the polyhydroxyalkanoate (PHA) produced via a microbiological shake flask experiment utilizing oxidized polypropylene (PP) waste as an additional carbon source. The bacterial strain Cupriavidus necator H16 was selected as it is non-pathogenic, genetically stable, robust, and one of the best known producers of PHA. Making use of PHA oligomers, formed by controlled moderate-temperature degradation induced by carboxylate moieties, by examination of both the parent and fragmentation ions, the ESI-MS/MS analysis revealed the 3-hydroxybutyrate and randomly distributed 3-hydroxyvalerate as well as 3-hydroxyhexanoate repeat units. Thus, the bioconversion of PP solid waste to a value-added product such as PHA tert-polymer was demonstrated.

Waste management (New York, N.Y.), 2018

Prediction studies of advanced (bio)degradable polymeric materials are crucial when their potenti... more Prediction studies of advanced (bio)degradable polymeric materials are crucial when their potential applications as compostable products with long shelf-life is considered for today's market. The aim of this study was to determine the effect of the polylactide (PLA) content in the blends of PLA and poly(butylene adipate-co-terephthalate) (PBAT); specifically how the material's thickness corresponded to changes that occurred in products during the degradation process. Additionally, the influence of talc on the degradation profile of all samples in all environments was investigated. It was found that, differences in the degradation rate of materials tested with a similar content of the PLA component could be caused by differences in their thickness, the presence of commercial additives used during processing or a combination of both. The obtained results indicated that the presence of talc may interfere with materials behavior towards water and consequently alter their degrada...

Biomacromolecules, Feb 9, 2018

The herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) conjugated with poly(3-hydroxybutyrate-c... more The herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) conjugated with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was prepared via a melt transesterification route. The resultant bioactive oligomer was then mixed with a blend of polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) with different loadings to manufacture films to be used as a bioactive, biodegradable mulch to deliver the herbicide to target broadleaf weed species. The biological targeting of the MCPA-PHBV conjugate in the mulch film was investigated under glasshouse conditions using faba bean (Vicia faba) as a selective (nontarget) model crop species having broadleaf morphology. The presence of the MCPA-PHBV conjugate in the biodegradable PBTA/PLA blend was shown to completely suppress the growth of broadleaf weed species while displaying only a mild effect on the growth of the model crop. The degradation of the mulch film under glasshouse conditions was quite slow. The release of the MCPA-P...

Journal of The American Society for Mass Spectrometry, 2017

The novel copolymers composed of poly-γ-glutamic acid (γ-PGA) and oligoesters have been developed... more The novel copolymers composed of poly-γ-glutamic acid (γ-PGA) and oligoesters have been developed. The structures of the obtained copolymers including variety of end groups were determined at the molecular level with the aid of electrospray ionization multistage mass spectrometry (ESI-MS n). The fragmentation experiment performed for the selected sodium adducts of the copolymers confirmed that the developed methods lead to the formation of graft copolymers composed of poly-γ-glutamic acid (γ-PGA) backbone and oligoesters pendant chains. Moreover, it was established that fragmentation of selected sodium adducts of graft copolymers proceeded via random breakage of amide bonds along the backbone and ester bonds of the oligoesters pendant chains. Considering potential applications of the synthesized copolymers in the area of biomaterials, the hydrolytic degradation under laboratory conditions and in vitro cytotoxicity tests were performed. The ESI-MS n technique applied in this study has been proven to be a useful tool in structural studies of novel graft copolymers as well as their degradation products.

Bioengineering, 2017

There is an increasing demand for bio-based polymers that are developed from recycled materials. ... more There is an increasing demand for bio-based polymers that are developed from recycled materials. The production of biodegradable polymers can include biotechnological (utilizing microorganisms or enzymes) or chemical synthesis procedures. This report demonstrates the corroboration of the molecular structure of polyhydroxyalkanoates (PHAs) obtained by the conversion of waste polyethylene (PE) via non-oxygenated PE wax (N-PEW) as an additional carbon source for a bacterial species. The N-PEW, obtained from a PE pyrolysis reaction, has been found to be a beneficial carbon source for PHA production with Cupriavidus necator H16. The production of the N-PEW is an alternative to oxidized polyethylene wax (O-PEW) (that has been used as a carbon source previously) as it is less time consuming to manufacture and offers fewer industrial applications. A range of molecular structural analytical techniques were performed on the PHAs obtained; which included nuclear magnetic resonance (NMR) and electrospray ionisation tandem mass spectrometry (ESI-MS/MS). Our study showed that the PHA formed from N-PEW contained 3-hydroxybutyrate (HB) with 11 mol% of 3-hydroxyvalerate (HV) units.

Green Polymer Composites Technology, 2016

Materials, 2016

We report on the ability of bacteria to produce biodegradable polyhydroxyalkanoates (PHA) using o... more We report on the ability of bacteria to produce biodegradable polyhydroxyalkanoates (PHA) using oxidized polyethylene wax (O-PEW) as a novel carbon source. The O-PEW was obtained in a process that used air or oxygen as an oxidizing agent. R. eutropha H16 was grown for 48 h in either tryptone soya broth (TSB) or basal salts medium (BSM) supplemented with O-PEW and monitored by viable counting. Study revealed that biomass and PHA production was higher in TSB supplemented with O-PEW compared with TSB only. The biopolymers obtained were preliminary characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The detailed structural evaluation at the molecular level was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The study revealed that, when TSB was supplemented with O-PEW, bacteria produced PHA which contained 3-hydroxybutyrate and up to 3 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units. The ESI-MS/MS enabled the PHA characterization when the content of 3-hydroxybutyrate was high and the appearance of other PHA repeating units was very low.

Desalination and Water Treatment, 2016

AbstractZeolite X was synthesized in the laboratory and was characterized using X-ray diffraction... more AbstractZeolite X was synthesized in the laboratory and was characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, energy dispersive X-ray spectrometer, and Fourier transformed infrared spectrometry. Desalination activity of zeolite X was investigated by the ion-exchange process. The pH of the seawater prior to desalination analysis was 7.87 ± 0.03 through the period of the investigation. The conductivity of the seawater was found to be 16.2 ± 0.01 mS/cm. Effect of time on ion removal was measured. Removal efficiencies of ions showed a trend of Ca2+ > K+ > Mg2+ > Na+. Equilibrium data were fitted by Langmuir and Freundlich isotherms and parameters were evaluated using these models. Adsorption capacities obtained followed the order Ca2+ > K+ > Mg2+ > Na+ with R2 values K+ > Na+ > Ca2+ > Mg2+ for both Langmuir and Freundlich parameters. Equilibrium kinetic data were analyzed using adsorption kinetic models: pseudo-first-order and pseudo-second-order kinetic models. ...

Materials, 2016

Poly-γ-glutamic acid (γ-PGA) is a naturally occurring polymer, which due to its biodegradable, no... more Poly-γ-glutamic acid (γ-PGA) is a naturally occurring polymer, which due to its biodegradable, non-toxic and non-immunogenic properties has been used successfully in the food, medical and wastewater industries. A major hurdle in bacteriophage application is the inability of phage to persist for extended periods in the environment due to their susceptibility to environmental factors such as temperature, sunlight, desiccation and irradiation. Thus, the aim of this study was to protect useful phage from the harmful effect of these environmental factors using the γ-PGA biodegradable polymer. In addition, the association between γ-PGA and phage was investigated. Formulated phage (with 1% γ-PGA) and non-formulated phage were exposed to 50˝C. A clear difference was noticed as viability of non-formulated phage was reduced to 21% at log 10 1.3 PFU/mL, while phage formulated with γ-PGA was 84% at log 10 5.2 PFU/mL after 24 h of exposure. In addition, formulated phage remained viable at log 10 2.5 PFU/mL even after 24 h of exposure at pH 3 solution. In contrast, non-formulated phages were totally inactivated after the same time of exposure. In addition, non-formulated phages when exposed to UV irradiation died within 10 min. In contrast also phages formulated with 1% γ-PGA had a viability of log 10 4.1 PFU/mL at the same exposure time. Microscopy showed a clear interaction between γ-PGA and phages. In conclusion, the results suggest that γ-PGA has an unique protective effect on phage particles.

The kinetics of the release profile of silver ions from zeolite X framework and its effect on fat... more The kinetics of the release profile of silver ions from zeolite X framework and its effect on fatty acid composition of two gram-negative: Escherichia coli K12 W-T and Pseudomonas aeruginosa NCIMB 8295 and one gram-positive Staphylococcus aureus NCIMB 6571. Silver ions were released from the zeolite framework in ananomalous manner with time. The fatty acid composition was significantly altered when they were exposed to silver-loaded zeolite X. Interaction of silver ions with fatty acid of bacterial cells is likely to affect the survival of the cell.

International Journal of Polymer Science, 2014

The properties of PHB may be affected by the carbon source used in its production and this may af... more The properties of PHB may be affected by the carbon source used in its production and this may affect nanofibres made from this polymer by electrospinning. In this study, P(3-HB) was produced from glucose, rapeseed oil, and olive oil byRalstonia eutrophaH16. Cell growth and polymer production were higher in olive or rapeseed oil supplemented media compared to glucose supplemented media. FT-IR,1H-,13C-NMR, and ESI/MSnconfirmed that the synthesized polymers were P(3-HB). SEM micrograph showed the formation of nanofibres from P(3-HB) samples with the fibre diameters dependent on the source of the carbon used in polymer synthesis and the concentration of the polymer in the electrospinning solution. GPC showed that P(3-HB) from glucose (G-PHB) had a higher molecular weight (7.35×105 gmol−1) compared to P(3-HB) from rapeseed (R-PHB) and olive (O-PHB) oil. Differential scanning calorimetry (DSC) showed that the crystallinity of the electrospun polymers reduces with decreasing polymer conce...